ICES WGBAST REPORT Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST) March Turku, Finland

Transcription

1 ICES WGBAST REPORT 2018 ICES ADVISORY COMMITTEE ICES CM 2018/ACOM:10 Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST) March 2018 Turku, Finland

2 International Council for the Exploration of the Sea Conseil International pour l Exploration de la Mer H. C. Andersens Boulevard DK-1553 Copenhagen V Denmark Telephone (+45) Telefax (+45) info@ices.dk Recommended format for purposes of citation: ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), March 2018, Turku, Finland. ICES CM 2018/ACOM: pp. For permission to reproduce material from this publication, please apply to the General Secretary. The document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council International Council for the Exploration of the Sea

3 ICES WGBAST REPORT 2018 i Contents Executive Summary Introduction Participants Ecosystem considerations Salmon and sea trout in the Baltic ecosystem Effects of climate change Ecosystem impacts of fisheries and mixed fisheries overview Data for HELCOM salmon and sea trout core indicators Response to last year s Technical Minutes Salmon fisheries Description of Baltic salmon fisheries Commercial fisheries Recreational fisheries Broodstock fisheries Catches Catch development over time Catches by country (2017) Distribution of catches by countries compared with the TAC Discards, unreporting and misreporting of catches Discards Information by country Misreporting of salmon as sea trout in the Polish fishery Fishing effort Biological sampling of salmon Sampling by country (2017) Growth of salmon Tagging data in the Baltic salmon stock assessment Finclipping Estimates of stock and stock group proportions in the Gulf of Finland Baltic salmon catches based on DNA microsatellite and freshwater age information Methods Results Management measures influencing the salmon fishery International regulatory measures National regulatory measures Effects of management measures... 51

4 ii ICES WGBAST REPORT Other factors influencing the salmon fishery Dioxin Disease outbreaks River data on salmon populations Wild salmon populations in Main Basin and Gulf of Bothnia Rivers in assessment unit 1 (Gulf of Bothnia, SD 31) Rivers in assessment unit 2 (Gulf of Bothnia, SD 31) Rivers in assessment unit 3 (Gulf of Bothnia, SD 30) Rivers in assessment unit 4 (Western Main Basin, SD 25 and 27) Rivers in assessment unit 5 (Eastern Main Basin, SD 26 and 28) Rivers in assessment unit 6 (Gulf of Finland, SD 32) Potential salmon rivers General Potential rivers by country Reared salmon populations Releases Straying M74, dioxin and disease outbreaks M74 in Gulf of Bothnia and Bothnian Sea M 74 in Gulf of Finland and Gulf of Riga Disease outbreaks Summary of the information on wild and potential salmon rivers Reference points and assessment of salmon Introduction Historical development of Baltic salmon stocks (assessment units 1 6) Changes in the assessment methods Updated submodels Status of the assessment unit 1 4 stocks and development of fisheries in the Gulf of Bothnia and the Main Basin Status of the assessment unit 5 6 stocks Harvest pattern of wild and reared salmon in AU Stock projection of Baltic salmon stocks in assessment units Assumptions regarding development of fisheries and key biological parameters Results Additional information affecting perception of stock status Potential effects of M74 and disease on stock development Revision of basic input data Updated reference points for management (stock-specific MSY targets) Conclusions

5 ICES WGBAST REPORT 2018 iii 4.6 Ongoing and future development of the stock assessment Benchmark Road map for development of the assessment Needs for improving the use and collection of data for assessment Sea trout Baltic Sea trout catches Commercial fisheries Recreational fisheries Total nominal catches Biological catch sampling Data collection and methods Monitoring methods Assessment of recreational sea trout fisheries Marking and tagging Assessment of recruitment status Methods Data availability for status assessment Data presentation Trout in Gulf of Bothnia (SD 30 and 31) Trout in Gulf of Finland (SD 32) Trout in Main Basin (SD 22 29) Recruitment status and trends Recruitment status Recruitment trends Reared smolt production Recent management changes and additional information Management changes Additional information Assessment result Future development of model and data improvement Compatibility of the EU-MAP with the data needs for WGBAST Recommendations References Literature Annex 1: List of Participants Annex 2: Stock Annex for Salmon (Salmo salar) in subdivisions (Baltic Sea) Annex 3: Recommendations Annex 4: Smolts and PSPC per Assessment Unit for HELCOM salmon indicator

6 iv ICES WGBAST REPORT 2018 Annex 5: Technical minutes from the Review Group on Baltic Salmon Appendix 1: Results of an extended MCMC sampling

7 ICES WGBAST REPORT Executive Summary The Baltic Salmon and Trout Assessment Working Group [WGBAST] (Chair: Stefan Palm, Sweden) met in Turku, Finland, March A total of 28 experts from all nine Baltic Sea countries attended the meeting (whereof four were via correspondence). The group was mandated to assess the status of salmon in Gulf of Bothnia and Main Basin (subdivisions 22 31), Gulf of Finland (Subdivision 32) and sea trout in subdivisions 22 32, and to propose consequent management advices for fisheries in Salmon in subdivision were assessed using Bayesian methodology, with a stock projection model (data up to 2017) for evaluating impacts of different catch options on the wild river stocks. Section 2 of the report covers catches and other data on salmon in the sea, and summarizes information affecting the fisheries and management of salmon. Section 3 reviews data from salmon spawning rivers, stocking statistics and health issues. Status of salmon stocks in the Baltic Sea is evaluated in Section 4. The same section covers also methodological issues of assessment as well as sampling protocols and data needs for assessment. Section 5 presents data on sea trout and stocks status. The total salmon catch in 2017 (including recently revised estimates of trolling catches; below) was the lowest in the time-series since the 1970s. Catch levels have decreased continuously since the 1990s, although more slowly in recent years. Efforts in several important commercial salmon fisheries remained on a historically low level. The total level of estimated misreporting (of salmon as sea trout) increased to salmon in 2017, almost twice as much as estimated for The total share of recreational catches of Baltic salmon in the sea and rivers has increased over time. In particular, the offshore trolling fishery has developed rapidly. According to updated estimates, the total recreational catch has in recent years been about salmon larger than previously known. The new time-series of trolling catches was included in the stock projection model. The natural salmon smolt production has gradually increased in the Gulf of Bothnia and Gulf of Finland rivers. For most rivers and assessment units, either increasing or stable smolt production is predicted also for 2018, as a result of good spawning runs in The current (2017) total wild production in all Baltic Sea rivers is above 3.5 million smolts, corresponding to about 86% of overall potential smolt production capacity. In addition, about 4.3 million reared salmon smolts were released into the Baltic Sea in Over time, an increasing proportion of the wild stocks have reached the management target (75% of potential smolt production capacity) with high or very high certainty, especially in the northern Baltic Sea. At current levels of fishing pressure and natural mortality, a continued positive status development is predicted. As previously, most weak stocks are located in the Main Basin and Gulf of Finland rivers, but also in these southern areas some stocks have improved. In particular, wild Estonian (Gulf of Finland) stocks show recovery. The exploitation rate of Baltic salmon in the sea fisheries has been reduced to such a low level that most stocks (for which analytical projections are currently available) are predicted to recover. However, many weak stocks also

8 2 ICES WGBAST REPORT 2018 need longer term stock-specific rebuilding measures, including fisheries restrictions in estuaries and rivers, habitat restoration and removal of potential migration obstacles. M74-related juvenile mortality increased in , and is expected to remain at about the same level in spring It is hard to predict if high levels of M74 will persist beyond Also, other health issues (disease outbreaks, cause still unknown) with large numbers of dead spawners and collapsed parr densities in some wild rivers are still topical and therefore of concern for the future. Some positive development can be seen for sea trout in the Baltic Sea region, but many populations are still considered vulnerable. Stocks in the Gulf of Bothnia are particularly weak, although spawner numbers and parr densities are improving. Stock statuses are generally higher in the Main Basin and in southern Gulf of Finland. In general, exploitation rates in most fisheries that catch sea trout in the Baltic Sea area should be reduced. This also holds for fisheries of other species where sea trout is caught as bycatch. In regions where stock status is good, existing fishing restrictions should be maintained in order to retain the present situation.

9 ICES WGBAST REPORT Introduction 1.1 Participants Janis Bajinskis (part of meeting) Latvia Rafał Bernaś Poland Johan Dannewitz (part of meeting) Sweden Piotr Debowski Poland Harry Hantke (part of meeting) Germany Kelsey Hartikainen (part of meeting) Finland Martin Kesler Estonia Vytautas Kesminas (part of meeting) Lithuania Anders Kagervall (by correspondence) Sweden Marja-Liisa Koljonen (by correspondence) Finland Antanas Kontautas (part of meeting) Lithuania Adam Lejk Poland Katarina Magnusson (Skype) Sweden Hans Jakob Olesen Tapani Pakarinen Denmark Finland Stefan Palm (chair) Sweden Stig Pedersen Wojciech Pelczarski Denmark Poland Christoph Petereit (part of meeting) Germany Henni Pulkkinen (part of meeting, Skype) Finland Atso Romakkaniemi Stefan Stridsman Finland Sweden Oula Tolvanen (part of meeting) Finland Susanne Tärnlund Sergey Titov Sweden Russia Didzis Ustups (part of meeting) Latvia Simon Weltersbach (part of meeting) Germany Rebecca Whitlock (Skype, by correpondence) Sweden 1.2 Ecosystem considerations Salmon and sea trout in the Baltic ecosystem Salmon (Salmo salar) and sea trout (Salmo trutta) are among the top fish predators in the Baltic Sea. Together with European eel (Anguilla Anguilla) and migratory whitefish

10 4 ICES WGBAST REPORT 2018 (Coregonus lavaretus/coregonus maraena) they form the group of keystone diadromous species in the Baltic Sea. On the species level, based on the IUCN criteria, salmon and the sea trout has been categorised as vulnerable (VU) by HELCOM. As a result of precise homing of salmon and sea trout to their natal rivers, each river and even in some cases each river section, may have a genetically unique and demographically largely independent population; thus the conservation of biodiversity requires safeguarding of the genetic variation and integrity of local populations. Likewise, the development and status of single river stocks of salmon and trout needs to be accounted for, to allow an effective resource management. Salmon and sea trout are anadromous, i.e. they hatch in freshwater, spend one to five years in river and after this migrate for a long period to the sea, then return to freshwater to spawn. Therefore, good connectivity between the sea and rivers, as well as in the rivers, is of ultimate importance for the existence of these species. Salmon has the widest migration routes over the Baltic Sea catchment area. As an example, salmon juveniles occupy the headwaters of the River Tornionjoki km upstream from the sea, which is the northernmost point of the Baltic Sea drainage area. After 3 5 years growth in freshwater, juveniles migrate to the sea, at first feeding on insects and other invertebrates and half a year later, they shift to feed on herring and sprat in the southwestern part of the Baltic Sea proper. Salmon mature after 1 4 years growth on the feeding grounds, after which they migrate the 2000 km distance back to their natal headwater rivers for spawning. Sea trout basically has the same life cycle as salmon. The most important difference is that most strains do not migrate as far as the salmon. Instead, they spend the time in sea in coastal waters where the majority of sea trout from a specific strain stay within a few hundred kilometres from their home river. Some specimens, however, migrate further and in some strains in the Southern Baltic most sea trout seem to migrate longer distances into the open sea. Sea trout spawn and live during the first period of life in smaller streams than salmon. For this reason, the connectivity from sea to spawning areas may be even more critical, compared to salmon, due to possible minor barriers in the small streams. In the Baltic Sea area, sea trout are found in a much larger number of streams than salmon. Many of these streams are in lowland areas that are often strongly influenced by human activity. One effect from this is for example elevated siltation, deteriorated spawning possibilities and reduced survival of eggs. At each stage of migration and life cycle, salmon occupies a specific niche that cannot be occupied by any other species in the ecosystem. For instance, salmon juveniles are one of the few species that can utilise fast-flowing freshwater habitats in the large northern rivers. No other fish species was able to replace salmon juveniles in fish production and populate the empty rearing habitats during the deep depression in salmon abundance in the latter half of the 20th century. Salmon is adapted to uniquely utilise and link the low-productive, fast-flowing river habitat, which is a good environment for reproduction, with the pelagic sea habitat, which offers good conditions for fast growth due to the high abundance of prey species (Kulmala et al., 2013). Sea trout has adapted to live in the smaller tributaries and at slightly lower water velocities than salmon. All this demonstrates how connectivity between river habitat, coastal transitional zone and open sea is the lifeline for Baltic salmon and sea trout, and how the requirements imposed to biotic and abiotic habitat vary in time and space, depending on the life stage of the species concerned. Today, Baltic salmon reproduce naturally in nearly 40

11 ICES WGBAST REPORT rivers. In the past, however, the number of rivers with wild Baltic salmon stocks is known to have been considerably higher, i.e. around one hundred rivers. Also, the number of rivers with wild sea trout stocks has declined considerably. Damming, habitat destruction, pollution and intensive fishing have been identified as the main causes of the decline. Presently, a majority of the wild salmon originates from rivers located in Sweden, Finland, Latvia and Estonia. Most of the current spawning rivers of wild sea trout stocks are located in Denmark and Sweden. Salmon and sea trout play an important role in maintaining the balance in riverine foodwebs, both by harvesting invertebrate populations and also providing an important food source for other predatory species (Kulmala et al., 2013). The total nutrient transportation between freshwater and sea is nowadays lower than in the past due to damming and other human activities, which have decreased fish abundance, destroyed natural migration and life cycle of salmon in many spawning rivers. Salmon and sea trout turns over gravel in the river bed while spawning. This bioturbation cleans river bed from, for example, organic particles the sedimentation of which is high in the Baltic rivers. Spawning removes also macrophytes and invertebrates from the sediment, which may more easily be fed by river fish. Salmon is a top fish predator in the Baltic Sea that mainly eats sprat and herring (in the south mainly sprat and towards the north increasingly herring). Thus, salmon in one sense refines various micronutrients for use of other top predators like mammals, including humans (Kulmala et al., 2013). Salmon muscle indeed contains plenty of polyunsaturated fatty acids, which are beneficial for human circulatory system. However, being at the top of the food chain salmon unfortunately also accumulates harmful substances, i.e. various environmental toxicants (e.g. dioxins). Salmon and sea trout are frequent prey species of grey seals, especially in the Gulf of Bothnia (e.g. Lundström et al., 2010). The increasing seal population is likely to consume more salmonids, which is expected to impact salmon and sea trout population principally in a similar manner as fishing (Hansson et al., 2017). The thiamine deficiency syndrome M74 is a reproductive disorder, which causes mortality among yolk-sac fry of Baltic salmon (see Annex 2 and Section 3.4). The development of M74 is caused by a deficiency of thiamine in the salmon eggs that, in turn, is suggested to be coupled to an abundant but unbalanced fish diet with too low concentration of thiamine in relation to fat and energy content (Keinänen et al., 2012). The intake of thiamine for Baltic salmon in relation to energy and fat remains lowest by eating young clupeids, especially young sprat (Keinänen et al., 2012). Total biomass of sprat in the Baltic main basin and salmon growth are positively correlated. Further, variation in the condition factor of pre-spawning salmon is explained by fluctuations in the biomass of sprat (Mikkonen et al., 2011). The high growth rate of salmon seems not as such be the cause, but rather the abundance of prey and its quality are responsible for M74 (Mikkonen et al., 2011). To inhibit M74, great variation in the size of prey stocks utilized by salmon should be avoided. In the Baltic main basin, where sprat reproduce, the size of the sprat stock needs to be under control, and possibly not allowed to exceed that of herring. The safest strategy for attaining this objective would be to ensure a large, stable cod stock (Casini et al., 2009), to prey on the sprat. Alternatively, increased fishing on sprat would have the same inhibiting effect on M74 (Keinänen et al., 2012) Effects of climate change An additional concern for salmon and trout in the Baltic area are the alterations in environmental conditions occurring as a result of climate change. Addressing the implications of climate change is particularly pertinent, considering that air temperature in

12 6 ICES WGBAST REPORT 2018 this area, an important indicator of climate change, has risen faster than the global average (HELCOM, 2013). Other changes that may be relevant to Baltic salmonids during the sea phase of their lifecycles are changes in sea surface temperature and ice cover. Ice cover extent and duration have decreased in the Baltic Sea over the last century (HELCOM, 2013), with ice cover extent decreasing by 20% and ice cover duration decreasing by 18 and 41 days in the Bothnian Bay and Gulf of Finland, respectively (HEL- COM, 2013). Mean annual sea-surface temperatures have also risen by as much as 1 C per decade between 1990 and 2008 (HELCOM, 2013). Notably, the greatest changes in sea-surface temperature have occurred and are predicted to continue to occur in the Bothnian Bay (HELCOM, 2013), which is site of the majority of Baltic salmon production. Such changes in environmental condition may exacerbate one another, a point exemplified by the fact that reduced ice cover in the Baltic has likely contributed to the steep rise in sea surface temperature (HELCOM, 2013). Changes in freshwater systems in the Baltic area are also likely, as increasing temperatures and climate variability are expected to impact freshwater systems worldwide, particularly at northern latitudes (IPCC, 2014; ICES, 2017b). Examples of relevant changes in freshwater systems are rising water temperatures and reduced water quality resulting from increasing runoff (IPCC, 2014). Additionally, projections for the Baltic area anticipate increased rainfall in the northern portion of the region and reduced rainfall in the south, resulting in increased discharge from rivers and streams in the north and reduced discharge in the south (HELCOM, 2013). Although limited research has been conducted regarding the effects of climate change on Baltic salmon and trout to date, climate change is expected to influence aquatic communities in the Baltic area (e.g. Mackenzie et al., 2007). The effects of climate change on Atlantic salmon, though not specifically in the Baltic portion of their range, have been studied extensively (ICES, 2017b) and may serve as a reasonable first estimation of the impacts climate change may have on salmonids elsewhere. Jonsson and Jonsson s (2009) review of the effects of climate change on Atlantic salmon and anadromous brown trout suggests that changing water temperatures and flow may result in earlier smolt migration, later spawning, smoltification and sexual maturity at younger ages, and increased mortality. River production capacity for parr may also change as rivers wetted area shrinks or swells in response to changing precipitation patterns (Sundt- Hanssen et al., 2018; ICES, 2017b). Climate change may also affect Baltic salmonids indirectly, via foodweb interactions, for example. The distribution of freshwater species in the brackish Baltic Sea is likely to expand, while the distribution of marine species contracts as sea salinity decreases (Mackenzie et al., 2007), another potential effect of a changing precipitation regime. This in turn, could reduce cod populations, increasing sprat populations as they are released from the pressure of cod predation (HELCOM, 2013). From there, salmon predation on this unexploited food source may increase, potentially increasing the prevalence of M74 along with it. Depending on the speed of these climate change-related effects, Baltic salmonids may adapt to their new environment (ICES, 2017b), particularly with the assistance of management strategies targeted to counteract or ease their severity. A shift towards earlier timing of smolt migration in parallel with earlier springs has been documented across the Atlantic salmon s entire natural distribution, indicating that adaptation is already occurring. (Otero et al., 2014).

13 ICES WGBAST REPORT Ecosystem impacts of fisheries and mixed fisheries overview In a timespan of about one century, salmon fishing has first moved from rivers and coastal areas near the river mouths to the offshore. And again, during the last two decades, the balance has shifted back to mainly coastal and river fishing. The expansion of offshore fishing coincided with the expansion of hatchery-rearing and stocking programmes of salmon juveniles for fishing. Stocking volumes have lately somewhat decreased. Catch of sea trout, especially in the coastal gillnet fishery, both as a targeted and as a non-target species poses a problem for the recovery of threatened sea trout stocks in many Baltic Sea areas. Sea trout are also caught as bycatch of some river fishing targeting salmon. Discarding of seal damaged salmon occurs mainly in the coastal trapnet and gillnet fishery, but also in the offshore longline fishery. Some specimens of seals drown in trapnets. Seal-safe trapnets have been developed, which has lately decreased seal damages, discarding and seal deaths in gear. Salmon and sea trout are caught by several gear types, and in some cases this has decreased the reliability of catch estimates of the TAC controlled salmon fishery vs. the non-controlled sea trout via misreporting of salmon as sea trout. This skews speciesspecific estimates of fishing pressure and undermine effectiveness of management measures Data for HELCOM salmon and sea trout core indicators The core indicator used by HELCOM for evaluation of salmon stock status is based on the comparison of assessed smolt production versus assessed potential smolt production capacity on the assessment unit (AU) level. To facilitate data transfer, AU-specific smolt production estimates needed for the HELCOM indicator are presented in Annex 4, where AU 1 2 have been combined to better match the division used for HELCOM assessment units. The indicator for evaluation of sea trout stock status is based on the comparison of observed to expected (potential) parr density in various habitats concerned. Assessment results presented in Section 5.5 support the HELCOM evaluation.

14 8 ICES WGBAST REPORT Response to last year s Technical Minutes The aim of this section is to facilitate efficient use by the WG of constructive questions and comments presented in the Technical Minutes of last year report, as well as a feedback to the review group how its advice is being used to improve the assessment. Below, the 24 general and specific comments from last year s review are repeated, with responses from the group in italics. Note that some minor errors and clarifications were handled last year already, before the 2017 WG report was published. General comments 1 ) Several revisions to modelling approach were suggested at recent Benchmark Workshops, and partially (?) implemented in the February 2017 run of the FLHM used in this assessment. The Annex summarizing modelling approaches may be out of date and I suggest updating it concurrently with the model. These Annexes are helpful for documenting when and exactly which changes occurred in the assessment model. The model (data until 2015) used for last year s assessment (ICES, 2017a) did not include any of the approaches evaluated during the benchmark (ICES, 2017d). The reason was that the benchmark was still not finished, and furthermore that the new model versions used in that process did not contain all stocks and datasets. It is correct that the stock annex (Annex 2) is partly out of date and needs to be updated. As mentioned in Chapter 4 (present report), this will be done by the group later this year (2018). 2 ) In particular, did the FLHM run used in this assessment include the alternative parameterization of the stock recruitment model considered at the Benchmark workshop (or were those only implemented in JAGS)? I noticed that Emån is still not predicted to recover in the absence of fishing, suggesting these revisions were not included? As mentioned under p.1, no new elements from the benchmark had been implemented in the model (FLHM) used last year, so the assessment retains the original stock recruitment model. Referring to Figure d (ICES, 2017a), Emån does recover with F=0. In 2017, because of a shortage of time to correct the WinBUGS assessment model, temporary changes were made to the scenarios (forward projections) code to make the population dynamics the same in both assessment model and forward projections with F=0 (See second paragraph). In 2018, assessment, the population dynamics equations for Emån have been corrected in both the assessment and projections codes. Specific comments 3 ) Section Are methods for eliciting time-series of recreational trolling documented (in an Annex, or other report)? I suggest using expert-derived estimates rather than guestimates, assuming some objective approach for eliciting these data was used. Words were replaced as suggested already in last year s report. 4 ) Section Recreational trolling was not included in the assessment model, but were also excluded from Table on non-commercial catches. It may be useful and appropriate to include them here? Recreational salmon trolling has been practiced in the Baltic Sea for more than 30 years. The magnitude of this fishery varies between countries, and while in some

15 ICES WGBAST REPORT countries trolling effort has levelled off it has just started developing in others. Despite this, catch data from trolling fisheries from individual countries are still incomplete or missing, and work on quality assurance is still ongoing. One reason for this is that trolling data collection is often not yet included or sufficiently covered in national marine recreational fisheries surveys. Therefore, no table has yet been compiled presenting detailed data on trolling catches. Due to fact that catch surveys on salmon trolling have been done in many countries just in very recent years, or are just about to be started, it will not possible to survey these catches retrospectively to the history. Therefore, only relatively rough expert estimates will be possible to get for years back in time, which however are deemed reliable enough for assessment model inputs. These expert estimates will be considered to be presented in the catch tables in the future. However, in Table in the present report it is possible to compare the magnitude of recreational river catches with the corresponding ones from coastal and offshore (pooled) recreational fisheries for example for year 2017 when also the German catch estimate is included for the first time. 5 ) Section states In the Danish LLD fishery approximately 15% (5% 30%) of the catch was seal damaged. If LLD= longline (though not defined in text), this number disagrees with Table It was clarified in last year s report that LLD=longline. 6 ) Section Besides, there is no estimate on the potential unreporting of bycatch of legally sized salmon in the pelagic trawl fishery. Are there incentives to not report? If catches are usually below quota, then perhaps incentives to not report are low, and this effect would be minor? Some reported catches exist also from the pelagic trawl fishery, indicating that at least some bycatch of larger salmon. Because of the evidently very small catches there should be no more incentives to not report in this particular fisheries, than in the actual salmon fishery, meaning that same rate of unreporting can be assumed for pelagic trawl fishery as for other fisheries (unreporting rates presented in Table 2.3.1). It should also be mentioned that, as discussed in the 2011 WGBAST report, a potentially large bycatch of smaller salmon (post smolts) may also exist in the pelagic fishery, which is likely unnoticed. 7 ) Section 2.4. In Table 2.4.3, cpue for Poland is missing (why?), but Table suggests that effort (numbers of days) is greatest for Poland. No cpue data from Polish offshore fisheries are currently included in Table because of needs for quality assurance (presently being discussed in Poland). 8 ) Section 2.8, Results subsection. Results focus on changes in catch composition from 2015 to However, it s unclear to what extent interannual variability in catch composition is due to sampling variability instead of biologically meaningful differences. This may be especially relevant for Swedish estimates, since those samples don t seem to be representative of the total coastal catch. Long-term trends may be more relevant if short-term trends are dominated by sampling variability. We agree that long-term trends are more important than short-term fluctuations. However, our reporting (written results) have still focused much on recent changes as these are new information from last year, whereas earlier results and trends (seen in tables and figures) have been treated in previous reports. Temporal fluctuations in estimates of stock and stock-group proportions for catches (based on DNA and smolt-age information) typically reflects a combination of sampling variability and biological meaningful differences (i.e. true changes in

16 10 ICES WGBAST REPORT 2018 stock composition). The sampling variability reflects random error (due to sample size error), which is taken into account in the probability intervals of the estimates, but also where and when catch samples are collected, and how well they represent the total catch of a specific fishery (i.e. the fishery sampling). With respect to the Swedish catch samples mentioned, we have pointed out that these estimates cannot be seen as representative for the total Swedish coastal fishery, as they are known to be highly dependent on where (and when) they have been collected. The same problem is believed to be less pronounced for the Main Basin and the Finnish coast, where more or less the same stocks are presumed to occur mixed in the whole area. The Finnish coastal samples analysed are assumed to be representative for the whole coastal catch, as it is resampled representatively from the total scale sample distribution collected annually (over the whole fishing season and from many sampling sites). The total sample size is also sufficient for the number of stocks and stock groups observed in Finnish catches. As there are markedly fewer stock migrating along the eastern Finnish side of Gulf of Bothnia and they are all from northern rivers, the stocks also mix more evenly in the Finnish coastal catches. The analysed Main Basin sample size is large and the salmon stocks occurring there are also well mixed, in contrast to coastal spawning migrating fish from different stocks which tend to gather close to river mouths (especially a complication in Sweden, where rivers are more abundant and widespread than in Finland). There has neither been much annual variation in the stock proportion estimates in the Finnish and Main Basin catches, which tells that the fishery sampling variation cannot be large. Finally, it should be noticed that the sampling always represents and describes the proportions of stock in the catches, not necessarily the abundance of all populations in the sea (if they don t contribute evenly into catches). 9 ) Section When methods for monitoring spawning run changed, was there any effort to calibrate the new methods against the old ones (to ensure time-series were consistent)? (E.g. in Simojoki switching from split-beam to DIDSON echosounder). An effort was made to compare split-beam the DIDSON counting in Simojoki during Both these echo sounders were mounted in the river at a short distance from each other, and data was collected simultaneously over a 4-day period. The results indicated that the DIDSON detected more salmon the than split-beam sounder, probably due to better coverage of the river transect. The split-beam technique is sensitive to any hitting of the sound beam on bottom structure, therefore any irregularities in the river channel transect forces aiming of the split-beam too high in the water column and salmon (which are typically bottom-oriented) often may become undetected. The period of simultaneous data collection was too short to properly calibrate the results of these two methods. Therefore, results of the splitbeam sounding are not utilised in the assessment model. 10 ) Section Is the hierarchical linear regression = the river model? If so, I suggest keeping the terminology consistent. If not, is the hierarchical linear regression documented elsewhere? We added a clarification in last year s report that hierarchical linear regression is also referred to as river model. 11 ) Section This section is very thorough. For Kågeälven, the occurrence of naturally spawning fish since 2013 may not be stable given three year

17 ICES WGBAST REPORT declining trend ( ). The fish may be poorly adapted to natural environment. For Öreälven, the text states In 2016 the densities were halved compared to in the previous year (Table ), but the table shows only a minor decline from Last year we corrected this error in Table , and slightly adjusted the corresponding sentence about densities in Öreälven. 12 ) Section 4.1. What are the main differences between assessment model projecting into the future (WinBUGS) and the projection model (R code). Would you expect them to give similar predictions under status quo harvest given that the projection model uses posterior estimates from the assessment model? The assessment model (also called WinBUGS/JAGS model or full life-history model, FLHM) and the projection model (scenarios, in R code) are essentially the same model. The FLHM does not contain future predictions, except in specific cases for e.g. near future smolt abundances where river model estimates based on parr abundances are available. The purpose of the procedure is to take the posterior distributions from the FLHM and include scenarios of future vital rates (Mps, M74, maturation) and future fishing patterns to predict future abundances. However, some slight differences may occur when historical estimates are compared. For example, process errors for survival are included in the FLHM but missing in the scenarios code. 13 ) Section In Figure , dotted lines are not visible, only dashed lines. Were new priors on PSPC used? This error was fixed already in last year s report. 14 ) Section ) Why have PSPC estimates declined in this assessment compared with previous model run in 2015? (Is it related to changes in the estimates of steepness?). I see that PSPC is likely underestimated in several rivers in AU 1 3 because of low-quality priors, but I don t think these were changed between assessments. Given the complexity of the model, it is difficult to say, but a guess would be the higher estimate of annual natural mortality in the 2017 assessment compared with 2015 (0.15 in 2017 vs in 2015). This would have been associated with lower estimates of R0/PSPC as well as EPR and stock recruit steepness ) Section also describes challenges applying PSPC to stocks recovering from depletion where locally intense competition may result in transitory density-dependence, and appearance of capacity in stock recruitment analyses, which are actually underestimates of true the long-term capacity. For these stocks, might it be better to use expertderived PSPCs (as for AU 5 6), since the stock recruitment data give inappropriate estimates? The issue referred to, discussing estimation of PSPC for recovering stocks is one detail among many contributing to the total uncertainty in these estimates. It needs further thought and discussion within the working group. Ideally, we would like to minimise bias in estimates of stock-recruit parameters, and using a whole-river PSPC or carrying capacity (i.e. expert priors only) could also lead to biased parameter estimates if density-dependence starts to act at much lower population levels than expected from the whole

18 12 ICES WGBAST REPORT 2018 river area; hence the best way to deal with this issue is not yet clear, but perhaps some more mechanistic description of SR dynamics would help. There is now a PhD student in Sweden working on this issue, and we hope to make progress in the next year or so ) The model predicting recovery in AU4 does not account for recent occurrence of M74 (as far as I can tell?), and so recovery trends may, in reality, not be as strong. The statuses also do not account for new priors for Mörrumsån and Emån, as stated earlier in the text. The M74 projections account for the fact that an increase in M74 levels is observed, assuming future stable survival level to be around 89% that is the historical median. As explained in the text, it is very difficult to predict exact development of the future M74 levels. However, M74 are followed closely and in case further increase will be observed, that will be accounted for in the future stock assessments. Regarding the statuses of Mörrumsån and Emån, it is noted in the report that these are not considered entirely valid, since only PSPC priors (and not accompanying smolt production estimates) had been updated in the 2017 assessment (see third paragraph) ) Also, for AU5, the FLFM model predicts a notable increase in smolt abundances over the last two years, but Section 3.5 describes the relatively poor status of many rivers within AU 5 (especially Pärnu, but including others), which are likely at higher risk of extinction. These results seem conflicting. The AU 5 stocks are not included in the FLHM; instead, the status of these stocks is expert evaluated. Thus, there should not be any conflict here ) The perception about the overall stock status (amount of rivers in difference status classes) has become more positive compared to earlier years assessments. Is this because smolt production has gone up, or estimate of PSPC has gone down (or both)? The text states earlier that PSPC estimates are biased for several rivers (underestimated in AU1 3 rivers), which may overestimate status, but it s not clear if this could explain changes in status from last year to this year or not. I suggest adding any such caveats to the text describing Table , including high uncertainty in PSPC for Tornionjoki due to high autocorrelation in MCMC samples. In the 2017 assessment, it appeared that both lower estimates of PSPC and increased smolt production in 2016 in many rivers had contributed to more positive status evaluations. The biases mentioned for PSPC estimates for AU 1 3 rivers are not new to the 2017 assessment, but are mentioned in the light of ongoing work. These should not therefore impact status updates between 2015 and The reviewer is correct in pointing out that where estimates of PSPC are thought to be biased (e.g. AU 4 stocks in 2017) or are unconverged, this may result in artefactual updates of stock status ) This section might be better labelled Status of the assessment units 1 6 stocks... instead of Status of the assessment units 1 4 stocks ) Question of clarification: Do the probabilities in of achieving PSPC in Figure include both uncertainties in current smolt abundances

19 ICES WGBAST REPORT and uncertainties in PSPCs? I assume the expert-derived classification of status for Testeboån and AU5 6 stocks are reviewed/documented elsewhere? Yes, Figure includes uncertainties both from current smolt abundances and PSPCs. Expert judgements are used to classify the status in AU5-6 and Testeboån, but unfortunately these procedures are not uniform among experts and documentation is largely lacking on which exact method each of them have been using for their calculations. 15 ) Section Similarities in trends between River Model and FLHM support use of the FLHM for assessments of AU1 4 in Table However, there are some river-specific differences, e.g. for AUs 1 and 3 river-model predicts a larger increase than FLHM, and larger decrease for AU 4 than the FLHM, and Vindelälven where M74 may have reduced smolt abundances. If the river-model estimates of smolt abundances instead of the FLFM estimates were used for assessment against PSPC (i.e. using priors for FLFM as the posteriors), would the statuses be the same or would they differ? If they are the same, then a statement indicating so would strengthen current results given inability to update FLHM with 2016 data. In the 2017 assessment/data up to 2015, a likelihood approximation is used in the FLHM for estimates of smolt production up to and including the assessment year (i.e. 2016). This makes posterior estimates of smolt production from the FLHM and river model very close to each other during these years. From 2017 onwards, FLHM smolt production estimates are a prior generated using the estimated stock recruitment parameters (with no likelihood approximation). This was modified in 2018 so that the likelihood approximation is used for an additional two years in the FLHM. As noted above, both smolt production and PSPC estimates can effect changes in estimated stock status. The river model does not produce estimates of PSPC. If smolt production priors (posteriors from the river model) were used in combination with PSPC priors, status estimates would likely be rather different. If PSPC posteriors from the FLHM were used in combination with smolt production priors (posteriors from the river model), status estimates should be very similar, but small changes could be expected for rivers where there are non-negligible updates to smolt abundance within the FLHM. E.g. slightly lower status evaluations for AU 3 stocks using raw river model smolt estimates (Figure ). 16 ) Section Emån shows no recovery over the projections under fished scenarios, but this is not mentioned in the text. I assume this is related to corrections to the FLHM which have been implemented in JAGS, but not WinBugs? As noted above and in Section in last year s report, population dynamics in the assessment and forwards projections codes were the same in the 2017 assessment. However, since the error was not yet fixed in the assessment (WinBUGS) model, estimates of the stock recruit alpha for Emån are artificially high/low egg survival at low population density (Table , cf assessment). It is this low estimated egg survival (partly real (after correction alpha for Emån is still significantly higher than for other stocks), partly result of an error), that leads to lack of recovery for Emån with fishing scenarios. This issue has been fixed for the present (2018) assessment. 17 ) Section 4.5 (Conclusions)

20 14 ICES WGBAST REPORT ) The text states that the current fishing mortality will allow for gradual recovery of stocks in AU4 6, and so the WG does not recommend reducing fishing mortality. However, it s worth noting that the model predicts <50% probability of recovery before 2030 for Emån (possibly a statistical artifact), Simojoki, and Rickleån (though trending upwards for this stock) (Figure ). If near-term recovery of these stocks is critical, then reduced fishing effort may be warranted. Otherwise, a clear statement on trade-offs would be valuable. As noted above the issue with Emån was partially solved in 2017, but the low probability of recovery is likely over-pessimistic (see previous point). Currently, there are no rules or guidelines for how fast (within which time frames) weak salmon stocks should recover, or when a certain proportion of all stocks should have obtained their management goal. Therefore, under current conditions, we agree that any catch advice for the Baltic mixed-stock salmon fishery is associated with trade-offs. We have briefly commented on this in Section 4.5 ( Conclusions ) below ) This section states two omissions from the assessment model that result in increased uncertainties: a recent M74 outbreak and increasing recreational trolling. However, it s likely that the recent M74 outbreak is more problematic than the increased trolling effort, as the model likely accounts for recreational trolling with increased natural mortality, with little (perhaps?) impact smolt abundances. The model in last year with the most recent data (including 2016) did not work, and the resulting omission of the recent M74 increase was indeed problematic (discussed at several places in last year s report). Luckily, this year s new model (JAGS instead of WinBUGS) could be run with updated data (up to 2017). For the same reason, in last year it was not possible to include our new (higher) expert catch estimates for the recreational trolling. We agree that this extra fishing removal has likely been interpreted as natural mortality in our past assessments, and this we also pointed out in last year s report (e.g. in the extended summary). 18 ) Section ) The list of revisions and analyses listed in Ongoing work is ambitious. More modelling support may be required. I want to emphasise, this is not due to lack of expertise; your team includes very skilled modellers. However, models with this level of complexity in North America would typically include 3 4 modellers, especially when major revisions are being considered. It s not clear to me if /how this work can be completed prior to the proposed autumn 2018 Benchmarks meeting. We appreciate the recognition of modelling expertise in our group! Our list of ongoing and/planned work is indeed quite long, and it is true that modelling support is a limiting factor for how fast amendments to our assessment approach can be implemented. In the present report (Section 4.6.2) we have partly revised our list, and at present it seems as if next benchmark will have to take place later than previously scheduled. However, we believe it will be possible to continuously make progress when it comes to the listed issues ) Will the evaluation of alternative stock recruitment models (bullet 1) and migration from WinBUGS to JAGS include testing of JAGS

21 ICES WGBAST REPORT using simulated data (self-tests) to ensure models outputs aren t biased? I recall this as a recommendation from the 2017 Benchmarks meeting for the next Benchmarks meeting, and am not sure how it fits in with this list of ongoing work. Evaluation of the assessment model with simulated data was one of many good suggestions from reviewers at the benchmark. Generally speaking, it would be beneficial for all models used within ICES to be simulation-evaluated. Simulation evaluation of the FLHM is challenging because of the long run time needed (still 2 3 weeks with the JAGS model which is ~10 times faster). This any simulation study would have to be fairly limited in terms of the number of simulated datasets evaluated. This remains on our long to-do list, but there are known omissions/areas for development of the model e.g. addition of repeat spawners that are expected to cause possibly large biases, that should be addressed first. Most likely, it will not be done in ) Will the JAGS model (with suggested revisions) be implemented for next year s assessment (2018) prior to the benchmarks meeting that fall? (as stated in the 1st bullet). As mentioned above, the present assessment (2018) is based on the JAGSmodel including suggested revisions from the benchmark and some corrections discovered during the process. Section in the present report contains descriptions of these new elements and the interim evaluations that were carried out since last year ) Do analysts expect the model run issues (related to initialization) to be resolved by using JAGS? Model initialisation issues are now solved using JAGS, we have yet to encounter any problems with initialisation (the model has always initialised with the first set of random initial values generated). 19 ) Section Does Denmark monitor its sea trout populations but not make data available, or does it not monitor those populations? The first sentence of the first two paragraphs of the section seem contradictory. These previously contradictory sentences were modified and clarified already in last year s report. 20 ) Section 5.4 states, in the rivers with the highest numbers of spawners, there was a decrease in the spawning run. However, the strongest negative decline in recruitment was for Area 29 (Sweden), for which sizes and statuses were very uncertain. That being said, I agree that status for Areas was also declining, where most of the large runs are. We agree. 21 ) Given large uncertainties in the trends in recruitment status due to variability in the underlying data, it might be informative to show probabilities of trends using a Bayesian regression, for example, to provide the probability that the trend is >0. Even if the Pearson r is >0, the probability that the actual trend is <0 may be surprisingly large (but <50%) if the scatter is large. When the current model was constructed, calculation of confidence levels for trend analysis were not included. To statistically analyze trends in status would be valuable. To do this, however, further model development and evaluations appear needed (e.g. of alternative statistical approaches and importance of the number of years included).

22 16 ICES WGBAST REPORT ) The last sentence of Section 5.6 should specify smolt equivalents of trout released as eggs, alevins, fry and parr. This sentence was adjusted in last year s report. 23 ) Given requirements to further reduce fishing mortality to allow for recovery (especially in Gulf of Bothnia), are any enforcement measures in place to ensure regulations are adhered to, and/or is implementation of these regulations measured? In Finland, a new regulation was implemented in 2016 for improving the poor status of sea trout stock in the region. For instance, allowable mesh size of gillnets was increased, maximum number of gillnets per fisherman was reduced and landing of wild sea trout (adipose fin not clipped) became banned. 24 ) Section I suggest that the list of recommendations include further evaluation of the application of the assessment model to areas beyond where it was developed (as stated in the paragraph above). Are other variables required in different areas? Given differences in landscapes across the region, these differences would be expected, and a thorough evaluation is critical to justify the statuses these assessments provide. In the Recommendation for sea trout, we have added a further point in line with this comment in the present report (Section 5.10). When it comes to questions about which variables to use, etc., work is ongoing within WGTRUTTA and we are presently awaiting those results (see Section 5.8.1).

23 ICES WGBAST REPORT Salmon fisheries 2.1 Description of Baltic salmon fisheries In this section, the present status of commercial, recreational, and broodstock salmon fisheries is presented. Descriptions are given on how the salmon fisheries are currently carried out, including brief information on main fishing areas (sea, coast, rivers) and gears. If applicable and available, information on types of vessels, approximate size of fleet and number fishers is presented. Supplementary information on these topics will be included in connection with future work. General descriptions are provided for the different fisheries and gears, but in the Stock Annex (Annex 2) more comprehensive descriptions of commercial and recreational Baltic salmon fisheries can be found. Extensive descriptions of gears, as well as historical gear development in Baltic salmon fisheries, are also available in ICES (2003). Country-specific information has been compiled when relevant. In Section (commercial fisheries) the information by country is incorporated into the gear subsections. In Section (recreational fisheries), information by country is provided at the very end of the section. Section (broodstock fisheries) is mainly focused on countryspecific information. To get an idea of the current importance of a specific commercial fishery compared with other(s), information on this is to some extent included. But, there is no information on trends and history of the fisheries in these descriptions. More information on catches and effort in the commercial fisheries is provided in Sections 2.2 and Commercial fisheries In this section the main commercial salmon fisheries: offshore longlining, offshore fishery with floating anchored gillnets, coastal trapnet fishery and river fishery are described. Offshore longlining Currently, only Denmark and Poland use longlines in the offshore commercial salmon fishery. Main fishing areas for the Danish fleet are waters around Bornholm (SD 24 and 25). The main salmon fishing grounds for the Polish fleet are located N of Łeba and Ustka (SD 25) and E and NE of the Hel Peninsula (SD 26), both areas are within the Polish EEZ. The salmon longline fishery mainly takes place from late autumn (October/November) to spring (April/May). Both fleets use gears of similar construction (most of Polish gears were purchased in Denmark) with the same hook size, 6/0 Mustad stainless salmon hook, 19 mm between point and shaft. The number of hooks used depends on the size of vessel, usually it varies between Fishers use fresh sorted sprat as bait. Hauling of the gear is usually hydraulically or, on smaller vessels, done by hand. In 2017, the Polish offshore longline fleet consisted of 44 vessels with a size range of m LOA. The Danish fleet consisted of around 15 vessels with a size range of m LOA. The share of longline offshore catch to total commercial catch in 2017 was 100% for Denmark (in total 2988 salmon) and 67% for Poland (4426 salmon). Polish vessels operate both with longlines and gillnets and about 14% of the Polish offshore operating vessels use both gillnets and longlines when targeting salmon. The

24 18 ICES WGBAST REPORT 2018 choice of gear for Polish vessels mostly depends on seasonal environmental (hydrological) conditions. Danish vessels targeting salmon only use longlines. Floating anchored gillnets Floating anchored gillnets are used in the Polish offshore salmon and sea trout fishery. Note that although this fishery is herein referred to as offshore, it can also be practised in coastal waters. Fishers use standard driftnets, consisting of several (up to 15) nets with a length of m and a height of 6 m. Nets have a leaded bottom line and are anchored in one end. Usually the effort is nets per day of fishing, depending on weather and equipment on deck. Hauling is done mechanically. In general, the mesh size is 140 mm, in accordance with regulations, but also nets with larger mesh size can be used. The legal maximum length of each set is 500 m. The typical soak time is hours, or in case of seal damages, shorter. Anchored gillnets are mostly used during spring and autumn, but also in winter, depending on weather conditions. In 2017, the Polish offshore gillnet fleet consisted of 54 vessels of size m LOA. The share in 2017 of floating anchored gillnets in offshore catch to the total country catch in Poland was 19% (1277 salmon). As described above, 14% of the Polish vessels operating offshore targeting salmon, use both longlines and gillnets. Floating anchored gillnets are also used for salmon fishing at the Åland Islands, Finland, where fishermen started use them in 2008 when driftnets became banned. However, the method applied differs to the one Polish fishermen are practicing; the nets are modified (from regular 30 m long 6 8 m high driftnets) by adding an extra lower snare to make them hanging better vertically in sea currents. Sets of three nets (about 100 m long) are used, anchored from one end (two 20 litre floats before the anchor line). More than three nets per set cannot be used because otherwise the set would sink from the pressure of sea currents. In a set, the first two nets become tighten very tense and work as a lead, while the third net flutter at the end and fish are thus entangled solely there. The Åland fishers operate simultaneously with 7 10 sets (i.e nets in total) in about 50 m deep water (using about 200 m braided 6 mm anchor rope and a 6 7 kg anchor). Because of the seals present in the area, fishers have to guard the nets during the whole fishing session (about eight hours) and pick up the salmon immediately when entangled in the net (utilising floats in the upper snare as indicators). In 2017, about 70% (about 800 salmon) of the catch in the Åland area was taken by these gillnets. About a dozen fishers participated in the fishery and the generated a total effort of 2000 netdays (i.e. a short season in June). The cpue is about 0.5 salmon per net day (i.e. per net in an eight hour fishing session). Coastal trapnets Coastal trapnetting for salmon is mainly conducted in Finland and Sweden, but to some extent also in Estonia and Latvia (see country descriptions below). In the Baltic Sea, the trapnet fishery is mainly commercial; however in Sweden, some recreational fishermen are fishing with trapnets as well. The standard gear is a floating wedge formed netpen with bottom and two valves, mesh size mm, moored above depths of up to 50 m. The leader (up to 300 m and 3 5 m deep) usually reaches into shallow water. The construction of the gear is special for each individual fishing ground. Various types of synthetic fibres are in use, multifilament as well as multi-monofilament twine. Occasionally along the coast,

25 ICES WGBAST REPORT salmon are caught in other types of trapnets targeting herring, common whitefish and vendace. In Estonia about 12% of total salmon catch (1 t) in 2017 was taken in trapnets. About 75% of annual catch is taken in September, October and November and nearly all caught salmon are spawners. In Finland large trapnets (higher than 1.5 m) are allowed for commercial fishermen only. All commercial salmon catch was taken in the coastal fishery mainly by trapnets and the catch decreased about 10% from In the coastal fisheries, 179 fishermen caught salmon with 400 trapnets. Total effort in the trapnet fishery was geardays being about 22% less than in There are strict regulations on the fisheries e.g. season, effort and areas. In 2017 in terminal fishing areas the number of trapnets and fishing period was even more restricted than years before. Earlier in terminal fishing areas, the number of trapnets was unlimited and only in Kemi terminal area there was a closure in the early summer. Now the regulation in terminal areas is more similar to the rest of the region. In Latvia trapnets are set near the coastline in Gulf of Riga; the highest trapnets landings (94% of all such landings) are from the east coast in the Gulf. Salmon trapnet fishing at the Latvian Main Baltic coast is not common, due to the high possibility of destroyed gears in stormy weather. Different types of net material are used, mainly synthetic mono-multi-material. Mesh sizes range from 40 to 100 mm. The main fishing season is from June to September. In 2017, about 9% of the total coastal salmon catch (or 19.6% of the commercial) was taken with trapnets. In Sweden, 99% of the 2017 commercial catch of salmon (in number) were from coastal fishing with trapnets and fykenets, located mainly in the Gulf of Bothnia (SD 30 and 31). The main bulk of the catches are caught with so-called pontoon trapnets. This is a gear developed to protect the catch from foraging seals. The use of pontoon trapnets has increased in the latest two decades, in conjunction with the increasing number of seals in the Baltic Sea. Furthermore, some salmon are occasionally caught (bycaught) in poundnets. There is no Swedish coastal fishery with stationary standard gillnets. However, in the southern part of the Swedish coast (SD 25), a minor coastal salmon fishery is conducted with an older type of gear where the fish is entangled (in contrary to how fish is caught in a trapnet). Total Swedish effort in 2017 was 9796 trapnet days, and the total catch was salmon. Due to a ban for recreational fishermen to sell their catches, many recreational fishermen have applied for a commercial licence. Therefore, their trapnet catches are nowadays included in the commercial catch, and thus counted against the national TAC. River fishery Whether it is legal to fish commercially for salmon within rivers or not varies between the Baltic countries (see Section 2.9), and other differences also exist (i.e. presence of salmon rivers or not). Below follows short country-by-country information: No commercial riverine fisheries exist in Denmark, Estonia, Finland, Germany, Lithuania, Poland or Russia. Latvia: in River Daugava use of trapnets is allowed. However, effective fishing is limited due to active shipping traffic. The commercial Latvian river

26 20 ICES WGBAST REPORT 2018 catch in 2017 consisted of 558 salmon (2.4 tonnes), to compare with the remaining river catches where 43 salmon were caught for broodstock purposes and 53 salmon were taken by anglers. Sweden: commercial catches of salmon were in 2017 reported from one river in the Gulf of Bothnia (Luleälven, SD 31) where in total 41 tonnes (8681 salmon) were caught. No commercial catches were recorded in Ljusnan (SD 30) which is the second of the two Swedish rivers where there has been an active commercial fishery in more recent years. All commercial river catches are from reared populations. It is mandatory to report catches from the commercial river fisheries, but information on effort is not included in the national reporting system. The commercial river catches are not counted against the TAC since they are caught in freshwater (and not in the sea) Recreational fisheries In 2018, WGBAST continued work initiated in 2017 to pay extra attention to recreational salmon fisheries that is becoming proportionally more important. Below follow descriptions of the main fisheries. For the growing trolling fishery, an updated timeseries of trolling catches from a recent expert elicitation (ICES, 2017; 2017d) is included. Finally, a summary of more general aspects on needs and complexities associated with data collection from recreational fisheries is provided. Trolling fishery Recreational trolling is an increasingly common and popular fishing method to catch salmonids in the Baltic Sea. The name originated from the verb to troll, describing a fishing practice of slowly dragging a lure or bait from a moving boat. Thereby, recreational fishermen troll a number of fishing lines, baited with lures or natural bait through the water. Fishing lines are spread horizontally with help of planer boards and vertically using downriggers and stackers. Common trolling speeds vary from knots. Small boats used for trolling vary between 3 and 8 meters. Fishing grounds are usually over deeper water, and boats may venture more than 20 nautical miles offshore. Therefore, weather conditions have a strong impact on the effort, and bad weather conditions may prevent trolling boats to leave their homeports periodically. The trolling season varies between the different sea areas and depends on the feeding and spawning migration of salmon and/or seasonal closures. In the west Baltic and the Main Basin, it typically starts in late fall and ends in the middle of May. In the Åland Sea and Gulf of Bothnia, the season starts at the end of May and ends in late summer. Trolling is not only practised in own boats by private anglers, but also by professional guiding operators. The recreational salmon fishery, including the trolling sector, supports an industry that provides jobs involved in manufacturing, sale or provision of tackle, boats, professional guide services, hotels, restaurants and more. Recent survey estimates from Germany revealed that trolling anglers spend on average 3500 annually (Kaiser, 2016). Recreational salmon trolling has been practised in the Baltic Sea for more than 30 years. The magnitude of this fishery varies between countries, and while in some countries trolling effort has levelled off (e.g. Sweden) it has just started developing in others (e.g. Poland and Lithuania). Despite this, catch data from trolling fisheries from individual countries are still incomplete or missing, and work on quality assurance is still ongoing. One reason is that trolling data collection is often not yet included or sufficiently

27 ICES WGBAST REPORT covered in national marine recreational fisheries surveys. Therefore, the working group has yet not compiled a separate table with detailed data on national trolling catch estimates. To account for trolling fishing mortality and to facilitate the inclusion of such catch data in the Baltic salmon stock assessment, a time-series comprising both retained and released components was developed last year as part of the recent benchmark (ICES, 2017d). National experts (members of WGBAST) were asked to reconstruct time-series of the number of retained and released salmon caught in the recreational trolling fishery, starting from 1987, by using quantitative data from surveys (if available) and/or qualitative data from inquiries of stakeholders (e.g. experienced trolling fishers, local authorities, guiding operators and angler associations). In addition to provide a mode number of retained and released salmon for each year and area, national experts were also asked to provide a minimum and maximum value (similar to a 95% probability interval) to provide a semi-quantitative measure of uncertainty. National estimates were asked to cover the three main areas with feeding or spawning migrating salmon (i.e. SD 22 28, SD and SD 32). Triangular probability distributions per year and area collected from national experts (min-mode-max) were combined into joint medians (with 90% probability limits) using the same transformation as applied to similar expert estimates of discarding and unreporting (see Section 2.3 and Annex 4 in ICES, 2016). The total number of retained salmon includes an assumed post-release mortality rate of 25% for trolling caught and released salmon. As no post-release mortality estimates for trolling caught Atlantic or Baltic salmon in marine waters exist, the 25% mortality rate was derived from a review of studies dealing with trolling caught Pacific salmon (Parker et al., 1959; Butler and Loeffel, 1972; Wertheimer, 1988; Wertheimer et al., 1989; Gjernes et al., 1993; Orsi et al., 1993). Resulting joint expert estimates for trolling catches in SD 22 28, SD and SD 32 over time are depicted in Figure The estimates were partly updated until 2018, to include trolling catches from 2017 and to take into account new information from earlier years. This update resulted in a slightly modified time-series compared to in 2017, with lower annual estimates for most years. The estimates are, however, still > salmon larger than previously assumed (i.e. for the assessments In contrast to in 2017, when the model did not perform, the new updated trolling catch estimates have been included in the 2018 stock assessment (Chapter 4). River fishery The river fishing for salmon in the Baltic region has a very long history, and up until the mid-1990s nets and weirs were used in many rivers throughout the Baltic region. Currently the river fishery for wild salmon is entirely recreational and to a major part restricted to angling (rod and reel fishing). Different types of tackles are used, the most popular being fly and lures. Fishing is usually carried out from river banks or as wading, but in some rivers angling from boat is also possible. The most productive wild Baltic salmon rivers are by far the Finnish and Swedish large rivers flowing into the northern Baltic Sea. The fishing season is usually from May September, during the spawning run. The recreational fisheries in these rivers are very popular, attracting several thousands of anglers every year. Whereas salmon trolling is a highly specialized fishery, often requiring big investments in boats and other equipment, the river fishery for salmon is more easily accessible. This makes the river fishery an important component in terms of potential removal of fish from the stocks,

28 22 ICES WGBAST REPORT 2018 although the introduction of regulations, e.g. catch and release and bag limits, have been implemented in many rivers. At the same time, the Finnish and Swedish river fisheries supports a local industry providing jobs involved in the manufacture, sale or provision of tackle, professional guide services, hotels, restaurants and more. The recreational river fishing for salmon in the other countries surrounding the Baltic Sea is more limited, although salmon is still being caught in Estonian, Lithuanian, Latvian and Polish rivers. The catches from rivers in these countries are, however, very small (Table 2.2.6). Russia has no recreational salmon fishery in their rivers feeding into the Baltic Sea, and no Baltic salmon rivers exist in Denmark and Germany. Other fisheries While the recreational salmon catch is largely dominated by angling (offshore trolling and in rivers) there are other types of recreational fisheries carried out in some countries. To a smaller extent passive gears such as trapnets, gillnets or longlines are being used for catching salmon, either as a target species or as a bycatch in coastal recreational fisheries. These catches are estimated to be of minor importance, in terms of impact on the stocks (i.e. removals). Assessing recreational salmon fisheries Commercial and recreational fisheries coexist and exploit the same stock. In the past 20 years, commercial salmon catches in the Baltic Sea have declined by nearly 80%, while recreational salmon catches remain high and/or are increasing (both freshwater and marine). In contrast to commercial catch data, which rely on mandatory reporting, recreational catch data rely on estimates provided by recreational fishing surveys. While many freshwater catches are fairly well covered, either on the level of individual rivers (reporting systems, e.g. by sport fishing clubs) or in larger national surveys with a focus on recreational freshwater fishers (e.g. Finland, Sweden), available data on marine catches are patchy and for most countries missing completely. Since 2002, European Member States (MS) are obliged to annually collect marine recreational fishery data of salmon in the Baltic Sea (EC, No 1639/2001). In 2016, the EU multiannual plan was prolonged, specifying that MS are obliged to collect numbers and weight or length for caught and released catch components of salmon and sea trout (including in freshwater) (EU, 2016/1251). There are usually three main notable challenges associated with recreational fisheries data collection: (1) there is no central registration of recreational fishers, (2) recreational catches are not documented, and (3) recreational fishers often fish in remote and hard to access areas. As a result, recreational fishing surveys are complex and difficult to conduct, often requiring a number of different surveys. The main drivers for the collection of recreational fishery data include: collecting recreational fishing mortality for inclusion in stock assessment, designing effective controls of recreational fishing and monitoring outcomes, estimating economic value and social benefits to local communities, developing long-term management plans, and supporting the delivery of environmental and marine spatial planning legislation (ICES, 2015b). The type of recreational fishery data needed involves information on the characteristics of the different types of recreational fisheries in a region, the size compositions for retained and released fish, and the numbers of fish retained and released per individual fishing trip.

29 ICES WGBAST REPORT WGBAST recognizes the need for developing the evidence base to support decisionmaking and scientific advice. It is now for each country to set up national data collection schemes that provide robust and accurate estimates, especially for the marine recreational salmon fishery (i.e. mainly trolling). Regional cooperation and coordination is needed to develop common methods, ensuring that data collected are comparable between countries. This has to be further elaborated by ICES WGRFS and RCG Baltic, possibly in collaboration with other regional coordination groups within EU-MAP. To estimate total catches and releases, the following information is usually needed (ICES, 2015b): Effort i.e. the total number of recreational fishers, boats, number of fishing trips or other measure of participation or fishing effort, generally estimated from a national survey. Catch-per-unit-effort (or catch per person or per boat, depending on the type of survey) recorded for a representative sample of fishers, boats or trips, etc., for example from on-site surveys of individual anglers or completion of catch diaries or vessel logbooks. Data are needed for the retained (harvested) catch as well as for released fish, if total fishery removals are to be estimated using data on post-release mortality. Demographic and avidity (frequency of fishing) data, if re-weighting of samples is needed to be more representative of the population thereby improving the accuracy of the estimate. Biological data on catches size or age composition are required both for caught and released components if catch-at-size or age is needed for an assessment model. Direct on-site measurements of fish length are known to be more accurate than self-reported data. To estimate the economic value of recreational fisheries, direct expenditure data by spend categories are also needed. This information should be collected alongside existing recreational fisheries surveys if possible, as the costs are not significantly greater. Collection of data on an annual basis is preferable, as imputations for missing years introduce uncertainty. There are strong indications that the spatial and interannual variability of fishing effort and catches is highly dynamic. Moreover, historical evidence shows that recreational fisheries may become more or less important over time, thus there is a need for time-series data to show trends. The most cost-effective way to conduct recreational fishing surveys is having a licence system in place where licence holders can be contacted. Lithuania even requires mandatory catch reporting allowing for a census of recreational catch data. If no national registry is available, a screening survey is required sampling from a broad coverage frame like residential households to obtain total numbers of recreational fishers. This is usually done by means of off-site surveys (telephone, mail, online). On-site surveys like access point intercept or roving creel surveys are conducted to obtain CPUE data. Visual surveys such as aerial or camera surveys are conducted to estimate effort. A combination of several survey methods is usually required to estimate recreational catch and effort. The following section gives a short description of the recreational salmon fisheries in each MS and provides an overview of the individual national surveys for the recreational marine salmon fisheries already in place or planned. Survey types are described in more detail in 2013 report of ICES Working Group on Recreational Fisheries Surveys (WGRFS) (ICES, 2013b).

30 24 ICES WGBAST REPORT 2018 Country specific information In Denmark the recreational Baltic salmon fishery is almost entirely trolling. The data collection is carried out through a combination of on-site and off-site surveys. A new project is aiming at obtaining knowledge of these survey methodologies for collecting catch and effort data from the trolling fishery ( The offsite part is a recall based Internet questionnaire survey targeting licence holders. This survey runs on a biannual basis. Self-reporting is also made possible after each fishing trip, either by using a smartphone app or by filling in a questionnaire. The on-site part is a combination of access-point surveys, where a staff member interviews anglers returning to harbour after a fishing trip, and camera surveillance used in three harbours for estimating total effort in terms of boat trips/hours at sea. The information obtained is used to extrapolate effort from other harbours with the self-reporting option. The recreational salmon fishery in Estonia is carried out as trolling, coastal gillnetting and river fishery. Recreational salmon and sea trout angling is allowed in rivers Narva, Purtse, Selja, Valgejõgi, Jägala, Vääna (since 2007) and Pirita. The fishery is controlled by licences and with regulations on effort in terms of length of nets (standard length of a net is 70 m). Licences are distributed annually. In Finland angling from land or trolling are two of the main recreational salmon fisheries. The river catches in Tornionjoki and Simojoki are estimated by annual surveys, and in other salmon rivers by interviews and voluntary riverside catch statistics. In 2017, all river catches were recreational. In the Gulf of Bothnia catches were mainly from River Tornionjoki, whereas in the Gulf of Finland all catches were from River Kymijoki. Finnish coastal (or at sea) recreational catches are estimated as follows: An official catch estimate is based on the National Survey carried out every second year. The last survey covers year 2016 and was conducted in Note that in this national survey, salmon (and sea trout) catch estimates are highly uncertain because these fishers are so rare in the total population (e.g. only 17 respondents had been trolling for salmon). For the missing odd years, the same sea catch estimates are assumed as in the preceding year. In 2017, the salmon catch estimate for the whole Finnish sea area was about (+/-7000) salmon, out of which about 90% was taken by trolling. In 2017, the Finnish Federation for Recreational Fishing conducted a questionnaire among salmon trolling skippers (92 replies were received). The skippers are considered to represent the active part of all trolling fishers. An expert estimate of the total number of active trolling boats in Finland is In addition, about the same amount of less active boats exist that only go to sea 1 2 days per year (maybe not trolling). The responding skippers fished on average eight days in 2017 (range: 0 25 days) and the average catch was 0.2 salmon per fishing day in the Gulf of Finland and 0.4 salmon per fishing day at the Åland Islands and in Gulf of Bothnia. Extrapolation of these parameters to the estimated whole fleet suggests a total catch of about salmon in In summary, the trolling catch estimate of Finnish national survey and the other questionnaire provide catch estimates of complete different magnitudes. Therefore, the current estimates of Finnish recreational salmon sea catches should be taken with caution. For example, a potential error in the National survey may occur if respondents have announced the annual catch of the whole crew and not only their own share.

31 ICES WGBAST REPORT In Germany, recreational salmon fishing occurs almost exclusively as trolling in the waters off the island of Rügen (SD 24). Since 2016, a regular survey has been established to monitor the German salmon trolling fishery. Trolling fishing effort is evaluated by boat trip counting via remote cameras in three relevant marinas on Rügen (covering ~60% of the total fishing effort) (see Kaiser, 2016 for details). Salmon trolling effort from marinas not monitored by cameras (n = 4) is extrapolated using monthly instantaneous trolling boat counts covering all marinas, and the proportions of boats that went out for fishing derived from the marinas with camera monitoring. The camera monitoring is complemented by random on-site interviews of anglers in four relevant marinas (including those where trolling boat trip counting was conducted) to determine catch per unit of effort. The information obtained is used for estimating catches and releases, and to collect biological catch data and socio-economic information. There is no directed recreational salmon fishery in freshwater, as there are recently and historically no rivers with relevant salmon populations along the German Baltic coast. In Latvia, trolling of salmon and sea trout is currently not popular, and according to expert estimates only a limited amount of boats (4 8) are participating in this fishery. Information from recreational river fishery is available only from two rivers (Venta and Salaca) where licensed fishery is organised. Recreational fishery in the coastal zone of the Baltic Sea is conducted by self-sustainable fishermen. Only limited amounts of gillnets and longlines are allowed, and it is forbidden to sell any fish. Every fisher should report all fishing activities in logbooks, and those detailed data are available for the national institute (BIOR). In 2017, all salmon in the self-sustainable fishery were caught by gillnets. Starting from 2018, it is planned (within the EU-MAP Data Collection Programme) to estimate the Latvian recreational catches of salmon (and also sea trout, cod and eel). Recreational catches of salmon (and sea trout) will be estimated by contracting the company offering trolling trips in the sea. Catch and biological information will be collected on board and later, and applying a snow ball method total landings will be estimated. Information on the licensed fishery in the rivers will be used to estimate the catches from the river recreational fishery. In Lithuania, recreational fishery for salmon (and sea trout) is allowed only in designated rivers on a licence basis. Currently, new rules are in use concerning catch and release in the period from October 1st to 15th. Since 2015 recreational (anglers) sea trout catches are estimated by an online survey, a face to face interview survey, and individual interviews and catch reporting with diaries of selected anglers and experts. Catch per unit of effort data (catch per person and day) is estimated from survey data and combined with number of licences sold to anglers to calculate the total catch. In 2015, the online survey, face to face interview survey, and individual angler interviews were conducted, in 2016 and 2017 only online surveys were carried out. Trollling is the main recreational salmon fishery in Poland. Different methods are applied to monitor the composition, effort and catches of the recreational fishery: A study on the use of remote CCTV cameras for monitoring of salmon trolling fishery effort revealed that this is a cost-efficient method, providing accurate estimates of effort that helps to reduce bias in catch estimates. Results will be provided in The method is supplemented by direct counting of trolling boats in harbours with a one month interval. As a further complement, on-site and off-site questionnaire interviews are also conducted, and trolling boats skippers/owners are invited for filling in annual

32 26 ICES WGBAST REPORT 2018 fishing logbooks. To determine catch composition and collect basic biological data, observers from the national institute (NMFRI) participate in trolling cruises targeting salmon and sea trout. Onboard observations at sea, on-site interviews and data collected through CCTV cameras will serve to verify the reliability/accuracy of the catch volumes estimates. A pilot study for the estimation of Polish river recreational catches started in No recreational fishery targeting Baltic salmon is allowed in Russia. Recreational salmon fishing in Sweden is conducted as angling in rivers and at sea (trollling), seine and gillnet fishing in some rivers and coastal trapnet fishing. In recent years the estimated total recreational catch has been of the same order of magnitude as the commercial one, and for the recreational fishery the trend has been increasing angling and decreasing coastal trapnetting (the latter due to regulatory measures). Both for trolling at sea and angling in rivers, there is an increasing share of fishermen practicing catch and release, either on voluntarily basis or due to regulatory measures. There is no general licence or a central register for recreational fishing, and the fishery statistics represents a combination of reported and estimated catches. Recreational fishers in Sweden are generally not required to report their catches, although local exceptions exist and most salmon rivers have some kind of reporting system. However, at present the quality of the catch data collected varies heavily between rivers. Methods for collecting recreational fishery catch statistics include direct contacts with representatives for local fishery management areas and censuses addressed to broodstock fisheries. Probability sampling surveys are also conducted. These surveys are made if not on a yearly basis, so regularly every fourth year. Next study of the Swedish trolling fishery is scheduled for 2019, and development of methods for assessing this fishery are needed. In the recreational catch statistics reported to WGBAST, broodstock fisheries in reared rivers (for compensatory hatchery production) are also included. However, as described below, those catches are rather limited Broodstock fisheries Broodstock fisheries are aimed at collecting mature individuals for breeding purposes. Below follows country-by-country information about broodstock salmon fisheries: In Denmark there is no broodstock fishery. In Estonia, reared fish in the Gulf of Finland region originate in the River Kunda stock. A captive broodstock are kept at the Põlula state-owned hatchery. The captive stock is supplemented every year by spawners from the wild. Reared salmon released in Pärnu river (Main Basin) originate in the River Daugava river in Latvia. In 2017, 24 spawners were also collected from the Pärnu river. Two thirds of those fish had the adipose finclipped i.e. they were of the reared Daugava stock. The caught fish are stripped from milt and eggs at the river, and whenever possible released. Those fish are not included in catch statistics. The broodstock fishing is carried out in cooperation between Estonian Marine Institute, University of Tartu and Põlula Fish Farm. In Finland, broodstocks of five different Baltic salmon stocks (Tornionjoki, Simojoki, Iijoki, Oulujoki and Nevajoki) are kept in hatcheries. Fertilised eggs are produced at four state hatcheries (Luke). One private hatchery maintain their own Neva broodstock. Apart from the four state hatcheries, five private hatcheries also raise salmon

33 ICES WGBAST REPORT smolts. The private hatcheries mostly buy their eggs from the state hatcheries. Broodstocks are kept in captivity and renewed partly or completely in 3 5 year intervals with eggs collected from broodstock fisheries in Tornionjoki, Simojoki, Iijoki, Oulukoki and Kymijoki (Neva stock), usually located close to the river mouth. Technicians from the state hatcheries perform the broodstock fishing. No information exists on numbers of salmon collected in When broodstock fishing is conducted, usually just some tens (<100) of spawners are collected. Salmon from the broodstock fishery have so far not been reported in the Finnish national report delivered to WGBAST. In Germany there have been no official releases of salmon in rivers with outlet into the Baltic Sea in 2017, and no regular release program or broodstock fishery exists. In Latvia the artificial salmon reproduction is based on sea-run adults of wild and hatchery origin. Broodstock fisheries are carried out in the rivers Daugava and Gauja (Gulf of Riga) and Venta (Main Baltic) in October November. In 2017, 43 salmon were caught for breeding purposes. The largest share was caught in Daugava. Broodstock collection is performed by contracted fisherman who carries out a specialized fishery. All salmon catches for reproduction are indicated in the Latvian national report as fish caught for breeding purposes. Salmon broodstocks in Lithuania are collected each year from wild fish ascending spawning grounds in the Neris River basin. No hatchery origin broodstock are used for breeding. Apart from the Neris main river, salmon is also collected from the tributaries Vilnia and Siesartis. Occasionally fishermen also catch a few individuals in the Šventoji River. In 2017, 26 salmon were caught for breeding purposes: 16 females and ten males. Broodstock collection is performed as a specialized fishery carried out by the Fisheries Service. All salmon catches for reproduction are indicated in the Lithuanian national reports as fish caught for breeding purposes. In Poland, stocking has been based on a hatchery broodstock of Daugava origin, supported by some spawners collected in rivers stocked with salmon (these catches are reported to WGBAST as commercial river fisheries). However in 2017, no river spawners were caught. In Russia broodstocks are collected both from spawners kept in hatcheries and caught in rivers. For artificial production in the Neva and Narova hatcheries, broodstocks are collected in the two respective rivers. For the Luga hatchery, a mix of spawners from the hatchery and the river is used. In 2017, a total of 380 of adults were used for broodstock purposes (208 in Neva, 138 in Narova, 38 in Luga). All salmon catches for reproduction are reported in the Russian national report as broodstock fish. In Sweden, broodstock salmon consist of ascending spawners returning from the sea after having been released in the river as reared smolts. Broodstock fish are collected annually in all rivers with compensatory releases: Luleälven, Skellefteälven, UmeälvenÅngermanälven, Indalsälven, Ljusnan and Dalälven. According to court decisions, it is the owners of the hydroelectric power stations that have the responsibility of catching broodstock fish and performing compensatory releases of salmon smolts. In 2017, a total of 3205 (Range: 40 to 1033) adult salmon were caught for broodstock purposes. To WGBAST, Sweden delivers data on broodstock fisheries as recreational river catches.

34 28 ICES WGBAST REPORT Catches This section contains information on commercial and recreational Baltic salmon catches from sea, coast and rivers taken in 2017 and over time. Commercial catch statistics provided for ICES WGBAST are based on EU logbooks, national reporting system for vessels not obliged carrying logbook and/or sales notes. As described in Section noncommercial (recreational) catches are typically estimated by a combination of different types of national surveys targeting various recreational fisheries (e.g. using accesspoint surveys, questionnaires, camera surveillance, etc.) and expert opinion guesstimates. Further details on collection of catch statistics in the Baltic Sea (in total and by country) are given in the Stock Annex (Annex 2). In summary, the following seven tables with nominal salmon catches divided in various ways (as described below) are presented: Table 2.2.1: reported and total (including discard and unreported) salmon catches in weight by country ( ), including separate columns for non-commercial catches, discard and unreported catches from 1981 and onwards. Additionally, in a separate column, non-commercial (recreational) catches in are presented. Table 2.2.2: corresponding salmon catches (as in Table 2.2.1) in numbers ( ) with additional column for estimated misreporting. Table 2.2.3: nominal catches in weight from sea, coast and rivers divided by region (22 29, and 32) and country ( ). Table 2.2.4: nominal catches in numbers from sea, coast and rivers divided by region (22 29, and 32) and country ( ). Table 2.2.5: nominal catches from last year (2017) in weight and numbers from sea, coast and river divided by country and by subdivision. Table 2.2.6: nominal recreational (non-commercial) catches in numbers from sea and coast pooled, and river divided by country and region (22 31 and 32) ( ). Corresponding time-series for estimated trolling catches, based on expert elicitation combined with survey data (Section 2.1.2) are depicted in Figure Table 2.2.7: nominal commercial landings in numbers ( ) from sea and coast compared to TAC, divided by fishing nation and region (SD and 32). Discards and unreported catches are not included in nominal catches; instead, they are presented separately. Values on discards and unreported catches are calculated using conversion factors and reported in terms of the most likely value with a 90% probability interval (PI). More details on discards and unreporting and estimating procedures are given in Section 2.3 (see also the Stock Annex; Annex 2). In the latter, an overview of management areas (regions) and rivers is also presented Catch development over time There has been a decline of the total nominal catches in the Baltic Sea, starting from 5636 tonnes in 1990 and decreasing to 900 tonnes in Since then, catches increased somewhat again in In the last three years, the total nominal catch has again decreased, and in 2017, it was 761 tonnes, the lowest value so far recorded (Table 2.2.1).

35 ICES WGBAST REPORT In Figure 2.2.1, proportional catches (of the total) by gear type are presented. After the driftnet ban was enforced in 2008, the percentage of the total catch by this gear has been zero. At the same time, catches with trapnets along the coast have increased their share. Consequently, the proportion of the coastal catch has gradually increased over time, and in 2017 it was 57% out of the nominal total (in weight; Table 2.2.3). In the same year, approximately 69% of all commercial catches were taken in coastal trap (or fyke) nets. The proportion of non-commercial catches has grown in relation to the commercial catches. In 1994, non-commercial catches comprised just 10% of the total nominal catches (in tonnes). In 2017, this share reached above 40%. The proportion of the noncommercial part of the total catches (including river catches and expert trolling estimates) from 2004 and onwards is illustrated in Figure Catches by country (2017) Denmark: The Danish salmon fishery is an open sea fishery. The total commercial and recreational catch in 2017 was 9488 salmon. Almost all catches, including the recreational ones, were caught in ICES SD The commercial fishery uses longlines and it takes place from late autumn to spring (October May). In 2017, the commercial catch was 2988 salmon (14.4 tonnes), a marked decrease from in 2016 (9684 salmon). It is likely that the effort in the commercial fishery has decreased in recent years due to the increasing number of seals in the waters close to the Island of Bornholm. The recreational fishery is mainly trolling, but some recreational passive gear fishing, i.e. longlining, also takes in place in waters close to Bornholm. It is estimated that the total recreational catch in 2017 was 6500 salmon (a decrease from the 2016 estimate of 8000 salmon). However, the estimate resulting from an Internet based recall survey targeting annual licence holders yielded a result for 2017 for trolling alone of only 2749 salmon. Estonia: There is no specific Estonian salmon fishery. In the coastal fishery, salmon is a bycatch and the main targeted species are sprat, flounder and perch. The share of salmon in the total coastal catch is less than 1%. In 2017, similar to in previous years the Estonian salmon sea catch was below 1 tonne. The coastal catch (commercial and recreational) was 12 tonnes, which is slightly less than in last year. The vast majority of salmon is caught in the Gulf of Finland (SD 32).There are about 570 commercial fishermen in Gulf of Finland, and in addition up to 6433 monthly gillnet (standard length of a net is 70 meters) licences are distributed annually. Commercial fishermen take 68% of the total catch. The vast majority of salmon (88%) is caught in gillnets and the rest in trapnets. About 75% of the annual catch is taken in September, October and November. Nearly all caught salmon are spawners. Finland: In 2017 Finnish fishers caught a total of salmon (358 tonnes) in the Baltic Sea (including Gulf of Finland), in weight 20% less than in The commercial catch was salmon (160 tonnes). The recreational catch (including river catches) was salmon (184 tonnes). The residuals are discarded or seal damaged salmon. Both commercial and recreational catches decreased, but the recreational decrease was greater. Since 2012, there has been no commercial fishery for salmon in the Southern Baltic Sea by Finnish vessels. Hence, the commercial catch was taken in the coastal fishery, mainly in trapnets where the catch decreased with about 10% compared to in Commercial catch data from year 2017 are preliminary. River catches (recreational) were salmon (88 tonnes), a decrease with 35% compared to in The estimates of recreational salmon catches in the sea for are based on the results of the Finnish Recreational Fishing 2016 survey. National surveys are carried out every second year. For the missing odd years, the same sea catch

36 30 ICES WGBAST REPORT 2018 estimate as in the preceding year is assumed. The catch estimate from the recreational fishery in the sea in 2016 was highly uncertain ( tonnes, salmon). In the Gulf of Finland, the Finnish commercial catch in 2017 was 6053 salmon (34 tonnes), and the recreational catch was 3208 salmon (21 tonnes). The river catch (all recreational) was 208 salmon (1 tonne) taken mainly from river Kymijoki. In 2016 (the latest survey year), approximately one third of the total recreational catch of all Finnish sea areas ( tonnes) was taken from the Gulf of Finland (3000 ± 3000 salmon, 20 ± 19 tonnes, notice the high uncertainty). Germany: The total reported commercial salmon catch in 2017 (SD 22 25) was 4.0 tonnes (795 individuals), which was 50% less compared to in In recent years, virtually no German commercial fishery has directly targeted salmon; hence, most of the salmon are caught as bycatch in other fisheries (mainly passive gear fisheries). As described above, recreational salmon fishing in Germany occurs almost exclusively as trolling. The total number of landed salmon was estimated to be 4576 (CI ± 1569) salmon. In addition, 701 (CI ± 473) salmon have been released, resulting in a release rate of 13.3%. There are no data available on freshwater catches, but such commercial and recreational catches are most likely insignificant as there are no rivers with a significant salmon spawning along the German Baltic coast. Latvia: The total nominal catch in 2017 was 1759 salmon (5.5 tonnes), which is approximately at the same magnitude as in The commercial fisheries along the coast (gillnets and to a smaller extent fykenets) and in rivers (fykenets) caught about 60% (1062 salmon, 3.9 tonnes) of the total catch. In 2015 one Latvian vessel reported 137 salmon caught by longlines. However, in 2016 and 2017, there were no Latvian vessels longlining. Lithuania: In 2017, Lithuanian commercial fishers caught 176 salmon (0.6 tonnes), a decrease compared to in last year. Most of the salmon were caught in the Curonian Lagoon (128 salmon). Additionally, 26 salmon were caught in rivers for artificial reproduction (broodstock fishery) and 21 for scientific purposes. Total catches of salmon in 2017 in the recreational fishery was about 1573 salmon (7.8 tonnes): seashore 15 individuals (0.07 tonnes), open sea (trolling) 996 salmon (4.9 tonnes) and in rivers 562 (2.8 tonnes). Poland: The total offshore and coastal catch in 2017 was 6558 salmon (39.3 tonnes). This is 56% higher than in 2016, mainly due to additional quota exchange with other countries. Most of the Polish salmon catch was taken from SD 26. No river catches were recorded in Russia: There is no specific salmon fishery, but salmon (and sea trout) can be caught as bycatch in the coastal fishery (trapnets and gillnets) where the main targeted species are herring, sprat, smelt, perch and pikeperch. No official statistics on bycatches are available. No salmon were caught in offshore and coastal fisheries. In 2017, 380 spawners (1.6 tonnes) were caught in the rivers during broodstock fishing (208 in Neva River, 138 in Narva River and 34 in Luga River). Sweden: The total salmon catch in 2017 was salmon (277 tonnes) which is less than in This is the lowest recorded annual catch since Overall, the commercial catch is of the same order of magnitude as the recreational one. The total coastal catch, mainly consisting of commercial trapnetting in Gulf of Bothnia (SD 30 31), decreased from 197 tonnes in 2016 to 157 tonnes ( salmon) in One reason for the decrease was that the commercial fishery in 2017 was closed before the total Swedish TAC was filled. During the same time period, river catches also decreased from 182 tonnes in 2016, to 104 tonnes in The 2017 river catch included commercial

37 ICES WGBAST REPORT fisheries from the reared river Luleälven (SD 31) where 41 tonnes (8681 salmon) were caught. No commercial catch was recorded in Ljusnan (SD 30), the second river with compensatory releases in Sweden where there has been an active commercial fishery in recent years. Commercial catches taken in river mouths (i.e. freshwater) are not counted against the Swedish TAC. In the Swedish recreational fisheries, a total of salmon (63 tonnes) were landed in 2017, mainly in the SD rivers (wild and reared). Approximately 90% of the total estimated recreational salmon catches in numbers were riverine. The remaining 10% of the recreational catches, 1603 salmon (16.4 tonnes), were taken offshore by trolling (main part in SD 25, a smaller fraction in SD 29). The estimated 2017 trolling catch is based on a survey conducted in Both in rivers and at sea there is an increasing trend of catch and release, either voluntarily or due to regulatory measures. This may affects interpretations of catch numbers, as these consist only of landed salmon Distribution of catches by countries compared with the TAC Until 1992, Baltic salmon TAC was given in tonnes but from 1993, it has been given in numbers. Commercial landings in numbers (excluding river catches) compared to TAC, by fishing nations and areas in , are given in Table Discards, unreported and misreported catches are not included in the utilisation of the TAC, but in Figure total catches of salmon including such catches and discards are presented as a percentage of TAC. In 2017, 60% of the TAC in SD was utilised. Total TAC was individuals (according to COUNCIL REGULATION (EU) 2016/1903 of 28 October 2016). In the Gulf of Finland, 57% of the EC TAC of individuals was utilised. The Russian salmon catch in the Gulf of Finland was zero. It should be noted that occasionally there could be some quota swapping between countries, which may result in exceeded original national TACs. In 2017 such an exchange took place in Poland where initial TAC was 6030 salmon. An additional quota of 7663 salmon were exchanged with Latvia, and the final TAC for Poland was therefore salmon. Finland also exchanged part of their salmon quota with Estonia in SD 32.

38 32 ICES WGBAST REPORT 2018 The total TAC for salmon was allocated and utilized in the following manner in 2017: SUBDIVISION (SD) SUBDIVISION (SD) 32 Contracting party Quota Sea/Coast Catch Quota Catch Utilized (%) (nos.) (nos.) Utilized (%) (nos.) (nos.) Denmark Estonia Finland* ) Germany Latvia Lithuania Poland* ) Sweden Total EU Russia 1) TOTAL ) No international agreed quota between Russia and EC. * With use of swapped quota. Over time the proportion of the annual commercial catch (regulated by the TAC) out of the total has decreased, at the same time as the proportion of the recreational catch has increased (See Figure 2.2.2). Hence, the importance of TAC as a means of fishery control has decreased. In 2017, non-commercial catches (from coast, sea and river) constituted approximately 38% (in weight) of the total reported salmon catches (Table 2.2.1). In addition, new information shows that the recreational salmon catch has been even higher than previously recognised; in recent years, total Baltic trolling catches appear to have been severely underestimated (Section 2.1.2). 2.3 Discards, unreporting and misreporting of catches Estimation procedures for discards and unreported catches for years and misreported catches for years are described in the Stock Annex (Annex 2). In general, data for years on discards and unreporting of salmon from different fisheries in the Baltic Sea are incomplete and fragmentary. For years , the estimates for discards and unreporting have been computed with a new method based on updated expert evaluations (adopted in WGBAST 2013). Coefficient factors for unreporting and discarding by country and fisheries were updated for fishing years during the IBPSalmon in autumn 2012 (ICES, 2012b), and subsequently for years (see WGBAST reports ). Expert evaluations have been provided from Poland, Denmark, Sweden and Finland for all relevant fisheries of each country, respectively. These four countries cover the main salmon fisheries, and together they have caught more than 95% of the total Baltic salmon catch in the last several years. Parameter values for the elicited priors and pooled (average)

39 ICES WGBAST REPORT probability distributions for different conversion factors (by country and year period) are given in Table In WGBAST the average conversion factors were calculated for all parameters separately for years before and after 2008, because of the change in relative weight between the fisheries in 2008 due to ban of driftnet fishing. In addition, Finland and Sweden banned salmon offshore fishing in the Main Basin in 2013, which further changed the relative weight between the fleets. Therefore the relevant conversion factors were computed separately for fishing years from 2013 and onwards. Since WGBAST 2015, the average conversion factors for certain parameters have not been used in computations, since they were considered to give a too biased estimate for certain fisheries and fleets. For example, the average share of seal damaged salmon in the offshore fishery based on Swedish, Danish and Finnish data was considered to give too high estimates for discarded seal damaged salmon in the Polish offshore fishery before year The average values of the following parameters were seen inapplicable and consequently abandoned: (i) share of unreported catch in offshore fisheries, (ii) share of unreported catch in coastal fisheries, (iii) share of discarded seal damaged salmon in longline fisheries, (iv) share of discarded seal damaged salmon in driftnet fisheries and (v) share of discarded seal damaged salmon in trapnet fisheries. The average values of these parameters were removed from the Table Instead of average values, a minimum available observed value of the parameter concerned was used for the countries and fisheries, where neither data nor expert evaluation were available. Apart from the parameters listed above, average values were used for German, Lithuanian, Latvian, Estonian and Russian fisheries, as country-specific expert evaluations of coefficient factors were missing for those countries. However, the catches of these countries represent less than 5% of the total catch of Baltic salmon. Details on the transformation method of parameters of expert elicited triangular probability distributions into parameters of lognormal distributions is presented in ICES, 2016 (Annex 4). Assumptions used in estimation of unreported catch and discards are as follows: In the estimation of unreported catch in the Polish salmon fishery, it was assumed that the same rate of unreporting prevails in misreported as in reported catch. In the estimation of seal damages and discarded undersized salmon in all fisheries, the unreporting (and misreporting in the Polish offshore fishery) was counted into the total catch, i.e. similar rates were assumed for unreported catch components as for the reported catch. In the Finnish salmon fisheries, seal damaged catch is derived from logbook records. These catches were raised by the relevant unreporting rates, i.e. the same unreporting rate was assumed for the seal damaged catch as for the unharmed catch. For seal damaged catch in the Swedish salmon fisheries, the same assumption is due. Here, though, the official statistics do not contain a complete quantitative measure of seal damaged catch, and instead the seal damaged catch is estimated (see below for more details). Estimated unreported catch and discarding for the whole Baltic Sea are presented in Tables and Comparison of estimated unreporting and discard between the year period and shows that the main difference is in the order of magnitude of estimates in discards. This is mainly because of updated expert opinions

40 34 ICES WGBAST REPORT 2018 and partly the adoption of new computing model in Main part of the discards is seal damaged salmon, which occurs in the coastal trapnet and gillnet fishery, but also in the offshore longline fishery (Table ). Small amounts of undersized salmon were estimated to be discarded in the offshore longline fishery. Since 2015 there has been landing obligation in longline fishery; however, it has not fully implemented since little reporting of such landings has occurred. Country specific estimates for discards and unreporting are presented in Table The estimates are uncertain and should be considered as a rather rough magnitude of discards and unreporting Discards In 2017, approximately 9500 salmon were discarded due to seal damages (Table 2.3.2). More than half of these discards (5700 salmon) took place in the Danish and Polish longline fishery in the south Baltic Sea (Table 2.3.2). Estimates were based on the observed proportion of seal damaged catch in subsamples that has been extrapolated to the total catch. In this calculation also potential misreporting and unreporting was included in the total catch. In , in the Danish longline fishery approximately 50% (5% 65%) of the catch was seal damaged, and in the Polish longline fishery in SD 26 about 35% (5% 65%). Representativeness of these estimates is unknown to the WG, but the amount of seal damaged catches in the Main Basin have undoubtedly increased to significant rates in the last few years, and monitoring will be needed to attain reliably estimates of the seal damages in the region. In the north Baltic Sea, seal damages started to escalate gradually from 1993, but since the introduction of seal safe trapnets the catch losses in coastal fisheries have levelled off. In 2017, the total seal damaged discards was about 1650 salmon in the Gulf of Bothnia and 750 salmon in the Gulf of Finland. Most of the damages were reported from Finnish coastal trapnet fisheries. In Finland, data on seal damages are based on logbook records. In Sweden, the level of seal damages is estimated based on data from a voluntary logbook system and available data on seal interaction in the official statistics, for which an additional expert assessment has been made. The reported amounts of seal damaged salmon should, however, be regarded as a minimum estimate. The reporting rate of the seal damaged catch is assumed to be the same as for the undamaged catch in the coastal fishery. In 2017, seal damages in the Finnish trapnet fisheries comprised about 10% of the total salmon catch. The last estimates from Sweden are from 2011, and the same rate of damage is assumed for the fishing years In the next few years, more data on seal damages from coastal fishery are expected to emerge also from Latvia where new studies on the subject have been started. Dead discards of undersized salmon in 2017 were estimated to about 2100 salmon in the whole Baltic Sea (Table 2.3.2). Proportions of undersized salmon in the catches of different fisheries are mainly based on the sampling data (Table 2.3.1) and are considered rather accurate. Mortality estimates of the discarded undersized salmon released back to the sea are based on expert opinions. Mortality of the undersized salmon released from longline hooks is currently assumed to be high (around 80%), but few studies have been carried out on this issue and the true rate is uncertain. In the trapnet fishery post-release mortality is assumed to be lower (around 40%), but again the true rate is uncertain. Both the experimental design and the settings to study these mortalities are challenging, but such empirical studies are needed in order to get better estimates on the survival rate of salmon discarded. Post-smolts and adult salmon are frequently caught as bycatch in pelagic commercial trawling for sprat (mostly for supplying fish for production of fishmeal and oil), but

41 ICES WGBAST REPORT are probably often unreported in logbooks because the relative amount of salmon in these catches is low and can be identified only during unloading (ICES, 2011). Estimates of these potential removals, however, are so uncertain because of insufficient data that they are not taken into account in the present assessment. Besides, there is no estimate on the potential unreporting of bycatch of legally sized salmon in the pelagic trawl fishery. Only the reported catch from the trawls is accounted for in the catch data, although it has been very low over the years Information by country Below follows more detailed information on discards, misreporting and unreporting of catches, country by country: Denmark has no information in the official statistics from which it is possible to estimate discard percentages, even if this should be available from the DCF/EU-MAP data collection. Since the quota for salmon in recent years has not been fully utilized, it seems unlikely (however uncertain) that there are unreported catches in the commercial salmon fishery. On two trips with on-board observer in March 2017, 1.2% of the catch was below 60 cm. On the other hand, restrictions in possibilities for marketing larger salmon due to restrictions from dioxin contents could result in unreported catches. Damage by seals to caught salmon has been reported from fishermen to be reaching 40 50%. However, in two trips in December 2015 with inspector on board, the proportion seal-damaged salmon was approximately 4%, and on two other trips in February 2016, the proportion was 0.8%. There are no records of misreporting of salmon as other species (e.g. sea trout). Recently seals have been observed to attack salmon being hooked in the trolling fishery. Anglers have also observed seal-damaged salmon in their catches. The bycatch of salmon in other fisheries has been observed to be quite low. Observers from the DTU-Aqua participated in the Baltic herring and sprat fishery in the winter 2007/2008 for about 50 days, and bycatches of only a few salmon were observed in this fishery. In Estonia, seal damage is a serious problem in the coastal gillnet fishery where salmon and sea trout are caught. Information from fishermen shows that damages by seals have increased over time. A quantitative assessment of these damages is not available, however, as fishermen in most cases do not present claims for gear compensation. No further information on discards, misreporting and unreporting in Estonia is available. In Finland, logbook reported discards of seal damages were 2660 salmon (13 tonnes) in 2017, about the same level as in the previous year. Seals caused severe damages to all fisheries and comprised 10% of the total commercial removal. The rate of unreporting of catches is considered to have decrease to a very low magnitude as a consequence of the recent developments in the fishing regulations. In 2017, the salmon fishing in Finland an individual quota system implemented and each fisher s share of quota depends on the catch history. This probably has motivated fishers to report their catches carefully in In 2017, all traded (round) salmon had to carry a landing mark which probably steers to a careful catch reporting. In addition the compensation of seal damages is based on the recorded catches (all species accounted), which is considered to improve the reporting. In Germany, there are no data available on predation by seals. The current seal population in German Baltic waters is small. Concerning the current seal density and the low level of the commercial catches, it seems unlikely that predation by seals is an important issue in the commercial fishery in German waters. However, German commercial fishers reported increased predation rates on salmon longline catches around the

42 36 ICES WGBAST REPORT 2018 island of Bornholm in recent years, which led to the cessation of the directed salmon fishery by German vessels in Also in the recreational trolling fishery, anglers have started to report predation by seals during fish retrieval. Further, Germany has only scattered information on potential discards (BMS) in the commercial fishery in Concerning the low catches, it is unlikely that there is a discard problem in the commercial fishery, but there could be some unknown unreported salmon catches. Misreporting may be an issue concerning salmon catches, where salmon may be reported as sea trout. This could either occur deliberately, since sea trout catches are generally not limited by quota, or unintentionally through species misidentification. In 2013, the federal state authority of Mecklenburg-Western Pomerania initiated a pilot study to investigate the level of misreporting. Within the remits of this study fin samples were genetically analysed. Preliminary results show that misidentification occurred in 30 40% of the commercially landed salmon and sea trout, but that the misidentification was evenly distributed between the species, thus indicating no directed misreporting (Landesamt für Landwirtschaft, Lebensmittelsicherheit und Fischerei Mecklenburg-Vorpommern, pers. comm.). In Latvia the direct catch losses of salmon due to seal damages has increased significantly from In the most affected area, the southern part of the Gulf of Riga, the percentage of salmon damaged by seal in the coastal fishery increased from 5% in 2002 to 40% in 2003, and to 60% in In recent years, the number of seals has continued to increase. Due to this, the salmon fisheries in late autumn in the coastal waters of Latvia have become economically unfavourable. This holds especially for the gillnet fishery. Experimental fishing with a seal-safe gear (produced in Sweden) was unsuccessful. The gear was too fragile for fishing in the open Latvian coastal waters, with a dominating SW-NW wind direction. No updated information on discards, misreporting and unreporting is available. In Lithuania information on discards, misreporting and unreporting is not available. In Poland, a rapidly increasing amount of seal damages has been observed in recent years, both in offshore and coastal fisheries in SDs 25 and 26 (Gulf of Gdańsk area). No damages have been reported so far in SD 24. Preliminary national data from 2013 indicate that the share of seal damaged fish in separate catches was on average 25% (minimum 5%, maximum 65%). In 2016 and 2017, losses of 721 and 383 salmon and 846 and 498 sea trout were recorded in logbooks, respectively. The seal colony at the Vistula River mouth has grown up to 300 individuals that are hunting on neighbouring fishing grounds. For two years, the large amount of seals in the area has almost completely stopped the previous salmon and sea-trout fishery in the lowest few kilometres of the Vistula. In the last few years no catch was reported, and in autumn no spawners of sea trout or salmon could be collected in the Vistula river mouth due to seal attacks. In the past, Vistula used to be the best places for sea trout fishing and for collecting live spawners. Further, sampling of longline catches resulted in a total of 2% undersized fish. No undersized salmon were reported in the gillnet fishery. There are no data available on unreported catches. In Russia information on discard, misreporting and unreporting is not available. However, unofficial information indicates presence of significant poaching of salmon and sea trout, both in the coastal area and in rivers. In Sweden earlier estimates on discards, misreporting and unreporting are still the best available (see WGBAST 2015 report). Further analysis is needed to evaluate the quality of these estimates and the data on which they are based. As described above, discards

43 ICES WGBAST REPORT due to seal damages have been estimated by expert assessment, using data from a voluntary logbook system and available data on seal interaction in the official statistics. Seal interaction includes seal damaged gears and/or seal damaged fish. Currently, in the official statistics it is possible to report if you have had seal interaction on a fishing trip. These records form the basis for the system that handles seal damage compensation from the government to commercial fishermen. It is also possible, but not mandatory, to report seal damaged salmon in the official statistics. In 2017 a total of 1120 seal damaged salmon were reported (compared to 51 in 2016 and 343 in 2015). Besides, information on salmon discarded out of other reasons should be included in the official statistics. In 2017, 1005 salmon were reported as discarded (compared to 1237 in 2016 and 744 in 2015) Misreporting of salmon as sea trout in the Polish fishery In the WGBAST 2014, the Polish misreporting was recomputed for years This was due to the WG receiving new data on the catch compositions in the Polish longline fishery. These data were collected by the (Polish) National Marine Fisheries Research Institute in DCF sampling trips on the Polish longline vessels which operated offshore in SDs 25 and 26 in the years (Table 2.3.3). The data are available in the ICES Regional Database Fish Frame (RDB). According to Polish experts, the sampling in 2010 represented only 0.5% of the total number of days at sea, and the proportion of sampled trips has also been low in Although there is a clear underrepresentation in the sampling of the total fishery, the observed proportion of salmon in the catches of the sampled trips is consistent and with little variation; none of the observations has indicated a substantial proportion of sea trout in the catch. These data suggest that the Polish longline fishery is an almost true salmon fishing with only few sea trout in the catches (approximately 0 3%; Table 2.3.3). These data correspond to catch compositions that have been observed in catches of other countries vessels fishing in the same area (ICES, 2012). Based on the given data, a 97% proportion of salmon was assumed in the total Polish longline catch for fishing years This is a conservative estimate, and it excludes potential misreporting in the Polish coastal fishery. Misreporting estimates for earlier fishing years ( ) were based on the assumption that catch per unit of effort in the Polish offshore fisheries (driftnet and longline) corresponded to 75% of the cpue of other countries fleets in the corresponding fishery and in the same area (see e.g. ICES, 2012). In WGBAST 2018, Polish catch data from were revised, because part of these catches (recorded as sea trout) taken with surface gillnets by large vessels (>12 meters) had earlier been classified as coastal and consequently were ignored in calculations of misreporting by the group. This was done despite the fact that sorting of Polish catches in general is based on vessel categories so that catches of vessels larger than or equal to 12 m LOA are counted as open sea catches and those of vessels below 12 m LOA as coastal. Reason for this exception in sorting was that it was seen that anchored surface gillnets could not be used in deep and strong current areas in open sea. However, closer exploration of VMS data from 2016 revealed that surface gillnets had been used in the open sea. Therefore, surface gillnet catches of larger vessels have now been classified as open sea catches, and consequently the catches from years have now been accounted for retrospectively in the calculation of misreporting. As a result, the estimates of misreporting in increased substantially for most of these years, compared to earlier estimates. Misreporting estimates for years before 2009 were not

44 38 ICES WGBAST REPORT 2018 revised, because earlier data on catch composition in Polish fisheries were not available for the WGBAST. The total catch of the Polish offshore fishery decreased significantly until 2014, but have increased again after that and it grew strongly in The total estimated misreporting in 2017 was salmon, almost twice as much as estimated for 2016 (Table 2.2.2). This increase was mainly due to an increase of effort in longline and surface gillnet fishing in the offshore. The Polish reported catch in the 2017 offshore longline and surface gillnet fishery was 5813 salmon and sea trout. Misreporting in the coastal gillnet fishery was not estimated, although a potential misreporting could take place there too. However, the Polish sampling data suggest very small proportions of salmon in coastal catches (annually maximum 5%). In 2014, Poland presented Regulation (EC) No 1223/2013, which was based on results of extensive EC and national controls (45% coverage of all landings) and gave a decrease by 23% of Polish TAC in Such a percentage as an official factor was proposed to WGBAST for using in the assessment of misreporting. A similar document (Commission Implementing Regulation (EU) No 871/2014), decreasing the Polish TAC by 3.2% in 2014, was presented to the WG in 2015, which make up proof of better control and lower level of potential misreporting of salmon in Poland. However, WGBAST have not used these sources of information in the assessment. The present misreporting estimates should be considered as rough. The WG would benefit from Polish contribution in providing more data or relevant reports that would support the estimation of misreporting rates in offshore and coastal salmon fisheries. Poland should make sure that the whole catch is counted during each of the EU-MAP sampling trips, and that the planned number of trips will be carried out with an appropriate areal and temporal coverage. Comments provided by Poland on Misreporting of salmon as trout in the offshore fishery Poland sustains most of its explanations and comments given in its statements in WGBAST Report 2012 and Data on proportion of salmon and sea trout in Polish LLD fishery, considered for use in WGBAST 2015 and further in ,based on Polish DCF/EU- MAP sampling, have only indicative not quantitative value. DCF salmon/sea trout sampling is aimed for collecting biological measurements, not for assessing share of catch, because it is not only based on sampling at sea but also on sampling on land, where catch is already separated and do not necessarily reflect the real share of both species in a single catch. Moreover, EU_MAP sampling at sea has very low representativeness concerning days at sea comparing to yearly amount of days at sea of the whole Polish salmon LLD fleet (e.g. 0.2% in 2007, 0% in 2008, and 0.5% in 2010 and similar % for the following years). Thus, it cannot be considered as a reliable source for obtaining the share of salmon and sea trout respectively in the catches. 2.4 Fishing effort The total fishing effort by gears in the Main Basin, and in the three main assessment areas for the coastal commercial salmon fishery (AU 1 3), excluding Gulf of Finland, is presented in Table This table includes Baltic salmon fishing at sea and along the coasts in The coastal fishing effort on AU 1 stocks (Table 2.4.1) refers to the total Finnish coastal fishing effort and partly to the Swedish effort in SD 31. The coastal fishing effort on AU 2 stocks refers to the Finnish coastal fishing effort in SD 30 and partly to the Swedish coastal fishing effort in SD 31. The coastal fishing effort on stocks of AU 3 refers to the Finnish and Swedish coastal fishing effort in SD 30. Because sea

45 ICES WGBAST REPORT trout in Poland is targeted with the same gear type as salmon, effort from the Polish fishery targeting sea trout was included in the table before Development over time in fishing effort for the offshore fishery is presented in Figure 2.4.1, and for the coastal fishery in Figure The fishing effort is expressed in number of gear days (number of fishing days times the number of gears). The total effort in the longline fishery in 2017 decreased to hookdays, compared to in 2016 and in 2009 (Figure 2.4.1). The effort in the 2017 trapnet fishery was somewhat higher (17%) than the effort reported in 2016 (Figure 2.4.2). An overview of the number of fishing vessels engaged in the offshore fishery for salmon in SD during the last 19 years is presented in Table Notably, 93 Polish vessels were engaged in the offshore fishery in 2017, a number significantly higher than 2016 (53 vessels). Also note that when fishing effort is not presented for the Danish offshore fishery this is due to that effort data for vessels <12 meters is not included in the national catch statistics (instead statistics for smaller vessels has to be collected via sales notes). Catch per unit of effort (cpue) on a country-by-country level for offshore driftnetting (until 2008) and longlining in SD is presented in Table For the Finnish trapnet fishery in the Gulf of Finland, cpue has remained at 0.8 salmon per gear and day in the last three years ( ) (Table 2.4.4). Regarding Swedish cpue, further analysis is needed to evaluate the quality of past effort data in official catch statistics (especially for offshore fisheries). 2.5 Biological sampling of salmon General information on the structure of data collection in different fisheries, including length of time-series, is presented in the Stock Annex (Annex 2). The national work plans under the EU-MAP include data collected offshore, along the coast and in rivers. Biological sampling is conducted both in commercial, recreational and broodstock fisheries. Biological sampling is also included in surveys targeting smolts. General and future perspectives on sampling is further elaborated on in Section Sampling by country (2017) The below table gives an overview of EU-MAP age samples (biological sampling) collected in Included are also information on Russian biological sampling in 2017 (although not member of the EU). In the biological sampling, a set of individual information (scales for age and/or genetic analysis, length, weight, sex and wild/reared origin) is typically collected.

46 40 ICES WGBAST REPORT 2018 Number of scale samples for ageing collected in 2017 by country and subdivision(s): Country Month number Number of sampled fish by SD Fishery Gear(s) Total Denmark 2 Offshore Longlines Estonia 1 12 Coastal Gillnets Finland 5 9 Coastal Offshore Trapnets + longlines 5 8 River Germany 1 5 Offshore Angling Latvia 2 11 Coastal + River Gillnets + Trapnets Lithuania 8 10 Coastal Gillnets Poland 2 12 Offshore Longlines Russia 9 11 River Gillnets + Trapnets Sweden 4 7 River Various Total Short country-by-country summaries of biological sampling of salmon in 2017: Denmark: 79 scale samples were collected from the Danish salmon landings. All samples were age read and DNA-analysed (in Finland by Luke). Estonia: 100 age samples were collected. Sampling takes place occasionally, and it is carried out in cooperation with fishermen who collect scales. Finland: 2112 scale samples were collected from the Finnish commercial salmon fisheries, and 488 samples from the recreational river fisheries. The samples were distributed in terms of time and space. The whole pool of samples was resampled by stratification according to the total catches. The final amount of analysed samples was optimally adjusted to meet the quality criteria of EU-MAP. Finally, total numbers of samples were analysed by scale reading and part of these (830) were also analysed using DNA-markers (microsatellites). Germany: From the commercial fishery, there is no new information available in Catch sampling of salmon from the commercial fishery is very challenging as salmon are only bycaught and the total catch is low (n = 795 in 2017). Furthermore, in most cases only very few individuals are caught per trip. Sampling of biological data from the recreational trolling fishery off the Island of Rügen is ongoing since In 2017, scale and tissue samples from 15 salmon were collected and stored for further analyses. Latvia: In the coastal and river trapnet fisheries, biological sampling in 2017 was carried out from February to November. In total, 378 salmon were sampled in both fisheries. None of Latvia s vessels have been engaged in salmon offshore fisheries since In general, sampling of salmon in the commercial fisheries is very challenging

47 ICES WGBAST REPORT due to lack of a targeted Latvian salmon fishery and that salmon is usually taken as bycatch (with few individuals per fishing trip). Lithuania: a total of 21 samples were collected in the Curonian lagoon (SD 28). No Lithuanian fishermen were engaged in commercial fishery targeting salmon. Poland: a total 594 salmon were sampled from landings and from catch on-board. Sampling covered longline and trawl fishery, and was conducted in ICES SD in January April and in SD 25 in December (only one sample). Russia: There is no ongoing biological sampling programme running in Russia. Despite this, 341 salmon were collected and sampled for age, length and weight in Since Russia is not an EU member state, the country is not obliged to follow EU regulations. Sweden: Age sampling of smolts in rivers is included in the Swedish EU-MAP work plan. In 2017, a total of 611 smolts were sampled for age (118 in SD 25, 169 in SD 30 and 324 in SD 31). In the commercial coastal fishery, no biological sampling of salmon was planned since these data in the stock assessment. Therefore, an exemption was applied in the Swedish national work plan. Occasionally, outside the EU-MAP, age samples are from time to time also collected from the broodstock fishery and from salmon caught by anglers Growth of salmon Below a short summary of an ongoing study on growth of Baltic salmon in relation to composition of the overall fish community is presented. The average weight of salmon by age group increased around year 1990, simultaneously with an increase in sprat abundance (Figure 2.5.1). Despite some annual variation, the level of growth has remained rather stable. In , catch samples indicate a slight increase in mean weights by age (particularly in the A.3 and A.4 groups) which is potentially a result of strong 2014 year classes of sprat and Baltic herring. Despite that salmon shares feeding areas with cod in the southern Baltic Main Basin, there is no clear reduction in the growth rate of salmon as has been observed for cod in the last few years. The estimated post-smolt survival decreased strongly from the mid-1990s until 2005 (Figure ) but this cannot be recognised in the growth data. Mortality mechanisms seem to affect salmon population in such a way that survived individuals grow approximately as large in periods of high mortality as in periods of low mortality. 2.6 Tagging data in the Baltic salmon stock assessment Tagging data, mainly from Carlin tags, have been used historically within the Baltic salmon assessment, to estimate population parameters as well as exploitation rates by different fisheries (Table 2.6.1; see Annex 2 for further details). For various reasons, the number of tag returns has become very sparse after 2009, and therefore, in later years, tag return data have not been used in the assessment. As the tagging used are from external tags, it is vital that fishermen find and report tags. However, earlier reports (summarised in e.g. ICES, 2014) indicate an obvious unreporting of tags. As the tag return data influence e.g. the annual post-smolt survival estimates, which is a key parameter in the Baltic salmon assessment, there is a need to supplement or replace the sparse tagging data in the near future. The WGBAST 2010 (ICES, 2010) dealt with potential measures to improve and supplement the tagging data, including alternative tagging methods and supplementary catch sample data. In 2010, the WG also

48 42 ICES WGBAST REPORT 2018 noted need for a comprehensive study to explore potential tagging systems, before a change to a new system in the Baltic Sea may be considered. Since smolt abundance is included as a parameter in the EU-MAP, tagging has to be carried out as part of the data collection (for mark recapture experiments). Furthermore, salmon smolts are tagged for other monitoring purposes (Table 2.6.1). In 2017, the total number of Carlin tagged reared salmon released in the Baltic Sea was 8990 (Table 2.6.2), which was 41% less than in 2016 and 61% less than in Carlin tagged salmon smolts were released by Finland, Sweden and Latvia. As alternative methods, T-bar anchor tags are also used for tagging of smolts in Finland and Estonia, and in Sweden PIT-tags have also been used in several wild (index) rivers and also reared rivers (Table 2.7.2). As mentioned above, tag return rates show decreasing trends, as illustrated in Figures and for salmon tagged and released in the Gulf of Bothnia and Gulf of Finland, respectively. In 2015 and 2016, the return rate of Finnish Carlin tagged reared salmon smolts released in the Gulf of Bothnia and Gulf of Finland was close to zero (Figure 2.6.1). The return rate of 1-year old Carlin tagged salmon smolts in the Gulf of Finland in Estonian experiments varied around 0.2% in years There were no returns of tags in 2006, but in the following year the recapture rate exceeded 0.8%. Because of the low recapture rate and changes in stocking practices, no 1-year-old salmon smolts have been Carlin tagged in Estonia since The mean recapture rate of 2-year-olds in Estonian experiments for years was 0.7% and varied around 0.1% in years (Figure 2.6.2). Since 2015, only T-bar anchor tags are used in Estonian experiments for tagging of salmon smolts. The mean recapture rate was around 0.24% for years A similarly low recapture rate has been seen for Polish Carlin tags, where the reporting rate was around % in but since 2009 has decreased below 0.5% (Figure 2.6.3). No salmon tagging with Carlin tags and other tagging methods was conducted in Poland in 2017, because of low recapture rate in previous years (only two returned tags in 2017). 2.7 Finclipping Finclipping makes it possible to distinguish between reared and wild salmon in catches. Such information has been used, e.g. to estimate proportion of wild and reared salmon in different mixed-stock fisheries. However, since only a part of the Baltic salmon smolt released are currently finclipped, this type of information is not directly utilised in the WGBAST assessment model. In Table the proportion of adipose finclipped salmon in Latvian offshore catches is presented for together with information on total number of released adipose finclipped salmon for the years In 2017, the total number of finclipped young salmon released was , an increase of 36% compared to in Out of this total, were parr and smolts (Tables and 2.7.2). Compared to in 2016, the number of finclipped smolts increased with about 34%, while the number of finclipped parr increased with about 78%. Most finclipping (in numbers) were carried out in SD 30 31, but part of the finclipped fish were also released in SD (Table 2.7.2). In Finland about 46% of the released 1-year old parr were finclipped in Additionally, in Sweden and Estonia a total of parr and smolts were finclipped and stocked in 2017 (Tables 2.7.2).

49 ICES WGBAST REPORT Since 2005 it has been mandatory in Sweden to finclip all released salmon (and sea trout). All reared Estonian and Latvian salmon smolts released in 2017 were also finclipped. In Poland, all types of tagging were stopped in 2013 and 2014, because of national veterinarian s objections. In 2015, tagging was again permitted in Poland; however, since 2016 finclipping of smolts has not continued. From 2017 and onwards, all salmon released in Finland will be finclipped (except releases for enhancement purposes). Salmon smolts released 2017 in Russia, Lithuania, Poland, Germany and Denmark were not finclipped. 2.8 Estimates of stock and stock group proportions in the Gulf of Finland Baltic salmon catches based on DNA microsatellite and freshwater age information Combined DNA- and smolt-age-data has been used to estimate stock and stock group proportions of Atlantic salmon catches in the Baltic Sea with a Bayesian method since year 2000 (Pella and Masuda, 2001; Koljonen, 2006; ICES, 2017). So far, focus has been mainly on analyses of catches from the Main Basin and Gulf of Bothnia (e.g. ICES, 2017), and stock and stock group proportions have not been analysed annually for the Gulf of Finland. This is mainly because there is relatively little native natural salmon production in rivers draining into AU 6 (estimated total of ca wild smolts in recent years; Table ) compared to smolt releases in the same area ( reared smolts annually; Table 3.3.1). In recent years, the total annual salmon catch in the Gulf of Finland (including rivers) has been about salmon. A majority of the salmon production into the Gulf of Finland is coming from releases. In terms of smolt numbers, the major part of smolt releases take place in the Russian rivers Neva, Luga and Narva (about smolts annually). In Finland a Finnish Neva stock with genetic origin from Russian Neva River is used for releases in the region (about smolts annually). In Estonia releases are regularly carried out in six Gulf of Finland rivers (Kunda stock, up to smolts annually). In the Finnish rivers draining into the Gulf of Finland there are no native Atlantic salmon stocks left anymore, but enhancement releases have been done, especially in the Kymijoki River. In Kymijoki there has been a gradually increasing amount of natural smolt production in the last few years, representing offspring to spawners originally coming from smolt releases. In addition, some native natural wild salmon production occurs in Russian river Luga, in the Russian-Estonian border river Narva, and in some ten smaller wild and mixed-stocks from Estonian rivers. Neva wild and hatchery stocks cannot be reliably distinguished genetically from each other, but other stocks are possible to separate (Figure 2.8.1). With the exception for Neva salmon, previous genetic results have shown that Russian and Estonian salmon stocks have not been regularly included in Finnish coastal catch samples (Koljonen, 2006, Table 2.8.3) Methods The same genotype baseline data were used for the catch samples (Table 2.8.1, Figure 2.8.1). The current baseline stock dataset includes information on 17 DNA microsatellite loci assayed in samples from 39 Baltic salmon stocks from six countries, totalling 4453 individuals (Table 2.8.1). In all, 840 samples were analysed from Gulf of Finland salmon catches, and DNA results were received from 811 fish. In 2018, Finnish catches from the Gulf of Finland were analysed from the years 2009, 2010, 2011, 2015 and Previously analysed data were available from the years and 2014 (Koljonen, 2006; ICES, 2008; ICES, 2015).

50 44 ICES WGBAST REPORT 2018 Because smolt age information was used for stock proportion estimation, the fish in the catch samples were divided into two smolt-age classes according to the smolt age information from scale reading: 1 2-year old smolts and 3 5 year old smolts. As all released hatchery smolts are younger than three years, salmon in catch samples with a smolt age of older than two years originated presumably, or a priori, from any of the wild stocks, whereas individuals with a smolt age of one or two years might have originated from either a wild or a reared stock. This same assumption is used in scale reading as well, when defining wild and reared fish. Correspondingly, smolt-age distributions were needed for all baseline stocks in addition to genetic data (Table 2.8.5). The smolt age distributions for Tornionjoki wild, Kalixälven, Råneälven and Simojoki were updated to correspond to the mean distribution of smolt year classes from 2014 to 2016, of which the catches of adult salmon in 2017 were mainly composed. For the other stocks an average of smolt ages over the years was used (Table 2.8.5) Results There was quite much annual variation in the proportions of Bothnian Bay salmon included in the Gulf of Finland catches, and this proportion also varied much depending on the sampling site on the gulf (east Loviisa/west Inkoo) and time of the fishing season (early/late) (Table 2.8.2). Samples from the western part of the Gulf (Inkoo area) were available only from the previous 2014 catch analysis. All other samples analysed were from the eastern part of the Gulf. The proportion of northern Bothnian Bay salmon has been higher on the western part of the gulf and earlier during the fishing season. Some of the reared northern salmon stocks (mainly Finnish) occur in the Gulf of Finland at the same time as well. Currently there is only an active trapnet fishery along the eastern part of the Finnish coast in the gulf. In the analysed samples, the maximum proportion of Gulf of Bothnia wild salmon was 51% in the 2011 year sample, whereas the range over the years was 14 51% (Table 2.8.2; Figure ). Correspondingly, the proportion of Gulf of Finland stocks, mainly reared Neva salmon, varied from 38% to 67%. The proportion of wild Gulf of Bothnia salmon in the Gulf of Finland catches has decreased in recent years and has been below 20% since When the 2017 catch sample was divided into two groups of about the same size according to catch date, and analysed separately as samples from early A (from June 6th to July 19th) and late B (July 20th to August 30th) season, their composition differed clearly. In the early season, before July 19th, Gulf of Bothnia wild salmon composed 30% of the catch samples in the eastern part of the gulf, whereas in practice they had disappeared in the late season catch (2%) when their spawning migration time is over. In contrast, the Neva salmon made up a large majority of the total catch (83%; Table 2.8.2) later in the season. Among individual stocks the Neva salmon was clearly the most abundant in all samples, having a mean of 50% (38 67%; Table 2.8.3). Other commonly occurring stocks in these coastal trapnet catch samples were salmon from the large wild stocks from Bothnian Bay rivers Tornionjoki (mean 19%; 10 28%) and Kalixälven (16%; 3 28%), and also some reared salmon of the Tornionjoki hatchery stock (8%; 1 15%). All other individual stocks contributed less than 5% into the total catch (Iijoki, Luleälven, and some others with about 1% contribution). The only wild Gulf of Finland stock that appeared was the Estonian Kunda in the 2017 sample (<0.5%; Table 2.8.3). When analysing group proportions on the basis of assessment units (AU), the results were very similar; on average about half of the catch came from Gulf of Finland stocks (AU6) and the other half from Bothnian Bay (AU1) wild (32%) and hatchery (12%) salmon (Table 2.8.4).

51 ICES WGBAST REPORT In the observed salmon stock group estimates (Table 2.8.2), the proportion of naturally produced salmon in 2017 differed from the corresponding proportion calculated from scale reading for the same individuals; scale reading values were higher than the genetic estimates (Table ). For the other years, the scale reading percentage was within the 95% probability interval of the stock group estimate of the wild Gulf of Bothnia group. Notably, in the 2017 catch there were individuals with only two smolt years that still were classified as wild by scale reading, differing in that respect from Bothnian Bay wild fish (which usually are more than two smolt years old). According to genetic data, these individuals with high probability originated from the Neva stock. It has previously been assumed that all Neva salmon originate only from hatchery releases, and this stock has therefore been included in the hatchery production in the group estimate. However, by scale reading it is possible to distinguish wild from hatchery smolts, which explains the difference observed in Table between wild stock group estimates based on genetics and scale reading. In recent years, River Kymijoki has produced to naturally reproduced salmon smolts of genetic Neva origin, and in 2017 as much as smolts left the river (Section 3). In parallel with this increase in natural smolt production in River Kymijoki, the number of released hatchery reared Neva salmon smolts in the Kymijoki River has markedly decreased, from a maximum of released smolts in 2004 to an annual level of about released smolts per year. Thus in 2014, when the number of released hatchery smolts was and the estimated number of naturally produced smolts was , the natural production represented as much as 22% of the total Finnish Neva smolt production. In the 2017 salmon catch data there were 268 individual fish assigned into the Neva-FI origin, with a mean of 0.99 assignment probability, and among those 58 (21,7%) individuals were defined as wild by scale reading. Notably, this is very close to the estimated wild/reared smolt production ratio for the current Finnish Neva salmon stock (wild and released smolts in River Kymijoki). Because Finnish wild and hatchery Neva salmon are originating from the same broodstock (Luke Laukaa hatchery), it is not possible to differentiate them by genetic methods alone. The individual stock specific proportion estimates as a whole, however, still hold for Gulf of Finland, as both hatchery and wild produced Neva salmon are expected to be correctly assigned and are unlikely to be mis-assigned Bothnian Bay salmon. Scale reading or finclipping is needed to further distinguish between hatchery reared and wild individuals from the genetically same stock. Both 2-year old smolts and 1- year old juvenile Neva salmon and even roe have been released into the Kymijoki River, but only 2-year old smolts have been finclipped. There has not been any intention to finclip 1-year old river juveniles, partly because those fish are regarded as enhancement releases that should be saved from fishery. In addition, the tendency is to move more towards 1-year river juveniles. Both finclipping and scale reading (wild/reared information) can be included into the Bayesian identification model if decided, if correct information is available for the analysed catch year from the baseline stocks using finclipping proportions, and/or if scale reading is regarded trustworthy enough for young released fish as well. The naturally produced salmon in River Kymijoki is not of native genetic origin, but anyway wild. As a result, for Gulf of Finland (AU6), wild vs. hatchery proportions in catches could not be identified by genetics, as the hatchery group also included salmon from the enhanced new natural production of the Kymijoki River. It needs to be decided how valuable this natural salmon production is regarded for the region from a

52 46 ICES WGBAST REPORT 2018 fisheries management point of view, and if it should be given the same conservation status as to rivers with native salmon stocks. For a more complete picture of how fisheries in Gulf of Finland affects local wild stocks, it would be valuable to perform additional analyses of catches from the Estonian coastal fishery where salmon is taken as bycatch. Additional wild and mixed Estonian rivers in the Gulf of Finland and updates of certain old samples should also be added to the genetic baseline. 2.9 Management measures influencing the salmon fishery International regulatory measures Detailed information on international regulatory measures is presented in the Stock Annex (Annex 2). National regulatory measures are updated quite often, sometimes on a yearly basis, and therefore they are presented below and not in the Stock Annex National regulatory measures In Denmark, no new national regulation measures were implemented in According to national regulations for the period the following rules must be followed: all commercial vessels fishing salmon needs to be registered as salmon fishing boats and have a specific permission for the fishery; one vessel is permitted a maximum of 10% of the TAC; discard is not allowed, however discarding of seal damaged salmon is allowed; vessels with a catch of ten or more salmon must notify the Fisheries Inspection before entering the harbour. All salmon (and sea trout) streams with outlets wider than 2 m are protected by closed areas within 500 m from the mouth throughout the year. Otherwise the closure period is four months at the time of spawning run. Estuaries are usually protected by a more extended zone. Gillnetting is not permitted within 100 m of the low waterline. A closed period for salmon (and sea trout) has been established from November 16th to 15th January in freshwater. In the sea, this only applies for sexually mature fish in spawning dress (coloured). In Estonia, no new national regulation measures were implemented in Since 2011, the following restrictions are in practice: no commercial fishery in salmon (and sea trout) spawning rivers is permitted, with the exception of lamprey fishing; licensed angling is permitted. Some specific management regulations are also in place in individual rivers: A closed period for salmon (and sea trout) angling is established in rivers Narva, Purtse, Kunda, Selja Loobu, Valgejõgi, Jägala, Pirita, Keila, Vasalemma, and Pärnu from 1 September 30 November, and in other rivers from 1 September till 31 of October. Exceptions for these closures are allowed by decree of the Minister of Environment in rivers with a reared (Narva) or mixed salmon stock (Purtse, Selja, Valgejõgi, Jägala, Pirita and

53 ICES WGBAST REPORT Vääna). Below of dams and waterfalls, all kind of fishing is prohibited at a distance of 100 m. In the River Pärnu, below Sindi dam, this distance is 500 m. Furthermore, there is an all-year-round closed area of 1000 m radius at the river mouths of the present or potential salmon spawning rivers Purtse, Kunda, Selja, Loobu, Valgejõgi, Jägala, Pirita, Keila, and Vasalemma, and at the river mouths of the sea trout spawning rivers Punapea, Õngu, and Pidula. Since 2011, the closed area for fishing around the river mouth was extended from m for the time period 1 September 31 October for rivers Kunda, Selja, Loobu, Valgejõe, Pirita, Keila, Vääna, Vasalemma and Purtse. In rivers Selja, Valgejõgi, Pirita, Vääna and Purtse, recreational fishery for salmon (and sea trout) is banned from 15 October to 15 November. In the case of the most important Estonian sea trout spawning rivers (Pada, Toolse, Vainupea, Mustoja, Altja, Võsu, Pudisoo, Loo, Vääna, Vihterpadu, Nõva, Riguldi, Kolga, Rannametsa, Vanajõgi, Jämaja) a closed area of 500 m is established from 15th August to December 1st. In most of the salmon (and sea trout) rivers, angling with natural bait is prohibited. In Finland the national coastal salmon fishing regulation for the Gulf of Bothnia was renewed in Furthermore, an individual quota system was implemented in the commercial salmon fishery (and as well as in the Baltic herring and sprat fishery). In the Main Basin, salmon fishery has been forbidden for Finnish vessels since year In the Åland Islands, a separate regulation is in place. In the Gulf of Bothnia, salmon fishing for commercial fishermen is allowed to start with one trapnet in the following dates in four zones: Bothnian Sea (59 00 N N) May 1st; Quark (62 30 N 64 N) May 6th; Southern Bothnian Bay (64 00 N N) May 11th; Northern Bothnian Bay (65 30 N >) May 16th. An increased effort (one additional trapnet) is allowed from the following dates: Bothnian Sea (59 00 N N) June 10th; Quark (62 30 N 64 N) June 15th; Southern Bothnian Bay (64 00 N N) June 20th; Northern Bothnian Bay (65 30 N >) June 25th. After one week from the above dates, two more trapnets are allowed (i.e. max of four trapnets per fisher per year). In the recently initiated individual quota system, all salmon have to be marked with a coded landing mark. In the first period of the season (when only one trapnet is allowed) fishers are allowed to utilize up to 25% of their individual quota. Also, in terminal fishing areas outside reared rivers, the number of trapnets and fishing period was restricted. Earlier, the number of trapnets in terminal fishing areas was unlimited, and only in the Kemi terminal area there was a closure in the early summer. Now the regulation in terminal areas is more similar to the rest of the region. Fishing with one trapnet is allowed to start at the same time as outside these areas, but the number of trapnets can be raised up to three on June 17th and up to eight on June 25th (with up to two and four traps for fishers with a turnover of less than or equal to , respectively). In the coastal area outside River Simojoki, salmon fishing may

54 48 ICES WGBAST REPORT 2018 start on July 16th, and outside the mouth of Tornionjoki on June 17th. Since 2015, recreational fishermen are not allowed to use larger fykenets (height limit 1.5 meters). In Germany there are two federal states bordering the Baltic coast: Schleswig-Holstein, (SH) and Mecklenburg-Western Pomerania (MV). Commercial (coastal) fishing and recreational fishing is under the jurisdiction of the German federal states. Consequently, marine coastal fishing is managed with different legislation. The fishing season is closed both for commercial and recreational fisheries during autumn, in SH October 1st December 31th (only coloured fish) and in MV September 15th December 14th. Closed areas in both federal states include protected spawning grounds in coastal waters, m around spawning streams/rivers. For commercial fisheries there is also a 200 m gillnet ban in front of the coastline. In MV, trolling fisheries is permitted at a distance >1 km from the coastline between September 15th and March 15 th and there is a rod limit of 3 rods per angler in place. In MV, there is also a bag limit in place allowing landing of three salmonids (sea trout or salmon) per day and angler. Recreational fishery for salmon (and sea trout) is allowed on a licence basis. In Latvia no new fisheries regulations were implemented in In summary, current national legislation in offshore and in coastal waters includes the following restrictions: In the Gulf of Riga, salmon driftnet and longline fishing is not permitted; In coastal waters, salmon fishing is prohibited from October 1st November 15th; Salmon fishing in coastal waters has been restricted indirectly, by limiting the number of gears in the fishing season. In rivers with natural reproduction of salmon, all fisheries targeting salmon (and sea trout) are prohibited, with the exception of licensed angling permitted in rivers Salaca and Venta during spring. The daily bag limit is one salmon or sea trout. From 2003, all fisheries by gillnets are prohibited all year-round in a 3 km zone around the River Salaca outlet. Fisheries restriction zones were enlarged around rivers Gauja and Venta in 2004, from 1 to 2 km. In rivers Daugava and Bullupe (that connects rivers Lielupe and Daugava), fishing with gillnets is prohibited. However, angling and commercial fishing with trapnets in these two rivers, are allowed from In Lithuania, no new fisheries regulations were implemented in Commercial fishery is regulated during salmon (and sea-trout) migration in the Klaipėda strait and the Curonian lagoon. Fishing is prohibited all year-round in a predefined part of the Klaipėda strait. From September 1st October 31st, during the salmon (and sea trout) migration, fishing with nets is prohibited on the eastern stretch of Curonian lagoon between Klaipėda and Skirvytė, at a 2 km distance from the eastern shore. Recreational salmon (and sea trout) fisheries along the coast are regulated by one set of rules, whereas in inland waters another set of rules regulates the fisheries. For recreational fishing of salmon (and sea trout) in the Baltic Sea, you either need to buy a fishing ticket or be entitled to special fishing rights to fish. In inland waters, you need a recreational fishing card for fishing. Both in the sea and in inland waters, there is a bag limit of one salmon or sea trout per angler and fishing day. In inland waters, the minimum size has been extended to 65 cm. In the period September 15th October 31st, recreational fishing is prohibited within a 0.5 km radius from the Šventoji and Rėkstyne river mouths, and from the southern and northern breakwaters of Klaipėda Strait. During the same period, commercial fishing is prohibited within a 0.5 km radius from Šventoji River mouth, and 3 km from the

55 ICES WGBAST REPORT Curonian lagoon and Baltic Sea confluence. From October 1st to December 31st, all types of fishing are prohibited in 161 streams, because of brown trout and sea trout spawning. In larger rivers, such as Neris and Šventoji (twelve rivers in total), special protect zones have been selected where schooling of salmon and sea trout occurs. In these selected zones, licensed fishing is only permitted from September 16th until October 15th. Last year the angling of salmon and sea trout in this selected river zones was limited by the catch and release rule (from 1st until 15th October). From October 16th to December 31st any kind of fishing is prohibited in these areas. From January 1st, licensed salmon (and sea trout) kelt fishing is permitted in the Minija, Veiviržas, Skirvytė, Jūra, Atmata, Nemunas, Neris, Dubysa, Siesartis and Šventoji river. Fishing with a licence is allowed from January 1st to October 1st in designated stretches of the listed rivers. In the inland waters, regulation of fishing is more complex. In case of retaining a salmon (or sea trout), a specific part of the recreational fishing card must be removed not later than within five minutes. Such a marked recreational fishing card means that you are not allowed to continue fishing there and then. In Poland, in addition to EC measures, seasonal closures and fixed protected areas are in force within territorial waters managed by Regional Fisheries Inspectorates. Fishing for salmon (and sea trout) is not allowed between September 15th and November 15th within a predefined belt along the coastal zone. Since 2005, commercial fisheries for salmon (and sea trout) in rivers is based on new implemented rules. Fisheries opportunities were sold in 2005 by the state on a tender basis, where the bidder had to submit a fishing ten-year operational plan including restocking. New rules were recently introduced for recreational salmon fishing in Polish EEZ (Law on Fisheries of 19 December 2014). These include: catch quotas (per day/per angler); minimum size limits (TL.); protection periods and areas for fish species; minimum distance between anglers. Rod fishing (coastal fishing, boat/belly boat fishing, and organized cruises on board fishing vessels) and spear fishing is allowed. Recreational fishing with nets is not allowed. A new system of obtaining fishing licences has been established. Currently, proof of a bank transfer with specified personal information is needed for legal fishing. The licence can be issued for a period of one week, one month or one year. In case of rivers Ina, Reda, Parseta and Słupia, anglers must release all fish that have been caught. In Russia no changes in the national regulations has been implemented in the period The international fishery rules are extended to the coastline. In all rivers, and within one nautical mile of their mouths, fishing and angling for salmon is prohibited during all year, except fishing for breeding purposes for hatcheries. In Sweden, as in recent years, the main bulk of the national quota in 2017 for the salmon commercial fishery was allocated to the coastal fishery, as the Swedish offshore longline fishery targeting salmon was phased out in National management measures for salmon include an early summer ban. The aim of the early summer ban in the coastal fishery is to ensure that a part of the spawning migrating population ascend rivers before the fishing season starts. Starting dates of the commercial coastal fishing season in 2017 were the same as in North of latitude 62º55 N the fishing season started 17 June. Exemptions from this seasonal regulation of the salmon fishery was

56 50 ICES WGBAST REPORT 2018 allowed by the local county board to professional fishermen in the area north of latitude 62º55 N up to the border between the counties Västerbotten and Norrbotten, so that a limited fishery could start in 12 June. South of latitude 62º55 N, commercial coastal fishing in 2017 was allowed from 1 April. With the further aim of increase exploitation of reared salmon stocks and reducing exploitation of weak wild ones, the Swedish TAC is divided between coastal regionals (subdivisions). In addition, the regional quota in SD 31 is divided between wild (not finclipped) and reared (finclipped) salmon. When the limit of non-finclipped salmon is reached, only fishing for finclipped salmon in terminal fishing areas outside reared rivers, and in the restriction area outside River Umeälven, is allowed. In SD the regional quota is set to a low value, because of the higher expected proportion of salmon from weaker wild stocks in those catches (as compared to in SD 30 and 31). To further create a reserve for bycatches in fisheries targeting other species, a number of salmon is in each year not allocated to any specific coastal area. This reserve can also be used as buffer if catches in any of the areas would exceed the set regional quota. In 2017, the total Swedish TAC ( salmon) was divided as follows: SD salmon, SD salmon, SD wild and 6000 reared (plus a reserve of 2120 salmon). Commercial catches in reared rivers (freshwater) are not counted against the TAC (see Section 2.1.1), and therefore that fishery can continue after the commercial coastal fishery is stopped. Furthermore, Sweden has increased the Minimum Conservation Reference Sizes (MCRS) for salmon caught in SD 31 from the EU-regulated 50 cm to 60 cm. Recreational fisheries in the sea and in rivers are also managed through national regulations. Unlicensed trapnet fishery along the coast (right to fish limited to land owners) is regulated with a delayed fishing start compared to the commercial fishery. In 2017, the recreational trapnet fishery in counties Norrbotten, Västerbotten and (part of) Västernorrland was allowed from 1st of July until the quota of salmon within the commercial fishery was fulfilled. In recent years, the regional salmon quotas have been fulfilled already in the end of June with all fishery closed. Hence, no recreational fishing with trapnets has been conducted (in 2017 the commercial coastal fishery was terminated 29 June in SD 31). Futher, an enforced ban to sell fish from recreational fisheries is thought to have had a limiting effect on the number of fishermen using trapnets. Since 2013, the Swedish offshore trolling fishery (mainly in Main Basin) is only allowed to retain salmon without an adipose fin (i.e. finclipped reared salmon). In all rivers, there is a general bag limit of one salmon and one trout per fisherman and day. In addition, fishing periods are regulated on a national level. In Gulf of Bothnian wild rivers, for example, angling for salmon is forbidden from September 1st until December 31st, and in some rivers angling is also forbidden between May 1st and June 18th. In addition to national regulations, local fishing and management organizations may decide on more restrictive river-specific fishing regulations. Management of salmon fisheries in Torneälven/Tornionjoki, including also the coastal area directly outside the river mouth, is handled through a Swedish-Finnish agreement. This agreement includes, for example, a specified time period within which the commercial coastal fishery in the river mouth is allowed to start. Regulations targeting the river fishery are also handled in the agreement. Deviations from the agreed fishing regulations are negotiated and decided upon on an annual basis by the Swedish Agency for Marine and Water Management (according to a Government commission from the Swedish Ministry of Enterprise and Innovation) and the Finnish Ministry of Agriculture and Forestry.

57 ICES WGBAST REPORT Effects of management measures International regulatory measures Landing obligation Discarding refers to the practice of returning unwanted catch, dead or alive, back to the sea. During autumn 2014, the European Commission decided to introduce a discard ban for commercial fisheries, covering all species under TACs including salmon (Commission Delegated Regulation (EU) No 1396/2014 of 20 October 2014). The aim of the landing obligation is to stop the wasteful practice of discarding, promote development of more selective fishing gears and to increase the quality of catch data. Further, the Commission Delegated Regulation (EU) No 2018/211 of 21 November 2017 established an updated discard plan concerning fisheries for salmon in the Baltic Sea, in the absence of a multiannual plan applicable to Baltic salmon stocks and fisheries. The regulation states that until December 31st 2020, (1) the landing obligation shall not apply to salmon caught with trapnets, creels/pots, fykenets and poundnets on account of high survival rates, and further (2) salmon caught without an available quota or below the minimum conservation reference size shall be released back into the sea. The impact of an absolute landing obligation on salmon fisheries is expected to vary depending on geographical location and gear type used. In the Main Basin longline fishery, the share of undersized (unwanted) salmon has been estimated to be around 2 3 percent (Table 2.3.1), which means that the landing obligation has only had minor effects on this fishery. For countries that have applied for it, coastal fisheries using salmon traps (and a few other gears) are temporally exempted from the discard ban. In addition, seal damaged salmon do not fall under the landing obligation (but should be recorded in logbooks). Trapnet caught salmon are considered to have comparably high survival after release back into the sea. Knowledge of long-term survival rate and behaviour of salmon after release from trapnets is, however, limited and further investigations are needed. An eventual future discard ban that would involve also trapnet fisheries would probably affect the coastal exploitation pattern of both salmon and other species. The estimated share of undersized salmon in coastal fisheries with traps is low (1 5%), so a discard ban will not have any major impacts on the total amount of salmon caught. However, the possibility of releasing wild salmon back into the sea, as a measure to steer the exploitation towards reared (finclipped) salmon, would disappear. Also, under a discard ban, trapnet fisheries targeting other species (e.g. whitefish) may have to be more strongly regulated than today, if salmon are taken as bycatch (and must be counted against the quota). But such an effect may be overcome by development of selective gears that minimizes the bycatch of salmon. TAC For an evaluation of the TAC regulation, see the Stock Annex (Annex 2). Minimum Conservation Reference Size In conjunction with the landing obligation, the term Minimum Landing Sizes (MLS) has been changed to Minimum Conservation Reference Sizes (MCRS). In practice, no change in the salmon measures has occurred since The MCRS for Baltic salmon is 60 cm, except for in SD 31, where it has been decreased from 60 cm to 50 cm (only applied on the Finnish side). An evaluation of this change was provided in ICES (2007).

58 52 ICES WGBAST REPORT 2018 In the commercial offshore fishery the minimum landing size is particularly important. This is due to that longlines do not have the same pronounced size selectivity as the previously used driftnets, and because younger (smaller) salmon are feeding mainly in the Main Basin (where the offshore fishery mainly occurs). There is a minimum hook size of 19 mm set for longlining in EC Baltic Sea waters. An evaluation of the effects of the minimum landing size and minimum hook size was provided by ICES (2000). However, the changes in the regulatory measures in the EC waters (Council Regulation (EC) 2187/2005) might have changed the situation, compared to in years before the enforcement of this regulation. Summer closure and maximum hook number Since 2013 only Danish and Polish longline fleets operate in SD The previous summer closure for this fishery had a small effect, since longlining with a high cpue is possible only during winter months (from November/December to February or possibly March/April). The rule concerning a maximum number of hooks per vessel (previously 2000) has also been taken away from the EC Council regulation. This measure might contribute to an increased fishing effort by longlining. As longline fishery is very labour intense, it is not possible to increase the number of hooks so much. In addition, some of the boats involved in longline fishery are small and they do not have capacity to use more than 2000 hooks. Driftnet ban In the northern feeding areas, Bothnian Sea (SD 30) and Gulf of Finland (SD 32), offshore fishing with longlines would be theoretically possible with small boats and a small crew (1 2), but seals and a busy ship traffic practically prevent such fishing in these areas. Besides, this fishery was banned by Sweden and Finland in The present offshore fishing of salmon (currently only Denmark and Poland) takes place in the most southern part of the Baltic Main Basin. Previously important fishing took place also in the northern Baltic Sea at the Gotland Deep, and in the Bothnian Sea and Gulf of Finland. Fishermen have reported that densities of feeding salmon have been low in northern areas, and therefore they have switched to more southern fishing areas where catches are higher. The reason for the appearance of feeding salmon mostly in the waters off Bornholm and Gulf of Gdańsk is unknown. The share of undersized salmon in catches is most likely to be larger in offshore longline fishery than in the past driftnet fishery, mostly due to higher selectivity of driftnets compared with longlines. In the Danish offshore fishing in undersized salmon in longline catches varied between 1.7% and 20.3% (mean 11.5%), whereas in the driftnet catch, the mean percentage of salmon smaller than 60 cm was 3% (ICES, 2003b). Likewise, in Polish catch samples from the Main Basin longline fishery in , the proportion of undersized salmon was 1.5 4%. In fact, small salmon in longline catches is not a new finding, although small salmon have often been classified as sea trout. According to Järvi (1938), Polish salmon catches from the 1930s could be dominated by small salmon (post-smolts with an average weight of about 0.5 kg). Also, Alm (1954) discussed catches of small salmon with longlines in the Baltic Sea, and suggested that this fishery should be prohibited in winter (December March) because of the large proportion of post-smolts in catches during that time of the year. In summary, catch of undersized salmon in the present longline fishery may be noticeably, although additional information is needed on how it varies in time and space. Polish data from indicate that 20 30% of undersized released fish was alive.

59 ICES WGBAST REPORT However, long-term survival rate of salmon that have been released from hook and put back to sea is poorly known. Without such information, it is impossible to gauge the effects of this type of discard with respect to stock assessment and in terms of reduced catch options (i.e. by not catching the fish later in life, when it has grown larger). Therefore studies on survival would be of importance. In addition, on-board sampling is important to obtain further data on discards of undersized salmon. Delayed opening of the coastal salmon fishery ICES (2007) concluded that the delayed opening of the coastal salmon fishery is an effective measure for saving a proportion of the spawning run from being harvested. However, the run timing varies between years, which mean that with multi-annually fixed opening dates, the saved proportion of the spawning run is highly variable. Evidently this regulatory measure results in a higher harvest rate of late-migrating than early migrating salmon (ICES, 2007). As older fish and females dominate in the early part of the spawning run, a late opening of the fishery saves the most valuable part of the run. Also, it can be possible to direct the fisheries towards either wild or reared fish by changing the opening date, since a difference in the migration timing has been observed depending on origin (wild salmon tend to arrive somewhat earlier than reared). National regulatory measures Possible effects of national regulatory measures have not been evaluated by WGBAST in Other factors influencing the salmon fishery The incitement to fish salmon compared with other species is likely to be influenced by a number of factors, such as the possibilities for selling the fish, the market price for salmon compared to other species, eventual opportunities to target and catch other species and problems with damages to the catches caused by seals and eventual birds. The possibilities for selling the fish is evidently effected by co-factors such as levels of contaminants, e.g. dioxin, as well as the overall health status of the fish Dioxin The maximum level of dioxin and dioxin-like PCB set for salmon are set out in Commission Regulation (EC) No. 1881/2006, with updates in EC 1259/2011. Further, there is also an additional regulation (EC 589/2014) stating how a control program for sampling of dioxin in fish should be set up. Overall, levels of dioxin and related substances tend to increase with size (sea age) of the salmon, but also varies with the fat content in different parts of the flesh (Persson et al., 2007). In general, levels found in Baltic salmon are above the maximum EU-level. Finland, Latvia and Sweden have derogations from the regulation allowing domestic use of the salmon, providing that dietary advice is given to the public. These derogations are not time-limited. Export of wild-caught salmon to other EU countries is not permitted. In Denmark, the following restrictions for marketing of salmon are in force from 5th of December 2016: In ICES SD 24 26, salmon 5.5 kg gutted weight must be trimmed (deep skinned) before marketing. In the same subdivisions, salmon >5.5 kg and <7.9 kg can be marketed if trimmed and the ventral part of the fish is removed;

60 54 ICES WGBAST REPORT 2018 In ICES SD 27 32, each batch of salmon >2.0 kg caught, must be analysed for dioxin before marketing. Salmon >5.5 kg (gutted weight) are not permitted to be marketed within the EU. With these restrictions in place, it is possible to marketing salmon without seeking for derogations. The latest results from Denmark (2013) showed high levels of dioxins, comparable to those in However, in March 2011, deep-skinned salmon were analysed and since a general decrease in the dioxin content was then observed, these results confirm that the restrictions in practice are valid. In Sweden, the latest published report show elevated levels of dioxin in Baltic salmon caught along the coast (Fohgelberg and Wretling, 2015). The Swedish National Food Agency (Livsmedelsverket) is responsible for sampling and analysing, and they are also obliged to provide dietary recommendations regarding dioxin and other toxic substances in fish. Their recommendations focus on minimizing consumption of fat fish from the Baltic Sea for children and women of childbearing age (current guideline is maximum 2 3 times a year) and for all others a restrictive consumption is recommended (current guideline is maximum once a week). In Poland, samples of salmon were examined in 2005, 2006 and again in The results from these have not resulted in any marketing restrictions Disease outbreaks In coastal and offshore waters there are no known health issues that directly affect salmon fisheries. However, as described further in Section 3.4.3, disease outbreaks with potential local impact have in recent years been reported from several rivers in Finland, Sweden Poland and Latvia.

61 ICES WGBAST REPORT Table Nominal catches, discards (including seal-damaged salmon) and unreported catches of Baltic Salmon in tonnes round fresh weight, from sea, coast and river by country in in subdivisions The estimation method for discards and unreported catches are different for years and (90% PI = probability interval). Year Reported catches by country Reported catches Non commercial catch. Discard Total unreported catches 3) Total catches (included in Total Denmark Es tonia Finland Germany Latvia Lithuania Poland 1) Russia Sweden USSR total reported) median 90% PI median 90% PI median 90% PI na na na 13 na na na na na na na na na 17 na na na na na na na na na 20 na na na na na na na na na 10 na na na na na na na na na 7 na na na na na na na na na 6 na na na na na na na na na 4 na na na na na na na na na 4 na na na na na na na na na 22 na na na na na na )

62 56 ICES WGBAST REPORT 2018 Table Continued All data from includes sub-divisions 24-32, while it is more uncertain in which years sub-divisions are included. The catches in sub-divisions are normally less than one ton. From 1995 data includes sub-divisions Catches from the recreational fishery are included in reported catches as follows: Finland from 1980, Sweden from 1988, Denmark from Other countries have no or very low recreational catches. Danish, Finnish, German, Polish and Swedish catches are converted from gutted to round fresh weight w by multiplying by 1.1. Estonian, Latvian, Lithuanian and Russian catches before 1981 are summarized as USSR catches. Estonian, Latvian, Lithuanian and Russian catches are reported as whole fresh weight. Sea trout are included in the sea catches in the order of 3 % for Denmark (before 1983), 3% for Estonia, Germany, Latvia, Lithuania, Russia, and about 5% for Poland (before 1997). Estimated non-reported coastal catches in Sub-division 25 has from 1993 been included in the Swedish statistics. 1) Polish reported catches are recalculated for assessment purposes (see Section 5) 2) In 1993 fishermen from the Faroe Islands caught 16 tonnes, which are included in total Danish catches. 3) Including both unreporting for all countries and the estimated additional Polish catch

63 ICES WGBAST REPORT Table Nominal catches, discards (incl. seal damaged salmon) and unreported catches of Baltic Salmon in numbers from sea, coast and river by country in Subdivisions The estimation method for discards and unreported catches are different for years and (90% PI = probability interval). Year Country reported Discard Estimated Polish Total unreported catches 2) Total catches Denmark Es tonia Finland Germany Latvia Lithuania Poland Russia Sweden total median 90% PI misreported catch median 90% PI median 90% PI ) All data from , includes sub-divisions 24-32, while it is more uncertain in which years sub-divisions are included. The catches in sub-divisions are normally less than one tonnes. From 1995 data includes sub-divisions Catches from the recreational fishery are included in reported catches as follows: Finland from 1980, Sweden from 1988, Denmark from Other countries have no, or very low recreational catches. 1) In 1993 Fishermen from the Faroe Islands caught 3200 individuals, which is included in the total Danish catches. 2) Including both unreporting for all countries and the estimated additional Polish catch

64 58 ICES WGBAST REPORT 2018 Table Nominal catches of Baltic Salmon in tonnes round fresh weight, from sea, coast and river by country and region in S=sea, C=coast, R=river. Main Basin (Sub-divisions 22-29) Year Denmark Finland Germany Poland Sweden USSR Total S S+C S S S R S C+R S C+R GT

65 ICES WGBAST REPORT Main Basin (subdivisions 22 29) Year Denmark Es tonia Finland Germany Latvia Lithuania Poland Russia Sweden Total S C S C S C R S S C R S C R S C R S C R S C R S C R GT * na na 45 na na * na na 38 na na * na na 76 na na * na na 72 na na * na na 162 na na * na na 137 na na * na na 267 na na * na na 93 na na * na na 80 na na * na na 195 na na * na na 77 na na * na na 170 na na * na na 191 na na * na na 184 na na * na na na * na na na na * na na na

66 60 ICES WGBAST REPORT 2018 Table Continued. Gulf of Bothnia Main Basin+Gulf of (Sub-divisions 30-31) Bothnia (Sub-divs. Year Denmark Finland Sweden Total 22-31) Total S S S+C C S C R S C R GT S C+R GT Gulf of Bothnia Main Basin + Gulf of ( Sub-divisions 30-31) Bothnia (Sub-divisions Year Finland Sweden Total 22-31) Total S C R S C R S C R GT S C R GT )

67 ICES WGBAST REPORT Table Continued. Gulf of Finland (Sub-division 32) Sub-division Year Finland USSR Total S S+C C S C+R S C+R GT Gulf of Finland (Sub-division 32) Year Es tonia Finland Russia Total Sub-division Total S C R S C R C R S C R GT S C R GT ) All data from , includes sub-divisions 24-32, while it is more uncertain in which years sub-divisions are included. The catches in sub-divisions are normally less than one tonnes. From 1995 data includes sub-divisions Catches from the recreational fishery are included as follows: Finland from 1980, Sweden from 1988, Denmark from Other countries have no, or very low recreational catches. Danish, Finnish, German, Polish and Swedish catches are converted from gutted to round fresh weight w by multiplying by 1.1. Estonian, Latvian, Lithuanian and Russian catches before 1981 are summarized as USSR catches. Estonian, Latvian, Lithuanian and Russian catches are reported as hole fresh weight. Sea trout are included in the sea catches in the order of 3 % for Denmark (before 1983), 3% for Estonia, Germany, Latvia, Lithuania, Russia, and about 5% for Poland (before 1997). Estonian sea catches in Sub-division 32 in include a small quantity of coastal catches. Estimated non-reported coastal catches in Sub-division 25 has from 1993 been included in the Swedish statistics. 1) In 1993 fishermen from the Faroe Islands caught 16 tonnes, which are included in total Danish catches.

68 62 ICES WGBAST REPORT 2018 Table Nominal catches of Baltic Salmon in numbers, from sea, coast and river by country and region in S=sea, C=coast, R=river. Main Basin (subdivisions 22 29) Year Denmark Es tonia Finland Germany Latvia Lithuania Poland Russia Sweden Main Basin (sub-divisions 22-29) Total S C S C S C R S C S C R S C R S C R S C S C R S C R GT

69 ICES WGBAST REPORT Table Continued. Gulf of Bothnia ( Sub-divisions 30-31) Main Basin + Gulf of Bothnia Year Finland Sweden Total (Sub-divisions 22-31) Total S C R S C R S C R GT S C R GT

70 64 ICES WGBAST REPORT 2018 Table Continued. Gulf of Finland (Sub-division 32) Year Es tonia Finland Russia Total S C R S C R C 1) R S C R GT S C R GT Data from the recreational fishery are included in Swedish and Finnish data. Recreational fishery are included in Danish data from Other countries have no, or very low recreational catches. In 1996 sea trout catches are included in the Polish catches in the order of 5%. 1) Russian coastal catches have in earlier reports been recorded as sea catches. Sub-divisions Total

71 ICES WGBAST REPORT Table Nominal catches of Baltic salmon in tonnes round fresh weight and numbers from sea, coast and river, by country and subdivisions in Subdivisions S=sea, C=coast, R=river, W=weight (tonnes), N=number of fish. SD Fishery - DE DK EE FI LT LV PL RU SE Grand Total 22 S W 0 0 N 7 7 C W 0 0 N S W N S W N C W N S W N C W N R W 0 0 N S W N S W N C W N R W 3 3 N C W 0 0 N S W 0 0 N 3 3 C W N R W 2 2 N S W N C W N R W 0 0 N S W 0 0 N C W N R W N C W N R W N S W 1 1 N C W N R W N C W N Total S+C+R W N Total 32 S+C+R W N S W N C W Grand Total N R W N S+C+R W N

72 66 ICES WGBAST REPORT 2018 Table Non-commercial catches of Baltic Salmon in numbers from sea, coast and river by country in in subdivisions and Subdivision 32. (S = Sea, C = Coast, PI = probability interval). Sub-divisions Year Denmark Es tonia Finland Germany Latvia Lithuania Poland Russia Sweden S+C River Grand S+C S+C S+C (95% PI) River S+C S+C River S+C River S+C River S+C River S+C River Total Total Total 1997 na na na na na na na na na 0 na na na 0 na na na 9040 (±6370) 5100 na na na na na na 0 na na na na 9040 (±6370) 400 na na (±5490) 4150 na na na (±5490) 3750 na na 3640 (±1070) 3925 na na 3640 (±1070) 4525 na na (±7300) 5950 na na (±7300) 6725 na na 6180 (±3710) 2640 na na 6180 (±3710) 3590 na (±4380) na na 9090 (±4380) 7934 na na 3270 (±3600) 4910 na na 3270 (±3600) 5475 na na 3090 (±2830) na (±2830) na (±5450) na (±5450) na (±4000) na (±4000)

73 ICES WGBAST REPORT Sub-division 32 Sub-division Year Es tonia Finland Russia S+C River Grand S+C River GT S+C River S+C (95% PI) River S+C River Total Total Total Total Total 1997 na na na na na na na na na 5150 (±3630) 5100 na na (±3630) na (±5780) na (±5780) na 2550 (±750) na 2550 (±750) na 3090 (±1430) (±1430) (±110) (±110) (±350) (±350) (±400) (±400) (±3170) (±3170) (±3270) (±3270) (±3270) (±3000 )

74 68 ICES WGBAST REPORT 2018 Table Nominal catches (commercial) of Baltic Salmon in numbers from sea and coast, excluding river catches, by country in and compared with TAC. Subdivisions Years include also sea catch of the recreational fishery in Sweden and Finland. Baltic Main Basin and Gulf of Bothnia (Sub-divisions 22-31) Year Fishing Nation Total TO TAL Landing of Denmark Estonia Finland Germany Latvia Lithuania Poland Russia Sweden TAC TAC (in %) ,

75 ICES WGBAST REPORT Gulf of Finland (Sub-division 32) Year Fishing Nation Total EC Landing of Estonia Finland TAC TAC (in %) Russia All data from , includes sub-divisions 24-32, while it is more uncertain in which years sub-divisions are included Russia are not included in the TAC in Sub-division 31. The catches in sub-divisions are normally less than one tonnes. From 1995 data includes sub-divisions Estonia: Offshore catches reported by numbers, coastal catches converted from weight. Catches from the recreational fishery are included as follows: Finland from 1980, Sweden from 1988, and Denmark from Other countries have no, or very low recreational catches. Estimated non-reported coastal catches in sub-division 25, have from 1993 been included in the Swedish catches. Sea trout are included in the sea catches in the order of 5% for Poland before ) In 1993 Polish, Russian and Faroe Islands numbers are converted from weight. 2) In 1993 Fishermen from Faroe Islands caught 3100 salmons included in the total Danish catches. 3) In 1998 German numbers are converted from weight.

76 70 ICES WGBAST REPORT 2018 Table Summary of the uncertainty associated to fisheries dataseries according to the expert opinions from different countries backed by data (D) or based on subjective expert estimation (EE). The conversion factors (mean) are proportions and can be multiplied with the nominal catch data in order to obtain estimates for unreported catches and discards, which altogether sum up to the total catches. Driftnet fishing has been closed from Finland and Sweden have had no offshore fishing for salmon after Parameter Country Year Source min mode max mean SD DK EE FI EE PL EE Share of unreported catch in offshore fishery 2014 EE EE EE SE EE FI EE EE PL EE Share of unreported catch in coastal fishery EE SE EE SE EE SE EE FI EE Share of unreported catch in river fishery PL EE EE SE EE Average share of unreported catch in river fishery Others DK D, EE D, EE Share of discarded undersized salmon in longline fishery FI D, EE PL D D SE D, EE Average share of discarded undersized salmon in longline fisheryothers DK EE Mortality of discarded undersized salmon in longline fishery FI EE SE EE PL D, EE Average mortality of discarded undersized salmon in longline fis Others Share of discarded undersized salmon in driftnet fishery DK EE, D FI D Average share of discarded undersized salmon in driftnet fisheryothers Mortality of discarded undersized salmon in driftnet fishery DK EE, D FI EE Average mortality of discarded undersized salmon in driftnet fishothers FI EE Share of undersized salmon in trapnet fishery (released back to s 2017 D SE EE, D Average share of discarded undersized salmon in trapnet fishery Others Mortality of discarded undersized salmon in trapnet fishery FI EE, D SE EE, D Average mortality of discarded undersized salmon in trapnet fishothers FI D D SE EE, D DK EE, D Share of discarded sealdamaged salmon in longline and offshore gilnet fishery Share of discarded sealdamaged salmon in driftnet fishery and other open sea gillnet fishery (GNS in Poland) Share of discarded sealdamaged salmon in trapnet fishery EE EE, D EE D PL D EE, D D DK EE, D FI D PL EE,D D FI D SE EE, D

77 ICES WGBAST REPORT Table Estimated number of discarded undersized salmon and discarded seal damaged salmon by management unit in Estimates of discarded undersized salmon are proportional to nominal catches by the conversion factors (see Table 2.3.1). Estimates of seal damages age-based partly on the logbook records (Finland and Sweden) and partly to the estimates proportional to nominal catches by conversion factors. Estimates should be considered as a magnitude of discards. Discard undersized Discard seal damaged Management unit Year Driftnet Longline Trapnet Other gears Driftnet Longline TrapnetOther gears Total Disc_GND Disc_LLD Disc_TN Disc_OT Seal_GND Seal_LLD Seal_TN Seal_OT SD * * * Disc_GND Disc_LLD Disc_TN Disc_OT Seal_GND Seal_LLD Seal_TN Seal_OT SD * * * * There is a discard ban since year 2015, but data from reports of caught undersized fish are not available.

78 72 ICES WGBAST REPORT 2018 Table Number salmon and sea trout in the catch of sampled Polish longline vessels in (SAL=salmon and TRS=sea trout). SamplingType Year Month Trip_id SAL TRS % SAL Sea sampling % % % % % % % 2009 Total % % % % % % 2010 Total % % % % % % % 2011 Total % % % % % 2012 Total % % % % % % % % % % 2013 Total % 2014 Total % 2015 Total % 2016 Total % % % % % 2017 Total % % % % % Sea sampling Total % Market sampling % 2009 Total % % 2010 Total % Market sampling Total % Grand Total %

79 ICES WGBAST REPORT Table Estimated number of seal-damaged salmon, dead discard of undersized salmon, unreported salmon in sea and river fisheries and misreported salmon by country and management unit in Estimates should be considered as order of magnitude. Denmark Estonia Finland Germany Latvia Lithuania Poland Russia Sweden Seal damage Discard Unreported sea Seal damage Discard Unreported sea Unreported river Seal damage Discard Unreported sea Unreported river Seal damage Discard Unreported sea Seal damage Discard Unreported sea Unreported river SD SD Seal damage Discard Unreported sea Unreported river Seal damage Discard Unreported sea Unreported river Misreporte d Seal damage Discard Unreported sea Unreported river Seal damage Discard Unreported sea Unreported river

80 74 ICES WGBAST REPORT 2018 Table Fishing efforts of Baltic salmon fisheries at sea and at the coast in in subdivisions (excluding Gulf of Finland). The fishing efforts are expressed in number of geardays (number of fishing days times the number of gear) per year. The yearly reported total offshore effort refers to the sum of the effort in the second half of the given year and the first half of the next coming year (e.g. effort in second half of effort in first half of 1988 = effort reported in 1987, etc.). The coastal fishing effort on stocks of assessment unit 1 (AU 1) refers to the total Finnish coastal fishing effort and partly to the Swedish effort in Subdivision (SD) 31. The coastal fishing effort on stocks of AU 2 refers to the Finnish coastal fishing effort in SD 30, and partly to the Swedish coastal fishing effort in SD 31. The coastal fishing effort on stocks of AU 3 refers to the Finnish and Swedish coastal fishing effort in SD 30. AU 1 AU 2 AU 3 Offshore Offshore Commercial Commercial Commercial Commercial Commercial Commercial Commercial Year driftnet longline coastal coastal coastal coastal coastal coastal coastal driftnet trapnet other gear trapnet other gear trapnet other gear

81 ICES WGBAST REPORT Table Number of fishing vessels in the offshore fishery for salmon by country and area from Number of fishing days divided in four groups, 1 9 fishing days, fishing days, fishing days and more than 40 fishing days (from 2001 also and >80 days, total six groups). Subdivisions and Subdivision 32. Year Area Country Effort in days per ship > Total Number of fishing vessels 1999 Sub-divisions Denmark Estonia na na Finland Germany na na na na na Latvia Lithuania na na na na na Poland Russia Sweden Total Sub-div. 32 Finland Sub-divs Total Year Area Country Effort in days per ship > Total Number of fishing vessels 2000 Sub-divisions Denmark Estonia Finland Germany na na na na na Latvia Lithuania na na na na na Poland Russia na na na na na Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2001 Sub-divisions Denmark Estonia Finland Germany na na na na na na na Latvia Lithuania na na na na na na na Poland Russia na na na na na na na Sweden Total Sub-div. 32 Finland Sub-divs Total

82 76 ICES WGBAST REPORT 2018 Table Continued. Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2002 Sub-divisions Denmark Estonia Finland na na na na na na 0 Germany na na na na na na na Latvia Lithuania na na na na na na 0 Poland na na na na na na 50 Russia na na na na na na 0 Sweden Total Sub-div. 32 Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2003 Sub-divisions Denmark Finland Germany na na na na na na na Latvia Lithuania na na na na na na 0 Poland Russia na na na na na na 0 Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2004 Sub-divisions Denmark Finland Germany n.a. n.a. n.a. n.a. n.a. n.a. n.a. Latvia Lithuania Poland Russia na na na na na na n.a. Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total

83 ICES WGBAST REPORT Table Continued. Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2005 Sub-divisions Denmark Finland Germany na na na na na na na Latvia Lithuania Poland Russia na na na na na na na Sweden Total Sub-div. 32 Estonia na na na na na na na Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2006 Sub-divisions Denmark Finland Germany na na na na na na na Latvia Lithuania Poland na na na na na na na Russia na na na na na na na Sweden Total Sub-div. 32 Estonia na na na na na na na Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2007 Sub-divisions Denmark Finland Germany na na na na na na na Latvia Lithuania Poland na na na na na na na Russia na na na na na na na Sweden Total Sub-div. 32 Estonia na na na na na na na Finland Sub-divs Total

84 78 ICES WGBAST REPORT 2018 Table Continued. Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2008 Sub-divisions Denmark Finland Germany na na na na na na na Latvia Lithuania Poland Russia na na na na na na na Sweden Total Sub-div. 32 Estonia na na na na na na na Finland Sub-divs Total Continued Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2009 Sub-divisions Denmark Finland Germany na na na na na na na Latvia Lithuania Poland Russia na na na na na na na Sweden Total Sub-div. 32 Estonia na na na na na na na Finland Sub-divs Total Continued Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2010 Sub-divisions Denmark Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total

85 ICES WGBAST REPORT Continued Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2011 Sub-divisions Denmark Finland Germany Latvia Lithuania Poland Russia Sweden Continued Total Sub-div. 32 Estonia Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2012 Sub-divisions Denmark Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total Continued Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2013 Sub-divisions Denmark Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total

86 80 ICES WGBAST REPORT 2018 Continued Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2014 Sub-divisions Denmark n.a. n.a. n.a. n.a. n.a. n.a. n.a Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2015 Sub-divisions Denmark n.a. n.a. n.a. n.a. n.a. n.a. n.a Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2016 Sub-divisions Denmark n.a. n.a. n.a. n.a. n.a. n.a. n.a Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total Year Area Country Effort in days per ship >80 days Total Number of fishing vessels 2017 Sub-divisions Denmark n.a. n.a. n.a. n.a. n.a. n.a. n.a Finland Germany Latvia Lithuania Poland Russia Sweden Total Sub-div. 32 Estonia Finland Sub-divs Total

87 ICES WGBAST REPORT Table Catch per unit of effort (cpue), expressed as number of salmon caught per 100 nets and per 1000 hooks, by fishing season in the Danish, Estonian, Finnish, Latvian, Russian and Swedish offshore fisheries in the Main Basin, in the Gulf of Bothnia, and in the Gulf of Finland from 1980/1981 to 2017 (Denmark from 1983/84 to 2016). No data included from Polish offshore fisheries, due to that work on needed quality assurances is discussed. Fishing Denmark season Sub-divisions Sub-divisions Driftnet Longline Driftnet Longline 1983/ / n.a / n.a / n.a / / / / / / / / / / / / / / n.a. 0.0 n.a n.a. 0.0 n.a n.a. 0.0 n.a.

88 82 ICES WGBAST REPORT 2018 Fishing Finland season Sub-divisions Sub-divisions Sub-division 32 Driftnet Longline Driftnet Longline Driftnet Longline 1980/ n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / n.a / / / / / / /

89 ICES WGBAST REPORT Table Continued. Fishing Es tonia Latvia season Sub-divisions Sub-divisions and Driftnet Driftnet Driftnet Longline Driftnet Longline Driftnet Longline 1980/1981 n.a. n.a n.a. 0.0 n.a. n.a. 1981/1982 n.a. n.a n.a. 0.0 n.a. n.a. 1982/1983 n.a. n.a n.a. 0.0 n.a. n.a. 1983/1984 n.a. n.a n.a. 0.0 n.a. n.a. 1984/1985 n.a. n.a n.a. 0.0 n.a. n.a. 1985/1986 n.a. n.a n.a /1987 n.a. n.a n.a /1988 n.a. n.a n.a /1989 n.a. n.a n.a /1990 n.a. n.a n.a /1991 n.a. n.a n.a /1992 n.a. n.a n.a / n.a / n.a / n.a / n.a / n.a / n.a / / /2001 n.a. n.a n.a. n.a n.a. n.a n.a. n.a n.a. n.a n.a. n.a n.a. n.a n.a. n.a n.a All data from 1980/ /1994 includes sub-divisions 24-32, while it is more uncertain which years sub-divisions are included. The catches in sub-division are normally less than one ton. From 1995 data includes sub-divisions Estonian data from sub-div has earlier been given as sub-div Russia Sub-division Sweden Sub-divisions

90 84 ICES WGBAST REPORT 2018 Table Catch per unit of effort (cpue) number of salmon per trapnet days in the Finnish fisheries in Subdivision and trapnet effort and Effort Cpue

91 ICES WGBAST REPORT Table Number of tagged hatchery-reared and wild salmon smolts released in assessment units 1, 2 or 3 and used in the salmon assessment (data not updated since 2012). RELEASE YEAR Reared salmon stocked in rivers without natural reproduction Reared salmon stocked in rivers with natural reproduction Wild salmon AU1 AU2 AU3 AU1 AU2 AU3 AU Table Number of Carlin-tagged salmon released into the Baltic Sea in Country Total Denmark 0 Estonia 0 Finland 1,990 1,990 Sweden 5,000 5,000 Poland 0 Russia 0 Lithuania 0 Germany 0 Latvia 2,000 2,000 Total , , ,990

92 86 ICES WGBAST REPORT 2018 Table Releases of adipose finclipped salmon in the Baltic Sea and the number of adipose finclipped salmon registered in Latvian (subdivisions 26 and 28) offshore catches Releases of adipose fin clipped Latvian offshore catches salmon, Sub-divs Sub-divs. 26 and 28 Year Adipose fin Sample Parr Smolt clipped salmon N in % , , , ,149 69, , , , , , , , , , , , , , , , , ,165, , , , , , , ,626, , , , , ,004, , ,284, , , , , , , , , ,500 2,124, ,714 1,753, ,126, ,984 2,450, ,731 2,325, ,123 2,084, ,496 2,341, ,094 1,971, ,200 1,768, ,670 2,038, ,361 2,690, ,113 2,777, ,364 3,728,

93 ICES WGBAST REPORT Table Adipose finclipped salmon released in the Baltic Sea area in 2017 (and clipped or unclipped tagged using other methods). Country Species Stock Age Number Subparr smolt division River Other tagging Estonia salmon Daugava 2 yr 10,500 Pärnu T-bar salmon Kunda 1 yr ,500 Purtse 32 salmon Kunda 2 s 5,200 Purtse 32 salmon Kunda 2 yr 5,500 Purtse 32 salmon Kunda 1 yr 3,500 5,500 Selja 32 salmon Kunda 2 yr 5,700 Selja T-bar salmon Kunda 1 yr 3,100 5,500 Loobu 32 salmon Kunda 2 yr 5,200 Loobu T-bar salmon Kunda 1 yr 13,100 11,800 Valgejõgi 32 salmon Kunda 2 yr 5,100 Valgejõgi T-bar salmon Kunda 2 s 16,000 Valgejõgi 32 salmon Kunda 2 yr 5,400 Jägala T-bar salmon Kunda 2 yr 5,400 Pirita T-bar Russia salmon Neva 1 yr Gladyshevka T-bar (Finnish tags) Finland salmon Tornionjoki 2 yr 3,125 Aurajoki 29 salmon Tornionjoki 2 yr 5,208 Eurajoki 30 salmon Tornionjoki 1 yr 10,730 Kokemäenjoki 30 salmon Tornionjoki 2 yr 13,863 Kokemäenjoki 30 salmon Iijoki 2 yr 26,756 Kokemäenjoki 30 salmon Iijoki 1 yr 19,230 Kiiminkijoki 31 salmon Iijoki 2 yr 36,144 Kiiminkijoki ARS salmon Iijoki 2 yr 282,104 Iijoki T-bar, ARS salmon Tornionjoki 2 yr 381,829 Kemijoki Carlin, 997 T-bar, ARS salmon Iijoki 2 yr 342,017 Kemijoki Carlin, 966 T-bar, ARS salmon Oulujoki 1 yr Oulujoki 31 salmon Oulujoki 2 yr 218,810 Oulujoki T-bar salmon Neva 2 yr 44,689 Kymijoki T-bar, 3060 PIT-tag salmon Neva 2 yr Karjaanjoki/Mustionjoki radio-transmitters salmon Neva 2 yr 48,276 at sea T-bar Sweden salmon Luleälven 1 yr 224,567 Luleälven 31 salmon Luleälven 2 yr 296,249 Luleälven Carlin salmon Skellefteälven 1 yr 126,753 Skellefteälven 31 salmon Skellefteälven 1 yr 6,156 Gideälven 30 salmon Umeälven 1 yr 26,314 Umeälven PIT-tag salmon Umeälven 2 yr 58,872 Umeälven PIT-tag salmon Rickleån wild smolts Rickleån PIT-tag salmon Vindelälven wild smolts Vindelälven PIT-tag salmon Ångermanälven 1 yr 189,618 Ångermanälven 30 salmon Ångermanälven 2 yr 47,622 Ångermanälven 30 salmon Indalsälven 1 yr 298,300 Indalsälven 30 salmon Ljusnan 1 yr 166,128 Ljusnan 30 salmon Testeboån wild smolts Testeboån PIT-tag salmon Dalälven 1 yr 5,625 Dalälven 30 salmon Dalälven 1 yr 136,958 Dalälven PIT-tag salmon Dalälven 2 yr 17,083 Dalälven 30 salmon Dalälven 1 yr 6,000 Motala ström 27 salmon Dalälven 1 yr 12,000 Stockholms ström 27 salmon Mörrumsån wild smolts Mörrumsån PIT-tag Latvia salmon Daugava 1 yr 399,658 Daugava Carlin salmon Daugava 2 s Daugava 28 salmon Gauja 1 yr 155,780 Gauja 28 salmon Venta 1 yr 61,075 Venta 28 Total salmon 166,364 3,728,054

94 88 ICES WGBAST REPORT 2018 Table List of Baltic salmon stocks included in the genetic stock proportion estimation of catches. Stock Sampling year Propagation N 1 Tornionjoki, W 2011 Wild Tornionjoki, H 2006, 2013 Hatchery Simojoki 2006, 2009, 2010 Wild Iijoki 2006, 2013 Hatchery Oulujoki 2009, 2013 Hatchery Kalixälven 2012 Wild Råneälven 2003, 2011 Wild Luleälven 2014 Hatchery 90 9 Piteälven 2012 Wild Åbyälven 2003, 2005 Wild Byskeälven 2003 Wild Kågeälven 2009 Wild Skellefteälven 2006, 2014 Hatchery Rickleå 2012, 2013 Wild Säverån 2011 Wild Vindelälven 2003 Wild Umeälven 2006, 2014 Hatchery Öreälven 2003, 2012 Wild Lögdeälven 1995, 2003, 2012 Wild Ångermanälven 2006, 2014 Hatchery Indalsälven 2006, 2013 Hatchery Ljungan 2003, 2014 Wild Ljusnan 2013 Hatchery Testeboån 2014 Wild Dalälven 2006, 2014 Hatchery Emån 2003, 2013 Wild Mörrumsån 2010, 2011, 2012 Wild Neva, Fi 2006 Hatchery Neva, Rus 1995 Hatchery Luga 2003, 2011 Wild, Hatchery Narva 2009 Hatchery Kunda 2009, 2013 Wild, Hatchery Keila 2013 Wild Vasalemma 2013 Wild Salaca 2007, 2008 Wild Gauja 1998 Hatchery Daugava 2011 Hatchery Venta 1996 Wild Neumunas Hatchery 166 Total 4453

95 ICES WGBAST REPORT Table Medians and probability intervals of stock group proportion estimates (%) in Atlantic salmon catch samples in the Gulf of Finland based on microsatellite (DNA) and smolt age classes. Proportions of wild salmon estimated by scale reading for the same samples are given for comparison (with range for cases where prop. wild has been calculated with/without fish with missing data). F Finnish catches. Catch data from 2014 are calculated also separately for two sampling sites at eastern (Loviisa area) and western (Inkoo area) part of the coast. Catch data from 2017 were divided in two temporal samples (A, B) with catch dates given in the table. Gulf of Bothnia, wild 2.5 % 97.5 % G. of Bothnia, hatchery, FIN 2.5 % 97.5 % G. of Bothnia, hatchery, SWE 2.5 % 97.5 % Gulf of Finland, wild 2.5 % 97.5 % Gulf of Finland, hatchery 2.5 % 97.5 % Western Main B., wild, SWE 2.5 % 97.5 % Eastern Main Basin 2.5 % 97.5 % Gulf of Finland 2009 F % 2010 F % 2011 F % 2014 F % 2015 F % 2017 F % Mean Sample size Sampling date Scale reading - wild % 2014 F East % 2014 F West % 2017 F A % 2017 F B %

96 90 ICES WGBAST REPORT 2018 Table Medians of individual river-stock proportion estimates in Finnish Atlantic salmon catches from the Gulf of Finland. Data shown for individual salmon stocks, which had any contribution to Finnish catches. (for rounding purposes: - = no value at all, 0 = values between 0 and 0,5). Tornionj.Wild Tornionj. Hatch. Simojoki, W Iijoki, H Oulujoki, H Kalixälven, W Råne, W Luleälven, H Byskeälven, W Kågeälven, W Skellefteälven, H Ricleå, W Sävarån, W Gulf of Finland Mean Vindelälven, W Umeälven, H Indalsälven, H Emån, W Mörrumsån, W Neva-FI, H Neva-RU, H Kunda, W Salaca, W Daugava, H Neumunas, H Sample size Sampling dates 2014 EAST WEST A B

97 ICES WGBAST REPORT Table Atlantic salmon catches from the Gulf of Finland by assessment units, from 2009 to Estimate AU1 Wild; Fin, Swe AU1 Hatchery, Fin AU2 Wild, Swe AU2 Hatchery, Swe AU3 Wild, Swe AU3 Hatchery, Swe AU4 Wild, Swe AU6 Wild, Est, Rus AU6 Hat., Est, Fin, Rus AU5 Wild, Lat, Lit AU5 Hatchery, Lat, Pol Year 2009 Median ,50 % ,50 % Median ,50 % ,50 % Median ,50 % ,50 % Median ,50 % ,50 % Median ,50 % ,50 % Overall mean NO ASSESSMENT UNIT RIVERS COUNTRY 1 AU1 Wild Simojoki, Tornionjoki; W, Kalixälven, Råne 4 Fin, Swe 2 AU1 Hatchery Tornionjoki; H, Iijoki, Oulujoki 3 Fin 3 AU2 Wild Pite, Åby, Byske, Kåge, Ricleå, Säverån, Vindel, Öre, Lögde 9 Swe 4 AU2 Hatchery Luleälven, Skellefteälven, Umeälven 3 Swe 5 AU3 Wild Ljungan, Testeboån 2 Swe 6 AU3 Hatchery Ångerman, Indals, Ljusnan, Dalälven 4 Swe 7 AU4 Wild Emån, Mörrumsån 2 Swe 8 AU6 Wild Luga, Kunda, Keila, Vasalemma 4 Est, Rus 9 AU6 Hatchery Neva-FI (wild and hatchery), Neva-RUS, Narva 3 Est, Fi, Rus 10 AU5 Wild Salaca, Gauja, Venta, Neumunas 4 Lat, Lit 11 AU5 Hatchery Daugava 1 Lat

98 92 ICES WGBAST REPORT 2018 Table Prior proportion of 1 2 year old smolts in the Atlantic salmon baseline stocks used for Baltic salmon catch composition analysis for River stock Smolt age 2.5% Median 97.5% Years 1 Tornionjoki, W 1-2 years 4,3 5,6 7, Tornionjoki, H 1-2 years 99,8 100,0 100,0 All 3 Simojoki 1-2 years 32,9 42,2 51, Iijoki 1-2 years 99,8 100,0 100,0 All 5 Oulujoki 1-2 years 99,8 100,0 100,0 All 6 Kalixälven 1-2 years 3,8 5,7 7, Råneälven 1-2 years 2,7 6,2 11, Luleälven 1-2 years 99,8 100,0 100,0 All 9 Piteälven 1-2 years 16,6 20,0 23,8 All 10 Åbyälven 1-2 years 22,0 30,2 40,0 All 11 Byskeälven 1-2 years 22,4 30,7 39,5 All 12 Kågeälven 1-2 years 21,8 30,3 39,8 All 13 Skellefteälven 1-2 years 99,8 100,0 100,0 All 14 Rickleå 1-2 years 19,7 25,2 31,8 All 15 Säverån 1-2 years 19,6 25,1 31,8 All 16 Vindelälven 1-2 years 30,7 37,0 43,6 All 17 Umeälven 1-2 years 99,8 100,0 100,0 All 18 Öreälven 1-2 years 14,4 21,6 29,4 All 19 Lögdeälven 1-2 years 21,2 29,4 38,4 All 20 Ångermanälven 1-2 years 99,8 100,0 100,0 All 21 Indalsälven 1-2 years 99,8 100,0 100,0 All 22 Ljungan 1-2 years 27,8 37,4 46,4 All 23 Ljusnan 1-2 years 99,8 100,0 100,0 All 24 Testeboån 1-2 years 28,8 37,1 46,4 All 25 Dalälven 1-2 years 99,8 100,0 100,0 All 26 Emån 1-2 years 92,8 97,1 99,3 All 27 Mörrumsån 1-2 years 92,9 97,0 99,3 All 28 Neva, Fi 1-2 years 99,8 100,0 100,0 All 29 Neva, Rus 1-2 years 85,9 90,0 93,3 All 30 Luga 1-2 years 92,8 96,1 98,1 All 31 Narva 1-2 years 99,8 100,0 100,0 All 32 Kunda 1-2 years 97,7 99,0 99,7 All 33 Keila 1-2 years 97,9 99,0 99,6 All 34 Vasalemma 1-2 years 97,8 99,0 99,6 All 35 Salaca 1-2 years 97,9 99,0 99,7 All 36 Gauja 1-2 years 99,8 100,0 100,0 All 37 Daugava 1-2 years 99,8 100,0 100,0 All 38 Venta 1-2 years 99,8 100,0 100,0 All 39 Neumunas 1-2 years 99,8 100,0 100,0 All

99 ICES WGBAST REPORT Trolling catches of salmon (SD 22-28) Trolling catches of salmon (SD 29-31) Trolling catches of salmon (SD 32) Figure Combined expert estimates of total trolling catches in numbers (including retained fish and a 25% post-release mortality for released fish) for Baltic salmon, (medians with 95% p.i.).

100 94 ICES WGBAST REPORT Recreational catches of salmon from rivers (SD 22-31) Recreational catches of salmon from rivers (SD 32) Figure Recreational river catches for Baltic salmon, Catch in numbers.

101 ICES WGBAST REPORT % 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% AN GND GNS LLD LLS OT TN Blank Figure Proportion of catch of Baltic salmon by weight in different types of gear Variables: GND=driftnet, AN=angling, GNS=gillnet, LLD=longline, OT=other, TN=trapnet. Blank=unidentified gear. Commercial and total recreational salmon catches (SD 22-32) Figure Commercial (black columns) and recreational (grey columns) catches of salmon in numbers in years for all subdivisions. The recreational catch proportion of the total catch (commercial and recreational) is shown for the same time period (grey line). The recreational catches include all components (river, coastal and sea), also the expert opinion trolling estimates depicted in Figure

102 96 ICES WGBAST REPORT 2018 Figure Catches of salmon in % of TAC in For years ( for Gulf of Finland) it is not possible to divide the total reported catch into commercial and recreational catches. Estimates of discards and unreported catches are presented separately in Table

103 ICES WGBAST REPORT Offshore driftnet fisheries Offshore longline fisheries Effort Year Figure Fishing effort in Main Basin offshore fisheries (x 1000 geardays) in Coastal driftnet fisheries Coastal trapnet fisheries Coastal gillnet fisheries Effort Year Figure Effort in Main Basin and Gulf of Bothnia coastal fisheries (x 1000 geardays) in

104 98 ICES WGBAST REPORT A.1 A.2 A.3 A Weight (kg) Year Figure Mean weight of spawners in the Gulf of Bothnia by year. Values in from catch statistics in the Rivers Oulu and Torne. Values in are from Swedish tagging records and in from the Finnish catch sampling data. Weights of A.4 salmon based on small material in some years in

105 ICES WGBAST REPORT Figure Return rates of Finnish Carlin tagged reared salmon released in Gulf of Bothnia and Gulf of Finland in (updated in March 2018, no returns from 2013, 2015 and 2017 cohorts). Figure Recapture rate (%) of two-year-old Estonian salmon smolts tagged and released in the Gulf of Finland. Carlin tags used , T-bar anchor tags since Year on x-axis is tagging year.

106 100 ICES WGBAST REPORT 2018 Figure Number of Polish Carlin tagged salmon and return rate (%) for salmon in (updated in March 2018; no tagging after 2012).

107 ICES WGBAST REPORT Genetic distances between Atlantic salmon baseline stock samples in Tornionj. Wild 37 Tornionj. Hatch. 28 Kalixälven Simojoki 83 Iijoki 62 Råne 81 Oulujoki Kågeälven 48 Åbyälven 100 Byskeälven Säverån 97 Öreälven 99 Lögde Luleälven 91 Piteälven Skellefteälven 81 Ricleå Vindelälven 100 Umälven 82 Ångermanälven Indalsälven 98 Ljungan Ljusnan 47 Testeboån 99 Dalälven Emån 100 Mörrumsån Neva, Fin 100 Neva, Rus Kunda 54 Keila13 25 Vasalemma Luga 29 Narva 31 Daugava 28 Gauja 36 Salaca 13 Venta 71 Neumunas Figure Neighbour joining dendrogram (based on Nei s pairwise DA genetic distances) depicting genetic relationships among Atlantic salmon baseline samples for catch analysis. Numbers represent percentage support values based on 1000 bootstraps.

108 102 ICES WGBAST REPORT % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % Gulf of Finland, Neva G. of Bothnia, hatchery, SWE G. of Bothnia, hatchery, FIN Gulf of Bothnia, wild Figure Proportions of Atlantic salmon stock groups in Finnish salmon catches from the Gulf of Finland. Note that Gulf of Finland wild and hatchery stocks are included in the same group.

109 ICES WGBAST REPORT River data on salmon populations The Baltic salmon rivers are divided into four main categories: wild, mixed, reared and potential. Details on how rivers in countries and assessment units (AU:s) are classified into these four categories are given in the Stock Annex (Annex 2). According to the 2018 ToR:s (Section 1.1) the group should review the list of Baltic Sea wild salmon rivers in Annex I of the EC Multiannual plan on Baltic Sea salmon and review existing rivers in Annex I and identify if any other existing rivers with self-sustaining wild salmon populations with no or limited release of reared salmon not currently included on the list. The Annex I of the EC Multiannual plan was drafted in Following that year, the formerly potential salmon rivers Testeboån (AU 3) and Kågeälven (AU 2) in Sweden received status as wild, as they had fulfilled criteria previously set up by WGBAST (ICES, 2008d). The original salmon populations in Testeboån and Kågeälven became extinct in the 1960s and 1870s, respectively. Around 1990 reintroduction programmes based on releases of reared salmon (mainly fry) from neighbouring rivers were instigated in both rivers. The last releases of newly hatched fry occurred in 2004 (Kågeälven) and 2006 (Testeboån). Presence of salmon parr seen at electrofishing surveys in subsequent years demonstrated occurrence of natural spawning. After long enough time periods, when wild-born salmon mainly must have been offspring of salmon which themselves were also wild-born, the rivers did receive wild status by WGBAST. Further details on the upgrading of status for Testeboån and Kågeälven are given in the 2013 and 2014 working group reports (ICES, 2013; 2014). Baltic salmon rivers currently considered as potential are described in Section 3.2. At present, there are 22 such potential rivers from five countries listed (Table ). As recently highlighted in the benchmark on Baltic salmon (ICES, 2017d), there is a need to review this list of potential rivers, for example in Sweden. However, none of the current potential Baltic salmon rivers is considered to be close to fulfilling the criteria for having its status upgraded to wild. Among the 13 Baltic salmon rivers currently classified as mixed (i.e. having both wild production and stocking), the present level of salmon releases in Estonian rivers Pirita and Väänä (AU 6) are already close to the threshold of less than 10% reared smolt production adopted by WGBAST as a criteria for wild rivers (Annex 2, Table A.1.2.1). Hence, if stocking would be further reduced or stopped, these rivers could become candidates for receiving wild status by WGBAST. River Pärnu in Estonia (AU 5) is currently listed as wild. However, its salmon production has remained very low for many years, and in 2012, a restoration programme including substantial annual releases of hatchery-reared juveniles was initiated. Therefore, this river should currently be considered mixed and not wild (Section 3.1.5). Likewise, salmon production in the wild river Barta/Bartuva (Latvia/Lithuania, AU 5) has remained very low for many years (salmon is often not found at electrofishing). Therefore, under the present conditions, it is questionable if this river can hold a selfsustaining population, and its status as a wild river should be assessed and possibly re-evaluated. The Nemunas river basin (tributary Zeimena, AU 5) in Lithuania was listed in the Annex I of the EC Multiannual plan, but is currently not classified as a wild salmon river.

110 104 ICES WGBAST REPORT 2018 Salmon does not reproduce in the main river, and the tributary Zeimena is the only one in the system that holds a wild original population considered as self-sustainable, whereas substantial stocking is carried out in all other tributaries having salmon. Therefore, the Nemunas river basin as a whole has so far been classified as mixed by WGBAST. It is possible, though, that the Zeimena tributary could receive status as a wild river. For this, Lithuania has to ask the working group to review the data available and take a decision (similar to what was done for Testeboån and Kågeälven). In the coming years, WGBAST plans to review and update their classification list of wild, mixed, and potential salmon rivers, according to the above information. 3.1 Wild salmon populations in Main Basin and Gulf of Bothnia Current wild salmon rivers in Main Basin and Gulf of Bothnia are listed per country and assessment unit in the Stock Annex (Annex 2) and above Rivers in assessment unit 1 (Gulf of Bothnia, SD 31) River catches and fishery During the past centuries and even during the early 1900s, AU 1 river catches were generally on a much higher level than during the late 1900s, as illustrated by catch statistics from Tornionjoki (Figure ). During the 1980s, river catches were the lowest ever recorded: only kg/year in Simojoki, and some tonnes/year in Tornionjoki and Kalixälven, indicating that the escapement to the spawning grounds was very low (Table , Figure ). In river catches increased and they peaked in 1997, with 4, 74 and 10 tonnes in Simojoki, Tornionjoki and Kalixälven, respectively. Thereafter the catches again decreased to 25% 60% of that of 1997, until two new prominent rises; first in 2008 and second in Exceptional circumstances (warm and low vs. high and cool river water) may have affected fishing success in some years, but the catches generally reflect trends in the abundance of salmon in spawning runs (Table , Figure ). In 2012, the catch in Tornionjoki was three times higher than in 2011 and exceeded for the first time 100 tonnes since the beginning of the time-series of annual catch statistics (Table ). In 2014, catch rose to 147 tonnes. Catch somewhat decreased in 2015 (131 tonnes), but rose again in 2016 and reached a new record, 161 tonnes (Table ). In 2017, however, the catch again declined to 92 tonnes. Catch levels similar to those observed in were observed in the early 20th century (Figure ). Salmon catch in Simojoki did not rise much in , which is partly due to a low fishing effort. However, in 2014 and 2015 there was a clear increase in the catch and the rising trend continued to 2016, when the catch was 1800 kilos (Table ). The 2017 catch estimate of Simojoki is not yet available, but preliminary information indicates a clear decrease also in this river. The catches in Kalixälven have decreased and in latest years do not correspond to the registered number of salmon that have passed the fishway. A special kind of fishing from boat (rod fishing by rowing) dominates salmon fishing in Tornionjoki. This fishing also occurs in Kalixälven, but there it is not as dominating as in Tornionjoki. Cpue of this fishery in Tornionjoki has increased tens of times since the late 1980s (Table ), apparently reflecting the parallel increase in the abundance of spawners in the river. The cpue has been high (over 1000 grammes/fishing day) in 1997, 2008 and , when the total river catches were also peaking. In

111 ICES WGBAST REPORT the cpue dropped to 860 g/day. Annual changes in cpue and in total river catch follow each other rather closely. In Råneälven the local administration has since 2014 utilized a seasonal catch bag limit regulation of maximum of three salmon per person and season. Both obligatory tagging of killed fish and a digital catch reporting system has been utilized to aid in enforcement. Most (80 90%) of the salmon caught with rod are released back; in 2017 a total of 56 salmon were caught, out of which 45 were released. Spawning runs and their composition In Kalixälven monitoring of migrating fish has been performed in the Jokkfall fishway since The fishway is located ca. 100 km from the sea, and not all salmon ascending river is counted. Until 1997 the fish passage was monitored by manual controls. From 1998 an electronic, infrared fishcounter, Riverwatcher (Vaki Aquaculture System Ltd, Iceland) has been used. Registration of species has been carried out during the whole migration seasons of Every species passing both up- and downstream is identified using video recording. Totally six fish species (salmon, trout, whitefish, grayling, bream, and ide) have been registered during In 2001 and 2002 over 8000 salmon passed the Kalixälven fishway. During the run in the fishway was over 6000 individuals. The run in 2011 was the lowest in the past ten years. In 2012 the run increased to the same level as in 2001 and 2002, but with the difference that number of multi-sea winter salmon was the highest recorded. In 2013, the run increased to the highest level observed when more than salmon passed the fishway. The counted runs in stayed at a lower and similar level (around 8000 salmon) but in 2017 the run decreased with nearly 40% (to about 5200) compared to the preceding years. No reared salmon (adipose finclipped) was registered in , and registrations of adipose finclipped salmon in previous years has been very few. A hydroacoustic split-beam technique was employed in to count the spawning run in Simojoki. It seems evident that these counts covered only a fraction of the total run, as there are irregularities in the river bottom at the counting site, allowing salmon to pass without being recorded. Since 2008, the split-beam technique has been replaced by an echosounder called DIDSON (Dual frequency IDentification SONar). According to the monitoring results, seasonal run size has ranged from less than 1000 up to more than 5000 fish (Table ). Spawning runs gradually increased from 2004 to , but again dropped in In 2012, the run increased fourfold from the previous year (to about 3000) and was about as high also in 2013 and 2015 (ca. 3100). In 2014 the run peaked to 3800 salmon, and in 2016 the run was record-high with 5400 salmon counted. In 2017 the run dropped to about 1900 salmon, which is the smallest number since in 2011 (Table ). A lot of back-and-forth movement of salmon has been detected in Simojoki, which erodes the accuracy of the counts. There have also been problems connected to the separation of species. The spawning runs into Tornionjoki have also been monitored using the DIDSON technique since The observed seasonal run size has ranged from (year 2010) to (year 2014) salmon (Table ). The run size in 2016 ( salmon) was almost as high as in the record year 2014 ( salmon), but as in the Simojoki, the run dropped in 2017 (about salmon). The counting site is located about 100 km upstream from the river mouth. Therefore, salmon which are either caught below the site or stay to spawn below the site must be assessed and added into the hydroacoustic count, in order to get an estimate of the total run size into the river (Lilja et

112 106 ICES WGBAST REPORT 2018 al., 2010). Also, according to auxiliary studies, a small fraction of the spawners pass the counting site via the fast-flowing mid-channel without being detected by sonars. In 2017, the total amount of spawners entering the river mouth probably was somewhere between individuals. By subtracting the river catch from this number, the 2017 spawning population in the Tornionjoki is estimated to be 25 29% smaller ( spawners). Grilse account for a minority (7 21%) of the annual spawning runs. In the spawning run into Råneälven has been monitored with an ultrasound camera called SIMSONAR. The technique is similar to that used in Tornionjoki and Simojoki. The counting site is located about 35 km upstream from the river mouth, and the counts represent the total run of salmon (no spawning areas downstream). The total counted salmon runs in 2014, 2015, 2016 and 2017 was 3756, 1004, 1454 and 1781 individuals, respectively. About catch samples have been collected from the Tornionjoki salmon fishery since the mid-1970s. Table shows sample size, sea age composition, sex composition and proportion of reared fish (identified either by the absence of adipose fin or by scale reading) of the data for the given time periods. Caught fish have generally become older, and the proportion of repeat spawners has increased in parallel with a decreasing sea fishing pressure (see Chapter 4). The strong spawning runs into Tornionjoki in were a result of fish from several smolt cohorts. In these years the proportion of females has been fairly stable, about two thirds of total biomass. The proportion of repeat spawners decreased in to 6 8%, after the record high level (14%) observed in 2014, and in 2017, the proportion decreased further to 3%. Although there is no direct evidence to prove the hypothesis, it is possible that the recent drop in the proportion of repeat spawners is due to the disease outbreak during the last 2 3 years (cf. Section 3.4.3); mortality among spawners has been higher, which reduces the amounts of kelts which survive back to the sea and potentially come to spawn again in the later years. In recent years, very few salmon with reared origin have been observed in the Tornionjoki catch samples (Table ). Parr densities and smolt trapping The lowest parr densities in AU 1 rivers were observed in the mid-1980s (Table , Figures and ). During the 1990s, densities increased in a cyclic pattern with two jumps. The second, higher jump started in Between these increases there was a collapse in densities around the mid-1990s, when also the highest M74 mortality was observed (see below). Average parr densities are nowadays 5 60 times higher than in the mid-1980s. Since the turn of the millennium, annual parr densities have varied 2 6 fold. In Simojoki, some years with higher-than-earlier densities of 0+ parr have been observed recently, but annual variation has been large and densities of older parr have not increased in this river. In the other AU 1 rivers, however, parr densities have continued to increase rather steadily. In some years, like in 2003, high densities of parr hatched despite relatively low preceding river catches (indicating low spawner abundance) in Simojoki, Tornionjoki and Kalixälven. Similarly, high densities of 0+ parr were observed in Tornionjoki in 2008 and 2011, although river catches in the preceding years were not among the highest. Possible reasons for this inconsistency include exceptionally warm and low summer-time river water, which might have affected fishing success in the river and even measurements of parr densities. In years 2006, 2013 and 2014 conditions for electrofishing were favourable because of very low river water levels, whereas they were the opposite in 2004 and These kinds of changes in electrofishing conditions may have

113 ICES WGBAST REPORT affected the results, and one must therefore be somewhat cautious when interpreting the data obtained. In Simojoki the mean density of one-summer old parr increased by about 50% from 2015 to 2016 and it continued to increase in 2017 (Table ). The 2017 density of 0+ parr (38.1 ind./100 sqm) is record high in the time-series, although most of the uppermost sites still lack 0+ parr. The density of older parr doubled from 2015 to 2016 and again doubled from 2016 to 2017 to the all-time high level of 28.4 ind./100 sq.m. In Tornionjoki the densities of 0+ parr in 2014 and 2015 were clearly higher than in any earlier year in the time-series. In 2016, the average density of 0+ parr on the sampled sites was somewhat lower than in Several flood peaks due to heavy rains prevented electrofishing on the lower and on some of the middle and upper sections of the river system. In 2017, the average density of 0+ parr increased slightly from 2016 and was the third highest in the time-series (28.5 ind./100 sqm). The average density of older parr in 2017 (16.1 ind./100 m 2 ) dropped from the two earlier years and was close to the average density level observed in Tornionjoki during this decade. In Kalixälven the density of 0+ in 2016 decreased with more than 50% compared to in 2015 and remained at a similar level in The older parr density has also decreased with more than 50% in the latest four years, and is now at the same level as in the early 2000s (Table ). In Råneälven the density of 0+ parr has decreased with about 50% in the three latest years. In 2017, it stayed at the same low level as in Older parr density also decreased compared to in the two preceding years. However, due to high water level in late autumn, only one third of the sites could be fished which may have affected the results. Smolt production has been monitored in Simojoki and Tornionjoki by annual partial smolt trapping and mark recapture experiments (see Annex 2 for methodology) since 1977 and 1987, respectively (Table ). A so-called river model (also referred to as hierarchical linear regression analysis ) has been applied to combine the information from electrofishing and smolt trapping results, to obtain updated estimates of the wild smolt production in the rivers, including years when high water flow has prevented complete smolt trapping. With a 1 3 year time-lag (needed for parr to transform to smolts) wild smolt runs have followed changes in wild parr densities. In the late 1980s, the annual estimated wild smolt run was only some thousands in Simojoki and less than in Tornionjoki (Table ). The first increase in the production occurred in the early 1990s, and a second, higher jump occurred in the turn of the millennium. Since then, smolt runs have not increased in Simojoki, while in Tornionjoki the runs have continued to increase especially during the last ten years. Since the turn of the millennium, annual estimated runs of wild smolt have exceeded and smolts with high certainty in Simojoki and Tornionjoki, respectively. Since 2008, estimates of wild smolt runs have exceeded one million smolts in the Tornionjoki. In 2017, smolt trapping was carried out in Tornionjoki; the estimated number of smolts was only about 1 million smolts, i.e. there was a drop of as high as 2 million smolts in point estimates from 2016 to 2017 (Table ). However, these estimates are very uncertain (e.g. 95% PI of 2017 estimate is million). The river model with the newest data (up to 2017) updates the 2017 smolt run for Tornionjoki to about 2.0 million (90% PI million) and predicts slightly less than 2 million smolts for the years 2018 and For Simojoki, the river model with electrofishing data up to 2017 and smolt trapping data up to 2016 estimates a smolt run of about for 2017 (90% PI ). Moreover, the river model predicts an increase to approximately

114 108 ICES WGBAST REPORT for the years 2018 and This high smolt runs have not been reported in Simojoki since the 1970s Rivers in assessment unit 2 (Gulf of Bothnia, SD 31) River catches and fishery The 2017 catches in Piteälven and Åbyälven stayed at the same low level as in previous years (Table ). The catch in Byskeälven decreased to the smallest number since the mid 1990s, reflecting a high level of catch and release (almost 80% of the caught salmon were released). In Kågeälven (wild river since 2014) the sport fishery was regulated in 2012 by the local administration to become 100% catch and release, with all fish released to be registered in the obligatory reporting system. In the period on average about 50 salmon per year (range: 18 to 92) have been caught and released in Kågeälven. In Sävarån the catches have been very low in recent years; in 2017 no salmon were caught, compared to in 2016 when 13 salmon where caught and released. The catches in Ume/Vindelälven decreased from 215 salmon (whereof 125 released) in 2016 to only 32 salmon (one released) in All reported caught salmon showed signs of disease. In Öreälven the 2017 catch decreased to 95 salmon (whereof 60 released) compared to 600 (400 released) in In Lögdeälven the catch in 2017 were 143 salmon (whereof 61 released), compared to 135 (28 released) in Spawning runs and their composition In almost all AU 2 rivers upstream migration in fishways is counted by electronic, infrared fish counters ( Riverwatcher, Vaki Aquaculture System Ltd, Iceland). In Piteälven a power plant station (the only one in the river) equipped with a fishway was built in the end of the 1960s, about 40 km from the river mouth. In 1992, the power plant company built a new ladder, and in 1998 they installed an electronic fish counter. In 2001 a camera was also installed for detection of species. The run counted is the entire run, as no salmon spawning areas exist downstream the fishway. In 2016 the counted run was the highest ever recorded (1907 salmon). In 2017 it decreased to 1455 individuals (Table , Figure ). The fish passage solution at the power station in Sikfors is complex. In the tailrace area (turbine outlet) where 250 m³/s (at maximum) is running through the turbines, the fish must detect the 15 m³/s attraction water (spill water) coming out from the old riverbed. When the fish have identified the water from the old riverbed and swum up to the spillgate area, they must also identify the outlet (2 m³/s) from the fishway. When the discharge exceeds the turbine capacity, water are spilled through the spillgates, which decreases the proportion of attraction water coming from the fishway entrance. This may cause a delay in the fish migration. In Piteälven, an ultrasound camera (Simsonar) was operated by the County Administrative Board of Norrbotten in 2015 and 2016; one kilometre below the tailrace. One purpose of the survey was to evaluate the total number of ascending salmon and sea trout below the power plant in relation to the number of fish passing the fishway. Another aim was to identify potential delays in the migration. Due to a broken storage disc, the collected data from the survey in 2016 have not yet been fully analysed. The result from 2015 revealed a delay of 3 5 weeks from when the fish passed the ultrasound camera, and were registered in the fishway. In addition, the total counted run was 22% lower in the fishway compared to the ultrasound camera. The delay accrues both in the tailrace and at the spillgate close to the outlet of the fishway. At the end of the study, close to the beginning of the spawning period, downstream migration of fish

115 ICES WGBAST REPORT was recorded with the ultrasound camera, indicating that fish were leaving the area below the entrance to the fishway. During earlier spawning runs no downstream migration occurred in the fishway, except for a few kelt at the beginning of the migration run. In Åbyälven a power plant station (the only one in the river) equipped with a fishway is located 30 km from the river mouth. In the year 2000, the power plant company installed an electronic fish counter, and in 2009 a camera was added to allow identification of species. The number of salmon passing the fishway only represents a small part of the entire run. In 2017, the counted run decreased to 108 salmon compared to 155 in 2016 (Table , Figure ). Low water levels can cause shut downs of the power plant, which makes it almost impossible for fish to enter the fishway. In autumn 2013, the power company filled pits with stones and concrete to prevent fish from getting caught in the pits when closing the spill gates. However, a test with water spill in the former river bed to study the undertaken measurers to steer salmon when spill occurs, attracted more fish into the former river bed than was counted in the fishway during the total season (approximately compared to 113 that passed the fishway). This observation strongly indicates that there are problems for salmon to find the fishway, or problems within the fishway causing fallbacks. A project has been started to find measures for optimising up- and downstream passage, and in 2017, a new entrance to the fishway was tested with no clear improvement to attract fish to the entrance of the fishway. In Byskeälven, about 40 kilometres from the river mouth, a new fishway was built in 2000 at the waterfall Fällforsen on the opposite side to the old fishway. The number of fish counted in the two fishways only represents a part of the entire run, and the waterfall is just a partial obstacle for salmon. In 2000, an electronic fish counter (Riverwatcher) was also installed in the new fishway, whereas a Poro counter (camera) was installed in the old fishway. The latter was replaced with a Riverwatcher (VAKI) in The water level in the natural waterfall at Fällfors affects the possibilities for salmon to pass the fall without being counted. In 2016, the run was the highest recorded so far with 7280 salmon counted. In 2017, the run was halved compared to in the previous year (Table , Figure ). In Rickleån the power plant company built four (two at the lowermost power plant) fishways in 2002 at the three hydropower stations located in Robertsfors, some 15 kilometres upstream from the river mouth. Fish migration is controlled using an electronic counter placed in the uppermost fishway. Before the fishways were constructed, salmon migration had been impossible since the early 1900s (for over 100 years) when the first power plant station was built. The counted number of fish is just a small part of the entire run. No salmon were counted in the fishways in compared to one, six, seven and five in In,2014 the number increased to 27 salmon, which is the largest number recorded until present. In 2017, a total of 15 salmon passed the fishways, which is at the same level as in the two past years (Table ). The water level does not affect the migration in the four fishways except when being extremely low; then the migration can decline or even stop. The fishway in Ume/Vindelälven is located at Stornorrfors, about 25 km from the sea. The original fishway built in 1960 was replaced by a new one in 2010, opened before the start of the migration season. The new technical fishway has a length of ca. 350 m, and is thus one of the longest in Europe. It is constructed to also serve as a passage gate for downstream migrating fish. It is also designed to allow monitoring of downstream

116 110 ICES WGBAST REPORT 2018 migrating smolts and kelts passing through the fishway. No spawning areas exist below the fishway, and all spawners must pass the fishway to find their spawning areas located in the main tributary Vindelälven, merging with Umeälven ca. 10 km upstream the Stornorrfors dam. The salmon run in Ume/Vindelälven is much affected by fluctuations in the amount of water in the old riverbed leading up to the fishway, which influences the possibilities for salmon and sea trout to find their way upstream. As compensation for hydropower exploitation of Umeälven, where no salmon production remains, hatchery reared smolts are released annually at Stornorrfors (Section 3.3). From the early 1970s, the total salmon run into Ume/Vindelälven has been divided into wild and reared (absence of adipose fin) salmon. In 2012, the run of wild salmon increased to 8058 which was 65% higher compared to 2011, and in 2013 the run was the highest recorded with wild salmon passing the fishway. In 2017 the run decreased with more than 50% and a total of 4100 salmon passed the fishway (Table , Figure ), whereof 3490 were wild and 610 reared. The new fishway in Ume/Vindelälven has now been used for eight years. Some construction modifications were carried out in 2013 that may have resulted in improved possibilities for the fish to force former thresholds in the river section below the fishway, and to detect the entrance of the technical fishway. In further tests and modifications were carried out in the first pool section to create stronger water velocity into and out of the diffuser to attract salmon into the fishway. Measures to assist the fish passage in the lowermost rapid section, Baggböleforsen, to reduce its steepness were also carried out in In Öreälven the control of ascending fish ended in 2000 (Table ). The reason was high water levels that destroyed the part of the dam where the fish trap was located. Parr densities and smolt trapping Densities of salmon parr in electrofishing surveys in AU 2 rivers (Gulf of Bothnia, ICES SD 31) are shown in Table and in Figures and During these timeseries, same groups of people have made most of the electrofishing in all (AU 1 4) Swedish salmon rivers. At the beginning of the surveys the average size of the sites monitored was large (around m²), especially in AU 1 and 2. The reason for using large monitoring sites was to increase the possibility to catch salmon parr at a time when wild populations had poor status. From 2003 and onwards, however, the sizes of sites in AUs 1 and 2 have been reduced to about m² due to higher parr densities. In the summers of 2006, 2013 and 2014 conditions for electrofishing were extraordinary because of very low water levels, i.e. opposite to the conditions prevailing in For the electrofishing carried out in 2009, 2010, 2012 and 2015, the water levels were normal, but in 2011 and 2016 high water levels due to rain prevented surveys in several rivers. Due to problems to electrofish large parts of Piteälven, the number of ascending adults is used instead of parr densities (as in other rivers) for estimating prior smolt abundances (details in Section 4.2.2). No consistent electrofishing surveys were made during the 1990s. The density of 0+ parr has been rather low in most of the years (Table ). No surveys were done in 2011 and 2012 due to high water levels. In 2014 the densities of 0+ parr was the highest recorded (12 parr/100 m²). In 2016, the average density increased compared to in the previous year. The density of older parr has also been low, varying between 4 9 parr/100 m² the latest four years. No surveys were carried out in 2017.

117 ICES WGBAST REPORT In Åbyälven, the mean densities of 0+ parr in were about 3 parr/100 m². In 1999, the densities of 0+parr increased to 17 parr/100 m², about five times higher than earlier. In 2016, the average 0+ density increased to the so far highest recorded level (37 parr/100 m²) and it stayed at about that level in The densities of older parr have been stable in the last seven years with a mean of 14 parr/100 m², and the densities 2017 were the highest observed so far (Table ). In Byskeälven, the mean densities of 0+ parr in were about 5 parr/100 m². In the densities increased to about 11 parr/100 m², and in 1999 and 2000 the 0+ parr densities increased further (they were about 70% higher than in ). During the 2000s, the densities have been on rather high levels with a few exceptions, and in 2016 the 0+ density increased to the so far highest recorded level (43 parr/100 m²) and it stayed at the same high level in The densities of older parr have remained rather stable during later years with a mean around 20 parr/100 m² (Table ). In Kågeälven, the last releases of reared salmon parr were made in 2004, which means that the wild-born 0+ observed in 2013 were mainly offspring of spawners, which themselves were also wild-born. Stable occurrence of 0+ parr in recent years, indicates that the population has become self-sustaining, although the 0+ density in 2016 decreased somewhat (Table ). Spawning occurs along the whole river stretch available for salmon. In Rickleån, the mean density of 0+ parr were only about 0.5 parr/100 m² in , whereas since 1998 the mean density has been around 3.7 parr/100 m². The mean 0+ density decreased slightly in 2017, compared to in In Table , also average densities from extended electrofishing surveys in Rickleån are presented, including sites in the upper part of the river that was recently colonized (for more details see Section in ICES, 2015). For some years, weighted mean densities that include these extended electrofishing surveys are used as input when using the river model to calculate prior smolt abundance. In , smolts of salmon and sea trout were counted during their downstream migration in Rickleån using a smolt wheel ( Rotary-Screw-trap ) and mark recapture experiments. The trap was positioned close to the river mouth. In 2014, a total of 434 salmon smolts were caught. The calculated recapture rate for tagged salmon was 20.3%, which was used to estimate the total smolt production to 2149 (Table ). Because of many breaks in drifting of the screw-trap in 2015, no reliable estimate of the smolt production could be obtained in that year. In 2016 and 2017, the estimated total run was about 4000 and 4800 salmon smolts, respectively (Table ). In Sävarån, the mean densities of 0+ parr in were about 1.4 parr/100 m². In 1996, the average density increased to 10.3 parr/100 m², and in 2000 to 12.8 parr/100 m². No electrofishing was made in 2001 and The 0+ density in 2015 was the so far highest recorded (45 parr/100 m²) followed by the highest for older parr in 2016 (34 parr/100 m²), whereas the 0+ density in 2016 decreased to 32 parr/100 m². The densities 2017 of 0+ parr decreased, whereas the density of older parr stayed at the same level as previous years (Table ). From 2005 to 2013, smolts of salmon and sea trout were caught on their downstream migration in Sävarån using a smolt wheel (originally two parallel wheels were used). The trapping site was positioned 15 km from the river mouth. Estimates of total salmon smolt production are presented in Table On average ca. 470 wild salmon smolts per year were caught from mid-may to mid-june. Smolts were measured for length and weight, with scale samples taken for age determination and genetic analyses. The

118 112 ICES WGBAST REPORT 2018 dominating age group was three years. The proportion of recaptured tagged fish in the trap varied between 4 31%. No trapping of smolts has been carried out since 2014, as the smolt trap was moved and used in Rickleån during (see above). In Ume/Vindelälven, mean densities of 0+ parr in were only about 0.8 parr/100 m². In,1997 the average density increased to 17.2 parr/100 m². During the 2000s, densities have fluctuated a lot within the range of 5 25 parr/100 m². No surveys were carried out in 2011 due to high water level. In 2014, the density of 0+ parr increased to the so far highest recorded (39 parr/100 m²) followed by a decrease in 2015 with almost 50%. In 2016 and 2017 the mean 0+ parr density has declined to very low values (<5 parr/100 m²), a level not seen in the river since the peak years of the M74- disease in the early 1990s. The reason for the low density seems to be linked to the record small number and proportion of females passing the fishway in Stornorrfors in 2015 (Table ; Figure ) combined with a large proportion of the ascending spawning fish suffering of disease and fungus in recent years (Section 3.4.3). The establishment of fungus weakened the fish and resulted in high mortality, which was observed in the fishway and at the intake grid to the hydro power station, and also in the hatchery facilities where fish died long before spawning time (when fish are stripped). In addition the M74-frequency increased in the spawning years 2015 and 2016 (Section 3.4) These factors combined probably led to a low egg deposition in the autumns 2015 and 2016, and the very low densities of one summer old salmon parr seen in 2016 and In Table , average densities from extended electrofishing surveys in Vindelälven are also shown, including additional sites from upper parts in the river that recently have been colonized (see Section in ICES, 2015). For some years, mean densities that include these extended electrofishing surveys are therefore used as input in the river model to calculate prior smolt abundances. A smolt fykenet for catching smolts, similar to the one used in Tornionjoki, was operated in Vindelälven between 2009 and The entire smolt production area is located upstream of the trapping site. On average around 2500 salmon smolts were caught annually from 2009 to 2015, and the proportion of recaptured tagged fish in the varied between %. In 2009, the trap was operating from end of May to beginning of July, and smolts were likely caught during the whole time period with a peak in mid- June. In 2010, a pronounced spring flood caused problems to set up the fykenet and a considerable part of the smolt run was missed. In 2011, an episode late during the season with very high water flow again prevented smolt trapping. Although the break was rather short (six days) a very high smolt catch the day immediately before the break indicated presence of a significant peak that was missed. In , several episodes of high water flow again resulted in repeated breaks, and for those years, it was difficult to even produce crude guesses of the proportion of the total smolt run that was missed. Due to the above mentioned interruptions in the function of the trap, direct smolt estimates from the mark recapture experiments with the fykenet have not been possible to produce. However, estimates have still been possible to calculate based on data for returning 1SW adults (grilse) that are possible to identify from their smaller body size (without age data). Since 2010, all captured smolts have been marked using PIT-tags. VAKI counters and PIT-antennas in the Ume/Vindelälven fishway record all marked and unmarked wild returning spawners. Assuming a common smolt-to-adult survival rate for marked and unmarked grilse, the size of a given smolt cohort has thus been possible to estimate indirectly (see Table ).

119 ICES WGBAST REPORT Since 2016, the Vindelälven smolt trapping has been moved to a newly built permanent smolt trap within the fishway at Stornorrfors (hydropower dam that must be passed by down-migrating smolts) just a few kilometres downstream the former trapping site. In , however, there were technical problems with the new smolt trap, and as a consequence only few smolts were caught and marked. In Öreälven, mean densities of 0+ parr in were very low, just about 0.5 parr/100 m². The densities increased somewhat during the early 2000s, and then stayed around 3 10 parr/100 m² until in 2015 when the density increased by three times compared with earlier to the highest value recorded so far (21.6 parr/100 m²). In 2016, the mean 0+ density was nearly halved compared to in the previous year, and in 2017, it stayed at about the same level (Table ). In Table , also average densities from extended electrofishing surveys in Öreälven are shown; including sites from upper parts of the river that recently have been colonized (see Section in ICES, 2017). For the present assessment, mean densities that include these extended electrofishing surveys was for the first time used as input in the river model when calculating prior smolt abundances (Chapter 4). In Lögdeälven, mean densities of 0+ parr in were about 1.4 parr/100 m². In 1998, the density increased to 13.7 parr/100 m². Densities during the 2000s have fluctuated between three and almost 15 parr/100m². In 2017, the mean 0+ density decreased with about 50% compared to in the three previous years (Table ). In Table , also average densities from extended electrofishing surveys in Lögdeälven are shown, including sites from upper parts of the river that recently have been colonized (see Section in ICES, 2017). For the present assessment, mean densities that include these extended electrofishing surveys were used for the first time as input in the river model when calculating prior smolt abundances (Chapter 4). In , a smolt wheel was operated in Lögdeälven, close to the river mouth. The number of caught salmon smolts were 299 (2015) and 463 (2016), with 11% and 10% of the marked smolts being recaptured. In 2015, the trap had to be closed before the migration was finished, and the total smolt run for this year was therefore likely underestimated. In 2016, however, the whole run was monitored, yielding an estimate of about 5200 smolts. No smolt trapping was done in 2017 (Table ) Rivers in assessment unit 3 (Gulf of Bothnia, SD 30) Spawning runs and their composition In Testeboån, an electronic fish counter (Riverwatcher) was installed in late August 2015 in the new built fishway; a total of five salmon and 54 sea trout were counted in that (incomplete) season. Almost all spawning areas are located upstream of the counting site. At higher flows, water is spilled through the weir, which makes fish passage possible over the weir. In 2016, salmon may have passed beside the counter in early June when high water occurred, but on the other hand, salmon migration may not have started at that time of the year. In 2017, in principle the entire run salmon passed through the fishway. In 2016 and 2017, a total of 73 and 67 salmon were registered in the fishway, respectively. River catches and fishery In Ljungan, the salmon angling catch in 2017was only 53 salmon (whereof 48 released), compared to an average annual total catch of 110 salmon in the period In general, the catches have increased since the early 2000s, but in the last year, the catch

120 114 ICES WGBAST REPORT 2018 decreased to a level similar to that in the early 2000s. As detailed below, Ljungan is one of the wild salmon rivers where considerable disease problems have occurred in recent years. In Testeboån, (wild river since 2013) landing of salmon is not allowed. Parr densities and smolt trapping Parr densities from Ljungan are missing for several years due to high water levels in late autumn, making electrofishing impossible. For example, the relatively high value for 2012 only mirrors data from one electrofishing site (Table ) as the other sites could not be fished due to high water levels. Recoded average densities of 0+ salmon varied markedly from three to 45 parr/100 m² between 1990 and 2008, but without any clear trend (Table and Figure ). However, in 2012, 2014 and 2015 (especially) parr densities showed signs of increase. In 2017, the mean 0+ density in Ljungan dropped markedly to just 0.8 parr/100 m², which is the lowest observed density in the whole time-series. This low density could reflect that many adults died before spawning in the preceding autumn (Section 3.4.3). Testeboån received status as a wild salmon river by ICES, WGBAST in The latest releases of reared salmon (fry) in the river were made in 2006, which means that the wild-born 0+ parr observed at electrofishing from 2012 and onwards, most likely were offspring of salmon which themselves were wild-born. Fairly stable levels of 0+ parr densities in recent years, except for in 2008 when 0+ parr were absent, due to a very poor spawning run in 2007, indicates that the population is self-sustaining (Table ). The densities of 0+ parr decreased in 2014 compared to in the four previous years, but after that year it increased, and in 2016 it was the so far highest recorded (about 28 parr/100 m²). In 2017, the average 0+ density decreased to about the same level as in Smolt trapping using a smolt wheel has taken place in Testeboån since In 2015, the river was equipped with permanent facilities for counting of both smolts and ascending adults. Hence, in coming years the plan is to utilize Testeboån as a full index river. Annual estimates of the total smolt runs in have varied in the range from about 2000 to 4300 smolts Rivers in assessment unit 4 (Western Main Basin, SD 25 and 27) River catches and fishery In Emån, anglers have increasingly applied catch and release over the past years, and the river fishery is nowadays, basically, a no-kill fishing. Therefore, the landed catches have decreased markedly, from more than 100 salmon fish per year in the early 2000s to nearly zero in recent years. In 2017, the total river catch was 83 salmon, out of which none was retained. In 2016, the total catch was 57 salmon (whereof 49 released back). In Mörrumsån the landed catch has decreased from more than 200 salmon in 2010 (207 retained) and in 2012 (288 retained), to less than 50 in 2017 (41 retained). Over the same period, the total river catch has on average been 795 salmon, with large annual variation (range: ). Similar to in Emån, anglers have increasingly applied catch and release, which largely explains the decline in landed catches seen in recent years.

121 ICES WGBAST REPORT Parr densities and smolt trapping Parr densities from electrofishing surveys in the two AU 4 rivers are displayed in Table , and in Figures and For Emån, only densities of parr in electrofishing surveys below the first partial obstacle are displayed in the graphs referred to above. The densities of 0+ parr in the lowermost part of the river varied between parr/100 m² during , with a mean density of 43. The highest 0+ density so far occurred in The density of 0+ parr was 53 parr/100 m² in 2016 and stayed at about the same level in 2017, which is just over the mean value for earlier years in the time-series. The densities of older parr have varied from 1 10 parr/100 m² during the period with a mean value of 7 parr/100 m² in recent years. Table also contains average densities calculated across all sections in Emån that are accessible for salmon, including sites above partial obstacles (dams with fish ladders) located in habitats that currently seem to be recolonized. For the present assessment, these weighted mean densities were used as input in the recently developed Southern river model (ICES, 2017d) to calculate prior AU 4 smolt abundances (Chapter 4). The estimated smolt production in River Emån has appeared very low compared to the presumed production capacity. In 2007, an overview of the conditions in the river concluded that probably the difficulties for particularly salmon spawners, and to a minor extent also sea trout, to ascend fishways may give rise to low production of juveniles above the fishways. Electrofishing sites in these upstream areas do therefore normally show low juvenile abundance. On the other hand, there is a highly successful sea trout and salmon fishery in the lower part of the river (at Em), and this fishery has not shown signs of lesser abundance of either species. On the contrary, salmon seems to have increased in abundance. Monitoring of salmon migration in one fishway during also suggested that very few salmon could reach some of the upstream potential spawning areas. In 2006, the lowermost dam (at Emsfors) was opened permanently, and since then increased electrofishing densities for salmon have been recorded at the closest upstream electrofishing site. Activities are also ongoing to facilitate up- and downstream migration at the second dam counted from the sea, above which significant habitats regarded suitable for salmon reproduction are located. In order to get a quantitative estimate of the smolt run in the river, smolt traps were operated in the river Emån in 2007 and The primary purpose was to get an overview of the smolt production in the river. Two smolt wheels were installed within 200 m from the river mouth. In 2008, the smolt traps were operating through most of the smolt migration period. Almost the entire catch of salmon and sea trout smolts in the traps were utilized for mark recapture estimation, and the trap efficiency was estimated to 6.1%. The estimated salmon smolt run in 2008 was smolts (95% confidence interval: ). A considerable emigration of Salmo sp. fry (species not identified more precisely) in the length interval mm occurred in both 2007 and 2008, indicating that this could be a recurrent phenomenon. It was not possible to estimate the catch efficiency for small fry, but it is likely much lower than for smolts. Assuming that the trap efficiency for fry is half that of salmon smolts, or 3%, the estimated number of fry emigrating from the river would be in the order of However, the actual numbers might be much

122 116 ICES WGBAST REPORT 2018 higher if the trap efficiency is even lower. This kind of mass emigration has not been observed in any other Baltic salmon river where smolt wheels have been operated. In Mörrumsån, 0+ parr densities in the period varied between parr/100 m² (Table , Figures and ). The by far highest average density so far was observed in 1989 (>300 parr/100 m²). In 2011, the average 0+ density decreased to 36 parr/100m², the lowest value since the mid-1990s. One reason for the low density in 2011 could be high water level, as only part of the survey sites was possible to electrofish. However, it should be noted that the number of ascending salmon counted in the preceding autumn (2010) was the lowest recorded at the Marieberg power plant, ca. 13 kilometres from the sea, since an electronic counter was installed in the fishway (in 2002). Table also contains average densities calculated across all sections in Mörrumsån (weighted according to relative habitat areas) that are currently accessible for salmon, including sites in upstream habitats that recently have been recolonized following the construction of two fishways in 2004 (see below). For the present assessment, these weighted mean densities have been used as input for the recently developed Southern river model (ICES, 2017d) to calculate prior AU 4 smolt abundances (Chapter 4). Since 2015, the average parr densities in Mörrumsån has decreased, and in 2017 the 0+ density was almost half of the mean for the years The recent decline may reflect current disease problems, with a large number of dead and affected salmon seen in the river since Notably, however, this decrease cannot be seen in the average densities for all river sections (above). Whereas a decline can be seen mainly in downstream river sections, the uppermost (recently accessible) part seems still to be in a building-up phase, with increasing densities. Therefore, two contrasting trends are partly counteracting each other in the weighted averages used for the smolt prior estimates. In river Mörrumsån, hybrids between salmon and trout have been found during electrofishing since the early 1990s. In , the proportion of hybrids was high, up to over 50% in some sampling sites. After that, the occurrence of hybrids has varied. In 1995 and 1996, it was only some percent of the total catch. In 2005, the density of 0+ hybrids were 14 parr/100 m² which is higher than in the three years before. The amount of hybrids has decreased during In 2017, the densities of hybrids were 2.4 parr/100 m². In 2004, two new fishways were built at the power plant station about 20 km from the river mouth, which opened up about 9 km of suitable habitat for salmon, including about ha of production area. In , a smolt wheel has been operated in Mörrumsån, ca. 12 km upstream from the river mouth. About 55% of the total production area for salmonids is located upstream the trap. A main reason for choosing this upstream, location was that ascending adults are counted in a nearby fishway close to the smolt trap site, which should allow comparisons among numbers of ascending spawners and smolts from the upper part of Mörrumsån. So far, however, only preliminary numbers of ascending adult spawners exist; to obtain such reliable estimates, further work will be needed that accounts for (i) a relatively large share of missing or unclear species identifications (due to absent or low quality camera images from the fishway) and (ii) the fact that a rather large proportion of salmon trout hybrids exists in the river (Palm et al., 2013).

123 ICES WGBAST REPORT In , the estimated smolt production in the upstream parts of the river was lower than expected (ca per year). As a comparison, Lindroth (1977) performed smolt trapping in at a site close to the one currently used, and estimated the average annual salmon smolt production to (range ). However, since 2013, the smolt production in the monitored upper reaches of Mörrumsån has increased. In 2013, it was estimated to ca , and in 2014, it was estimated to be the highest recorded so far (ca ). In 2015, the estimated smolt production decreased to ca , but in 2016, it again increased to ca In 2017, the smolt production decreased further to Rivers in assessment unit 5 (Eastern Main Basin, SD 26 and 28) Estonian rivers The River Pärnu flows into the Gulf of Riga, and is the only Estonian salmon river in the Main Basin. The first obstacle for salmon migrating in the river is the Sindi dam, located 14 km from the river mouth. The fish ladder at the dam is not effective due to its small size and the location of the entrance. Electrofishing surveys on the spawning and nursery ground below the dam have been performed since 1996; the number of parr/100 m² has been very low during the whole period (Table and Figure ). No salmon parr were found in 2003, 2004, 2007, 2008, 2010 and In 2017, the 0+ parr density below Sindi dam was 10.2 parr/100 m². The habitat quality below the dam is poor, and that is the main cause for the low parr density. Since 2013, electrofishing is also carried out upstream from the Sindi dam. Above the dam salmon parr are found in only some years, and the densities have been very low. In 2017, however, average 0+ parr density (four sites electrofished) was 26 parr/100 m 2. The quality of spawning areas above the dam is relatively good, and parr abundancy is associated with poor accessibility. Future plans to restore the Pärnu salmon population include reconstruction of the Sindi dam in A juvenile supplemental release programme was also initiated in The first juvenile salmon was released in 2013, and as pointed out initially in this chapter, Pärnu should be considered as a mixed river under the present conditions with large numbers of juveniles being stocked every year. Latvian rivers There are ten wild salmon rivers in Latvia, mainly flowing into the Gulf of Riga. Some rivers have been annually stocked with hatchery-reared parr and smolts, with the result that salmon populations in these rivers consist of a mixture of wild and reared fish. In 2017, salmon parr were found at 28 sites (eleven rivers) sampled by electrofishing. Parr densities are presented in Table and Figure The wild salmon population in river Salaca has been monitored by smolt trapping since 1964 and by parr electrofishing since From 2000, no releases of artificially reared salmon have been carried out. In 2017, eleven sites were electrofished in the river and its tributaries. All sites in the main river held 0+ age salmon parr. Salmon 0+ parr also occurred in the tributaries Jaunupe, Svētupe and Korģe. The average density of 0+ salmon was 88 parr/100 m², whereas the density of 1+ and older parr was 7/100 m². The smolt trap in the river Salaca was in operation between April 10 and May 28, In total 1024 salmon and 540 sea trout smolts were caught; 503 of them were marked using streamer tags for total smolt run estimation. The smolt trap catch efficiency was 10.5%. Thus, in total salmon and 5400 sea trout smolts were estimated to have migrated from the Salaca in 2017.

124 118 ICES WGBAST REPORT 2018 In the river Venta, wild salmon parr were only found below the Rumba waterfall in 2016 and The small number of 0+ parr seen in 2016 stayed at the same level in 2017, when only 2.2 parr/100 m² were caught. In river Gauja, wild salmon 0+ parr production was very low in 2016, but it increased in 2017 when six parr/100 m² were caught. In Amata, which is a tributary to Gauja, salmon 0+ parr were found at a low density in 2017 (1.6 parr/100 m²). In 2017, wild salmon parr were also found in the small Gulf of the Riga rivers Vitrupe, Aģe and Pēterupe. Age structures of parr in these rivers testify that salmon reproduction does not occur in every year. Only 0+ parr in low densities were caught in the Main Basin river Užava. No wild salmon parr were caught in Irbe and Tebra (Saka river system) in Lithuanian rivers Lithuanian salmon rivers are typical lowland ones, and many of them are tributaries in the Nemunas river system. They are mainly sandy, gravely rivers flowing in the heights of upper and lower Lithuania. Salmonids inhabit more than 180 rivers. Leaning on historical data and today s situation, Lithuanian salmon rivers can be divided into the same groups as for Baltic salmon in general (see Annex 2): i.e. rivers inhabited by wild salmon, rivers inhabited by artificially reared salmon, rivers inhabited by a mixed (wild and reared) salmon population, potential rivers, i.e. where salmon occurs only occasionally, and rivers where salmon has gone extinct (Kesminas et al., 2003). There are 12 rivers in Lithuania inhabited by salmon populations of different abundance and with different status. Purely natural salmon population are inhabiting Žeimena and its tributaries Mera and Saria. The index river Žeimena has never been stocked with artificially reared salmonids. Mixed populations are found in the rivers Neris, Šventoji, Vilnia, B. Šventoji, Dubysa, Siesartis, Širvinta, Virinta, Minija and Vokė. Reared populations occur in the Jūra river and some smaller tributaries. In these rivers, salmon releases are made regularly for several years. Electrofishing is the main monitoring method for evaluation of occurrence and densities of 0+ and older salmon parr. Monitoring covers all main salmon rivers (including all potential rivers). Parr densities in Lithuanian rivers are presented in Table and Figures and The abundance of salmon parr depends on hydrological conditions, spawning success, and protection of spawning grounds. In 2017, the average density of salmon 0+ parr in the index river Žeimena decreased further to 2.8 parr/100 m² and no older (>0+) parr were caught. Salmon parr were caught at five sites in the main river and in one site on Serdyksna, a tributary of Žeimena. The 2017 results are close to the mean values for the whole survey period. Close to average parr abundances were also registered in Neris, where wild salmon parr were caught in eight out of 11 sites in Abundance of 0+ parr increased somewhat to 3.0 ind./100 m 2 and >0+ juveniles amounted to 0.2 ind./100 m 2 (Table ). A contributing factor to low parr densities seen in southeastern Lithuanian rivers during 2017, might be very high water levels in autumn this year. Efforts to increase the area of suitable salmon habitats in Lithuania have been successful in the Šventoji, Siesartis, Vilnia, Vokė and Dubysa rivers. Salmon also spawn in lower reaches of many small rivers (Mera, Kena, Musė, Širvinta, Virinta, Dūkšta, Žalesa, Saria).

125 ICES WGBAST REPORT A restocking programme was carried out in Lithuania during , and monitoring and stocking is still ongoing. There are many measures implemented every year to augment salmon populations, including artificial rearing, construction of fishways, protection of spawning grounds, stock monitoring and scientific projects. Despite measures taken, data from monitoring show that the smolt production in the Nemunas basin is increasing very slowly. A notable increase in production has only been observed in more recent years; during the period estimated total smolt production increased substantially from about to individuals. However, adverse ecological conditions in 2010 significantly decreased parr abundances in many important salmon rivers. Consequently, the estimated total smolt production in 2011 decreased to less than 7000 individuals. After that year, production has again been higher. In 2017, the total estimated smolt production decreased to compared to ca in 2015 and Salmon smolt production estimates for single rivers also slightly decreased in Siesartis, Vilnia, Virinta, Neris, Žeimena, Šventoji, Vokė, Virinta, B. Šventoji, Dubysa and Minija. The correlation between salmon juvenile density and water temperature during July, the hottest month of the year, has been investigated in two rivers characterized by different thermal regimes; Neris (r = -0,530, p =0,035) and Žeimena (r = -0,555, p =0,021). It was found that during a period of several years, water temperatures in July varied within a range of a few degrees (19.1 C on average). However, in 2010 it reached 22.6 C, which could have had a lethal impact on some of the weaker juveniles in the river. In that year, the parr density was also estimated to be the lowest in Žeimena; only 0.2 parr/100 m². Average temperature during July in Neris is 20.9 CA. Temperatures above the stress level (>22 C) were seen six times during a period of 16 years, in 2001, 2002, 2006, 2010, 2012 and The result of this study demonstrated that the thermal regime is very important for salmon production in Lithuanian rivers. Other concerns include pollution, and that rivers are of lowland type with scarce parr rearing habitats. Finally, quite high mortality rates are expected due to predation; densities of several predators are significantly higher than in more northern Baltic salmon rivers Rivers in assessment unit 6 (Gulf of Finland, SD 32) All three wild salmon populations in the Gulf of Finland area are located in Estonia: Kunda, Keila and Vasalemma. These rivers are small and their potential production is small. In addition, there is natural reproduction supported with regular releases in ten other rivers: Kymijoki, Gladyshevka, Luga, Purtse, Selja, Loobu, Valgejõgi, Jägala, Pirita and Vääna. In these mixed rivers, natural reproduction is variable, and enhancement releases have been carried out since year The salmon in rivers Narva, Neva and Vantaanjoki are of reared origin. Status of wild and mixed AU 6 populations Parr density in the wild river Keila started to increase significantly in 2005; and in 2017 the 0+ parr density reached its so far highest reported density (283 parr/100 m²). Therefore, it can be stated that the river Keila population is in a good and seemingly stable state (Figure ). The parr densities in river Kunda have been varying and a positive trend is only evident in the past three years (Table ). In comparison, the river Vasalemma is in a more precarious state, although some stronger year classes have occurred. The average 0+ density in 2017 increased to 52 parr/100 m², which is the so far highest recorded density. The most important change in the 1990s was the occurrence of salmon spawning in the Estonian mixed rivers Selja, Valgejõgi and Jägala, after many years without natural

126 120 ICES WGBAST REPORT 2018 reproduction. In 2006, wild salmon parr was also found in rivers Purtse and Vääna. Since then, a low and varying wild reproduction has occurred in all these mixed rivers (Table ). In the period , parr densities increased to relatively high levels in these rivers. However, in 2016 parr densities were very again low. In 2016, the Kotka dam in river Valgejõgi broke, and it will not be rebuilt. Thus in autumn of 2016, salmon were able to ascend to potential spawning areas that before were not accessible, and a considerable increase in salmon abundance may be expected in coming years. Parr densities in 2017 were high in most Estonian mixed rivers. However, the density remained low in Jägala, and at an average level in Valgejõgi. No parr were found at the newly reopened habitat in Valgejõgi. Salmon releases are carried out annually in Valgejõgi (since 1996), in Selja (since 1997), in Jägala and Pirita (since 1998), in Loobu (since 2002) and in Purtse (since 2005). According to the rearing programme by Estonian Ministry of Environment (for the period ) releases will be continued in these rivers. Salmon used for stocking in late 1990s originated from spawners caught in the river Narva and Selja broodstock fisheries. In addition, salmon from the Neva strain were imported as eyed eggs from a Finnish hatchery in In , brood fish were again caught from river Narva. A captive broodstock based on salmon from wild river Kunda was established in 2007 at Polula Fish Rearing Centre, and all salmon releases in Estonia (SD 32) are nowadays based on that stock. In river Vääna, releases were carried out from 1999 to The stocking was stopped due to the high risk of returning adults straying into the neighbouring Keila, considered to be a wild salmon river. On the north side of AU 6 all wild salmon populations in Finland were lost in the 1950s due to gradual establishment of a paper mill industry and the construction of hydroelectric dams. The geographically nearest available strain, Neva salmon, was imported from Russia in the late 1970s, and releases into the rivers Kymijoki and Vantaanjoki started in The water quality in the mixed river Kymijoki has improved significantly since the early 1980s. Reproduction areas exist on the lowest 40 kilometres of the river. Water conditions in winter influence the hatching success in productions areas below the lowest dams. In general, parr densities have been on a moderate level, but some improvement have occurred over time (Table ). In 2011 and 2012, parr densities were low because of exceptional flow conditions, whereas higher water levels in mild and rainy winters were followed by high parr densities in 2005 and 2015 (when the 0+ density increased to its long-term maximum of 113 parr/100 m²). In 2016, the parr density again decreased to 33.7 parr/100 m², and in 2017 it dropped further to 11.3 parr/100 m². Despite rainy autumns, most of the nursery areas in the lower part of Kymijoki dry out, because of water regulation between the power plants. Good quality habitats are located above the lowest power plants, but currently spawners can only access those areas via two branches where the dams are equipped with fishways. The fish ladders in the Langinkoski branch do not function well, and salmon can ascend the dam only in rainy summers when the discharge is high. Because of higher outflow, usually most of the spawning salmon ascend to the Korkeakoski branch, where a fish pass at the hydropower station was finished in So far, the smolt production areas beyond the dams are only partially utilized. The new fish pass is expected to allow access of a much larger number of spawners to the better spawning and rearing habitats above the dams. If the fish pass will work well, it will increase the natural smolt production of the river significantly. However, in autumn 2016 only ten salmon ascended through the new fish pass, although a much larger number of spawners were observed below the dam. Also in 2017, a very small number of salmon passed the fish way.

127 ICES WGBAST REPORT Natural smolt production in Kymijoki has been estimated to vary between 7000 and in the last fifteen years. Along with the gradual increase in natural production, smolt releases have been decreased in the last few years. The released number of smolts (on average per year, ) is, however, still clearly larger than the estimated natural production (on average smolts per year, ). The broodstock of salmon is held in hatcheries, and it has frequently been partially renewed by ascending spawners. An inventory of rearing habitats in the river Kymijoki suggests 75 ha of smolt production area in the eastern branches of the river, between the sea and Myllykoski (40 km from the river outlet). Out of this total, about 15 ha of the rapids are situated in the lower reaches with no obstacles for migration, whereas about 60 ha are located beyond dams. Potential smolt production has been assessed based on assumed parr den-sity (max >1 parr/ 1 m²), and smolt age distribution (1 3 yr). The annual mean potential was calculated to 1,34 smolts per ha, yielding a total potential of the river of about smolts per year. From this potential, annually about smolts could be produced in the lower reaches and in the upper reaches of the river (Table ). In the river Vantaanjoki, electrofishing surveys in have shown only sporadic occurrence of salmon parr at just a few sites. In Russia, Luga and Gladyshevka are the only rivers with wild Baltic salmon reproduction. In Luga the salmon population is supported by large and long-term releases. The released smolts are based on ascending Luga and Narva river spawners, as well as on a broodstock of mixed origin. In the mixed River Luga, a smolt trapping survey has been conducted since The natural production has been estimated to vary from about 2000 to 8000 between years. There has been some increase in the wild smolt production during the last years; about 6700 wild smolts were estimated in 2010 compared to 4000 smolts in 2009 and 3000 smolts in In 2017, the smolt trapping indicated some decrease (2000 wild smolts). The total potential smolt production of the river has been assessed to be about smolts, and the current wild reproduction is thus very far from its maximum level. The main reason for this poor situation in believed to be intensive poaching in the river. 3.2 Potential salmon rivers General The definition of a potential salmon river is a river with potential for establishment of natural reproduction of salmon (ICES, 2000). The current status of restoration programmes in Baltic Sea potential salmon rivers is presented in Table Releases of salmon fry, parr and smolt have resulted in natural reproduction in some rivers (see Table ). Reproduction and occurrence of wild salmon parr has, in some potential rivers, occurred for at least one salmon generation. Before any of these rivers may be transferred to the wild salmon river category, the Working Group needs more information of river-specific stock status Potential rivers by country Finland Nine potential salmon rivers are listed in Table Out of these three rivers Kuivajoki, Kiiminkijoki and Pyhäjoki were selected to be included in the Finnish Salmon

128 122 ICES WGBAST REPORT 2018 Action Plan (SAP) programme. These SAP rivers are all located in AU 1 (Subdivision 31). Densities of wild salmon parr in electrofishing surveys in the SAP rivers are presented in Table Hatchery reared parr and smolts have been stocked annually in the rivers since the 1990s. Due to poor success of stock rebuilding to date, especially in the Pyhäjoki and Kuivajoki, the monitoring activities and stocking volumes have been decreased. Current activities include regular salmon releases only in Kiiminkijoki. In 2017, smolts and one-year old parr of river Iijoki origin were stocked in Kiiminkijoki. Electrofishing is currently conducted irregularly in Kiiminkijoki. In the average densities of wild 0+ (one-summer old) parr ranged between individuals/100 m 2 (Table ). There has been no electrofishing in due to high summer water levels in the river. In rivers Kuivajoki and Pyhäjoki, the observed densities in ranged from and parr/100 m 2, respectively. The poor success of stock rebuilding is probably due to a combination of fishing pressure, insufficient quality of water and physical habitat in rivers and their temporally low flow, which together keep the lifetime survival and reproductive success of salmon low. Small-scale natural reproduction has also been observed in rivers Merikarvianjoki and Harjunpäänjoki (tributary of Kokemäenjoki at the Bothnian Sea, Subdivision 30), and in the Vantaanjoki at the Gulf of Finland (Subdivision 32). Lately, plans have emerged for building up fish ladders and rebuilding migratory fish stocks in several former large Finnish salmon rivers. Projects are underway to study the preconditions for such activities in rivers Kemijoki, Iijoki, Oulujoki and Kymijoki. For instance, salmon have been caught from the mouths of Iijoki and Kemijoki, tagged with radio transmitters, transported and released to upstream reproduction areas. In River Oulujoki, a catching cage for spawners was constructed in 2017 at the Montta hydro power station. From the cage, spawners are transported by a truck into two upstream tributaries. The in-river behaviour of these salmon were monitored until spawning time. Also, downstream migration and survival of smolts through dams have been studied in these rivers. Sweden Three potential Swedish salmon rivers are listed in Table : Moälven, Alsterån and Helgeån. Densities of wild salmon parr in electrofishing surveys in Alsterån are presented in Table In recent years, the former potential rivers Testeboån (2013) and Kågeälven (2014) did receive status as wild rivers by WGBAST. Restoration efforts are ongoing at the regional local level in several of the remaining potential Swedish salmon rivers. However, so far recent stocking activities and/or too low natural production have prevented them from having their status upgraded. Until next year (2019), the intention is to review and potentially update the list of Swedish potential salmon rivers. Lithuania Two potential Lithuanian salmon rivers, Sventoji and Minija/Veivirzas, are listed in Table River Venta, previously included as a potential salmon river, has been removed.

129 ICES WGBAST REPORT In May 2017, a total of salmon smolts were released into four rivers: Neris, Šventoji (Neris basin), Dubysa and Jūra. In addition, a total of salmon fry were released into the Neris basin (rivers Neris, Vilnia, Muse, Vokė, Dūkšta and Kena); into the Šventoji basin (Šventoji, Širvinta, Siesartis, Virinta); into the Dubysa basin, into the Minija basin and into the Jūra basin. It has been observed that restocking efficiency in smaller rivers is much greater than in larger ones, which is in line with a survey that indicated that in larger rivers mortality of juveniles is greater. Electrofishing densities of wild salmon parr in potential (mixed) Lithuanian rivers are presented in Table In some larger tributaries of Neris and Šventoji, salmon densities in 2017 were relatively close to the long-term average. However, parr densities in Šventoji basin decreased 4.2 times, compared to in the last year. Average total parr densities in this river were close to the mean levels for the whole study period and reached 0.74 ind./100 m 2 (0.64 ind./0+ and 0.1 ind./ >0+). Also, parr densities slightly decreased in all tributaries in the Šventoji river. In the Siesartis tributary, average density of salmon juveniles was 4.9 ind/100 m 2 (3.1/0+ and 1.8/>0+). Density notably decreased 13.4 times this year in Virinta, to 0.35 ind/100 m 2 (0.35/ 0+ ). In Vilnia and Vokė, the density of juvenile salmonids increased, compared to the previous year and was sufficiently high, with 23.1 ind./100 m 2 (16.7/ 0+ and 6.3/ >0+) in Vilnia and 8.5 ind./100 m 2 in Vokė (6.8/ 0+ and 1.7/ >0+). In west part, Lithuanian potential salmon rivers parr density was 3.84 ind./100 m 2 in B. Šventoji; ind./100 m 2 in Dubysa; 3.9 ind./100 m 2 in Minija. Poland Restoration programmes for salmon in seven potential Polish rivers (Table ) were started in 1994, based on releases of hatchery reared Daugava salmon. To date, however, there is no good evidence of successful re-establishment of any self-sustaining salmon population. In 2017, the total number of released hatchery reared fry was (mainly in the Słupia and Łeba rivers, subdivision 25). In total, smolts were released, almost all into the Vistula River (subdivision 26). Since at least 2011, salmon spawners have been observed in the Vistula river system, but there are still no data on wild progeny. Salmon spawning has been observed in the Drawa River (Odra R. system) for some years, but the number of redds has stayed on a low level (not higher than ten per year). Until present, there is only one piece of evidence of a few wild salmon progeny born in the river (result from spawning in 2013). In almost all Pomeranian rivers, ascending and spent adult salmon have been observed and caught by anglers, but so far wild parr has only been found in the Slupia River. Due to high water level, no electrofishing surveys took place in 2017 Russia One potential Russian salmon river is listed in Table The Gladyshevka River was selected as a potential river for the Russian Salmon Action Plan. Stocking of salmon with hatchery-reared (Neva origin) young salmon is ongoing in this river. Since 2001, a total of nearly salmon parr and smolts has been released in the river. In addition one-year old salmon were released in 2017, of those 2000 tagged with T-bar tags. Densities of wild salmon parr from electrofishing surveys in Gladyshevka are presented in Table Since 2004, wild salmon parr have occurred in the river. In 2013,

130 124 ICES WGBAST REPORT 2018 total parr densities varied from parr/100 m 2 (average of 6 parr/100 m 2 ) in the different rapids; in 2014 from parr/100 m 2 (average about 2 parr/100 m 2 ). In 2015, densities increased significantly up to 26,7 40,0 parr/100 m 2 ; average 0+ parr density was 23.2 parr/100 m 2 (about 70% of the total number of juveniles). No electrofishing surveys were carried out in 2016 due to high water level. In 2017, wild parr densities varied from 5 to 40,0 parr/100 m 2 (total average 18.4 parr/100 m 2 ); about 60 70% of the total number of juveniles are 0+ parr. Estonia No potential salmon rivers have been pointed out in Estonia. Latvia No potential salmon rivers have been pointed out in Latvia. However, rivers Liela Jugla and Maza Jugla in the lower part of the river Daugava system are regularly stocked by one summer salmon and sea trout parr, and electrofishing and habitat mapping are carried out. Germany No potential Baltic salmon rivers have been pointed out in Germany. So far, no rivers with outlet into the Baltic Sea exist with a known (former) wild salmon population. However, in 2015 and 2016, a few salmon were caught during spawning migration in the river Warnow (W. Loch, pers. comm.). Nevertheless, there is potentially no significant natural salmon smolt production in the German Baltic catchment area. Denmark No potential Baltic salmon rivers have been pointed out in Denmark. 3.3 Reared salmon populations Releases The total number of salmon smolts released in reared rivers around the Baltic Sea in 2017 is presented in Table In AU 1 5 (subdivisions 22 31), it was about 3.8 million, with an additional 0.5 million in AU 6 (Subdivision 32), making a grand total of 4.3 million smolts released in Releases of younger life stages (eggs, alevins, fry, parr) are presented in Table These releases have in many areas consisted of hatchery surplus, often carried out at poor rearing habitats. In such cases, mortality among parr is high and releases correspond only to small amounts of smolts. On the other hand, when releases have taken place in potential, mixed or wild salmon rivers with good rearing habitats, they have had a true contribution to the smolt production. When comparing the total annual number of releases (of younger life stages) in the last two years, the number has decreased in AU 1 3, whereas in AU 5 6, the releases stayed at the same level. In AU 4, there have been no releases since in However, in a longer perspective, releases of younger life stages have decreased in the majority of the assessment units, with exception of AU 5 where the observed trend is not as evident. Roughly, these releases are expected to produce less than smolts in the next few years. However, the stocking statistics available to the working group do not allow distinction between single rivers and release categories (age stages), and

131 ICES WGBAST REPORT therefore the corresponding number of smolts expected from releases of younger life stages has not been possible to estimate properly. The yield from salmon smolt releases has decreased in the Baltic Sea during the last years, according to results from ongoing national tagging studies (Figures ). Possible explanations for lower catches include decreased offshore fishing and strong regulations in the coastal fishery. Initially, no substantial surplus of fish was observed in the rivers where compensatory releases were carried out, which most likely was due to decreased post-smolt survival. In recent years ( ), however, the amount of salmon returning to reared rivers has increased, in some cases even dramatically. In 2017, there was a decline in returning salmon to Swedish rivers with compensatory releases that may be connected to health issues described in Section 3.4. The wild smolt production has increased considerably since the mid-1990s. Catch samples from the years indicate that the proportion of reared salmon has decreased, and is currently well below 50 percent in most Baltic Sea fisheries (Table and Figure 2.8.1). Releases country by country Most releases in Sweden are regulated through water-court decisions. Since the reared (and wild) stocks were severely affected by the M74-syndrome in the early 1990s, the number of Swedish compensatory released salmon smolts in 1995 were only percent of the intended amount. However, already in 1996 the releases increased to the level set in the water-court decisions. From that year and onwards, the releases have been kept close to the intended level each year. In 2017, a total of 1.6 million salmon smolts were released in AU 2, AU 3 and AU 4. The releases in AU 4 are minor and amounts to less than one percent of the total Swedish releases (Table 3.3.1). The number of one-year-old salmon smolts released in Sweden has increased, especially in the most southern rivers. From the share of oneyear old smolts has increased from 23% to 75% of the total Swedish smolt releases. This development reflects a combination of high-energy feed and longer growth seasons due to early springs and warm and long autumns. Many broodstock traps in Swedish reared rivers were previously operated with equal intensity throughout the fishing season. The catch could therefore be considered as a relative index of escapement. However, only in two rivers (Skellefteälven and Ljusnan) has the broodstock trap been operated with equal intensity until present (until 2015 in Skellefteälven). The reduced fishing intensity in most rivers with smolt releases reflects the increasing abundance of returning adults during the last ten years. Broodstock fishing at low intensity during the migrating season is nowadays sufficient to get the amount of spawners (eggs) needed to fulfil terms in court decisions. Only in one river (Skellefteälven) was the broodstock trap operated with equal intensity until in The reduced fishing intensity in the rivers with smolt releases reflects the increased abundance of returning adults during the last ten years. In Finland, the production of smolts is based on broodstocks reared from eggs and kept in hatcheries. The number of captive spawners is high enough to secure the whole smolt production. A partial renewal of the broodstocks has been regarded necessary in order to avoid inbreeding, and is consequently enforced occasionally by broodstock fishing. In 2017, the total releases in AU 1 and AU 3 were 1.4 million smolts and in AU smolts (Table 3.3.1). When the Finnish compensatory release programmes were enforced in the early 1980s, the total annual salmon smolt releases were about 2 million in total, whereof 1.5 million released in AU 1 and AU 3, and 0.5 million

132 126 ICES WGBAST REPORT 2018 in AU 6. In recent years, the releases have gradually been reduced. As in Sweden, the reared stocks in Finland have been affected by M74 over the years. In Russia there are annual releases in AU 6; in 2017 a total of reared smolts were stocked. Occasionally, also Lithuania makes annual releases of a smaller number of smolts in AU 5; in 2017 a total of smolts were released (Table 3.3.1). In Estonia a rearing programme using the Neva salmon stock was started in Eggs were collected from the reared Narva stock and the mixed Selja stock. In the late 1990s eggs were also imported from Finland. A captive stock based on spawners from river Kunda was established in One hatchery is at present engaged in salmon rearing. In 2017, the total annual smolt production was smolts released in AU 6, and another smolts released in AU 5 (Table 3.3.1). In Latvia, the artificial reproduction is based on sea-run wild- and hatchery-origin salmon broodstock. The broodstock fishery is carried out in the coastal waters of the Gulf of Riga in October November, as well as in the rivers Daugava and Venta. The mortality of yolk-sac fry has been low, indicating that M74 might be absent in this region. In 2017, the annual smolt production in Latvian hatcheries was about 0.6 million (Table 3.3.1). This is below the average number of releases during the last decade. Earlier, from 1987 and onwards, the annual Latvian releases ranged up to 1.1 million smolts in several years. In Poland, the last wild salmon population became extinct in the mid-1980s. A restoration programme was started in 1984, when eyed eggs of Daugava salmon were imported from Latvia. Import of eggs continued until In , eggs for rearing purposes were collected from a salmon broodstock kept in sea cages located in the Bay of Puck. In subsequent years, eggs have been collected from returning spawners caught in Polish rivers, besides from spawners reared in the Miastko hatchery. Spawners are caught mainly in the Wieprza River and in the mouth of Wisla River, but also from rivers Drweca, Parseta, Rega and Slupia. The yearly production amounts to million eggs. Stocking material (smolts, one-year old parr and one-summer old parr) are reared in five hatcheries. In 2017, the total smolt production was released in AU 5 (Table 3.3.1), a much smaller number than in Starting from 1994, the annual releases have fluctuated between and 0.5 million smolts. In Germany, no regular release programme exists in the Baltic region, as there are no known natural salmon populations. Consequently, there were no official releases of salmon in rivers with outlet into the Baltic Sea in However, a few irregular releases have been reported recently and in the past (e.g. river Trave and river Warnow). There is a controversy regarding the potential historic existence of wild Baltic salmon populations in German rivers. Until 2005, a rearing programme was run in Denmark in a hatchery on the Island of Bornholm using the river Mörrumsån stock (AU 4). In the last year (2005), tagged smolts were released (Table 3.3.1). The year before (2004), a total of smolts were released, and one experiment on artificial imprinting and another on establishment of a Terminal Fishery was performed. No new releases have been planned Straying Observations on straying rates of released salmon vary between areas. The level of straying is evidently dependent on several factors. For example, in Finland rearing of smolts is based on broodstocks kept in hatcheries, whereas in Sweden it is based on annual broodstock fishing ( sea ranching ). These differences in rearing practices may

133 ICES WGBAST REPORT also influence straying rates. Strayers are often observed in the lower stretches of the rivers into which they have strayed. This may indicate that not all strayers necessarily enter the spawning grounds and contribute to spawning, but instead that a proportion of them may only temporally visit the wrong river. This also implies that the place and time of collecting observations about straying, is expected to influence the obtained estimates about straying rates. More information is needed to study these aspects of straying. According to scale analysis of catch samples collected from the Tornionjoki river fishery in , only eight salmon out of a total of 4364 analysed were identified as potential strayers from releases in other Baltic rivers. This indicates that about 0.2% of the salmon run into Tornionjoki were from other (reared) rivers, which corresponds to about 100 strayers per year, if one assumes an average spawning run into Tornionjoki of about salmon. Tag recapture data of compensatory releases in the Finnish Bothnian Bay indicate that the straying rate of these reared fish to other rivers is 3 4%. From all these releases, however, strayers were found only among the Tornionjoki hatchery strain stocked into the mouth of Kemijoki, and all these strayers were observed in the Tornionjoki. Using these tag recaptures to calculate the amount of strayers in the Tornionjoki, assuming no strayers from the Swedish releases, there would be annually about 200 strayers in the Tornionjoki spawning run (corresponding to 0.4% straying into the river, again assuming a spawning run of about salmon). In Sweden, tag recoveries indicate that the average straying rate of reared salmon into other rivers has been % on average, but for some releases, the straying rate has been as high as 10 30%. Highest straying rate of tagged salmon is often observed in reared rivers with annual releases, due to a high total exploitation rate from the commercial, recreational and broodstock collection, and probably also because broodstock fisheries are carried out close to river mouths. 3.4 M74, dioxin and disease outbreaks M74 in Gulf of Bothnia and Bothnian Sea When calculated from all Swedish and Finnish data, the proportion of salmon females whose offspring displayed increased mortality in 2017 was on average 34%, compared to 19% in the preceding year (Table 3.4.1). Hence, the M74 syndrome got worse in after having remained at a much lower level (1 6%) in the five preceding years. The thiamine (vitamin B1) concentrations in unfertilized eggs in autumn 2017 (reproductive period 2017/2018) from females in the River Simojoki increased somewhat compared to in the preceding year (Figure 3.4.1), but still remained considerably lower than in years when no M74-related mortality was observed in the Finnish M74 monitoring data (Table 3.4.2). Thus in spring 2018, M74 offspring mortalities are expected, but at a somewhat lower level compared to in 2017 (back to levels similar to those in 2016). In Swedish rivers, the proportion of offspring groups with increased M74-like mortality varied from 7 58% in 2017, compared to 4 39% in 2016 (Table 3.4.3; Börjeson, 2017). The average free thiamine concentration in eggs from salmon that ascended the River Simojoki in autumn 2017 had increased compared to in autumn 2016, but it remained lower than in autumn 2015 (Figure 3.4.1). For the third year, thiamine was also measured in unfertilized eggs of salmon ascended 2017 in the Swedish rivers Ume/Vindelälven and Dalälven, where the mean free thiamine concentrations were a little higher

134 128 ICES WGBAST REPORT 2018 than in the preceding year but, however, approximately as low as in autumn 2015 (Figure 3.4.2). Wiggling females (i.e. with an uncoordinated swimming behaviour) were not detected in Sweden in autumn 2017, but in one of the spawners from River Tornionjoki. In eggs of salmon from the R. Tornionjoki in autumn 2017, the free thiamine concentration was lower compared to the R. Simojoki, but higher compared to the R. Dalälven. The river-specific prognosis for the proportions of offspring groups in spring 2018 suffering from thiamine deficiency causing increased mortality varies from 13 20% up to 21 35%, depending on the river (Table 3.4.1). The prognosis is based on the concentration of free thiamine in eggs vs. yolk-sac fry mortality (%) in female-specific incubations (in Finnish M74 monitoring data from the reproduction periods 1994/ /2011, n = 799). The limit values of free thiamine used in prognosis are: for 100% mortality 0.2 nmol/g, for occurrence of M74 mortality 0.5 nmol/g and possible late M74 (M74?) 1.0 nmol/g. The M74 frequencies in Table predominantly represent the percentage of females in a hatchery with a recorded increase in offspring mortality. In the rivers Simojoki, Tornionjoki, and Kemijoki, however, mortalities are reported for the proportion of females affected by M74 and the mean percentage yolk-sac fry mortality (Table 3.4.2). In Finnish data, annual M74 figures are based on female-specific experimental incubations in which M74 symptom-related mortality has been ascertained by observations of yolk-sac fry (until the reproductive period 2010/2011) and/or comparing mortalities with the thiamine concentration of eggs (from 1994/1995 and onwards) (Figure 3.4.1). Three figures are presented: (1) the average yolk-sac fry mortality, (2) the proportion of females with offspring affected by M74, and (3) the proportion of those females whose offspring have all died (Keinänen et al., 2000; 2008; 2014; Vuorinen et al., 2014a). Mean annual yolk-sac fry mortalities and proportions of M74 females correlate significantly, but the M74 frequency has usually been somewhat higher than the offspring M74 mortality, especially in years when many offspring groups with mild M74 occur, i.e. when only a proportion of yolk-sac fry die. In years when the M74 syndrome is moderate in most offspring groups, the difference between the proportion of M74 females and mean yolk-sac fry mortality can exceed 20 percentage units (Keinänen et al., 2008). In contrast, Swedish data are based only on the proportion of females whose offspring display increased mortality (Table 3.4.3). Currently (from 2011/2012 on), in Finnish M74 monitoring the incidence of M74 is principally based on the three thiamine concentration of unfertilized eggs, which has a strong correlation with M74-related mortality of yolk-sac fry (Vuorinen and Keinänen, 1999; Keinänen et al., 2014). However, control female-specific incubations are run at a hatchery (Vuorinen et al., 2014a). In the hatching years , the M74 syndrome resulted in a high mortality of salmon yolk-sac fry with an M74 frequency (i.e. the proportion of the females whose offspring were affected) over 50% in most Swedish and Finnish rivers (Table 3.4.1). Since then the incidence of M74 has on average decreased. However, it has varied greatly even between successive years so that some years (e.g. 1999, 2002, and ) have displayed elevated mortalities compared to others (e.g. 1998, and ) with low or non-existent mortalities. In the reproductive period 2011/2012, the incidence of M74 could be considered as non-existent for the first time since the large outbreak in the 1990s. However, it returned in the reproductive period 2015/2016. In years of a high M74 incidence, there has been a tendency that estimates of M74- mortality have been higher in Finland than in Sweden, but this difference seems to

135 ICES WGBAST REPORT have disappeared in the years when the mortality has been low (Figure 3.4.3). The difference may be due to the fact that, in Finland all females caught for M74 monitoring have been included, whereas in Sweden females that have displayed uncoordinated swimming (wigglers) have been excluded from incubation. Wiggling females are known to inevitably produce offspring that all die from M74. The proportion of wiggling females was high in the early and mid-1990s (Fiskhälsan, 2007). Trends and annual fluctuations in average proportions of M74-affected females have been very similar in Swedish and Finnish rivers (Figure 3.4.3). However, in some years M74 has been insignificant or absent in the Finnish M74 monitoring, whereas rather high M74 frequencies have been reported from some Swedish rivers. It seems that those Swedish results may rather result from technical failures or too high or variable water temperatures, as reported by Börjeson (2013). In the Finnish M74 monitoring, but not in Sweden before 2015/2016, the mortality and female proportion figures for M74 incidence have been ascertained by measuring the thiamine concentration of eggs (Figure 3.4.1). In the Finnish M74 data, the annual M74 incidence among the monitored Bothnian Bay rivers has been very similar. Therefore, it is relevant to express the annual M74 mortality and proportion of M74 females as an average of all individual monitored salmon females (and respective offspring groups) that ascended those rivers (Keinänen et al., 2014). However, there may be some differences between salmon populations from rivers in the Bothnian Bay and in the Bothnian Sea, if migration routes and feeding grounds during the whole feeding migration differ. This would also explain different mortalities, reported during the early 1990s (Table 3.4.1), among offspring of salmon from the River Mörrum, from where smolts descend directly into the Baltic Proper. Apart from observations in hatcheries and experimental incubations, effects of the M74-syndrome was also observed as decreased parr densities in some of the wild salmon populations in and also in the years 1995 and 1996, despite a large number of spawners (Karlström, 1999; Romakkaniemi et al., 2003; 2014). In the Swedish wild salmon river Ume/Vindelälven in the Gulf of Bothnia, an estimate of the egg deposition is available together with an estimate of the parr densities derived from these brood year classes. It shows that the densities of 0+ parr were low in the years when the incidence of M74 was high, while parr densities were better correlated to the egg deposition in years when the incidence of M74 was low ( and ). Statistics from the Swedish River Dalälven collected during 14 years ( ) show that females (n = 1866) affected by M74 have a lower average weight than non-affected fish (Börjeson, 2011), and in also 3% lower condition factor (Börjeson, 2015). The reason for the weight difference is not known. It could be that affected M74 fish are younger than healthy females and contrary to older salmon have fed only on smaller and younger prey fish (Jacobson et al., 2018), or that they have grown less due to the nutritional conditions. Backman (2004) found that in wild salmon that ascended earlier and were larger had somewhat lower offspring M74 mortalities than fish that ascended later and were smaller. The same relationship was not found among reared salmon. In intra-annual comparisons among two sea-year salmon, only in some years with a low M74 incidence, a negative correlation between the weight or size of females and yolk-sac fry mortality was found. On the contrary, a large size (weight or length) or high condition factor of mature or prespawning female salmon was related to high yolk-sac fry mortality in years of relatively high M74 incidence (Mikkonen et

136 130 ICES WGBAST REPORT 2018 al., 2011). Although a high condition factor (CF >1.05) of prespawning salmon predicted high M74-related mortality, the high growth rate of salmon appeared not as such to be the cause of M74, but rather the abundance of prey and its quality (Mikkonen et al., 2011). Most Baltic salmon feed in the Baltic Proper, but reared salmon smolts have been found to remain to feed more often than wild salmon in the Bothnian Sea (Jutila et al., 2003), where salmon growth has generally been slower than in the Baltic Proper (Salminen et al., 1994; Niva, 2001; Keinänen et al., 2012). Evidently, because cod (Gadus morhua) compete with salmon for food in the Baltic Sea (Larsson, 1984), the annual growth rate and the condition factor of prespawning salmon were both inversely related to the size of the cod stock (Mikkonen et al., 2011). From the various stock factors of sprat (Sprattus sprattus) and Baltic herring (Clupea harengus membras) in the southern Baltic Proper, the biomass of sprat had the strongest positive relationships with the growth rate and condition factor of prespawning salmon, and the total prey biomass with yolk-sac fry mortality (Backman, 2004; Mikkonen et al., 2011). However, sprat was the dominant prey species of salmon in that feeding area in years of high M74 incidence, and already earlier M74 had been shown to be statistically well-correlated with parameters describing the sprat stock (Karlsson et al., 1999). The M74 syndrome has unquestionably been linked to a low concentration of thiamine in salmon eggs (Lundström et al., 1999; Vuorinen and Keinänen, 1999; Koski et al., 2001), although some other relationships have also been found. However, yolk-sac fry suffering from M74 can be restored in hatchery to a healthy condition by treatment with thiamine (Bylund and Lerche, 1995; Koski et al., 1999). A pale egg colour in M74 eggs (Börjeson et al., 1999; Keinänen et al., 2000) is a result of a low concentration of carotenoids, especially astaxanthine having antioxidant property (Lundström et al., 1999; Pettersson and Lignell, 1999; Vuorinen and Keinänen, 1999). An increase in the concentrations of particular organochlorines in salmon spawners ascending the River Simojoki, coincidentally with the outbreak of M74 at the start of the 1990s, was concluded to have resulted from enhanced feeding on sprat in which the concentrations of these organochlorines were high in younger age groups with the greatest fat content (Vuorinen et al., 2002). Bioaccumulation of specifically these organochlorines, coplanar PCBs, was most distinctly affected by the fat content of the prey and predator fish (Vuorinen et al., 2012). The fat concentration of sprat is on an average nearly twice that of herring, and it is highest in the youngest sprat (Keinänen et al., 2012). Both species are fattier in autumn than in spring. However, the lipid content of both species has differed between sea areas; it has been highest in the Bothnian Sea, average in the Baltic Proper and lowest in the (western) Gulf of Finland (Vuorinen et al., 2012; Keinänen et al., 2017). The percentage of lipid also varies more in sprat than in herring (Keinänen et al., 2012). The average thiamine concentration in sprat and herring (of the size preferred by salmon as prey) sampled in different seasons and years are quite similar (Keinänen et al., 2012; 2017), although in autumn samples, it was lower in sprat than in herring (Vuorinen et al., 2002). However, in both prey species the thiamine concentration by several times exceeded the nutritional guidelines on growth of salmon (see Keinänen et al., 2012). The thiamine concentration changed curvy linearly with the age of both sprat and herring, being lowest in the youngest age groups [and also in the oldest herring of length >19 cm, and hence not often included as salmon prey (Hansson et al., 2001; Vuorinen et al., 2014b)] and greatest at 6 10 years in sprat and 3 7 years in herring (Keinänen et al., 2012).

137 ICES WGBAST REPORT As thiamine has a central role in the energy metabolism, its nutritional requirement is determined by the energy density of the diet, which means the fat content of prey fish. Thus, ample abundance of young sprat (fatty) as food for salmon increases the requirement for thiamine. Contrary to demand, the thiamine content per unit fat and energy in the diet of salmon has been least during years and in areas where recruitment and biomass of sprat have been high (Mikkonen et al., 2011; Keinänen et al., 2012). An abundance of dietary lipid increases the content of unsaturated fatty acids, especially DHA, in the diet of salmon (Keinänen et al., 2017). These are susceptible to peroxidation and increase oxidative stress. Because of lipid peroxidation and the antioxidant property of thiamine, the thiamine reserves are further depleted at an increasing rate (see Keinänen et al., 2012; 2017) during the long spawning migration followed by a long prespawning fasting period of salmon (Ikonen, 2006). Diminished body stores do not allow adequate deposition of thiamine into developing oocytes; the development of offspring cannot be sustained until the end of the yolk-sac period, when fry start external feeding. Because M74 is induced by the ample but unbalanced food resources for salmon (primarily young sprat), the incidence of the M74 syndrome may be reduced and even prevented. The safest strategy for attaining this objective would be to ensure a large and stable cod stock in the Baltic Sea (Casini et al., 2009) to prey on the sprat, and possibly also by managing the sprat fishery in years when the cod stock is weak (Mikkonen et al., 2011; Keinänen et al., 2012). Evidently, as a consequence of strengthening of the cod stock and flattening out of the sprat stock (ICES, 2012a) the incidence of M74 decreased and was virtually non-existent in However, M74 returned, apparently principally as a consequence of an exceptionally strong year class of sprat in 2014 (ICES, 2017c). Young sprat were exceptionally numerous even in the northern areas of the Baltic Proper and Gulf of Finland. Moreover, the year class of herring in 2014 was strong, e.g. in the Bothnian Sea (Raitaniemi and Manninen, 2017). The thiamine concentrations in unfertilized eggs of salmon ascended the rivers of the Gulf of Bothnia decreased in autumn 2015 and were even lower in salmon ascended in autumn Thus, after several favourable years, M74 again impaired salmon yolk-sac fry survival in spring 2016, M74 mortalities further increased in spring 2017 and will prevail in spring The estimates for the cod stocks are not very reliable, but the stocks are not strong and cod reproduction in spring 2017 was not very successful (Raitaniemi and Manninen, 2017). Thus, the potential for strengthening of M74 exists in case of new strong year classes of sprat. In unfertilized eggs of salmon having ascended the Lithuanian River Neris in autumn 2017, the free thiamine concentrations were considerable higher compared to salmon of the Gulf of Bothnian rivers, and the incidence of M74 in spring 2018 will be low (or, based on a small number of sampled fish, almost insignificant). Apparently those salmon have been feeding in the southern Baltic Proper, where the presence of cod, contrary to the northern Baltic Sea, has reduced sprat from its exceptionally high year class 2014 (ICES, 2017c). Thus young sprat from the year 2014 has been less numerous in the southern Baltic Proper than in the northern areas of the Baltic Sea (Raitaniemi and Manninen, 2017), and the herring biomass as food for salmon, e.g. in SD 25, has been higher than that of sprat (Jacobson et al., 2018). In the Stock Annex (Annex 2, Chapter CA.1.6), a description is given of a Bayesian hierarchical model applied to the Gulf of Bothnian (GoB) monitoring data (Tables and 3.4.3) of M74 occurrence from rivers in Finland and Sweden, to obtain annual estimates of the M74-derived yolk-sac fry mortality. This information is needed to fully assess the effects of M74 on the reproductive success of spawners. Besides annual esti-

138 132 ICES WGBAST REPORT 2018 mates of M74 mortality in the rivers, where such has been recorded, the model provides annual estimates of the mortality for any GoB river, in which no monitoring has been carried out (Table , Figure ). Most of the wild stocks, including all smaller wild rivers in the GoB, belong to this group. The results demonstrate that in some years, the actual M74 mortality among offspring has been lower than the proportion of M74 females indicated, which apparently is related (see above) to mildness of the syndrome, i.e. to partial mortalities in offspring groups M 74 in Gulf of Finland and Gulf of Riga In the River Kymijoki in AU 6 (Gulf of Finland) the incidence of M74 has in many years been lower than in the northern AU 1 rivers Simojoki and Tornionjoki (Table 3.4.1; Keinänen et al., 2008; 2014). However, in the reproductive period 1997/1998, for example, when M74 mortalities among salmon yolk-sac fry of the Gulf of Bothnia rivers were temporarily low, the situation was vice versa; evidently this reflected variation in sprat abundance between the main feeding areas, i.e. the Baltic Proper and the Gulf of Finland. The long-term tendency has, however, been roughly similar. The River Kymijoki of the Gulf of Finland, with introduced salmon originating from the Neva stock, was included in the Finnish M74 monitoring programme from the year 1995, but no data for the years and exist, because of problems in salmon collection for monitoring. Therefore, the latest mortality data from the R. Kymijoki are from spring 2007 (Table 3.4.1). However, in autumn 2013 a few Kymijoki salmon females were caught for renewing of the broodstock. Based on relatively high thiamine concentrations in unfertilized eggs (mean 3.2 ± 1.1 nmol/g, N = 5) of all five females, M74 mortalities in spring 2014 were unlikely. In Estonia, M74 has been observed in hatcheries in some years during the period , but the mortality has not exceeded 15%. A small number of spawners is collected for broodstock from river Kunda since 2013, and no fry mortality has been observed. However, in 2016 the eggs from one female (out of four) displayed mortality after hatching. This recent observation indicates that the incidence of M74 may increase also in the Gulf of Finland, apparently as a consequence of the exceptionally strong 2014 year class of sprat (ICES, 2017c). According to Raitaniemi and Manninen, (2017) sprat has in subsequent years been highly abundant and more numerous than herring in the northern Baltic Proper and Gulf of Finland. There is no evidence to suggest that M74 occur in Latvian salmon populations. In the main hatchery Tome, the mortality from hatching until the start of feeding varied in the range of 2 10% in the years In addition, parr densities in Latvian river Salaca did not decrease during the period in the 1990s when salmon reproduction in the Gulf of Bothnia was negatively influenced by M74 (Table ). Before ascending the river, salmon from Daugava and Salaca feed in the Gulf of Riga, where the main prey species of salmon was herring during the years (Karlsson et al., 1999; Hansson et al., 2001). Although sprat was the dominant prey species in the Baltic Proper during that time period, the salmon diet in the Gulf of Riga did not include sprat. Furthermore, in contrast to salmon feeding in the Baltic Proper or in the Bothnian Sea, the proportion of other prey species, such as sandeel (Ammodytes spp.), perch (Perca fluviatilis), smelt (Osmerus eperlanus) and cod (Gadus morhua), was considerable in the Gulf of Riga (Karlsson et al., 1999; Hansson et al., 2001). Salmon in River Daugava moreover ascended later than salmon in Gulf of Bothnia rivers (Karlsson et al., 1999).

139 ICES WGBAST REPORT Dioxin In Sweden, the National Food Agency is responsible for sampling, analysis and dietary recommendations regarding dioxin in fish. In their latest report, the results indicate elevated levels of dioxin in Baltic salmon caught along the coast (Fohgelberg and Wretling, 2015). The Swedish control programme is set up in accordance with EU regulation 589/2014. Limits are set out in EU Regulation 1881/2006 with updates in EU Regulation 1259/2011. Sweden has an exception to the limits of dioxin when it comes to salmon and a few other fish species in the Baltic Sea and in Lakes Vänern and Vättern. Also Finland has an exemption to the EC regulation 1259/2011 which allows selling of Baltic salmon and sea trout in the domestic market. No export of wild-caught salmon or sea trout is allowed. In Denmark the following restrictions for marketing of salmon (and sea trout) were enforced from December 5th, 2016: Salmon 5.5 kg gutted weight caught in ICES subdivisions must be trimmed (deep-skinned) before marketing. In the same SDs salmon weighing >5.5 kg and <7.9 kg can be marketed, if trimmed and the ventral part of the fish is removed. Each batch of salmon >2.0 kg caught in ICES SD must also be analysed for dioxin before marketing. Dioxin levels found in samples taken in 2006 and 2013 were comparable, while samples from 2011 contained slightly lower concentrations of dioxin Disease outbreaks In the last 4 5 years, health issues for salmon related to specific rivers have been reported from several countries around the Baltic. There are similarities between these reports, but also differences, and there is a need for an evaluation of the status before any overall conclusions for the current health status of Baltic salmon can be drawn. Besides national sampling programmes, the ICES Working Group on Pathology and Diseases of Marine Organisms (WGPDMO) will have salmon health issues in its ToRs for the next three years period. Since 2014, an increasing number of reports from fishermen and local administrators of dying or dead salmon have come from Swedish and Finnish salmon rivers, spanning from Tornionjoki to Mörrumsån. The affected salmon have displayed various degrees of skin damage, from milder erythemas and bleedings, to UDN-like (Ulcerative Dermal Necrosis) lesions and more severe ulcers and traumatic wounds that are typically followed by secondary fungal infections causing death (SVA 2017). To some extent also other fish species, such as sea trout, whitefish and grayling have been reported with the same symptoms. The disease prevalence has varied considerably between both rivers and years. In some rivers, there are so far no reports of elevated levels of elevated salmon death. The most severe disease outbreaks occurred in Tornionjoki ( ), Kalixälven (2015), Ume/Vindelälven ( ), Ljungan (2016) and Mörrumsån ( ). In several cases, the number of dead salmon (and other species) has been considerable, although quantitative estimates of total death rates are missing. However, in e.g. Mörrumsån, it has been noted that following a year with disease very few overwintered spawners (kelts) appear to remain the following spring according to river catches. In 2015 and 2016, the Swedish National veterinary institute (SVA) and the Finnish food safety authority (Evira) conducted investigations aimed at identifying the cause of the salmon disease. Analyses of Tornionjoki salmon in 2015 showed that some of the sampled fish displayed UDN-like symptoms. Cultivation for virus and bacteria in 2016 did not provide conclusive answers, although in some cases bacteria associated with skin

140 134 ICES WGBAST REPORT 2018 lesions were identified. Next generation sequencing indicated presence of herpes- and iridoviruses in individuals with erythemas. These viruses may cause skin lesions, but these findings need to be investigated further (SVA and Evira, in prep.). Although it appears likely that the disease outbreaks in Swedish and Finnish salmon rivers during recent years have a common cause, this still remains to be proved. In 2018, Swedish SVA is planning to do further studies of the disease development and its cause(s). The failing health of returning salmon in Swedish rivers continued in The symptoms resembled those in previous years, again with large variation among rivers. The most severe problems with weak or dead wild fish were reported from Mörrumsån and Ume/Vindelälven. High frequencies of adult salmon with skin damage were also reported from the reared salmon rivers Indalsälven and Ångermanälven. In addition, salmon in several reared rivers was described as lethargic, quickly developing fungal infections and often dying in the hatchery facilities long before spawning. Some compensatory hatcheries (Ångermanälven, Umeälven, Ljusnan) also experienced difficulties in getting large enough numbers of adults for their broodstock collections. In Vindelälven low levels of 0+ salmon were again registered in 2017, in line with small numbers of ascending adults (especially females) in 2016 and rising levels of M74 (Sections and 3.4). Also Ljungan displayed very low 0+ densities in 2017, likely due to small number of spawners in 2016 (when many dead salmon were found) in combination with M74. Notably, only one out of 400 salmon (0.25%) tagged at the Ume/Vindelälven river mouth in 2017 managed to pass the counter in the Norrfors fishway. Most of these tagged salmon stayed further downstream for some time, without managing to migrate further upstream, before finally leaving the river (Kjell Leonardsson, SLU, pers. comm.). Finally it should be noted that in the past two decades the proportion of females in Ume/Vindelälven has decreased markedly over time; a development not yet seen in Torneälven/Tornionjoki (Figure ) or from more scattered data in other rivers with less pronounced salmon health problems. Late in 2017, prespawning mortality for sea trout and salmon was reported for the first time from river Gauja in Latvia. Similar to in Swedish rivers, the fish were described as apathetic; they showed slow response to irritants and were easily caught. There were also multiple observations of skin wounds with fungal infections. Sea trout and salmon from Gauja were examined for presence of viruses: IHNV (infectious hematopoietic necrosis virus), VHSV (viral hemorrhagic septicemia virus) and IPNV (infectious pancreatic necrosis virus) and bacteria: Aeromonas salmonicida, Aeromonas hydrophila, Yersinia spp., Salmonella spp., Pseudomonas spp. and Plesiomonas spp. In addition, search for parasites and histological examinations of wounds were carried out. The investigations showed that the above mentioned pathogens were not the cause for the observed disease and prespawning mortality in Latvia. Severe disease problems have occurred in all Polish Pomeranian sea trout rivers since Similar to in northern salmon rivers, the disease problems in Poland have been variable over time with peaks and drops (Bartel et al., 2009). Further, the affected sea trout display UDN-like skin damages followed by fungal infections, high mortality and lack of kelts. Also, salmon and grayling with symptoms have been observed. Polish veterinary studies have been performed, but so far without any clear conclusions, any virus or other uncommon bacteria were detected. In 2017, sea trout with symptoms were again observed, not only in Pomerania but also in the Vistula River. So far, there have been no reports of UDN-like disease problems in Lithuanian, Estonian and Russian rivers. Since spawning season 2011, an increasing number of fungal

141 ICES WGBAST REPORT infected sea trout have been reported from the Trave River, the largest Baltic Sea discharging river in German Schleswig-Holstein. As a consequence, project-based research ( ) on the health status of sea trout in the Trave has been launched. Potential consequences of health-related problems for the future development of wild salmon stocks, and how such extra mortality may be monitored and handled in stock assessment is briefly discussed in Section Summary of the information on wild and potential salmon rivers Wild smolt production in relation to the smolt production capacity is one of the ultimate measures of management success. Among the wild rivers flowing into the Gulf of Bothnia and the Main Basin (assessment units 1 5), smolt abundance is measured directly in the index rivers Simojoki and Tornionjoki/Torneälven (AU 1), Sävarån (AU 2, replaced with Rickleån since 2013), Vindelälven (AU 2), Mörrumsån (AU 4) and in the Latvian river Salaca (AU 5). In addition, a few years of smolts counting has also been performed in Lögdeälven (AU 2), Testeboån (AU 3) and Emån (AU 4) (Sections ) and counting in additional rivers may take place in the future. The river model (Annex 2), which utilises all available juvenile abundance data, is a rigorous tool for formal assessment of current smolt production. Differences in the status of wild stocks are apparent, not only in terms of the level of smolt production in relation to potential production (section 4.2), but also in terms of trends in various indices of abundance. Differences in trends are clear between regions: most Gulf of Bothnia (AU 1 3) rivers have shown increases in abundance while many of the Main Basin (AU 4 5) rivers have shown either decreasing or stable abundance and the development in the AU 6 rivers falls between these two regions. Rivers in the Gulf of Bothnia (assessment units 1 3) The parr production in the hatching years of was as low as in the 1980s (Tables , and , and Figures , , , and ), although the spawning runs were apparently larger (Tables , , and Figures , ). In those years, the M74 syndrome caused high mortality (Table and Figure 3.4.1), which decreased parr production considerably. In the hatching years , parr densities increased to higher levels, about five to ten times higher than in the earlier years. These strong year classes resulted from large spawning runs in and a simultaneous decrease in the level of M74. The large parr year classes hatching in resulted in increased smolt runs in 2000 and 2001 (Table ). Despite some reduction in parr densities during , parr densities and subsequent smolt runs stayed on elevated levels compared to the situation in the mid-1990s. In 2003, densities of one-summer old parr increased in some rivers back to the peak level observed around 1998, while no similar increase was observed in other rivers. From , densities of one-summer old parr showed a yearly increase in most of the rivers, but in 2007 the densities of one summer old parr again decreased. Despite the relative high spawning run in 2009 the densities of one summer old parr in 2010 decreased substantially in most rivers, compared to the densities in The densities of one summer old parr in 2012 stayed at the same level as in 2011, or even increased, despite the relatively weak 2011 spawning run. The increased spawning run in 2012 did not substantially increase the densities of one summer old parr in 2013, whereas the increased spawning runs in 2013 and 2014 resulted in elevated densities of one summer old parr. The increased spawning run in 2016 did not substantially increase the densities of one summer old parr in 2017.

142 136 ICES WGBAST REPORT 2018 Catch statistics and fishway counts also indicate some differences among rivers in the development in number of ascending spawners. To some extent, these differences may reflect problems with fish passages in certain rivers. For example, a survey in 2015 of the efficiency of the fishway in Piteälven indicated a large delay in the spawning run and loss of salmon and trout that didn t pass the fishway located below the spawning areas. Similar observations have also been identified in Åbyälven (Section 3.1.2). There has been pronounced annual variation in the indices of wild reproduction of salmon both between and within rivers. Variation in abundance indices might partly be explained to extreme summer conditions in the rivers during some years, e.g. in and in 2006, which might have affected river catches and the fish migration in some fishways. Counted number of salmon in 2007 increased with about 50% compared to The additional increase in fishway counts in 2008 is in agreement with increased river catches, which more than doubled in 2008 compared to 2007 and were almost as high as in the highest recorded years (1996 and 1997). The spawner counts in 2010 and 2011 in combination with information on river catches indicated weak spawning runs in those years. The large increased spawning run in Tornionjoki in 2012, 2013, 2014 and 2016, as compared to 2011, resulted in increased total river catches with 40 70% compared to the two previous years. The spawning run in 2017 decreases almost with half in all rivers compared with previous year and the same pattern was seen in decreased river catches. Most data from the Gulf of Bothnia rivers indicate an increasing trend in salmon production. Rivers in AU 1 have shown the most positive development, while stocks in the small rivers in AUs 2 3 have yet not shown as strong positive development. These small rivers are located on the Swedish coast close to the Quark area (northern Bothnian Sea, southern Bothnian Bay). The recent period of low M74-levels has most likely affected the wild production positively. In 2017, however, levels of offspring mortality again raised, and preliminary data from thiamine analyses of eggs from two Swedish and two Finnish stocks indicate that M74-mortality among offspring hatching in 2018 will decrease somewhat; preliminary results from Simojoki, Tornionjoki, Ume/Vindelälven and Dalälven indicate that offspring mortality for those rivers may be reaching around 15-35%. Disease outbreaks seen in recent years in several rivers is another mortality factor that may have a negative impact on future stock development (Sections 3.4 and 4.4.1). Rivers in the Main Basin (assessment units 4 5) The status of the Swedish AU 4 salmon populations in rivers Mörrumsån and Emån in the Main Basin differ, but they both show a similar slight negative trend in parr densities (Table and Figures and ). The outbreak of M74 mortality in the early 1990s might have decreased smolt production in mid-1990s, after reaching the historical highest parr densities in Mörrumsån at the turn of the 1980s and 1990s. In Emån, the smolt production has for long been far below the required level, which is most likely a result of insufficient numbers of spawners so far finding their way to reproduction areas further upstream in the river system. The present status of the population is probably higher in Mörrumsån than in Emån. Although average electrofishing densities have not increased since the mid-1990s in Mörrumsån, smolt trapping results for the production in the upper part of Mörrumsån shows a positive trend in the period (Section 3.1.4). Updated production capacity priors for Mörrumsån and Emån (ICES, 2015) and smolt estimates from the river model tailored for southern rivers (ICES, 2017d) are now used in the full life-history model. The improvements allow more reliable status assessment

143 ICES WGBAST REPORT of stocks in these rivers (Section 4.4). High disease related mortality among spawners in Mörrumsån (but yet not in Emån) in recent years is another factor that also may affect the future stock development (Sections 3.4 and 4.4.1). Among rivers in AU 5, the Pärnu river exhibit the most precarious state: no parr at all were found in the river in In the densities increased slightly, but in 2007, 2008, 2010 and 2011 again no parr were found. Reproduction occurred in 2008, 2011 and 2012 resulting in low densities of parr in 2009 and Parr density was remarkably high in 2017 (Table , Figure ). There has been very large annual variation in parr densities, both within and between rivers in AU 5. Since 1997, parr densities in the river Salaca in Latvia have been on relatively high levels (Table , Figure ), but in 2010 and 2011 the densities decreased to the lowest observed level since the mid-1990s. In 2015 the density increased to the highest observed so far, and in 2017 the densities increased compared with previous year. In river Gauja, parr density levels have been very low since In 2014, the 0+ parr density increased to a slightly higher level. It seems that in some of the smaller AU 5 salmon rivers (Saka, Pēterupe and Vitrupe) reproduction occurs only occasionally; as an example, salmon 0+ parr densities in 2015 increased to the so far highest observed in these small rivers, except in Pēterupe, whereas in 2016 the 0+ densities were again very low or even zero. Although only relatively short time-series of parr and smolt abundance are available from Lithuanian salmon rivers, the latest monitoring results (Table ) indicate somewhat similar variation in juvenile production as seen in Latvian rivers. The observed parr densities are very low in relation to observed parr densities in most other Baltic rivers. This illustrates the poor state of several wild salmon stocks in AU 5. These stocks might be in a higher risk of extinction than any of the stocks in AU 1 3 (Gulf of Bothnia). In Lithuania, measures have been carried out since 1998 to increase salmon populations (Section 3.1.5). Implementation of measures has stabilized the salmon populations in Lithuanian rivers, and the production is increasing very slowly. Pollution also affects the salmon rivers. Another important factor in Lithuanian rivers, which are of lowland type, is lack of suitable habitats for salmon parr and high summer temperatures. Besides regulation of fisheries, many of the salmon rivers in the Main Basin (AU 4 5) may need habitat restoration and re-establish connectivity, which aim at stabilizing and improving natural reproduction. For instance, in the Pärnu River, the Sindi dam to a large extent prevents access to over 90% of the potential reproduction areas. In the rivers Mörrumsån and Emån, new fish passes have increased significantly the available reproduction area to salmon. Rivers in assessment unit 6 (Gulf of Finland, Subdivision 32) The 0+ parr density in Estonian wild rivers Kunda and Keila were high in In Vasalemma the 0+ parr density increased, approaching the average level in the river. The status of river Keila and Kunda is considered to be good, whereas improvement has been modest in river Vasalemma. Because of highly variable annual parr densities in Vasalemma and Kunda, the status of these wild populations must still be considered uncertain. In the Estonian mixed rivers Purtse, Selja, Loobu, Valgejõgi, Jägala, Pirita and Vääna, wild parr densities mostly decreased in However, in the preceding three years ( ) parr density stayed above the long-term average in all of these rivers. In 2017, parr density increased to a very high level. The clearest positive trend can be seen

144 138 ICES WGBAST REPORT 2018 in Selja, Valgejõgi, Loobu and Pirita. However, because of the high fluctuations in recruitment, the status of these populations remains uncertain. To safeguard these stocks additional regulatory measures were enforced in 2011 (see Section 2.9) and positive effect of these measures can be seen as increases in wild parr densities and as a relatively satisfactory amount of ascending spawners to R. Pirita in recent years ( ). In Russia, wild salmon reproduction occurs in rivers Luga and Gladyshevka. The status of both these stocks is considered very uncertain. However, high densities of 0+ salmon parr occurred in Gladyshevka in 2015, whereas there was no monitoring in 2016 and in Since 2003, there is no information that suggests wild reproduction in river Neva. In Finland, natural reproduction in the mixed river Kymijoki has increased during the last ten years. However, reproduction varies a lot between years and it mainly takes place on the lower part of the river, although possibilities for salmon to access above the first dams have been improved. Smolt production still remains well below the river s potential (Section 3.1.6). Total natural smolt production in Estonian, Finnish, and Russian rivers in the Gulf of Finland area was estimated to about in In 2017, the estimated wild AU 6 smolt production slightly increased to about It is estimated that the wild smolt production will decrease in 2018 (ca smolts). The AU 6 smolt releases since year 2000 has been on a stable level. The exception was the year 2011, when releases were reduced to almost half (Table 3.3.1). The reduction in Russian smolt releases was caused by exceptionally warm climatic conditions in summer 2010, causing high parr mortality in hatcheries.

145 ICES WGBAST REPORT Table Salmon catches (in kilos) in four rivers of the Subdivision 31, and the catch per unit of effort (cpue) of the Finnish salmon rod fishing in the river Tornionjoki/Torneälven. Simojoki Kalixälven Byskeälven Tornionjoki/ Torneälven (au 1) (au1) (au1) (au2) Finnish Swedish Total CPUE catch, kilo catch, kilo catch, kilo catch, kilo catch, kilo catch, kilo grams/day ) ) 561 2) /736 3) * ) Ban of salmon fishing 1994 in Kalixälven and Byskeälven and the Swedish tributaries of Torneälven. 2) Calculated on the basis of a fishing questionnaire similar to years before ) Calculated on the basis of a new kind of fishing questionnaire, which is addressed to fishermen, who have bought a salmon rod fishing license. 4) 5 tonnes of illegal/unreported catch has included in total estimate. * preliminary

146 140 ICES WGBAST REPORT 2018 Table Numbers of wild salmon (MSW=MultiSeaWinter) in fishways and hydroacoustic counting in the rivers of the assessment units 1 and 2 (subdivisions 30 31, Gulf of Bothnia). Year Number of salmon Simojoki (au 1) Tornionjoki (au 1) Kalixälven (au 1) Råneälven (au 1) Piteälven (au 2) Åbyälven (au 2) Byskeälven (au 2) Rickleån (au 2) Ume/Vindelälven (au 2) Öreälven (au 2) MSW Total MSW Total MSW Total Total MSW Total MSW Total MSW Total Total MSW Females Total Total no control no control no control no control no control no control n/a n/a n/a n/a n/a ,326 23, ,828 59, ,580 52, , , ,456 57, ,137 98, ,409 40, Simojoki: Hydroacoustic counting near the river mouth, started Tornionjoki: Hydroacoustic counting 100 km upstream from the sea, started Kalixälven: Fishcounting in the fishway is a part of the run. No control during Råneälven: Hydroacoustic counting 40 km upstream from the sea, started Piteälven: New fishway built Fishcounting is the entire run. Åbyälven: New fishway built in Fishcounting is only part of the total run. Byskeälven: New fishway built Fishcounting is part of the total run. Rickleån: New fishways built Fishcounting is part of the total run. Umeälven/Vindelälven: Fishcounting in the fishway is the entire run. Öreälven: Fishcounting in the trap is part of the run. The trap was destroyed by high water levels in 2000.

147 ICES WGBAST REPORT Table The age and sex composition of ascending salmon caught by the Finnish river fishery in the River Tornionjoki since the mid-1970s. Year(s) N:o of samples A1 (Grilse) 9% 53% 35% 7% 20% 8% 10% 6% 11% A2 60% 31% 38% 59% 50% 53% 43% 76% 69% A3 29% 13% 24% 28% 26% 31% 38% 11% 18% A4 2% 2% 3% 4% 3% 6% 6% 5% 1% >A4 0% 1% <1 % 2% 2% 2% 3% 1% 1% Females, proportion of biomass About 45 % 49% 75% 71% 65% 67% 62% 67% 64% Proportion of repeat spawners 2% 2% 2% 6% 6% 8% 9% 8% 3% Proportion of reared origin 7% 46 %* 18% 15% 9% 1% 0.3% 0.3% 0.5% * An unusually large part of these salmon were not finclipped but analysed as reared on the basis of scales (probably strayers). A bulk of these was caught in 1989 as grilse.

148 142 ICES WGBAST REPORT 2018 Table Densities and occurrence of wild salmon parr in electrofishing surveys in the rivers of the assessment unit 1 (Subdivision 31). River Number of parr/100 m² by age group 2+ & older >0+ (sum of two previous columns) Sites with 0+ parr (%) Number of sampling sites year Notes Simojoki % 14 No age data of older parr available % 14 No age data of older parr available % 16 No age data of older parr available % 16 No age data of older parr available % 16 No age data of older parr available % 22 No age data of older parr available % % % % No sampling because of flood % % % % 29 No age data of older parr available % % 17 Flood; only a part of sites were fished % % % % % % 19 Flood; only a part of sites were fished % 27 Flood; only a part of sites were fished % % % % % % % % % % % % 37 Tornionjoki % % % % % 37 Flood; only a part of sites were fished % % % % % % % % % % % % 60 Flood; only a part of sites were fished % % % % % % % % % % % % 61 Flood; only a part of sites were fished % 80

149 ICES WGBAST REPORT Table Continued. River Number of parr/100 m2 by age group 2+ & older >0+ (sum of two previous columns) Sites with 0+ parr (%) Number of sampling sites year Notes Kalixälven % % % % % % % 11 Flood; only a part of sites were fished % % % % % % 9 Flood; only a part of sites were fished % % % % % % % % % % % % % 9 Flood; only a part of sites were fished % % % % % % 30 Råneälven % % % % % % 1 Flood; only a part of sites were fished % % % % % No sampling because of flood % % % % % % % % % % % % % 5 Flood; only a part of sites were fished.

150 144 ICES WGBAST REPORT 2018 Table Estimated number of smolt by smolt trapping in the rivers Simojoki and Tornionjoki (assessment unit 1), and Sävarån, Ume/Vindelälven, Rickleån and Lögdeälven (assessment unit 2). The coefficient of variation (CV) of the trapping estimates has been derived from the mark recapture model (Mäntyniemi and Romakkaniemi, 2002) for the last years of the time-series. In the Ume/Vindelälven, however, another technique has been applied, in which smolts are tagged during the smolt run and recaptures has been monitored from adults ascending the year 1 2 years later. The ratio of smolts stocked as parr/wild smolts in trap catch is available in some years although total run estimate can not be provided (e.g. in the cases of too low trap catches). The number of stocked smolts is based on stocking statistics. Tornionjoki (AU 1) Simojoki (AU 1) Sävarån (AU 2) Ume/Vindelälven (AU 2) Rickleån (AU 2) Lögdeälv (AU 2) Smolt trapping, original Ratio of smolts stocked as parr/wild smolts in catch Number of stocked reared smolts (point estimate) Smolt trapping, original Ratio of smolts stocked as parr/wild smolts in catch Number of stocked reared smolts (point estimate) estimate CV of estimate estimate CV of estimate estimate CV of estimate Smolt trapping, original estimate CV of estimate estimate CV of estimate estimate CV of estimate 1977 n/a 29,000 n/a n/a n/a n/a 1978 n/a 67,000 n/a n/a n/a n/a 1979 n/a 12,000 n/a n/a n/a n/a 1980 n/a 14,000 n/a n/a n/a n/a 1981 n/a 15,000 n/a n/a n/a n/a 1982 n/a n/a n/a n/a n/a n/a 1983 n/a n/a n/a n/a n/a n/a 1984 n/a 19,000 n/a n/a n/a n/a 1985 n/a 13,000 n/a n/a n/a n/a 1986 n/a 2,200 n/a n/a n/a n/a ,000 *) ,129 1, ,800 n/a n/a n/a n/a , ,300 1, ,700 n/a n/a n/a n/a 1989 n/a ,829 12, ,841 n/a n/a n/a n/a , ,545 12, ,100 n/a n/a n/a n/a , ,344 7, ,916 n/a n/a n/a n/a 1992 n/a ,000 17, ,389 n/a n/a n/a n/a , ,342 9, ,087 n/a n/a n/a n/a , ,317 12, ,862 n/a n/a n/a n/a 1995 n/a ,986 1, ,580 n/a n/a n/a n/a , ,858 1, ,153 n/a n/a n/a n/a ,000 **) 20,004 2, ,939 n/a n/a n/a n/a , ,033 9, ,942 n/a n/a n/a n/a ,000 17% ,771 8, ,815 n/a n/a n/a n/a ,000 39% ,339 57, ,100 n/a n/a n/a n/a ,000 33% ,000 47, ,111 n/a n/a n/a n/a ,000 12% ,998 53, ,300 n/a n/a n/a n/a ,000 43% ,032 63, ,912 n/a n/a n/a n/a ,000 33% ,000 29, ,900 n/a n/a n/a n/a ,000 25% ,000 17,500 28% ,800 3,800 15% n/a n/a n/a ,250,000 35% ,814 29,400 35% ,000 12% n/a n/a n/a ,000 48% ,458 23,200 20% ,000 3,100 18% n/a n/a n/a ,490,000 37% ,442 42,800 29% ,000 4,570 18% n/a n/a n/a ,090,000 42% ,490 22,700 29% ,000 1,900 49% n/a n/a n/a 2010 n/a ,965 29,700 28% ,240 1,820 32% 193,800 21% n/a n/a ,990,000 27% ,048 36,700 13% ,643 28% 210,000 14% n/a n/a 2012 n/a ,437 19,300 37% n/a 352,900 19% n/a n/a 2013 n/a ,300 37,000 11% ,548 31% 302,600 25% n/a n/a 2014 n/a ,800 36,600 19% n/a 180,600 13% 2,149 16% n/a ,032,000 47% n/a n/a 186,000 13% n/a n/a ,914,000 27% ,900 7% n/a n/a 3,961 15% 5,211 22% ,000 27% n/a n/a n/a 4,794 22% n/a *) trap was not in use the whole period; value has been adjusted according to assumed proportion of run outside trapping period **) Most of the reared parr released in 1995 were non-adipose fin clipped and they left the river mainly in Because the wild and reared production has been distinguished on the basis of adipose fin, the wild production in 1997 is overestimated. This was considered when the production number used by WG was estimated. Smolt trapping, original Smolt trapping, original Smolt trapping, original

151 ICES WGBAST REPORT Table Densities and occurrence of wild salmon parr in electrofishing surveys in the rivers of the assessment unit 2 (subdivisions 30 31). Detailed information on the age structure of older parr (>0+) is available only from the Åbyälven and Byskeälven. River Number of parr/100 m² by age group 2+ & older >0+ (sum of two previous columns) Sites with 0+ parr Number of sampling year (%) sites Notes Piteälven No sampling 1992 No sampling No sampling 1996 No sampling No sampling because of flood No sampling 2000 No sampling 2001 No sampling No sampling 2004 No sampling 2005 No sampling % % % No sampling % No sampling because of flood No sampling because of flood % % % % No sampling Åbyälven % % % % % % % % % % % % No sampling because of flood % % % % % % % % % % % % % % % % % % % 10

152 146 ICES WGBAST REPORT 2018 Table Continued. River Number of parr/100 m² by age group >0+ (sum of & older two previous columns) Sites with 0+ parr Number of sampling year (%) sites Notes Byskeälven % No sampling 1988 No sampling % % % % % % % % % No sampling because of flood % % No sampling because of flood % % % % % % % % % No sampling because of flood % % % % % % 15 Kågeälven % % % % % α 50% α 0% α 0% No sampling No sampling No sampling No sampling α 58% α 30% α 33% α 54% α 46% α 44% α 58% α 82% % % % % % % % % % % % 7

153 ICES WGBAST REPORT Table Continued. Rickleån * 0+ * > % % % % % % % % % % % % % No sampling because of flood % % % % 7/* % % 7/* % 7/* % % % % 7/* % 7/* % 7/* % 7/* % 7/* % 7/*11 *) Average densities from extended electrofishing surveys in Rickleån, also including areas and sites in the upper parts of the river which have recently been colonized by salmon (for more details se section 4.2.2). These average densities are used as input in the river model (see stock annex). α) stocked and wild parr. Not possible to distinguish socked parr from wild.

154 148 ICES WGBAST REPORT 2018 Table Continued. River Number of parr/100 m² by age group >0+ (sum of & older two previous columns) Sites with 0+ parr (%) Number of sampling sites year Notes Sävarån % % % % % % % % % % % % No sampling because of flood % , % No sampling because of flood % % % % % % % % % % % % % 9 Ume/Vindelälven * 0+ * > % % % % % % % % % 6 Flood; only a part of sites were fished % % % % % % % % 19/* % 19/* % 19/* % 19/* % 19/* No sampling because of flood % 19/* % 19/* % 18/* % 19/* % 19/* % 9/*15 Only 9 of 19 sites were fished because of flood

155 ICES WGBAST REPORT Table Continued. Öreälven * 0+ * > % % % % % % % % % % % % No sampling because of flood % % % % % % % % 10/* % 10/* % % 10/* % 9/* % 10/* % 10/* % 10/* % 10/*13 *) Average densities from extended electrofishing surveys in Vindelälven, Öreälven also including areas and sites in the upper parts of the river which have recently been colonized by salmon (for more details se section 4.2.2). These average densities are used as input in the river model (see stock annex).

156 150 ICES WGBAST REPORT 2018 Table Continued. River Number of parr/100 m2 by age group >0+ (sum of & older two previous columns) Sites with 0+ parr (%) Number of sampling sites year Notes Lögdeälven * 0+ * > % % % 8/* % % % % % % % % % No sampling because of flood % % % % % % % % 8/* % 8/* % % 8/* % 8/* % 8/* % 8/* % 8/* % 8/*11 *) Average densities from extended electrofishing surveys in Lögdeälven also including areas and sites in the upper parts of the river which have recently been colonized by salmon (for more details se section 4.2.2). These average densities are used as input in the river model (see stock annex).

157 ICES WGBAST REPORT Table Densities and occurrence of wild salmon parr in electrofishing surveys in the assessment unit 3 (Subdivision 30). Detailed information on the age structure of older parr (>0+) is not available. Number of parr/100 m² by age group Number of River year & older >0+ Sites with 0+ parr (%) sampling sites Notes Ljungan % % % % % % No sampling because of flood % % No sampling because of flood % % % % No sampling because of flood % % 3 Flood; only a part of sites were fished No sampling because of flood No sampling because of flood No sampling because of flood Only one site fished because of flood 2013 No sampling because of flood % % % % 10 Testeboån n/a n/a n/a n/a n/a n/a n/a % % % 11 n/a = reared parr, which are stocked, are not marked; natural parr densities can be monitored only from 0+ parr

158 152 ICES WGBAST REPORT 2018 Table Densities of wild salmon parr in electrofishing surveys in the rivers of the assessment unit 4 (subdivisions 25 26, Baltic Main Basin). River year Number of parr/100 m² by age group Number of sampling Number of parr/100m 2 by age group from extended surveys Number of sampling sites from extended surveys sites 0+ >0+ α) 0+ α) >0+ Mörrumsån * *) Flood, only a part of sites were fished. α) Average densities from extended electrofishing surveys also including areas and sites in the upper parts of the river which have recently been colonized by salmon. These average densities are used as input in the river model (see stock annex)

159 ICES WGBAST REPORT Table Continued. River year Number of parr/100 m² by age group Number of sampling Number of parr/100m 2 by age group from extended surveys Number of sampling sites from extended surveys sites 0+ >0+ α) 0+ α) >0+ Emån * * no sampling because of flood

160 154 ICES WGBAST REPORT 2018 Table Densities of wild salmon parr in electrofishing surveys in the Latvian and Estonian wild salmon rivers of the assessment unit 5 (Gulf of Riga. Subdivision 28). River Number of parr/100 m 2 by age group Number of sampling year 0+ >0+ sites Pärnu : : : 4** : 0 0 : : 4** : : 0 1 : 5** : : : 5** : : 0 1 : 4** Salaca

161 ICES WGBAST REPORT Table Continued. Gauja 2003 <1 < < < < Venta Amata 2) < * * 3 ²) tributaries to Gauja *) reard fish **) electrofishing site - below Sindi dam : upstrem Sin

162 156 ICES WGBAST REPORT 2018 Table Densities of salmon parr in electrofishing surveys in rivers in Lithuanian of the assessment unit 5 (Baltic Main Basin). River Number of parr/100 m 2 by age group Number of sampling year 0+ >0+ sites Neris Žeimena

163 ICES WGBAST REPORT Table Continued. Mera Saria n/a n/a n/a n/a n/a n/a 2011 n/a n/a n/a n/a 2014 n/a n/a n/a n/a 2017 n/a n/a

164 158 ICES WGBAST REPORT 2018 Table Estonian wild and mixed salmon rivers in the Gulf of Finland. River Wild or mixed Water Flow m³/s First quality 1) obstacle km Undetected parr cohorts Production of >0+ parr mean min Purtse mixed IV (since 2006) Kunda wild III Selja mixed V Loobu mixed II Valgejõgi mixed IV Jagala mixed II Pirita mixed V Vaana mixed V Keila wild V Vasalemma wild II ) Classification of EU Water Framework Directive Table Densities of salmon parr rivers with only wild salmon populations, Subdivision 32. River Number of parr/100 m 2 by age group Number of sampling year 0+ >0+ sites Kunda

165 ICES WGBAST REPORT Table Continued. Keila Vasalemma * * *) = no electrofishing

166 160 ICES WGBAST REPORT 2018 Table Table Densities of wild salmon parr in rivers where supportive releases are carried out, Subdivision 32. Number of parr/100 m 2 Number of Number of parr/100 m 2 Number of River by age group sampling River by age group sampling year 0+ >0+ sites year 0+ >0+ sites Purtse Valgejõgi Selja Jägala Table continue on next page *) = no electrofishing

167 ICES WGBAST REPORT Number of parr/100 m 2 Number of Number of parr/100 m 2 Number of River by age group sampling River by age group sampling year 0+ >0+ sites year 0+ >0+ sites Loobu Pirita * * * * Kymijoki NA NA NA NA NA 5 Vääna NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 5 *) = no electrofishing

168 162 ICES WGBAST REPORT 2018 Table Current status of reintroduction programme in Baltic Sea potential salmon rivers. Potential production estimates are uncertain and currently being re-evaluated. River Description of river Restoration programme Results of restoration Country ICES subdivision Old salmon river Cause salmon population extinction of Potential production areas (ha) Potential smolt production (num.) Officially selected for reintroduction Programme initiated Measures Releases Origin of population Parr and smolt production from releases Spawne rs in the river Wild parr production Wild smolt production Moälven SE 31 yes 3, no yes c,l 2 Byskeälven yes yes >0 >0 Alsterån SE 27 yes 2, no no c,g,l 4 ** ** yes >0 >0 Helgeån SE 25 yes 2, no yes c,e,m 2 Mörrumsån yes yes >0 >0 Kuivajoki FI 31 yes 1, yes yes b,c,f 2 Simojoki yes yes yes 0 Kiiminkijoki FI 31 yes 1, yes yes b,c,d,f 2 Iijoki yes yes yes >0 Siikajoki FI 31 yes 1,2, no yes b,g,m 1.4 m ixed yes * 0 0 Pyhäjoki FI 31 yes 1,2, yes yes b,c,d,f,m 2 Tornionjoki/Oulojo yes yes yes 0 Kalajoki FI 31 yes 1,2, no yes b,e, m 1,4 no * 0 0 Perhonjoki FI 31 yes 1,2, no yes b,f 2 Tornionjoki/Oulojo yes * 0 0 Merikarvianjoki FI 30 yes 1,2, no yes b,c,e 2 Neva yes yes >0 * Vantaanjoki FI 32 no? no yes b,c,f,m 2 Neva yes yes 0 0 Kymijoki FI 32 yes 2,3, no yes b,c,m 2 Neva yes yes yes Sventoji LI 26 yes 2, yes yes m,c 2 Nemunas yes yes Minija/Veivirzas LI 26 yes * yes yes c 2 Nemunas no no 0 0 Wisla/Drweca PL 26 yes 1,2,3,4 * * yes yes b,m 2 Daugava yes yes * * Slupia PL 25 yes 1,2,3,4 * * yes yes b,m 2 Daugava yes yes yes * Wieprza PL 25 yes 1,2,3,4 * * yes yes b,m 2 Daugava yes yes * * Parseta PL 25 yes 1,2,3,4 * * yes yes b,m 2 Daugava yes yes * * Rega PL 25 yes 1,2,3,4 * * yes yes b 2 Daugava yes yes * * Odra/Notec/Drawa PL 24 yes 1,2,3,4 * * yes yes b 2 Daugava yes yes * * Reda PL 24 yes? 1,2,3,4 * * yes yes b 2 Daugava yes yes * * Gladyshevka RU 32 yes 1,2, no yes a,g,k,n 2 Neva yes yes yes >0 Cause of salmon popul. extinction Measures Releases 1 Overexploitation Fisheries 1 Has been carried out, now finished 2 Habitat degradation a Total ban of salmon fishery in the river and river mouth 2 Going on 3 Dam building b Seasonal or areal regulation of salmon fishery 3 Planned 4 Pollution c Limited recreational salmon fishery in river mouth or river 4 Not planned d Professional salmon fishery allowed in river mouth or/and river * No data Habitat restoration Dam removal ** Not applicable e partial i planned f completed j completed g planned k not needed h not needed

169 ICES WGBAST REPORT Table Densities of wild salmon parr in electrofishing surveys in potential rivers. Note that all the Lithuanian rivers listed are currently stocked (and therefore could be called 'mixed'). Country Assess- Sub-div River Number of parr /100 m² Number of ment and year sampling unit 0+ >0+ sites Sweden 4 27 Alsterån no sampling no sampling 2017 no sampling Finland 1 31 Kuivajoki n/a n/a n/a n/a n/a n/a n/a n/a n/a no sampling 2009 no sampling 2010 no sampling 2011 no sampling 2012 no sampling 2013 no sampling 2014 no sampling 2015 no sampling 2016 no sampling 2017 no sampling Finland 1 31 Kiiminkijoki n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a no sampling n/a n/a n/a no sampling 2016 no sampling 2017 no sampling table continues next page * = stocked and wild parr. Not possible to distinguish stocked parr from wild. n/a = reared parr, which are stocked, are not marked; natural parr densities can be monitored only from 0+ parr

170 164 ICES WGBAST REPORT 2018 Table continues Country Assess- Sub-div River Number of parr /100 m² Number of ment and year sampling unit 0+ >0+ sites Finland 1 30 Pyhäjoki n/a n/a n/a n/a n/a n/a n/a n/a n/a no sampling no sampling 2013 no sampling 2014 no sampling 2015 no sampling 2016 no sampling 2017 Russia 6 32 Gladyshevka no sampling 2012 no sampling no sampling table continues next page

171 ICES WGBAST REPORT Table continues Contry Assess- Sub-div Number of parr/100 m 2 Number of ment River by age group sampling unit year 0+ >0+ sites Lithuania 5 26 Šventoji Lithuania 5 26 Siesartis Lithuania 5 26 Virinta no sampling table continues next page

172 166 ICES WGBAST REPORT 2018 Table continues Contry Assess- Sub-div Number of parr/100 m 2 Number of ment River by age group sampling unit year 0+ >0+ sites Lithuania 5 26 Širvinta no sampling Lithuania 5 26 Vilnia Lithuania 5 26 Vokė no sampling table continues next page

173 ICES WGBAST REPORT Table continues Contry Assess- Sub-div Number of parr/100 m 2 Number of ment River by age group sampling unit year 0+ >0+ sites Lithuania 5 26 B. Šventoji no sampling Lithuania 5 26 Dubysa Lithuania 5 26 Minija

174 168 ICES WGBAST REPORT 2018 Table Salmon smolt releases by country and assessment units in the Baltic Sea (x1000) in Year Assessment unit Country Age Finland 2yr yr Total Sweden 1yr yr Total Finland 1yr yr yr Sweden 1yr yr Total Denmark 1yr yr EU 1yr yr Sweden 1yr yr Total Estonia 1yr yr Poland 1yr yr Latvia 1yr yr Lithuania 1yr Total Assessment units 1-5 Total Estonia 1yr yr Finland 1yr yr yr 12 3 Russia 1yr yr Total Grand Total

175 ICES WGBAST REPORT Table Releases of salmon eggs, alevin, fry and parr to the Baltic Sea rivers by assessment unit in Assessment unit age eyed egg alevin fry 1s parr 1yr parr 2s parr 2yr parr year

176 170 ICES WGBAST REPORT 2018 Table Continued

177 ICES WGBAST REPORT Table The M74 frequency (in %) as a proportion of M74 females (partial or total offspring M74 mortality) or the mean offspring M74-mortality (see annotation 2) of sea-run female spawners, belonging to populations of Baltic salmon, in hatching years The data originate from hatcheries and from laboratory monitoring. Prognosis (min max) for 2018 is based on the free thiamine concentration of unfertilized eggs of autumn 2017 spawners and moreover, on the number of wiggling females. River Subdi Simojoki (2) Tornionjoki(2) *a Kemijoki Iijoki Luleälven Skellefteälven Ume/Vindelälven Angermanälven Indalsälven Ljungan Ljusnan Dalälven Mörrumsan Neva/Åland (2) Neva/Kymijoki (2) Mean River Simojoki and Tornionjoki Mean River Luleälven, Indalsälven, Dalälven Mean total ) All estimates known to be based on material from less than 20 females in italics. 2) The estimates in the rivers Simojoki, Tornionjoki/Torne älv and Kymijoki are since 1992, 1994 and 1995, respectively, given as the proportion of females (%) with offspring affected by M74 and before that as the mean yolk-sac-fry mortality (%). *a = with one wiggler included; without wiggler 12 26%.

178 172 ICES WGBAST REPORT 2018 Table Summary of M74 data for Atlantic salmon (Salmo salar) stocks of the Rivers Simojoki, Tornionjoki and Kemijoki or Iijoki (hatching years ), indicating the total average yolk-sac fry mortality among offspring of sampled females (%), the percentage of sampled females with offspring that display M74 symptoms (%) and the percentage of sampled females with 100% mortality among offspring (%). Data from less than 20 females is given in italics. NA = not available. Total average yolk-sac fry Proportion of females with Proportion of females mortality among offspring (%) offspring affected by M74 (%) without surviving offspring (%) Simojoki Tornionjoki Kemijoki/Iijoki Simojoki Tornionjoki Kemijoki/Iijoki Simojoki Tornionjoki Kemijoki/Iijoki NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 47 NA NA 74 NA NA 86 NA 50 NA NA 91 NA 50 NA NA 3 NA 3 NA NA 6 3 NA 6 0 NA NA 0 0 NA 0 0 NA NA 0 0 NA 0 0 NA NA NA 0 NA NA 0 NA NA NA NA 0 NA NA 0 NA NA NA NA 4 NA NA 4 NA NA NA NA NA 29

179 ICES WGBAST REPORT Table Summary of M74 data for nine different Atlantic salmon stocks (hatching years ), in terms of the number of females sampled with offspring affected by the M74 syndrome compared with the total number of females sampled from each stock. Luleälven Skellelteälven Ume/Vindel älven Angermanälven Indalsälven Ljungan Ljusnan Dalälven Mörrumsån M74 Total M74 Total M74 Total M74 Total M74 Total M74 Total M74 Total M74 Total M74 Total 1985 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 6 38 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

180 174 ICES WGBAST REPORT a) tonnes b) Illegal/unreported Sweden Finland tonnes Figure Total river catches in the River Tornionjoki (assessment unit 1). a) Comparison of the periods from 1600 to present (range of annual catches). b) From 1974 to present. Swedish catch estimates are provided from 1980 onwards.

181 ICES WGBAST REPORT Assessment unit Kg Simojoki Tornionjoki Kalixälven Year Figure Salmon catch in the rivers Simojoki, Tornionjoki (finnish and swedish combined) and Kalixälven, Gulf of Bothnia, assessment unit 1, Ban of salmon fishing 1994 in the river Kalixälven.

182 176 ICES WGBAST REPORT Assessment unit 1 and Kalixälven (au 1) Råneälven (au 1) Piteälven (au 2) Åbyälven (au 2) Byskeälven (au 2) Ume/Vindelälven (au 2) Number of wild salmon Year Figure Total wild salmon run in fish way (ecosounder in Råneälven) in rivers in assessment unit 1 and 2, in

183 ICES WGBAST REPORT Assessment unit 1 50 Number of 0+ parr/100m² Simojoki Tornionjoki Kalixälven Råneälven Year Figure Densities of 0+ parr in rivers in Gulf of Bothnia (Sub-division 31), assessment unit 1, in

184 178 ICES WGBAST REPORT Assessment unit Number of >0+ parr/100m² Simojoki Tornionjoki Kalixälven Råneälven Year Figure Densities of >0+ parr in rivers in Gulf of Bothnia (Sub-division 31), assessment unit 1, in

185 ICES WGBAST REPORT Assessment unit Number of 0+ parr/100m² Åbyälven Byskeälven Kågeälven Rickleån Sävarån Ume/Vindelälven Öreälven Lögdeälven Year Figure Densities of 0+ parr in rivers in Gulf of Bothnia (Sub-division 31), assessment unit 2, in

186 180 ICES WGBAST REPORT Assessment unit Number of >0+ parr/100m² Piteälven Åbyälven Byskeälven Kågeälven Rickleån Sävarån Ume/Vindelälven Öreälven Lögdeälven Year Figure Densities of >0+ parr in riveres in Gulf of Bothnia (Sub-division 31), assessment unit 2, in

187 ICES WGBAST REPORT Tornionjoki Ume/Vindel Figure Observed female proportions in Tornionjoki (catch samples) and Ume/Vindelälven (fish ladder data) with moving 5 year averages.

188 182 ICES WGBAST REPORT Assessment unit 3 90 Number of parr/100m² Ljungan 0+ Ljungan >0+ Testeboån 0+ Testeboån > Year Figure Densites of parr in Ljungan and Testeboån in the Gulf of Bothnia (Sub-division 30), assessment unit 3, in

189 ICES WGBAST REPORT Assessment unit Emån Mörrumsån 250 Number of 0+ parr/100m² Year Figure Densities of 0+ parr in rivers in the Main Basin (Sub-division 25-27), assessment unit 4, in

190 184 ICES WGBAST REPORT Assessment unit 4 Emån 75 Mörrumsån Number of >0+ parr/100m² Year Figure Densities of >0+ parr in rivers in the Main Basin (Sub-division 25-27), assessment unit 4, in

191 ICES WGBAST REPORT Assessment unit parr downstream from Sindi dam >0+ parr downstream from Sindi dam 0+ parr upstream from Sindi dam >0+ upstream from the Sindi dam 20 Number of parr/100m² Ye ar Figure Densities of parr in the river Pärnu Main Basin (Sub-division 22-29) assessment unit 5, in

192 186 ICES WGBAST REPORT Assessment unit Number of parr/100m² > Year Figure Densites of parr in the river Salaca Main Basin (Sub-division 22-29) assessment unit 5, in

193 ICES WGBAST REPORT Assessment unit 5 8 Number of parr/100m² 6 4 Neris Žeimena Mera Saria Year Figure Densites of 0+ parr in Lithuanian rivers in Main Basin (Sub-division 22-29) assessment unit 5, in

194 188 ICES WGBAST REPORT Assessment unit Number of parr/100m² Neris Žeimena Mera Saria Figure Densities of >0+parr in Lithuanian rivers in Main Basin (Sub-division 22-29) assessment unit 5, in Year

195 ICES WGBAST REPORT Kunda 250 Keila Vasalemma Numer of 0+ parr/100m 2 Figure Densities of 0+ (one-summer old) salmon parr in the three wild Estonian salmon rivers

196 190 ICES WGBAST REPORT 2018 Pirita 120 Selja Vääna 100 Loobu Number of 0+ parr/100m Jägala Valgejõgi Purtse Figure Densities of 0+ (one-summer old) salmon parr in seven Estonian salmon rivers were suportive releases are carried out.

197 ICES WGBAST REPORT Eggs, free thiamine 100 Free thiamine, nmol/g Yolk-sac fry mortality Mean yolk-sac fry mortality, % 0 0 Hatching year (number of females) Figure Relationship between the mean yolk-sac fry mortality (± SE) of River Simojoki salmon and the free thiamine concentration (± SE) in their unfertilized eggs (Vuorinen et al., unpublished data).

198 192 ICES WGBAST REPORT 2018 Figure Concentration of free thiamine in the unfertilized eggs of salmon returned to the Rivers Simojoki, Dalälven and Ume/Vindelälven in autumns Data include female wigglers in autumn 2016 (one in Simojoki and 16 in Dalälven), for which an estimated thiamine concentration (0.130 nmol g-1) was set. Box depicts the range of 25 75%, horizontal line the median, diamond the mean, whiskers the confidence level of 5 95% and stars the minimum and maximum observations. The reproductive period (spawning year / hatching year) and the number of females (in parentheses) are indicated below the x-axis.

199 ICES WGBAST REPORT (ICES 2005). Sweden Finland % Figure Proportion of M74 positive females in Swedish and Finnish hatcheries.

200 194 ICES WGBAST REPORT Reference points and assessment of salmon 4.1 Introduction In this chapter results of the assessment model and alternative future projections of salmon stocks in assessment units (AU) 1 4 are presented. Furthermore, the current status of salmon stocks in AUs 5 6 is evaluated against the reference points. The methodological basis and details of the assessment model and stock projections are given in the Stock Annex (Annex 2). Here we describe methodological updates, which are not reported yet in the recent benchmark (WKBALTSalmon, ICES, 2017d) or in the current version of the Stock Annex (to be updated later in 2018). Note that, as described below, the modelling results presented in this section originate from a run that had not fully converged at the time of the working group meeting. The approximations of posterior distributions of some parameters was therefore poor. Results originating from an extended (i.e. longer and more converged) model run were presented to the review group (RG) during the RG/ADG meeting, and the most important of these updated results are presented in Appendix 1. The advice draft document delivered by the Advice Drafting Group (ADG) is also based on these updated model results. Overall the differences between the results presented below and in the Appendix 1 are minor, and they do not affect conclusions or the perception of stock status and development. The input data used in the extended model run was also completed by correcting the piece of the model code, which reads in river specific smolt priors (derived mostly from the river model). The error in the code was located during the meeting and due to this error the last 2 years (2019 and 2020 in this year s assessment) of smolts priors became excluded from the model run. 4.2 Historical development of Baltic salmon stocks (assessment units 1 6) Changes in the assessment methods WinBUGS to JAGS During autumn 2016 and 2017, the FLHM was transferred from WinBUGS to JAGS (Just Another Gibbs Sampler; Plummer 2003). This work was initiated for the purpose of comparing alternative parameterisations of the stock recruitment function for the 2017 benchmark (ICES, 2017d) and continued thereafter to implement all stocks and observation models in the JAGS FLHM. This work has enabled continued use of the FLHM to assess stock status following technical failure to implement MCMC sampling of WinBUGS FLHM with updated time-series (ICES, 2017). The JAGS implementation of the FLHM has several advantages over WinBUGS. It is easy to run parallel chains, meaning that convergence can now be assessed quantitatively (e.g. using diagnostics such as the Gelman-Rubin statistic, Gelman and Rubin, 1992), in addition to visual inspection of trace plots. Although still computationally burdensome, the JAGS FLHM runs ~9 10 times faster e.g. taking around 16 days to run two chains with iterations each on a 64-bit Operating System machine with 32.0 GB of installed RAM. The runjags R package (Denwood, 2016) was used to implement parallel computing.

201 ICES WGBAST REPORT Correction of errors In the course of moving the FLHM from WinBUGS to JAGS, several errors were corrected. Most of these changes are inconsequential for model results and status evaluations, with exceptions described here. As noted last year (ICES, 2017), rates of natural mortality for Emån and Mörrumsån were inconsistent with those for other stocks, since Emån and Mörrumsån lacked natural mortality during the coastal fishery. This has now been corrected, so that natural mortality rates for these stocks are consistent with those for other stocks and with the forward-projection (scenarios) code. The number of months of natural mortality applied to wild and reared post-smolts was corrected to 12 instead of eleven and nine, respectively. While this is not expected to have made a large difference to model results (except to estimates of annual instantaneous post-smolt mortality) it resulted in inconsistency between the assessment model and projections (scenarios) code, with higher levels of post-smolt mortality applied in the latter. Hatchery-reared salmon juveniles stocked as parr in Torne River and Simojoki and returning to spawn were not available to counting in those rivers; this has now been corrected. Since releases of reared salmon have now been phased out in these rivers, this is only expected to affect estimates of historical stock development. New stock recruitment parameterization The JAGS FLHM uses an updated stock recruitment parameterization (Model 3 from WKBALTSalmon, ICES, 2017d). This comprises an eggs-per-recruit (EPR) calculation as a function of vital rates (survival, maturity, fecundity etc.), priors on maximum egg survival (1/α) instead of steepness, and transferal of stock-specific priors for unfished equilibrium smolt production (R0 or PSPC) to maximum recruitment (i.e. the stock recruitment carrying capacity).under this parameterisation, R0 varies by year (see ICES, 2017d for details). Since the benchmark, it was discovered that the stock recruitment alpha prior used there did not closely resemble that from Pulkkinen and Mäntyniemi (2012). The alpha prior has therefore been updated since the benchmark (Figure ). The alpha prior used in 2018 implies a steeper (median) slope at the origin (higher maximum egg survival) than in both the 2017 assessment and benchmark (Figure ). The new (2018) and old (2017) priors on R0 are shown in Figures a c. Slight modifications to the eggs per recruit calculation used in the benchmark were needed to account for model developments that affect population dynamics, namely river- and year- specific sex ratios, and the proportion of fish passing the ladder in Ume/Vindelälven (see below). A final consideration when using the new stock recruit parameterisation is the fact that status is assessed using the ratio of smolt production to unfished equilibrium smolt production (PSPC or R0). Now that R0 varies by year, an annual R0 or average thereof must be used as reference points for status evaluations. Year 2017 status is evaluated against R0 in that year, while we have chosen to use the average of the R0 estimates during the final five years of the assessment period ( ) in calculations of reference points and stock status in future years. Inclusion of recreational trolling catches and effort Updated recreational trolling catch estimates for the period (by expert elicitation ) are now accounted in the model as a part of the offshore longline fishery, by pooling the annual estimated trolling catches together with the reported longline catches (see Section for details of the estimation procedure for trolling catches).

202 196 ICES WGBAST REPORT 2018 The longline effort was increased proportionally, by annual trolling catch estimates divided by the cpue for reported longline catches and effort (all countries). Updates to prior distributions for the proportion of salmon that finds the Ume/Vindelälven fish ladder counter The hierarchical Bayesian mark recapture model used to obtain priors for the annual proportion of salmon that finds the fish ladder in Ume/Vindelälven was updated to account for the fact that in 2017 many of the tagged fish are believed to have ceased their upstream migration after tagging (cf. Section 3.4.3). This would otherwise result in a very low estimated proportion that finds the fish ladder in The model was modified by adding prior distributions for the annual proportion of salmon that continues migrating after tagging, based on expert opinion. The sample size of the Binomial observation model for the number of salmon counted in the ladder then becomes the number of tagged fish that continue their migration, rather than the total number of tagged fish. Priors for the proportion of salmon that continues migrating after tagging had a mean and standard deviation of 0.99 (0.01) from 1996 to 2016 and a mean and standard deviation of 0.10 (0.03) in FLHM priors (posteriors from the mark recapture model) and posteriors are shown in Figure Changes to population dynamics for Ume/Vindelälven Owing to observations of a decreasing proportion of females among spawers in Ume/Vindelälven over time, not seen in e.g. Torneälven/Tornionjoki (Figure ), the FLHM was modified to accommodate river- and year-specific spawner sex ratios. Spawner sex ratios are unchanged for all other rivers, but updated for Ume/Vindelälven. There have also been increased levels of mortality among spawners in Ume/Vindelälven in recent years (Sections and 3.4.3). This was accounted for in the FLHM by multiplying the annual proportion of females among spawners by the modal proportion that survives after counting. Annual proportions of salmon dying shortly after counting were set to zero until in 2013, whereas, based on local information and expert judgement, they were increased to 0.20, 0.02, 0.20 and 0.10 for years In addition to the changes listed above, the 2018 assessment also includes revised priors for the stock recruitment carrying capacity for Lögdeälven, Öreälven and Piteälven (ICES, 2017), and updated smolt production estimates for Mörrumsån, Emån (ICES, 2017d), and Piteälven (Section 4.2.2). Effect of changes on results and status evaluations In order to analyse and understand the effect of different changes made since the 2017 assessment, several additional comparison runs of the JAGS FLHM were made. These results were discussed in detail at the working group meeting. For brevity, they are not presented here, although they inform the following discussion. The extra comparisons were as follows: 1) 2017 assessment model configuration, i.e. same priors and data as in the 2017 assessment (data up to 2015) but with correction of errors noted above. 2) same model structure as the 2017 assessment but with data and priors updated for the 2018 assessment (data up to 2017) 3) updated data and priors plus new stock-recruitment parameterisation 4) as 3) but without new recreational trolling estimates. Changes in the assessment methods outlined above are expected to result in a number of changes to assessment results. The corrected (higher) natural mortality for Emån and Mörrumsån results in higher estimates of maximum egg survival (lower alpha) and stock recruit steepness and lower estimates of historical spawner abundances for

203 ICES WGBAST REPORT those rivers. It also rectifies the failure to recover with zero fishing mortality scenario in forward projections observed in earlier assessments (e.g. ICES, 2015). The corrected post-smolt mortality rates result in higher estimates of post-smolt survival, particularly for reared salmon, with more similar rates of post-smolt survival for wild and reared fish. This follows from the fact that the post-smolt mortality rate must be lower after correction when applied for 12 months, to achieve the same overall survival from natural mortality obtained when it was applied for only nine months. It should be noted that this correction is not expected to result in appreciable changes in estimates of other vital rates (adult survival, etc.) since the total annual mortality rate applied before and after the correction is comparable. It does however result in a difference in reconstructed abundances of reared salmon in scenarios (forward projections) where 12 months of post-smolt mortality have been applied also in previous years, regardless of the number of months applied in the FLHM. The new stock recruit alpha prior implies higher maximum egg survival than the prior used in last year (ICES, 2017), and together with EPR calculated from vital rates, higher stock recruit steepness for most stocks (with the notable exception of Ume/Vindelälven, which has a lower EPR because of a lower average spawner sex ratio, and the fact that not all spawners pass the fish ladder). The lower prior on PSPC or R0 (resulting from transferring the prior from R0 to K, and lower EPR in the case of Ume/Vindelälven; Figures a c) may account at least partially for lower posterior estimates of R0 for some stocks, especially those lacking smolt and spawner counting observations (e.g. Rickleån and Byskeälven, but also Ume/Vindelälven). Acting alone, this change could be expected to lead to slightly more favourable status evaluations for most rivers. However, acting together with the many other changes to data and priors between the 2017 and 2018 assessments, it is difficult to quantify the effect of individual changes on estimated stock status. Nonetheless, readers should be aware of the potential implications of changes to the assessment model in interpreting the results that follow Updated submodels The river model (hierarchical linear regression analysis) provides input about smolt production as likelihood approximations (these are sometimes called also pseudo observations in the literature, but for simplicity they are usually called smolt priors in this report) into the life cycle model, by analysing all the juvenile survey data from the rivers in AUs 1 3. For rivers in AUs 4 6, other methods are used to estimate smolt production (see Stock Annex, Section C.1.5 and ICES, 2017d). Results of the river model indicate a substantial increase in smolt abundance in AU 1 2 rivers since the late 1990s. At the moment (2017), smolt abundance is in its highest level in most of theses rivers, but the abundance is predicted to level off or even decrease during (Table ). The long-term increase in smolt production in AU 3 (R. Ljungan) is less apparent than in the AU 1 2 rivers, nevertheless smolt abundance is currently peaking also in this AU. For the rivers Tornionjoki, Simojoki, Ume/Vindelälven, Sävarån and Lögdeälven the results of the river model are more informative than for the other rivers, because of the availability of smolt trapping data. Also, smolt estimates of years without smolt trapping have become somewhat more precise in these rivers. Smolt trapping has been conducted only in one year (2016) in Lögdeälven, which increases the precision of Lögdeälven smolt abundances mainly in that specific year.

204 198 ICES WGBAST REPORT 2018 Smolt priors in River Piteälven A large part of the production areas in Piteälven (AU 2) are hard to electrofish. Therefore, this river is not included in the river model used for the other wild AU 1 3 rivers to derive input smolt estimates. Instead, in Piteälven smolt production have been estimated from numbers of eggs deposited based on the number of adults passing the fishladder at the Sikfors power plant station (which must be passed by all successful spawners). The calculated smolt numbers have been based on an assumed egg-to-smolt survival rate of 1% and constant proportions of 3 (62%) and 4 (38%) year old smolts (Annex 2). Because the fishcounter only provides total numbers of adults passing, annual information from river Ume/Vindelälven on average body size and sex ratio among spawners has been used toghether with data on size-dependent fecundities, to calculate egg numbers. A basic shortcoming with this simple approach used over the years for deriving smolt priors is that is assumes a stock recruit relationship without density-dependence. This may result in overestimation of smolt abundance when spawner numbers increase. On the other hand, the decreasing proportion of females seen in Ume/Vindelälven (Figure ) may be a river-specific problem, which when applied to Piteälven could result in underestimation of egg deposition and consequent smolt abundance. Further, the extra migration mortality among Piteälven smolts, known to occur when they have to pass the Sikfors dam, has so far not been accounted for. To accommodate for the above shortcomings, the method for calculating smolt priors for Piteälven was modified before this year s assessment. Same assumptions as previously were used for egg-to-smolt survival rate and smolt age distribution, but the information on spawners in Ume/Vindelälven was replaced with corresponding data from Torneälven/Tornionjoki (i.e. average number of eggs per spawner of both sexes and all age classes in that river). Density-dependence was accounted for by transforming estimated egg numbers into smolts following a Beverton Holt stock recruit function based on α=100 (i.e. same egg to smolt survival as before) and the recently updated carrying capacity (K=1/β) for Piteälven with associated 90% probability intervals (ICES, 2017). Based on congruent results from two telemetry studies in 2010 and 2015, smolt mortality when passing the Sikfors dam was set to 21%. The new and old smolt priors are depicted in Figure Until late 1990s, the difference is very small in absolute terms. Later, however, the new input is mostly higher than the old one, and for some years, it predicts more than additional smolts. The main reason is likely the female ratio in Ume/Vindelälven that since the late 1990s has been decreasing (Figure ). A model for M74 mortality provides input about mortality due to M74 into the life cycle model by analysing all data on incidence of M74 in the stocks (see Stock Annex, Section C.1.6). Figure shows the estimates for M74 mortality (median and 95% probability interval); within the last ten years, the mortality has decreased until the spawning year 2015 when it increased to the level of magnitude of 5 20%. The results from the 2016 spawning (Figure ) and the predictions made for 2017 spawning (Section 3.4) indicate similar level of mortality as in In general, the percentage of females with offspring affected by M74 overestimates the M74 mortality due to the fact that part of the offspring will die due to normal yolk-sac-fry mortality, unrelated to M74. Also, not all offspring necessarily die when affected by M74. Because of the decreasing trend in mortality among offspring of females affected by M74, the data on proportion of females affected by M74 especially overestimate M74 mortality in recent

205 ICES WGBAST REPORT years. Data on the total average yolk-sac-fry mortality are much better at tracking the general trend but overestimate the actual M74 mortality, because these data do not distinguish between normal yolk-sac-fry mortality and yolk-sac-fry mortality caused by the M74 syndrome. Table shows the actual values of the M74 mortality for the different salmon stocks. Figure illustrates the probability that offspring of M74-affected females would die, which has been possible to calculate for Simojoki, Tornionjoki and an unsampled salmon stock Status of the assessment unit 1 4 stocks and development of fisheries in the Gulf of Bothnia and the Main Basin The full life-history model (FLHM) was run with two chains for iterations after an adaptive phase of iterations. The first iterations were discarded as burn-in and the chains were thinned with an interval of 150 to yield a final sample size of 2000 (1000 iterations from each of two chains). Using the JAGS FLHM, convergence can now be assessed using metrics such as the Gelman-Rubin diagnostic, in addition to visual inspection of trace plots. Gelman-Rubin diagnostics indicated convergence for ~85% of model parameters (Gelman-Rubin diagnostic <1.2). Among key life-history and stock-status parameters, some annual post-smolt natural mortality rates (both wild and reared) as well as adult natural mortality rates (both wild and reared) had not reached convergence. Gelman-Rubin diagnostics further indicated lack of convergence for stock recruitment function alpha parameters for Torne River, Simojoki and Vindelälven, and several annual stock recruitment steepness estimates for the same rivers. Poor convergence was also noted for the estimated proportion of wild salmon in offshore catches in some years (corresponding to years in which post-smolt mortality rates showed poor convergence), maturation rates in some years (both wild and reared) and offshore abundances of salmon on May 1st. Caution must therefore be taken in the interpretation of results for these parameters/quantities. In the text and figures that follow, medians and 90% probability intervals (PI s), are used where possible as statistics of posterior probability distributions. The results indicate a decreasing long-term trend in the post-smolt survival until mid- 2000, after which survival has somewhat improved (Figure ). The lowest overall survival (median estimate around 6 8% among wild and 5% among reared smolts) was estimated for salmon that smolted in years and Low survivals were estimated for either wild or reared smolts also in some of the years , however, as pointed out above some of these parameters (mainly smolt years ) are not reliably estimated owing to the limited amount of MCMC iterations. After the last decade the survival has increased to 13 23% for wild smolts and 11 19% for reared smolts (median estimates in ). Survival improved especially among salmon that smolted in Currently survival is slightly lower than in the early 2000s, and less than half of the estimated survival level prevailing two decades ago. According to this year s assessment, the relative difference in survival of wild vs. reared post-smolts is much smaller than according to the earlier years assessments (see Section 4.2.1). The adult natural annual survival of wild salmon (median 93%, PI 88 96%) is estimated to be clearly higher than that of reared salmon (median 75%, PI 71 83%). Thus, the difference in total sea survival back to the spawning/stocking site for wild and reared salmon remains large also in this assessment, despite the smaller estimated relative difference in the survival of wild vs. reared post-smolts. Maturation of 1-sea winter salmon (grilse) has in most years been around 20% and 30 50% among wild and reared individuals, respectively (Figure ). Among 2-sea winter salmon maturation is estimated to have been mostly 30 60% (wild) and 40 75%

206 200 ICES WGBAST REPORT 2018 (reared) salmon. Also for 3- and 4-sea winter salmon the maturation rates of wild salmon have on average been somewhat lower that those of reared salmon, but the difference is small. The estimated maturation rates of 4-sea winter are on average lower than those of 3-sea winter salmon. This is against intuition but might be an artefact due to the inconsistency between current model assumptions (no repeat spawners, all fish mature at latest after five sea winters) and the biology of salmon (some repeat spawners exist and some salmon have a longer lifespan than five years at sea). The maturation rates were generally on low level around , but higher than average around and again around The full life-history model allows estimation of steepness of the stock recruit relationship (Table ) and the PSPC (Table ) for different salmon stocks. Figure gives an indication of river-specific stock recruit dynamics. The blue clouds in the figure panels indicate posterior probability distributions of all the historical estimates of yearly egg deposition and corresponding smolt abundance (the density of the cloud indicates the probability). Curves added in the figure panels are draws from the posterior distribution of the Beverton Holt stock recruit function. Adding the latest information about spawner and smolt abundance together with the latest changes in the model structure and priors of PSPC s has resulted in several changes in posterior probability distributions of the PSPC's, as compared to in last year (Figure , Table ). PCPC s of several rivers were significantly updated from last year s assessment especially in the AU 2. The largest updates were in the PSPC s of Öreälven (287% increase in median), Lögdeälven (252% increase), Piteälven (117% increase) and Sävarån (101% increase). In all these rivers, except in Sävarån, the priors for the PSPC s/k s have been updated much upwards, which probably explains most of increase in the posterior PSPC s (Section 4.4.2). Other remarkable updates (>10% change in median) to the PSPC s are seen in Emån (35% decrease), Rickleån (25% decrease), Ume/Vindelälven (20% decrease) and Kågeälven (18% decrease). There are no remarkable updates in the PSPC s of the rivers in AU 1. As pointed out above, care should be taken in the interpretation of these results because of changes in the assessment methodology (new stock recruit parameterization; see ICES, 2017d and Section 4.2.1). The total combined AU-specific PSPC estimates changed from the last year s assessment only by a few percent in AUs 1 and 2 (Table ). The PSPC estimates of AU 4 decreased by 15%, apparently mostly due to the various changes made to the input data of the AU 4 rivers. Total PSPC for AUs 5 and 6 were not updated in this year s assessment. The estimated grand total PSPC of AUs 1 6 (median 4.11 million) is only 3% (6000 smolts) higher than the corresponding estimate from the last year s assessment. Since the mid-1990s, the status of many wild salmon populations in the Baltic Sea has improved, and the total wild production has increased from less than 0.5 to over three million smolts (Figure , Table ). There are significant regional differences in trends in smolt production. For the wild salmon stocks of AUs 1 2, the very fast recovery of smolt production indicates high steepness for stock recruit relationships in these rivers. The recovery is most pronounced in the largest rivers, but recently also the salmon stocks spawning in the smaller forest rivers of the region (Åbyälven, Rickleån, Sävarån, Öreälven, Lögdeälven) have speeded up their recovery. However, their stock status (current production level against the potential) is generally assessed to be lower than that of the larger salmon rivers, as discussed below.

207 ICES WGBAST REPORT The only wild stock in AU 3 currently evaluated in the assessment model (Ljungan) has also recovered, but the estimates of both the current and the potential smolt production of this river are highly uncertain. Following the revision of the time-series of smolt production estimates used as input in the FLHM (Section 4.2.2), the perception about the development of AU 4 stocks has changed: the Mörrumsån stock has stayed relatively stable with only slight improvement seen towards the most recent years, while the abundance in Emån has been gradually increasing. Most of the AU 5 stocks are showing a decreasing trend in smolt abundance, but the stocks of AU 6 show improvements similar to in AU 3 (see Section 4.2.4). Smolt production in the AU 1 4 rivers is estimated to have jumped again to a higher level since 2017, which is a reflection of the further increase in the number of spawners in and beyond (Figure ). By comparing the posterior smolt production (Table ) against the posterior PSPC it is possible to evaluate current (year 2017) status of the stocks in terms of their probability to reach 50% or 75% of PSPC (i.e. R0 in 2017, Figures and , Table ). Table contains also AU 5 6 stocks and Testeboån, which are currently not included in the FLHM. These stocks have not been analytically derived, but expert judgments are used to classify their current status; see Sections (AU 5 6) and (Testeboån). The perception about the overall status of stocks (amount of stocks in different status classes) has markedly changed compared to the last year s assessment, which is probably a combined result of numerous changes made in the assessment model and by adding two more years of data ( ). All stocks in the AU 1 are estimated to have very likely reached 50% of their PSPC s, and three out of four stocks have likely or very likely also reached 75% of their PSPC s. The stock of Tornionjoki had very likely reached even 75% of its PSPC in 2017, when the smolt production in the river is estimated to have reached its all-time high. The lowest status in the AU 1 has been assessed for Simojoki: it is uncertain if the stock has reached 75% of its PSPC (Table ). Six out of nine stocks in the AU 2 are likely or very likely to have reached 50% of their PSPC s, but only three have (likely) reached the 75% target. The stock of Lögdeälven has unlikely reached even the 50% target, and Rickleån and Öreälven are uncertain to have reached this target. In AU 3, Ljungan is likely and uncertain to have reached 50% and 75% of PSPC, respectively, whereas Testeboån is uncertain and unlikely. In AUs 4 5, only Mörrumsån has likely or very likely reached both of the targets, whereas all the remaining 13 stocks are uncertain or unlikely to have reached even the 50% target (Table ). Out of the 41 assessed wild and mixed-stocks in Table , 34% (14 stocks) are likely or very likely to have reached 50% of PSPC, and 22% (nine stocks) are likely or very likely to have reached 75% of PSPC. The corresponding proportions calculated only for the 28 wild stocks are 50% and 32%. Generally, the probability to reach targets is highest for stocks in the largest northern rivers. A total of nine wild and 12 mixed-stocks are unlikely to have reached 50% of PSPC, i.e. they are considered to be weak. All except one of the weak stocks are located in AUs 5 6. While most of the AUs 1 2 stocks show strong indications of recovery over the years, the stocks in AUs 4 5 have mostly been unable to recover. Stocks in rivers situated between these areas (i.e. AU 3 and AU 6 stocks) have mostly shown modest indications of recovery (Figures , and Section 4.2.4).

208 202 ICES WGBAST REPORT 2018 The model captures quite well the overall historic fluctuation of catches in various fisheries (Figure ). However, the offshore catches from the early and mid-2000s become underestimated, and there is some tendency for the older part of time-series of the coastal catches to become overestimated. The model also does not fully capture the high river catches of the years The model is fitted to the proportion of wild and reared salmon (separately for ages 2SW and 3SW) in the offshore catches. The posterior estimates of wild vs. reared proportions follow rather closely the observed proportions (Figure ). However, for the MCMC was not able to reach convergence, which is reflected by the much more uncertain posterior estimates of those years than in other years. An increasing trend in the number of spawners is seen in most of the rivers of the AUs 1 4 (Figure ). Spawner abundance has increased, particularly in the years In Simojoki, the very high estimates of spawners around the turn of the millennium are a result of very intensive stocking of hatchery-reared parr and smolts in the river during the late 1990s. The model captures trends seen in fishladder counts, even short-term variation in rivers where the data are not used for model fitting (e.g. Byskeälven). Annual variation in river conditions affect the success of fish to pass through ladders and therefore the ladder counts themselves are not ideal indices of spawner abundance. For Ume/Vindelälven, however, fish counts are good approximations of the total amounts of fish reaching the spawning grounds, and the model based spawner estimates follow closely these observations. The good agreement between observations and estimates in the Ume/Vindelälven is expected because of the assumption that all spawners are counted in this river (Section 4.2.1). In Piteälven, the agreement is not particularly good, however, although all spawning grounds are located upstream the counter. In this river, spawner counts are currently not used directly for the assessment. One reason for the discrepancies may therefore be that the proportion of ascending spawners being counted fluctuates much between years (currently unknown) and this may result in mis-matches between model estimated and observed spawner numbers. In Kalixälven, Åbyälven and Rickleån the development of spawner abundance estimated by the model appears more optimistic than the development observed in the fishladder counts. In Kalixälven, the counter is located about 100 km from the river mouth with large spawning areas downstream. In Åbyälven and Rickleån fishladders are built up around the turn of the millennium and salmon are gradually repopulating the upstream sections of these rivers. Therefore, counts in these rivers account for a small fraction of the total spawner population and the counts may not well represent the actual development of the salmon stocks. The general synchronous drops and increases in the observed spawner counts are well-captured by the model, also the most recent drop observed from 2016 to This is probably a consequence of fitting the model to spawner counts in combination with assuming annually varying maturation rates; maturation rates are estimated to be low preceding poor spawning runs and high preceding high spawning runs (Figure vs. Figure ). Despite some fluctuations, there was a strong long-term decreasing trend in the harvest rate of driftnets until the total ban of this gear type in 2008 (Figure a). The combined harvest rate of longlining and trolling has been fluctuating much with peaks around the years 1990, 2000 and In the last 5 6 years this harvest rate has, however, stayed on the long-term average level without any clear trend. Recreational salmon trolling has been increasing (Section 2.1.2), especially during the 2010s, and it currently accounts for roughly half of the combined harvest rate of longlining and

209 ICES WGBAST REPORT trolling fishing (cf. ICES, 2017). Since the early 2000s the coastal harvest rate has decreased almost continuously, and after 2015 the harvest rate has stayed on its all-time low without any further decrease (Figure b). Estimates of harvest rates in the rivers are inaccurate and lack trends (Figure c). River-specific data indicate that there can be substantial variation in the harvest rate between rivers (Section 3.2.1), which is currently not taken into account in the model. The overall harvest rates (all gear types regionally combined) have been decreasing in both offshore and coastal fisheries (Figure ). However, most recently these trends have levelled off and the harvest rate in the offshore fishing shows even a slight increase in the last two years Status of the assessment unit 5 6 stocks Smolt production in relation to PSPC in the AU 5 stocks shows a negative trend in almost every wild and mixed river (Figures and ). During the last decade, smolt production dropped from 50% or higher to below 50% of PSPC. Thereafter smolt production has stayed on this low level except for in , when a sudden temporal increase was observed in most rivers (Figure ). In 2017, most AU 5 rivers were estimated to produce just about 10 30% of their PSPCs and they are therefore either unlikely or uncertain to reach 50% (given the associated uncertainties in estimation; Table ). In river Pärnu the smolt production has shown small signs of improvement. The second river in AU 5 which shows limited positive development is Nemunas. This is a large watercourse with several tributaries, and many of them have been subject to long-term restoration efforts (habitat restorations, restocking, etc. see Sections and 3.2.2). Despite the positive trend, the observed smolt production in the Nemunas in relation to PSPC is still far below 50% level. Rivers Salaca (AU 5) and Mörrumsån (AU 4) are both well-known salmon rivers with the most extensive and longest time-series of monitoring data in the Main Basin area (Sections and 3.1.5). The developments of parr densities in these two rivers roughly resemble each other since the early 1990s; an increase in the densities from the early to the late 1990s and a subsequent decrease starting in the early 2000s. Smolt production in the AU 6 stocks shows positive trends in most rivers but also a large interannual variation, especially in the smallest rivers (Figures to ). Among wild (Figure ) and mixed (Figure ) Estonian stocks the clearest positive trend exists in least two of the wild ones (Keila and Kunda) which have reached 75% of their PCPCs. However, smolt production in wild Vasalemma remained below 50% of PSPC in 2017 (Figure ). In the small Estonian mixed-stocks the trend has also been is also positive in recent years (Figures and ). However the current PSPC in some of these rivers is severely limited by migration barriers and there is also a lot of annual variation in these small populations. PSPC in mixed River Valgejõgi has increased since 2016 (from 1500 smolts to ) because salmon regained access to all potential historical spawning and rearing areas. The size and quality of spawning areas will be investigated in detail during In the Finnish mixed river Kymijoki no clear positive trend can be seen, although occasional stronger year classes have occurred. The smolt production has nevertheless remained far below the 50% level. In Russian river Luga wild smolt production is stable but low, and it has remained below 10% of PSPC despite large-scale annual smolt releases using salmon of local origin (Figure ).

210 204 ICES WGBAST REPORT Harvest pattern of wild and reared salmon in AU 6 Salmon originating in the Gulf of Bothnia and Baltic Main Basin contribute to the catches in the Gulf of Finland (Bartel, 1987; ICES, 1994). Salmon from the Main Basin stocks migrate to the Gulf of Finland for feeding, and salmon from Gulf of Bothnian stocks visit the Gulf of Finland area in early summer during their spawning migration to the Gulf of Bothnia. In (excluding and 2016) samples has been collected from Finnish commercial fisheries in the Gulf of Finland. These catch samples have been aged and wild/reared origin have been determined by scale reading. Stock proportions were also estimated by DNA-analysis (MSA). The MSA results from the earlier years ( ) suggested that the largest stock contribution (50 60%) was from locally released reared Neva salmon, whereas the average proportion of wild stocks originating in the Gulf of Bothnia was 40 55% (Section 2.8). In 2015 and 2017 the overall proportion of reared Neva salmon has been higher (up to 67%) whereas the share of wild GoB salmon was lower (10 15%). It should be noted that there were pronounced differences between sampling sites and sampling times between the years (Section 2.8). The share of Gulf of Bothnian salmon was clearly higher during the early fishing season (June), whereas the share of GoF Neva salmon was high later in the season. So far, apart from Neva salmon, the proportion of other Gulf of Finland stocks (Russia and Estonia) in genetically analysed catch samples from the area have been estimated to zero or close (<0.5% Kunda in 2017, Table 2.8.3). The numbers of feeding salmon from these wild and mixed rivers are expected to be low, and the probability to observe them is probably minimal in samples collected from fisheries in the feeding area in the Gulf of Finland (and the Main Basin). According to Carlin tag recaptures from releases made in Estonian rivers in the area (smolt cohorts ), only 19% of the stocked fish are harvested outside Gulf of Finland, 68% are harvested in the Gulf of Finland s Estonian coast and 13% of the recaptures originate in the Finnish side of the gulf (ICES, 2014). A substantial share of these returns, however, came from recreational fishery off the coastal area (trolling, etc.). The reduction of harvest rate in the Main Basin in the last few years has had a positive effect on the AU 6 wild stocks. The harvest rate in the Main Basin (driftnetting and longlining combined) was estimated to be 30 60% in 1990s, while currently the harvest rate (longlining and trolling combined) is estimated to be around 15 20% (Figures a and ). Most Estonian stocked parr and all stocked smolts have been adipose finclipped since late 1990s. The share of adipose finclipped salmon in Estonian coastal catches is monitored by gathering catch samples. If comparing the relative production of wild and reared smolts with the share of finclipped fish in coastal Estonian catch samples, it shows that the share of finclipped fish is clearly smaller than expected, and that the situation has remained relatively stable since 2010 (Figure ). This indicates that reared fish have had very low survival since 2010, and that wild fish are harvested in significant numbers. However, the river origin of the wild fish is not known. To further reduce the harvest rate on the regions stocks, the closed area at Estonian river mouths was in 2011 extended to 1500 m during the main spawning migration period (from 1st September to 31st October) in all wild (Kunda, Keila, Vasalemma) and most mixed rivers (Selja, Loobu, Valgejõe, Pirita, Vääna, and Purtse). Harvesting in the Main Basin has declined, particularly since Taking into account a rather large proportion of salmon from the Gulf of Bothnia observed in Finnish catch samples from the Gulf of Finland (Section 2.8) the exchange of salmon between areas

211 ICES WGBAST REPORT is considered to be significant, although the total magnitude still remains to be quantified. Comparison of the spatial distribution of tag recaptures from Gulf of Bothnian and Gulf of Finland stocks provides a qualitative overview on the rate of exchange (ICES, 2014), although this information is dependent not only on the distribution of salmon but also on the distribution of fisheries. As shown above, status of Estonian wild and mixed salmon stocks has shown improvements since 2005, followed by recent declines for mixed stocks since 2015 (Figures and ). 4.3 Stock projection of Baltic salmon stocks in assessment units Assumptions regarding development of fisheries and key biological parameters Table provides a summary of assumptions on which the stock projections are based. The basis has been kept as similar to the last full assessment (ICES, 2017) as feasible, in order to allow for a review of how the new information is affecting projections. However, inclusion of salmon trolling in offshore fisheries and some other changes made to the FLHM required further consideration in the scenarios, as described below. Fishing scenarios The base case scenario (scenario 1) for future fishing (2019 and onwards) equals to the commercial catch adviced by ICES for 2018, i.e. the median commercial removal would equal to salmon. Scenarios 2 and 3 correspond to a 20% increase and 20% decrease from the scenario 1, respectively. Scenario 4 equals to an F=0.1 harvest rule, applied for total commercial removals. Scenario 5 illustrates how recreational fishing alone would affect stock development. Finally, scenario 6 illustrates stock development in case all fishing (both at sea and in rivers) was closed. Similar to in previous years, fisheries in the interim year (2018) follow the scenarios, except for longline fishing during the first months of the year, which is estimated based on the effort observed during the corresponding months of Scenarios were computed by searching an effort that results in a median catch that corresponds to the desired total sea catch (depending on the scenario) in the advice year (2019). For example, in scenario 1 the total sea catch ( salmon) consists of total commercial sea catch ( salmon) and total recreational sea catch ( salmon). The recreational sea catch in 2019 is the same in all scenarios (Table ) except in scenario 6, which assumes closure of all fisheries. In scenarios 1 5, recreational fishery has the same effort in future years as in 2019, meaning that the annual recreational catches are proportional to the abundance. The recreational catch of salmon in 2019 consists of an estimated three year average ( ) offshore trolling catch ( salmon) and reported recreational catches other than offshore trolling in 2017 (9400 salmon). As the current model framework does not allow inclusion of recreational fisheries as a separate fishery, it is technically included as a part of offshore longline fishery, as described in Section As the scenarios are technically defined in terms of future fishing effort, the predicted catches have probability distributions according to the estimated population abundance, age-specific catchabilities and assumed fishing effort. Scenarios 1 4 assume the same fishing pattern in commercial fisheries (division of effort between fishing

212 206 ICES WGBAST REPORT 2018 grounds) as realized in Figure a b shows the harvest rates prevailing in the scenarios. In all scenarios it is also assumed that the commercial removal reported under the TAC covers 55% of the total commercial sea fishing mortality, whereas 45% of this mortality consists of discards, misreported, and unreported commercial removals. This corresponds to the situation assessed to prevail in 2017 (Figure ). According to expert evaluation, misreporting has increased significantly from 2016 to The share of misreporting out of the total commercial catch was evaluated to be 16% in 2016, whereas the corresponding share is evaluated to be as high as 29% in 2017 (Section 2.3.3). The share of other sources of extra mortality (dead discards and unreporting) is evaluated to remain roughly the same from 2016 to Because of the change in misreporting, the share of total removal originating from the reported commercial catches results become 13 percentage units smaller in 2017 than in Survival parameters In both the M74 and the post-smolt mortality (Mps) projections, an autoregressive model with one year lag (AR(1)) is fitted at the logit-scale with the historical estimates of the survival parameters. Mean values of the mean of the post-smolt survival over years (19%), variance over the same time-series and the autocorrelation coefficient are taken from the historical analysis into the future projections. The method for M74 is similar, but the stable mean for the future is taken as the mean over the whole historical time-series (85%). In addition, the forward projection for Mps is started from 2017 to replace the highly uncertain model estimate of the last year of the historical model. The starting point of M74 projections is Time-series for Mps and M74 survival are illustrated in Figure Adult natural mortality (M) is assumed to stay constant in future, equalling the values estimated from the history. Different fisheries occur at different points in time and space, and many catch only maturing salmon, which has been subject to several months natural mortality within a year. Thus, in order to increase comparability of abundances and catches, the abundances at sea have been calculated by letting M first to decrease the PFA (stock size at the beginning of year) of multi-sea-winter salmon for six months. Moreover, the stock size of grilse has been presented as the abudance after the period of post-smolt mortality and four months of adult natural mortality. This period is considered because the post-smolt mortality period ends in April, after which eight months of that calendar year remain during which grilse are large enough to be fished. Half of that period, i.e. four months, is considered to best represent the natural mortality that takes place before the fishing. Calculations for the F=0.1 scenario (Scenario 4) are also based on stock sizes which are first affected by M, as described above. Maturation Annual sea-age group-specific maturation rates are given as the average level computed over the historical period, separately for wild and reared salmon. This projection starts from 2019, as the maturation rates of 2018 can be predicted based on sea surface temperature (SST) information from early 2018 (ICES, 2014, Annex 4). The time-series of maturation rates are presented in Figure Releases of reared salmon The number of released reared salmon per assessment unit is assumed to remain at the same level in future as in 2017 (Table 3.3.1).

213 ICES WGBAST REPORT Results According to the projections, stock size on the feeding grounds (pre-fishery abundance, PFA) will be about 1.66 ( ) million salmon (wild and reared, 1SW and MSW fish in total) in 2019 (Figure a b). Of this amount, MSW salmon (i.e. fish which stay on the feeding area at least one and half years after smolting) will account for 0.76 ( ) million salmon. These MSW fish will be fully recruited to both offshore and coastal fisheries in From the predicted amount of 1SW salmon (0.84 million, million) at sea in spring 2019, a fraction (most likely 20 40%) is expected to mature and become recruited to coastal and river fisheries, while the rest of the 1SW salmon will stay on the feeding grounds and will not become recruited to the fisheries until next winter. The abundance of wild salmon at sea has fluctuated without any apparent trend until During the current decade the abundance has on average been higher than before, at or above one million (according to median values for 1SW and MSW wild salmon combined) (Figure ). Within the range of the scenarios, the abundance of wild salmon is predicted to stay with high probability on this elevated level in future. As one of the simplifying assumptions of the life cycle is that all salmon die after spawning, a lower maturation rate will increase the survival of the cohort to the next year compared to years with the same abundance but with average maturation. Similarly, a high maturation rate will decrease the abundance of MSW salmon in following years. Because of this feature, it is important to note that the predicted abundance may easily become over- or underestimated because of the (predicted) development of maturation rates. In contrast to wild salmon, the abundance at sea of reared salmon strongly decreased from the mid-1990s to the late 2000s, mainly due to the decline in post-smolt survival. In some occasional years in the early 2010s, substantial amounts of reared salmon have been assessed to recruit to the fisheries (which may be an artefact due to the poor estimation of e.g. Mps in those years, see Section 4.2.3), but thereafter the abundance has stayed on a rather low level, and it is predicted to stay low also during the coming years. Further reduction in the amount of reared salmon may take place in future, if the long-term declining trend since the early 2000s in the amount of stocked smolts will continue (Table 3.3.1). The combined wild and reared abundance (PFA) also declined substantially from mid-1990s until late 2000s, but thereafter the total abundance has increased and is expected to stay on this elevated level in future (Figure ). Table shows the predicted total catch by scenario for 2019, divided into the following components: commercial wanted sea catch, consisting of reported, unreported and misreported; commercial unwanted sea catch, consisting of discarded undersized and seal damaged salmon; recreational sea catch; and catch in the rivers. The table also shows the predicted fishing mortality (separate F of commercial fishing and F of all sea fisheries) as well as the predicted number of spawners in 2019 for the given fishing scenarios. The amount of unreporting, misreporting and discarding in 2019 is based on the expert evaluated share of those catch components compared to the reported catches in 2017

214 208 ICES WGBAST REPORT 2018 fisheries. In 2017, the wanted catch reported (commercial) accounted for about 55% from the corresponding estimated total commercial sea catch, this percentage being remarkably smaller than the one estimated for the three previous years (64 72%). Unreporting, misreporting and discarding in 2017 are considered to take, respectively, about 6%, 29% and 10% share of the total commercial sea catch. The share of the total catch by its components for the period is illustrated in Figure It is important to keep in mind that future changes in either fishing pattern or in fisheries control may easily lead to changes in the share of catch caught under the quota regulation. With the given set of scenarios (excluding the scenarios zero fishing and recreational fishing only ), the predictions indicate that the wanted catch reported (commercial) in year 2019 would be 56 95% ( salmon) compared to the TAC of 2018 (Table ). The corresponding total sea removal (including recreational fishing) would range from salmon. The harvest rule of F0.1 for commercial catch (scenario 4) results in the highest catch among the examined scenarios, indicating a wanted catch reported of salmon and about 8% smaller spawning stock than under Scenario 1. The amount of spawners would be about 5% higher in Scenario 3 than in Scenario 1, and the zero fishing scenario indicates about 57% increase in the number of spawners compared to the scenario 1. The scenario recreational fishing only illustrates the magnitude of the current level of the recreational fishing which is predominantly angling in rivers and trolling at sea: recreational fishing alone would decrease the number of spawners by 22% compared to the zero fishing scenario. Figure illustrates the longer term development of (reported) future catches given each scenario. Figure a d presents the river-specific annual probabilities to meet 75% of the PSPC under each scenario (note that river Testeboån is left out from river-specific results because it is currently not included in the FLHM; but see Table for Testeboån s current status). Under the scenarios 1 4, different amount of fishing has some influence on the level but not on the trend of the probability of meeting 75% over time. Only the zero fishing and recreational fishing only scenarios diverge clearly; several of the weakest rivers show a stronger positive effect in trends than for the other scenarios. As expected, changes in fishing has the smallest effect to those stocks that are close to their PSPC. As the overall level of fishing effort is rather low in these scenarios compared to in history, the examined range of fishing mortality only results in modest impacts on the chances of reaching the management objective. Table compares the probabilities of reaching 75% target around the years , which are approximately one full generation ahead from now. Evidently, the probabilities are higher for effort scenarios with low exploitation, but differences between scenarios are small except for the recreational fishing only (Scenario 5) and zero fishing (Scenario 6) scenarios. Figure a b illustrates by scenario the rate and the direction of change in smolt abundance in 2023/2024 compared to the smolt abundance in Future predictions about smolt abundance are naturally more uncertain than the estimated abundance in However, in those stocks that are close to their PSPC, also the predictions are rather certain, indicating that smolt abundance will stay close to PSPC in these rivers under different fishing scenarios. Figures a d show longer term predictions in the river-specific smolt and spawner abundances for three scenarios (1=removal which corresponds to ICES advice for 2018; 4=harvest rule of F0.1 for commercial catch; and 6=zero fishing). The two most

215 ICES WGBAST REPORT extreme scenarios (4 and 6) illustrate the predicted effects of contrasting amounts of fishing. 4.4 Additional information affecting perception of stock status Independent empirical information is important for the evaluation of model predictions and their key parameters. Over the years, repeated comparisons with different kinds of such independent information have been performed, and in several cases, these comparisons have prompted modifications or extensions to the full life-history model. For example, some years ago sea temperature data were introduced as a covariate of age-specific maturations rates, based on the analyses and development work carried out in the last inter-benchmark protocol (ICES, 2012b) and thereafter. Also, comparisons between model predictions and empirical results from genetic mixedstock analyses (MSA) have been used over the years to verify model performance (e.g. ICES, 2014). This section focuses on other auxiliary information important to complete evaluation of the current stock status. In particular, we highlight information about diseases and other factors that may affect development in stock status, but which are not fully taken into consideration in the current modelling. Likewise, weaknesses in input data used in the assessment model might affect the precision of status evaluations, and in the worst case introduce biases. Such shortcomings in the current assessment model, when it comes to input data and ways of handling those, are also discussed under this section. An example is the ongoing work of updating prior information on production areas and potential smolt production levels in salmon rivers, which may affect status evaluations of individual stocks Potential effects of M74 and disease on stock development If the increase observed in M74 in (and predicted in 2018; Section 3.4.1) should last for several years, this may gradually result in decreased stock status and reduced fishing possibilities. Occurrence of M74 more than half a year ahead (thiamine level in the spawned eggs indicates quite well M74 mortality among offspring hatching from these eggs, see Section 3.4) cannot currently be predicted, but many of the M74- fluctuations seen since the early 1990s have tended to last for some years before changing in direction (Figure 3.4.3). Also, the disease outbreaks reported in several rivers in recent years (Section 3.4) is a concern for the future. In contrast to M74, the cause(s) of the disease is still unknown, and to accurately quantify the amount of affected or dead salmon in a river appears difficult, if at all possible. Although future development and effects of M74 and other health issues are hard to predict, the development of individual stocks could depend on their current stock status. In populations where smolt production is approaching PSPC, density-dependent mortality is expected to become higher. Hence, in a recovered stock (with high status) elevated fry mortality may partly be compensated by the reduced density-dependent mortality among the offspring not affected by M74. For the same reason, stronger stocks may be less sensitive to a reduced number of deposited eggs due to adult female mortality. In contrast, among weaker populations the effects of M74 and other diseases on future smolt production could be more pronounced, because of the lack of the above described buffer effect of density-dependence in the reproduction dynamics. It should be emphasized, however, that so far empirical evidence in support for compensation of M74-related mortality is lacking.

216 210 ICES WGBAST REPORT 2018 Despite the recent increase in M74 and disease outbreaks, average salmon 0+ parr densities in have remained at seemingly normal levels in most AU 1 4 rivers, with the exceptions of Vindelälven and Ljungan. In Vindelälven the average 0+ density dropped drastically, from ca. 40 parr/100 m 2 in 2015 to only ca. 1 parr/100 m 2 in 2016, the lowest density observed since the 1990s (Table ). In 2017, the average 0+ density remained at a very low level (ca. 4/100 m 2 ). The reason for the decline is unclear, but likely reflects a combination of factors. In 2015, only 790 females were counted in the Norrfors fish ladder, which represented just 11% of the spawning run (18% among MSW salmon, if assuming 6% females among grilse). There was no indication of such a skewed sex ratio in the sea or at the river mouth. Hence, the recent disease problems in Ume/Vindelälven may for some reason have prevented particularly females from reaching the fish ladder. In 2016, the number of females counted was higher (2741; Table ), but a large proportion of the salmon passing the ladder had severe skin problems (fungus infections) and many died soon after having been counted (see Section on how this additional mortality has been handled in the assessment). Moreover, low levels of thiamine among spawners in 2015 and 2016 resulted in increased M74-mortality in the following hatching years (19% and 45% females affected in Vindelälven 2016 and 2017, respectively; Table 3.4.1). Also in Ljungan the average 0+ salmon density in 2017 was very low (<one parr/100 m 2 ) compared to in preceding years (average density of 61 in ; Table ). Notably, the collapsed parr density in 2017 followed after a year with many dead salmon observed in the river, combined with a high expected level of M74-mortality. The very low parr densities in Vindelälven ( ) and Ljungan (2017) are expected to result in a drastically reduced smolt production in However, it should be noted that the estimated pre-fishery abundance of Vindelälven salmon exploited in the fishery during the advice year (2019) is not affected by the reduced parr densities in Regardless, the situation in Ume/Vindelälven is alarming, and local management actions aimed at protecting ascending spawners appear warranted Revision of basic input data Colonization of salmon to new areas further upstream and/or restoration efforts improving or increasing river habitats will increase the potential smolt production capacity (PSPC) of rivers. If such changes are not accounted for, the status assessment will likely become biased. WGBAST is continuously revising important input data, such as e.g. production areas, to avoid such biases in status assessment. Factors affecting the PSPC include river production area, smolt production potential per unit area and mortalities during downward smolt migration. In the analytical assessment of Baltic salmon, all these quantities are used to formulate river-specific prior probability density functions (hereafter called priors ) for PSPC, which are updated by the model to posterior PSPCs when stock recruit data are included. Status of individual stocks is evaluated by comparing posterior estimates of current smolt production levels with posteriors of PSPC. In last year s report, we updated figures on production areas and information on maximal smolt production per unit of area for three Swedish rivers: Piteälven, Lögdeälven and Öreälven. The updated information on production area and smolt production potential per unit area was used in combination with information on other important factors, such as mortality during smolt migration, to formulate new priors for PSPC (ICES, 2017). These updated priors have now been included in the assessment model (Section 4.2).

217 ICES WGBAST REPORT Preparation for inclusion of Testeboån in the assessment model The work to revise model input data has continued also this year. Testeboån received the status of a wild salmon river in 2013, but the stock has not yet been included in the assessment model. A PSPC prior for Testeboån was formulated using expert opinions about relevant variables. A simple model (the same model used in previous years for e.g. Öreälven and Lögdeälven, see Annex 4 in ICES, 2015 for more information) was used to derive a probability distribution for PSPC as a function of the expert-elicited variables. The derived median value for the PSPC prior was 8895 (90% PI: ). To obtain smolt priors that would allow for inclusion of Testeboån in the assessment model, the river was included in the same river model as used to produce smolt prior estimates for Emån and Mörrumsån. For a detailed description of this Southern river model, see ICES, 2017d. Data from Testeboån comprised a time-series of electrofishing data for the period and smolt counting results from the years Derived estimates of smolt priors for Testeboån are presented in Table Because of time limitations, Testeboån was not included in the full life-history model this year, which means that we cannot properly assess status and evaluate the development of this stock in the near future (following the different fishing scenarios evaluated in Section 4.3). The river will be fully integrated in the assessment work in However, a preliminary status evaluation based on the priors for PSPC and current (2017) smolt production indicates that it is uncertain whether Testeboån has reached the 50% objective, and unlikely that the 75% objective has been reached (Table ) Updated reference points for management (stock-specific MSY targets) Suitable management reference points for Baltic salmon were explored in the Workshop on Baltic Salmon Management Plan Request (WKBALSAL, ICES, 2008); where it was proposed that the limit of natural smolt production should not be lower than 75% of the estimated R 0 for each stock. This 75% R 0 proxy was revisited at the 2016 assessment meeting (using results from the 2015 assessment), following development of a simulation algorithm to approximate MSY. However, the results from that exercise were inconclusive, e.g. estimated smolt production at MSY of 40 smolts (0% of R 0 ) for Emån (cf. 24% in ICES, 2008). This appeared to be related to problems identified with the stock recruitment model outlined above (estimated EPR 0 for Emån 2 3 times greater than that for most other stocks). The exercise was repeated during the benchmark, for a subset of stocks (Torne River, Simojoki, Emån and Mörrumsån) to investigate the effect of different stock recruitment parameterizations on estimated reference points (ICES, 2017d). While those results are comparable with each other, it is necessary to perform the exercise with the results of the full assessment model comprising all observation models (since this can affect estimates of stock recruitment parameters, survival, etc.). The procedure used to obtain reference points is described in ICES (2017d). Briefly, an optimisation routine is used to find the fishing effort (and mortality) that maximises the long-term stable catch in forward projection of stock dynamics. The distribution of effort among fisheries is assumed to reflect the status quo. Note that alternative distributions of fishing effort across fisheries for immature vs. mature fish may result in different estimates of MSY and associated measures of abundance. Recreational trolling effort was added to offshore longline fishing effort as in the scenarios for future stock development. Specifications for future vital rates are the same as in future fishing scenarios (Table ).

218 212 ICES WGBAST REPORT 2018 Results of simulations are shown in Table Note that R0 (PSPC) estimates presented below are the long-term average smolt production from projections with F = 0, and are slightly lower than assessment model estimates because of slightly lower survival rates etc. used in future projections. Estimates of the smolt production corresponding to MSY as a proportion of RR 0 ( RRMMMMMM ) were fairly variable among stocks ranging RR 0 from 49% to 80% (Table ). Thirteen stocks had an MSY proxy lower than 0.75RR 0, while three stocks had a higher MSY proxy. These results indicate that the use of a single stock-wide reference point is consistent with a precautionary approach for many but not all Baltic salmon stocks. Estimates of RRMMMMMM were generally lower than those reported in ICES, 2008 (Table , RR 0 ICES, 2008 and Table ), with the exception of Emån and Mörrumsån. This is likely the result of higher estimates of stock recruit steepness in 2018 compared with 2008 (because of higher assumed M74 and post-smolt survival in projections, higher prior steepness, higher estimated adult survival etc. in 2018). Note that in ICES (2008), the 75th percentile of the distribution for RRMMMMMM appears to have been reported together RR 0 with the 25th percentile for the harvest rate at MSY corresponding to a 25% risk level (e.g. a 25% probability that the true RRMMMMMM is greater than the estimated value). Here, RR 0 medians are reported (Table ). The results shown above are not directly comparable to those obtained in the benchmark (ICES, 2017d) owing to the fact that only a subset of stocks and incomplete assessment model were used in that earlier exercise. The variability in estimates of RRMMMMMM among stocks appears to be related largely to variability of Beverton Holt alpha parameters (since estimated EPRs are on the whole sim- RR 0 ilar among stocks, except for Ume/Vindelälven), where all else being equal, stocks with a lower posterior estimate of alpha (higher maximum egg survival) tend to have more curved stock recruitment relationship corresponding to higher RR MMMMMM and higher RRMMMMMM. RR Conclusions For most rivers included in the FLHM (i.e. rivers in AU 1 4), the smolt production is expected to stay at relatively high levels in the coming years. Also, the prefishery abundance is expected to increase slightly in the near future, indicating possibilities for maintained exploitation levels under Results from the stock projections indicate that the current exploitation rate will result in more or less positive developmental trends of all AU 1 4 stocks (Section 4.3.2). In addition, projections indicate that changes in sea removal of +/-20% have rather small effects on the development of these stocks, further indicating that fishing mortality is currently at fairly low levels compared to other (natural) sources of mortality. Obviously, probabilities to reach the objectives are higher for scenarios with lower exploitation, but differences between scenarios are small except for the ones with zero fishing and recreational fishery only. Wild stocks in AU 6 have also shown a positive development in recent years, indicating that current exploitation levels are compatible with a successive recovery of these stocks. There are, however, concerns for the development of some wild salmon stocks. In particular, a majority of the AU 5 stocks have not responded positively to previous reductions in fisheries exploitation, and many stocks in this area are still far below a good state, indicating that current exploitation and natural mortality rates do not allow for a recovery.

219 ICES WGBAST REPORT Within the current management of Baltic salmon, there are no rules or guidelines for how fast (within which time frames) weak salmon stocks should recover, or when a certain proportion of all stocks should have obtained their management goal. Therefore, under current conditions with only one TAC for SD and many stocks with variable status, any catch advice for the mixed-stock fishery on Baltic salmon will be associated with trade-offs (and some degree of subjectivity). For some weak stocks, additional measures (on top of restrictions through the TAC system) need to be directed to increase number of spawners, for example by reducing fisheries on mixedstocks in the Main basin (to reduce the exploitation of weak AU 5 stocks) and on the migration routes (e.g. close to the river mouth) where their share in catches becomes higher. Measures focused on the freshwater environment, such as work to improve river habitats and migration possibilities and actions to reduce poaching, may also be necessary to increase status. Thus, special actions (not only fishery-related ones) directed to the weakest stocks are likely required at the adviced TAC levels, especially in AU 5 but also for a few weak rivers in other AUs, to enable these stocks to recover. M74-mortality has increased in recent years, as well as reported deaths of spawners due to disease problems (Section 4.4.1). If the higher levels of M74 should prevail or increase further, this may gradually result in decreased stock status and reduced fishing possibilities, and may easily counteract any positive effects of higher-than-expected post-smolt survival, especially in weaker stocks. The two Swedish rivers Vindelälven and Ljungan have been particularly affected by disease problems, and the recruitment of parr has dropped markedly (see Section 4.4.1). National and local management organisations of these two rivers should consider introducing measures to increase number of spawners, for example by reducing exploitation rates on migrating spawners in the rivers and in coastal areas outside the river mouths. Also Mörrumsån has reported substantial disease problems (affected and dead adults) in recent years, but so far the parr densities have not decreased as dramatically as in the other rivers mentioned. Several of the northern stocks are close to or above the MSY-level (2017 smolt production; Table ), and the surplus produced by these stronger stocks could in theory be directed towards stock-specific fisheries. However, the current management system, with a single TAC for SD that is set at a relatively low level to safeguard weaker salmon stocks, prevents this surplus to be fully utilised by the commercial sea fishery. In a similar way, the surplus of reared salmon cannot be fully utilised today because reared salmon is also included in the TAC. Stock-specific management could be developed further, by implementation of more flexible systems for regulation of commercial fisheries with the aim of steering exploitation towards harvesting of reared salmon and stronger wild stocks, through e.g. areaspecific quotas and/or exclusion of certain single-stock fisheries from the quota system (such as fisheries in estuaries of rivers with reared stocks). Also, non-commercial coastal fishing, not regulated by international quotas, could be steered towards stockspecific harvesting. In contrast, the increasing recreational trolling in Main Basin is a true mixed-stock fishery where stock-specific harvesting is not possible, although regulations that only allow landing of finclipped (reared) salmon, such as has been implemented in Sweden since 2013, can somewhat reduce fishing mortality for wild stocks (given that post-release mortality is relatively low). A higher degree of stock-specific exploitation will also be necessary in future, if different management objectives should be decided upon for individual stocks (e.g. if to allow for a larger number of spawners than needed to fulfil the MSY-level in certain wild rivers).

220 214 ICES WGBAST REPORT Ongoing and future development of the stock assessment Benchmark The benchmark of Baltic salmon (WKBaltSalmon) convened into two workshops at ICES (Copenhagen, Denmark), a data evaluation workshop in autumn 2016 and a method evaluation workshop early in The work carried out is presented in a separate benchmark report (ICES, 2017d). The data evaluation workshop resulted in e.g. an updated description of available river monitoring data and a time-series of preliminary trolling catch estimates trough an expert elicitation. In addition, shortcomings in fisheries data were identified, and some outlining for an improvement work plan was done. A planned transfer of commercial fisheries data into ICES database InterCatch largely failed, however, and the aim is to solve the catch data issues in connection to next data call in late The method evaluation workshop focused on three major aspects: stock recruitment model selection, development of a smolt production model for southern Baltic Sea rivers, and an evaluation of the 75% objective as a proxy for MSY. The new parameterization of stock recruitement dynamics and a new smolt production model for southern Baltic Sea rivers have been implemented in this year assessment (see Section 4.2). An evaluation of the 75% objective as a proxy for MSY is presented in Section Further developments of the methodology, which have not yet been implemented in the assessment, are presented in the section below Road map for development of the assessment The tasks listed below refer to ongoing, planned and potential updates of the assessment methodology. Issues that were included in the benchmark assessment (WKBaltSalmon; ICES, 2017d) are indicated. Ongoing and short term Add Testeboån to the FLHM. In this year s report, the status assessment of river Testeboån is only preliminary and e.g. based on expert opinions on PSPC. The plan is to include the river in the FLHM Necessary preparations for this inclusion have already been carried out (see Section 4.4.2). Inclusion of the recreational sea fishery (mainly trolling) as a separate fishery (part of WKBaltSalmon). At present, trolling catch estimates are added to the offshore commercial ones in the FLHM (see Section 4.2). Because of the increase in the recreational trolling fishery at sea, it would be desirable to model recreational trolling as a separate fishery. This will require good quality data and catch estimates from countries with a significant recreational trolling fishery. During the benchmark, a plan for how to collect data and include recreational catches in the assessment model as a separate fleet was discussed and decided upon. Adding repeat spawners to the FLHM. Salmon are currently assumed to die after first spawning in the FLHM. This assumption is known to be unrealistic (repeat spawners in some stocks now account for ~10% of all spawners). This is likely to cause bias in estimated parameters such as survival rates and stock recruitment parameters, as well as potentially management reference points. Use spawner counting observations for Piteälven in the FLHM. Use of spawner counting observations directly in the FLHM for Piteälven would constitute

221 ICES WGBAST REPORT a more consistent use of available data, requiring fewer assumptions about stock recruitment parameters, etc. external to the model. Smolt production estimates would then be treated as missing for Piteälven. Medium-term, important issues planned to be dealt with in the next 2-3 years Continuing the work of including data from established index rivers and expanding data collection in other rivers. Some of the datasets collected in index rivers are still not used in the assessment model, such as e.g. spawner count data from River Mörrumsån. To improve precision in assessment results, there is also a need to increase collection of abundance data in non-index rivers. Therefore, a rolling sampling programme that regularly collects abundance data from rivers where limited data are currently available will be established in Sweden, starting in Improved estimates of the exploitation of stocks in the coastal fishery. There is a need to replace the crude assumptions about how the coastal fisheries affect development of the stocks with more precise stock-specific estimates as input in the assessment model. Therefore, a spatially and temporally-structured Bayesian population dynamics model that tracks the migration of Baltic salmon stocks from their feeding grounds in the Baltic Sea to their natal rivers has been developed (Whitlock et al., 2018). The model uses information about the proportions of different stocks in catch samples from Swedish and Finnish coastal fisheries at different points in space and time, as well as finclipping information about the proportion of wild and reared fish in catches (also for catches where no genetic data are available). Further development of the model to be able to estimate stock-specific exploitation rates in the coastal fishery using genetic mixed-stock analysis is in progress (Whitlock et al., in prep). The model can also be used as a tool to evaluate the effect of alternative management actions (fishing effort configurations) on the exploitation and development of wild salmon stocks. This is key to developing stock-specific management. Improving precision in short-term projections by including covariates for sea survival. The potential for incorporating covariates such as herring recruitment strength and sea surface temperatures will be investigated as means to increase precision in short-term projections. Inclusion of AU 5 stocks in the full life-history model. At present, these stocks are treated separately from the AU 1 4 stocks. Inclusion in the full life-history model will require updated information regarding e.g. smolt age distributions, maturation rates, exploitation rates and post-smolt survival. In addition, increased amounts of basic biological data (e.g. smolt and spawner counts, additional electrofishing sites) may be needed for some rivers. The smolt production model for southern stocks that has been developed could be used also for AU 5 stocks in future, to produce smolt production priors and estimates for the life-history model. Development of an analytical assessment of AU 6 stocks. Development of an assessment model for AU 6 has been started in Model structure will be based on the same life-history model as used for AU 1 4, but it will be modified to follow the migration and fishing patterns specific to the AU 6 stocks. Also, the prior information available about the productivity (S/R dynamics) of the AU 6 spawning rivers will be incorporated. The AU 6 model will not be integrated to the AU 1 4 assessment in the first phase, but will be run as

222 216 ICES WGBAST REPORT 2018 a separate unit of stocks. However, the model will take into account migrations of salmon between the assessment units, which will to some extent link the assessments of the AU 1 4 salmon and AU 6 salmon together. The aim is to run the analytical assessment for AU 6 stocks latest in WGBAST Long-term and/or less urgent issues, good to keep in mind Refine the two river models to improve smolt priors used in the FLHM. The present river models do not account for annual fluctuations in smolt age structure, which may result in biases. Development of the river models to account for fluctuations in parr growth rates and length-specific smoltification probabilities to improve estimates of smolt age structure would solve this question. Allow for fluctuations in the stock recruitment carrying capacity (K) over time in rivers. Changes in physical river characteristics (e.g. habitat restoration and removal of obstacles to migration) have likely led to increases in K over the assessment period for some rivers. The current model version cannot handle this which may lead to biases when using old stock recruit data. Inclusion of data on composition of stocks at sea: The life-history model has already been fitted to information on proportions of wild and reared salmon in Main Basin as determined from scale readings. The next step would be to include genetic information on proportions of fish from different AUs, separating also wild and reared salmon from those areas. Subsequently, information on the representation of single stocks may be included. See more on future MSA in ICES (2015), Section 4.7. Further use of scale-reading data: In addition to wild/reared proportions, age data from catch samples could be used to get improved knowledge of yearclass strength, maturation and natural mortality rates. 4.7 Needs for improving the use and collection of data for assessment Because requirements for data will always exceed available resources, preferences must be given. The identification and prioritisation of new data collection, or modifications to ongoing monitoring work, should be based on end-user needs, particularly ICES assessment needs, and is of importance with respect to the European data collection framework (EU-MAP). Over the years, the WG has repeatedly highlighted and discussed various needs for data collection (e.g. ICES, 2014; 2015; 2016). For example, three years ago (ICES, 2015) the need for genetic analysis to study stock composition in catch samples (MSA) was reviewed, with suggestions provided regarding future studies. In the WGBAST 2016 report (ICES, 2016) comments were also given to a comprehensive list of proposals for Baltic salmon data collection produced at an earlier ICES workshop in Further, the need for at least one wild index river per assessment unit was highlighted, with suggestions given on potential candidates in AUs 5 6 (where full index rivers are still missing). Finally, as part of the recent benchmark for Baltic salmon (WKBALTSalmon, ICES, 2017d) all different types of information needed as input for the Baltic salmon stock assessment (fisheries statistics, biological data, etc.) were reviewed with respect to needs, availability and quality. Data issues and questions listed in the report are rather extensive and prioritizations will be needed. However, this can be used as a basis for decisions about data collection included in EU-MAP.

223 ICES WGBAST REPORT In brief, WKBALTSalmon highlighted the below data needs and development areas, and WGBAST encourage member states to include these elements subjects into their national data collection programmes. River data Biological monitoring Expansion of networks for electrofishing sites, to cover also newly populated river stretches; Updates of estimates for river-specific reproduction areas using standardised methodology; Inventories of habitat quality, particularly in weak salmon rivers (i.e. with low status); Compilation of stocking data on young life stages combined with information that enables estimation of survival of these releases to smolts; Counting data of ascending spawners from additional rivers. Guidelines to assure the comparability of such data should also be compiled. In rivers where counting is ongoing but data are yet not used in the assessment, additional information may be needed (e.g. from tagging studies). River fisheries The amount and quality of catch statistics vary considerably between rivers and countries. There is a general need for improvement and harmonisation of methods used for data collection, including estimates of unreporting; River-specific salmon catches should be included in InterCatch (ICES database); Available effort data from river fisheries should be evaluated. Sea fisheries data The level of misreporting of salmon (as sea trout) in the Polish offshore fishery may still be underestimated. For the Polish coastal fishery, no misreporting is accounted so far, although it potentially occurs there too. Data on proportions of sea trout and salmon (separately) in offshore and coastal catches are needed to facilitate a more precise estimation of the misreporting rates; Recreational trolling open sea catches have been estimated to be higher than previously recognised. Time-series of country specific catch estimates by three main fishing areas should be estimated; Also estimates of other recreational salmon catches at sea (i.e. coastal fishing in Sweden and Finland) should be added into InterCatch; Unreporting of catches is challenging to estimate, and it is possible that higher than currently estimated unreporting takes place in some of the countries and fisheries. An expert elicitation covering all relevant fisheries is needed in order to update unreporting estimates. Also, discards may be substantially underestimated (both undersized and sea-damaged catch) and studies on these are needed; Commercial salmon and sea trout catch and effort data by fleets and half years from all countries should be added into InterCatch;

224 218 ICES WGBAST REPORT 2018 Shortcomings in currently available fisheries data may cause bias in mortality estimates (F and M). At present, the possible magnitude of such bias, and consequently its potential impact on conclusions regarding stock status and catch advice, has not been evaluated. The present assessment model is assumed to estimate the magnitude of total mortality reasonably reliably. However, an exercise exploring extra uncertainties emerging from data deficiencies (currently not accounted for), and how these may influence the catch advices (both qualitatively and quantitatively) should be carried out.

225 ICES WGBAST REPORT Table Likelyhood approximations for the wild smolt production (*1000) in the Baltic salmon rivers included in the Full Life-History Model (FLHM). The distributions are described in terms of their median, the 90% probability interval (PI) and the method on how these probability distributions have been obtained. These estimates will be updated in Section Wild smolt production (thousand) Method of estimation Assessment unit 1 1 Tornionjoki ,2 90% PI Simojoki ,2 90% PI Kalixälven % PI Råneälven % PI Total assessment unit % PI Assessment unit 2 5 Piteälven % PI Åbyälven % PI Byskeälven % PI Kågeälven NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA % PI NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA Rickleån ,2 90% PI Sävarån ,2 90% PI Ume/Vindelälven ,2 90% PI Öreälven % PI Lögdeälven ,2 90% PI Total assessment unit % PI Assessment unit 3 13 Ljungan % PI Total assessment unit % PI Assessment unit 4 14 Emån % PI Mörrumsån % PI Total assessment unit % PI Method of estimation: 1. Bayesian linear regression model, i.e. the river model (see the Stock Annex) 2. Sampling of smolts and estimate of total smolt run size. 3. Inference of smolt production from data derived from similar rivers in the region.

226 220 ICES WGBAST REPORT 2018 Table Median values and coefficients of variation of the estimated M74 mortality for different Atlantic salmon stocks (spawning years ). The values in bold are based on observation data from hatchery or laboratory monitoring in the river and year concerned. Grey cells represent predictive estimates for years from which no monitoring data were available Simojoki cv Tornionjoki cv Kemijoki cv Iijoki cv Luleälven cv Skellelteälven cv Ume/Vindelälven cv Ångermanälven cv Indalsälven cv Ljungan cv Ljusnan cv Dalälven cv Mörrumsån cv Unsampled stock cv

227 ICES WGBAST REPORT Table Posterior probability distributions for steepness, alpha and beta parameters of the Beverton Holt stock recruit relationship and eggs per recruit (EPR, millions) for Baltic salmon stocks. Posterior distributions are summarised in terms of their mean and CV (%). Assessment unit 1 Mean cv Mean cv Mean cv Mean cv 1 Tornionjoki Simojoki Kalixälven Råneälven Assessment unit 2 5 Piteälven Åbyälven Byskeälven Kågeälven Rickleån Sävarån Ume/Vindelälven Öreälven Lögdeälven Assessment unit 3 Alpha parameter Beta parameter 14 Ljungan Assessment unit 4 Steepness 15 Emån Mörrumsån EPR

228 222 ICES WGBAST REPORT 2018 Table Posterior probability distributions for the smolt production capacity (x 1000) in the AU 1 4 rivers and the corresponding point estimates in the AU 5 6 rivers. The posterior distributions are described in terms of their mode or most likely value, the 90% probability interval (PI) and the method by which the posterior probability distribution was obtained. These estimates serve as reference points to evaluate the status of the stock. For the updated estimates of the AU 1 4 rivers except Testeboån, medians as estimated by last year s stock assessment are also shown. This enables comparison of how much the estimated medians have changed compared to last year. Smolt production capacity (thousand) Method of Last year s median % change Mode Median Mean 90% PI estimation Assessment unit 1 1 Tornionjoki % 2 Simojoki % 3 Kalixälven % 4 Råneälven % Total assessment unit 1 Assessment unit % 5 Piteälven * % 6 Åbyälven % 7 Byskeälven % 8 Kågeälven % 9 Rickleån % 10 Sävarån % 11 Ume/Vindelälven % 12 Öreälven * % 13 Lögdeälven * % Total assessment unit % Assessment unit 3 14 Ljungan % 15 Testeboån % Total assessment unit 3 Assessment unit % 16 Emån * % 17 Mörrumsån * % Total assessment unit % Total assessment units 1-4 Assessment unit % 18 Pärnu % 19 Salaca % 20 Vitrupe % 21 Peterupe % 22 Gauja % 23 Daugava % 24 Irbe % 25 Venta % 26 Saka % 27 Uzava % 28 Barta % 29 Nemunas river basin % Total assessment unit % Assessment unit 6 30 Kymijoki % 31 Luga % 32 Purtse % 33 Kunda % 34 Selja % 35 Loobu % 36 Pirita % 37 Vasalemma % 38 Keila % 39 Valgejögi % 40 Jägala % 41 Vääna % Total assessment unit % Total assessment units % * River w ith recently updated prior for potential or current smolt production.

229 ICES WGBAST REPORT Table Wild smolt production in Baltic rivers with natural reproduction of salmon grouped by assessment units: posterior probability estimates derived from the Full Life- History Model (FLHM) for the AU 1 4 rivers (except Testeboån which is currently not included in the FLHM), and estimates derived by other means (inferred from parr densities, smolt trapping, etc.) for the rest of the rivers. Median estimates (x 1000) of smolts with the associated uncertainty (90% Probability interval) are shown. Also, the river-specific reproductive areas and the potential smolt production capacities (PSPCs) are shown as medians and 90% PIs. Reprod. area (ha, median) Potential (*1000) Method of Pred Pred Pred estimation Pot. Pres. prod. prod. Assessment unit, subdivision, country Category Gulf of Bothnia, Sub-div : Finland Simojoki wild % PI '3-8 '6-13 '8-17 '22-42 '37-62 '37-63 '34-59 '27-47 '22-37 '25-42 '26-40 '27-47 '20-37 '26-44 '33-47 '24-40 '32-43 '35-53 '23-44 '27-33 '31-56 '47-83 '19-65 '22-75 Finland/Sweden Tornionjoki;Torneälven wild % PI ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Sweden Kalixälven wild % PI ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Råneälven wild % PI '2-14 '2-13 '5-25 '6-31 '11-43 '12-49 '11-43 '12-45 '12-48 '15-57 '20-65 '18-60 '25-82 '21-73 '22-73 '24-76 '23-79 '24-78 '24-82 '27-90 ' ' ' ' ' Assessment unit 1, total % PI ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Piteälven wild % PI '4-5 '4-5 '5-5 '3-3 '1-2 '3-3 '6-6 '17-26 '16-25 '11-15 '14-21 '16-29 '23-46 '25-54 '27-58 '26-53 '22-39 '19-31 '22-36 '27-49 '24-43 '22-35 '30-61 '21-76 '23-78 Åbyälven wild % PI '1-8 '2-10 '3-12 '3-13 '5-20 '7-24 '5-20 '6-19 '5-18 '5-17 '6-20 '6-22 '8-28 '7-24 '6-22 '7-23 '7-22 '7-24 '8-25 '8-26 '9-32 '9-33 '10-35 '7-32 '8-34 Byskeälven wild % PI '15-71 '11-48 ' '26-91 ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Rickleån wild % PI '0-1 '0-1 '0-1 '0-1 '0-1 '1-3 '1-2 '1-2 '0-2 '0-2 '0-2 '1-2 '1-4 '1-3 '1-3 '1-3 '1-3 '1-4 '2-3 '1-5 '3-5 '4-7 '3-9 '2-8 '3-10 Sävarån wild % PI '0-1 '0-1 '1-3 '1-3 '1-3 '1-4 '1-3 '1-3 '1-4 '3-5 '3-4 '2-4 '3-6 '2-5 '2-4 '2-4 '2-7 '3-6 '3-8 '3-9 '4-11 '5-14 '6-17 '3-14 '4-17 Ume/Vindelälven wild % PI '8-33 '27-90 ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Öreälven wild % PI '0-1 '0-1 '0-2 '0-2 '1-4 '1-5 '1-4 '1-4 '1-4 '1-5 '2-8 '2-7 '3-12 '2-10 '2-10 '3-11 '3-14 '3-15 '4-17 '4-21 '7-32 '9-39 '11-49 '8-43 '10-56 Lögdeälven wild % PI '0-1 '0-1 '0-2 '1-3 '1-4 '1-5 '1-3 '1-3 '1-4 '1-5 '2-6 '2-6 '2-8 '2-6 '2-6 '2-7 '3-9 '3-10 '3-10 '4-12 '5-10 '7-20 '8-25 '5-25 '7-34 Kågeälven wild % PI '3-57 '3-54 '2-39 '1-30 '1-27 '2-43 '3-67 '3-61 '5-85 '13-58 '12-59 '8-57 '12-72 Assessment unit 2, total % PI ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Ljungan wild % PI '0-1 '0-2 '0-2 '1-2 '1-3 '1-3 '1-2 '1-3 '1-3 '1-2 '1-3 '1-2 '1-3 '1-3 '1-3 '1-3 '1-2 '1-3 '1-3 '1-3 '1-4 '1-4 '1-4 '1-4 '1-4 Testeboån wild % PI na Assessment unit 3, total % PI '0-14 '0-15 '0-13 '1-13 '1-17 '1-23 '1-25 '1-23 '1-31 '1-32 '1-32 '1-24 '1-23 '1-12 '1-15 '1-16 '1-17 '1-20 '2-9 '1-6 '2-6 '2-8 '1-24 '1-4 '1-4 Total Gulf of B., Sub-divs % PI ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '

230 224 ICES WGBAST REPORT 2018 Table Continued. 0 Method of Pred Pred Pred estimation Assessment unit, subdivision, Reprod. area Potential Pot. Pres. country Category (ha, median) (*1000) prod. prod. Sweden Emån wild % PI '0-3 '0-4 '0-6 '1-6 '1-6 '1-4 '1-4 '1-5 '1-6 '1-7 '1-5 '1-7 '2-4 '1-6 '2-7 '1-6 '1-7 '1-6 '1-6 '2-11 '2-12 '3-15 '2-11 '2-13 '2-12 Mörrumsån wild % PI '25-96 ' ' '27-95 ' '27-91 '29-96 ' '28-95 '26-95 '26-92 '29-92 '27-95 '25-90 '25-86 '24-90 '23-82 '24-80 '26-95 '28-88 '29-97 '28-93 '27-91 ' '26-96 Assessment unit 4, total % PI '53-96 '25-97 ' ' '29-98 ' '28-93 '31-98 ' '30-98 '30-98 '27-94 '32-96 '30-97 '28-94 '28-89 '27-93 '27-85 '27-83 '29-98 '33-94 ' ' '32-96 ' ' Estonia Pärnu mixed , 4 Latvia Salaca wild Vitrupe wild Peterupe wild , 5 Gauja mixed , 5 Daugava*** mixed , 6 Irbe wild Venta mixed , 5 Saka wild Uzava wild Barta wild Lithuania Nemunas river basin wild , 4 Assessment unit 5, total Total Main B., Sub-divs (AU's 4-5) Method of Pred Pred Pred estimation Assessment unit, subdivision, Reprod. area Potential Pot. Pres. country Category (ha, median) (*1000) prod. prod. Finland: Kymijoki mixed 15 1) +60 2) 20 1) +80 2) Russia: Neva mixed Luga mixed SE Estonia: Purtse mixed Kunda wild 1.9 2,1(3,7) Selja mixed Loobu mixed Pirita mixed , 3 90% PI Vasalemma wild Keila wild 3.5 5,4 (12) Valgejõgi mixed Jägala mixed Vääna mixed Assessment unit 6, total Gulf of B.+Main B.+ Gulf of F., Sub-divs % PI ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' = Low and uncertain production (not added into sub-totals or totals) ++ = Same method over time series; only the extension backwards preliminary Methods of estimating production Present production 7. Estimate inferred from stocking of reared fish in the river. Potential production 1. Bayesian full life history model (section 6.3.9) 8. Salmon catch, exploitation and survival estimate. 1. Bayesian stock-recruit analysis 2. Sampling of smolts and estimate of total smolt run size. 2. Accessible linear stream length and production capacity per area. 3. Estimate of smolt run from parr production by relation developed in the same river. Reared smolts *** = Tributaries 3. Expert opinion with associated uncertainty 4. Estimate of smolt run from parr production by relation developed in another river. *=Release river not specified **** = Only Latvian part, Lithuanian part of the river needs to 4) Below the lovest dams 5. Inference of smolt production from data derived from similar rivers in the region. be added 5) Above the lowest dams 6. Count of spawners. n/a No data available.

231 ICES WGBAST REPORT Table Overview of the status of the Gulf of Bothnia and Main Basin wild and mixed-stocks (grey rows) in terms of their probability to reach 50 and 75% of the smolt production capacity in 2017 (compared to PSPC in that year). Stocks are considered very likely to have reached this objective in case the probability is higher than 90%. They are likely to have reached the objective if the probability is between 70 and 90%, uncertain when the probability is between 30 and 70 % and unlikely if the probability is less than 30%. For the AU1 4 stocks except Testeboån, the results are based on the assessment model, whereas the categorization of Testeboån and AU5 6 stocks is based on expert judgments; for those rivers there are no precise probabilities (column 'Prob'). Prob to reach 50% Prob to reach 75% Stock Category Prob V.likely Likely Uncert. Unlikely Prob V.likely Likely Uncert. Unlikely Unit 1 Tornionjoki wild 1.00 X 0.95 X Simojoki wild 0.96 X 0.68 X Kalixälven wild 0.98 X 0.81 X Råneälven wild 0.95 X 0.71 X Unit 2 Piteälven wild 0.81 X 0.15 X Åbyälven wild 0.97 X 0.78 X Byskeälven wild 0.98 X 0.80 X Kågeälven wild 0.73 X 0.38 X Rickleån wild 0.45 X 0.12 X Sävarån wild 0.82 X 0.55 X Ume/Vindelälven wild 1.00 X 0.88 X Öreälven wild 0.37 X 0.15 X Lögdeälven wild 0.22 X 0.08 X Unit 3 Ljungan wild 0.87 X 0.66 X Testeboån *) wild n.a. X n.a. X Unit 4 Emån wild 0.45 X 0.17 X Mörrumsån wild 0.98 X 0.76 X Unit 5 Pärnu mixed n.a. X n.a. X Salaca wild n.a. X n.a. X Vitrupe wild n.a. X n.a. X Peterupe wild n.a. X n.a. X Gauja mixed n.a. X n.a. X Daugava mixed n.a. X n.a. X Irbe wild n.a. X n.a. X Venta mixed n.a. X n.a. X Saka wild n.a. X n.a. X Uzava wild n.a. X n.a. X Barta wild n.a. X n.a. X Nemunas wild n.a. X n.a. X Unit 6 Kymijoki mixed n.a. X n.a. X Luga mixed n.a. X n.a. X Purtse mixed n.a. X n.a. X Kunda wild n.a. X n.a. X Selja mixed n.a. X n.a. X Loobu mixed n.a. X n.a. X Pirita mixed n.a. X n.a. X Vasalemma wild n.a. X n.a. X Keila wild n.a. X n.a. X Valgejögi mixed n.a. X n.a. X Jägala mixed n.a. X n.a. X Vääna mixed n.a. X n.a. X *) Preliminary evaluation, see section

232 226 ICES WGBAST REPORT 2018 Table Key assumptions underlying the stock projections. The same post-smolt survival scenario and M74 scenario are assumed for all effort scenarios. Survival values represent the medians to which Mps and M74 are expected to return. Scenario Total commercial removal (dead catch) for year Removal that corresponds to ICES advice for fishing year % increase to scenario % decrease to scenario 1 4 F0.1 approach (commercial removal) 5 recreational fishing only 6 zero fishing In all scenarios we assume that the commercial removal (wanted catch reported) covers 55% of the total commercial sea fishing mortality, whereas 46% of this mortality consists of discards, misreported and unreported. Recreational fisheries in 2019 are assumed to have a catch that corresponds to the average catch in these fisheries in period, whereas in future years the effort component is the same for these fisheries but the catch varies according to abundance. (See text for details) Post-smolt survival of wild salmon Average survival between (19%) Post-smolt survival of reared salmon Same relative difference to wild salmon as on average in history M74 survival Historical median (85%) Releases Same number of annual releases in the future as in 2017 Maturation Age group specific maturation rates in 2018 are predicted using january-march 2018 SST data. For other years, average maturation rates over the time series are used, separately for wild and reared salmon. Ume/Vindelälven Average proportions (no. spawners passing ladder, MSW sex ratio passing ladder, extra mortality after ladder)

233 ICES WGBAST REPORT Table Estimates (in thousands of fish) of total removal in the commercial fishery at sea by scenario, and the corresponding reported commercial catch in total and divided between these fisheries in Calculations about how the total catch is divided between reported commercial catch and discards/unreporting/misreporting are based on the situation prevailing in 2017 (see text). The table shows also the predicted total number of spawners in 2019 (in thousands). All values refer to medians unless stated otherwise. Commercial catches (thousands of fish) at sea in SD in 2019 Wanted Catch Total inst. F of Reported Unwanted Catch (Dead+Alive) commercial comm. Scenario catch at sea Catch (% of 2018 EU TAC) Undersized Seal damaged Wanted Catch Unreported Wanted Catch Misreported % % % % % % Scenario Total sea catch (comm. + recr.) 2019 inst. F of total catch at sea Recreational catch at sea 2019 River catch 2019 Spawners

234 228 ICES WGBAST REPORT 2018 Table River-specific probabilities in different scenarios to meet 75% of PSPC in 2023/2024 (depending on the assessment unit) Probabilities higher than 70% are presented in green. Probability to meet 75% of PSPC River Year of Scenario comparison Tornionjoki Simojoki Kalixälven Råneälven Piteälven Åbyälven Byskeälven Rickleån Sävarån Ume/Vindelälven Öreälven Lögdeälven Ljungan Mörrumsån Emån Kågeälven

235 ICES WGBAST REPORT Table Estimated management reference points for Baltic salmon stocks. MSY smolt production, spawner escapement and R0 are given in thousands and are median values, likewise; MSY proxy values are ratios of medians. Harvest rates in the final two columns apply to salmon aged 2 and older (i.e. not post-smolts). MSY smolt MSY Stock production escapement R 0 MSY proxy MSY proxy ICES 2008 Immature harvest rate Mature harvest rate Tornionjoki % 83% Simojoki % 62% Kalixälven % 89% Råneälven % 83% Piteälven % 85% Åbyälven % 81% Byskeälven % 82% Rickleån % 78% Sävarån % 76% Vindelälven % 91% Öreälven % 79% Lögdeälven % 79% Ljungan % 74% Mörrumsån % 75% Emån % 24% Kågeälven % NA

236 230 ICES WGBAST REPORT 2018 Figure Prior probability distributions for the Beverton Holt alpha parameter (the inverse of the slope of the stock recruitment curve near the origin).

237 ICES WGBAST REPORT Figure a. Prior distributions for R0 (PSPC) from WGBAST ICES, 2017 (dashed line) and the updated stock recruitment parameterisation used in 2018 (final year R0, solid line). Dashed vertical lines indicate the medians in 2017 (grey) and 2018 (black). Note that updated (higher) priors for carrying capacity have been used 2018 for Piteälven, Öreälven and Lögdeälven (Section 4.2.2), and that updates have been done for Ume/Vindelälven (new priors on sex ratio and proportion of tagged ascending spawners finding the fish ladder; see Section 4.2.1).

238 232 ICES WGBAST REPORT 2018 Figure b. Prior distributions for R0 (PSPC) from WGBAST ICES, 2017 (dashed line) and the updated stock recruitment parameterisation used in 2018 (final year R0, solid line). Dashed vertical lines indicate the medians in 2017 (grey) and 2018 (black). Note that updated (higher) priors for carrying capacity have been used 2018 for Piteälven, Öreälven and Lögdeälven (Section 4.2.2), and that updates have been done for Ume/Vindelälven (new priors on sex ratio and proportion of tagged ascending spawners finding the fish ladder; see Section 4.2.1).

239 ICES WGBAST REPORT Figure c. Prior distributions for R0 (PSPC) from WGBAST ICES, 2017 (dashed line) and the updated stock recruitment parameterisation used in 2018 (final year R0, solid line). Dashed vertical lines indicate the medians in 2017 (grey) and 2018 (black). Note that updated (higher) priors for carrying capacity have been used 2018 for Piteälven, Öreälven and Lögdeälven (Section 4.2.2), and that updates have been done for Ume/Vindelälven (new priors on sex ratio and proportion of tagged ascending spawners finding the fish ladder; see Section 4.2.1).

240 234 ICES WGBAST REPORT 2018 Figure Probability that returning salmon find the fishladder in river Ume/Vindel. For years in which mark recapture study has not taken place, prior distribution is the predictive distribution that is based on other years mark recapture studies. See the text concerning the exceptional year Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

241 ICES WGBAST REPORT Figure Old and new (and updated) smolt production input to be used in the Full Life-history Model (FLHM) for River Piteälven (medians with 90% PI).

242 236 ICES WGBAST REPORT 2018 Figure M74 mortality among Atlantic salmon stocks within the Baltic Sea by spawning year class in Solid circles and whiskers represent the medians and 95% probability intervals of the estimated M74 mortality, respectively. Open circles represent the proportion of females with offspring affected by M74 and triangles the total average yolk-sac-fry mortalities among offspring.

243 ICES WGBAST REPORT Figure Estimated proportion of M74-affected offspring that die (i.e. mortality among those offspring that are from M74 affected females) by spawning year class in Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

244 238 ICES WGBAST REPORT 2018 Post-smolt survival 0.6 Survival Year Figure Post-smolt survival for wild (black) and hatchery-reared salmon (grey). Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

245 ICES WGBAST REPORT Maturation rates Grilse 2SW Proportion SW 4SW Year Figure Proportion maturing per age group and per year for wild (black) and reared salmon (grey). Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

246 240 ICES WGBAST REPORT 2018 Figure a. Distributions for egg abundance (million), plotted against the smolt abundance (thousand) for stocks of assessment units 1 4. Blue dots present the posterior distributions of annual smolt and egg abundances, red curves indicate the distributions of stock recruit relationship.

247 ICES WGBAST REPORT Figure b. Distributions for egg abundance (million), plotted against the smolt abundance (thousand) for stocks of assessment units 1 4. Blue dots present the posterior distributions of annual smolt and egg abundances, red curves indicate the distributions of stock recruit relationship.

248 242 ICES WGBAST REPORT 2018 Figure c. Distributions for egg abundance (million), plotted against the smolt abundance (thousand) for stocks of assessment units 1 4. Blue dots present the posterior distributions of annual smolt and egg abundances, red curves indicate the distributions of stock recruit relationship.

249 ICES WGBAST REPORT Figure d. Distributions for egg abundance (million), plotted against the smolt abundance (thousand) for stocks of assessment units 1 4. Blue dots present the posterior distributions of annual smolt and egg abundances, red curves indicate the distributions of stock recruit relationship.

250 244 ICES WGBAST REPORT 2018 Figure a. Prior and posterior probability distributions for the potential smolt production capacity (PSPC) obtained in the assessment in 2017 (thin line) and 2018 (final year, bold line). The 2017 assessment prior distributions for PSPC are shown by the grey dashed lines, while the 2018 assessment prior distributions for PSPC (final year) are shown by the black dotted lines.

251 ICES WGBAST REPORT Figure b. Prior and posterior probability distributions for the potential smolt production capacity (PSPC) obtained in the assessment in 2017 (thin line) and 2018 (final year, bold line). The 2017 assessment prior distributions for PSPC are shown by the grey dashed lines, while the 2018 assessment prior distributions for PSPC (final year) are shown by the black dotted lines.

252 246 ICES WGBAST REPORT 2018 Figure Posterior probability distributions for the total smolt production in assessment units (AU) 1 to 4 and in total. Vertical lines within each box show the median (solid line); whiskers denote the 90% PI for potential smolt production capacity (PSPC).

253 ICES WGBAST REPORT Figure Probability of reaching 50% of the smolt production capacity for different stocks of assessment units 1 4.

254 248 ICES WGBAST REPORT 2018 Figure Probability of reaching 75% of the smolt production capacity for different stocks of assessment units 1 4.

255 ICES WGBAST REPORT Catch (in thousands) River Catch (in thousands) Coast Year Year Catch (in thousands) Offshore Catch (in thousands) Total Year Year Figure Estimated posterior distributions of catches compared with corresponding observed catches (boxplots with medians, 5%, 25%, 75% and 95% quantiles). Offshore catches cover both commercial fisheries and recreational trolling. Observed catches have been recalculated to account for unreporting.

256 250 ICES WGBAST REPORT 2018 Wild proportion Proportion SW 3SW Year Figure Estimated proportions of wild in offshore catches compared with wild proportions observed in the catch samples among 2SW and 3SW salmon. Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

257 ICES WGBAST REPORT Number of spawners Torne Simo Kalix Number of spawners (1000s) Råne Pite Åby Byske Rickleån Sävärån Year Figure a. Estimated posterior distributions of the number of spawners (in thousands) in each river vs. number of observed in fish counters. Observations indicated with dots are used as an input in the full life-history model whereas the ones indicated with triangles are so far not used as an input. Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

258 252 ICES WGBAST REPORT 2018 Ume Öre Lögde Number of spawners (1000s) Ljungan Mörrum Emån Kåge Year Figure b. Estimated posterior distributions of the number of spawners (in thousands) in each river vs. number of observed in fish counters. Observations indicated with dots are used as an input in the full life-history model whereas the ones indicated with triangles are so far not used as an input. Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

259 ICES WGBAST REPORT Offshore driftnet HR 1SW MSW Harvest rate Year 0.0 Offshore longline HR 1SW 0.30 MSW Harvest rate Year Figure a. Estimated posterior distributions of the harvest rates (harvested proportion of the available population) in offshore driftnet and offshore longline fisheries separately for one-sea-winter and multi-sea-winter salmon. The offshore longline fishery contains now also recreational trolling (see Section for details). Note that the driftnet harvest rate in 2008 is not zero, since due to computational reasons it contains fishing effort from the second half of year Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

260 254 ICES WGBAST REPORT 2018 Coastal HR AU1 Grilse MSW 0.8 Harvest rate Year Coastal driftnet HR Grilse 0.12 MSW Harvest rate Year 0.00 Figure b. Estimated posterior distributions of the harvest rates (harvested proportion of the available population) in other coastal fisheries than driftnetting in AU1 and in coastal driftnetting (all AU s together) separately for one-sea-winter and multi-sea-winter salmon. Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

261 ICES WGBAST REPORT River HR Grilse MSW Harvest rate Year Figure c. Estimated posterior distributions of the harvest rates (harvested proportion of the available population) in the river fishery separately for one-sea-winter and multi-sea-winter salmon. Boxplots show medians with 5%, 25%, 75% and 95% quantiles. Combined offshore HR, Combined coastal HR, M Harvest rate Harvest rate Figure Combined harvest rates (harvested proportion of the available population, medians with 90% probability intervals) for offshore and coastal fisheries for MSW wild salmon in

262 256 ICES WGBAST REPORT 2018 Smolt production relative to PSPC (%) % level 50 % level Barta Irbe Peterupe Saka Salaca Uzava Vitrupe Nemunas Pärnu Figure Wild smolt production level in relation to the potential in AU 5 wild salmon populations. Figure Wild smolt production level in relation to the potential in AU 5 mixed salmon populations.

263 ICES WGBAST REPORT % 90% Smolt production relative to PSPC 80% 70% 60% 50% 40% 30% 20% 10% 0% Keila Vasalemma Kunda Figure Smolt production level in relation to the potential in AU 6 wild salmon populations. Note that the potential is calculated only up to the lowermost migration obstacle and that rivers have substantial rearing habitat areas above migration obstacles. Smolt production in relation to potential (%) % level 75% level Purtse Selja Loobu Pirita Valgeõgi Jägala Vääna Figure Smolt production level in relation to the potential in Estonian AU 6 mixed salmon populations. Note that the potential is calculated only up to the lowermost impassable migration obstacle and that many rivers have considerably higher total potential.

264 258 ICES WGBAST REPORT 2018 Smolt production in relation to potential (%) % level 50 % level Kymijoki Luga Figure Wild smolt production level compared to potential in river Kymijoki (Finland) and in river Luga (Russia). 100% 90% Smolt production relative to PSPC 80% 70% 60% 50% 40% 30% 20% 10% 0% Figure Average smolt production level in relation to the potential in AU 6 mixed salmon populations (with 90% probability interval). Note that the potential is calculated only up to the lowermost impassable migration obstacle and many rivers have considerably higher total potential.

265 ICES WGBAST REPORT The sahare of adipose fin-clipped salmon Figure Share of adipose finclipped salmon caught on the south coast of the Gulf of Finland.

266 260 ICES WGBAST REPORT 2018 Scenario 1 Scenario 2 LL HR for MSW wild LL HR for MSW wild Scenario 3 Scenario 4 LL HR for MSW wild LL HR for MSW wild Figure a. Harvest rates (median values and 90% probability intervals) for wild multi-sea winter salmon in offshore longline fishery (including also recreational trolling, see Section for details) within scenarios 1 4.

267 ICES WGBAST REPORT TN HR for MSW wild in AU Scenario 1 TN HR for MSW wild in AU Scenario TN HR for MSW wild in AU Scenario 3 TN HR for MSW wild in AU Scenario Figure b. Harvest rates (median values and 90% probability intervals) for wild multi-sea winter salmon in coastal trapnet fishery within scenarios 1 4.

268 262 ICES WGBAST REPORT 2018 Rate Post-smolt survival wild reared Year M74 survival Rate Year Figure Median values and 90% probability intervals for post-smolt survival of wild and reared salmon and M74 survival assumed in all scenarios.

269 ICES WGBAST REPORT Grilse 2SW Proportion mature wild reared Proportion mature Year 3SW Year 4SW Proportion mature Proportion mature Year Year Figure Median values and 90% probability intervals for annual proportions maturing per age group for wild and reared salmon in all scenarios.

270 264 ICES WGBAST REPORT 2018 Abundance (in 1000's) SW wild, scen 1 Abundance (in 1000's) SW wild & reared Abundance (in 1000's) MSW wild, scen 1 Abundance (in 1000's) MSW wild & reared Figure a. Pre-fishery abundances of MSW and 1SW wild salmon and wild and reared salmon together based on scenario 1 (medians with 90% probability intervals). PFAs reflect the abundance that is available to the fisheries. In case of MSW salmon natural mortality is taken into account until end of June of the fishing year and in case of post-smolts, until end of August (four months after post-smolt mortality phase). See text for details.

271 ICES WGBAST REPORT Abundance (in 1000's) SW wild, scen 6 Abundance (in 1000's) SW wild & reared Abundance (in 1000's) MSW wild, scen 6 Abundance (in 1000's) MSW wild & reared Figure b. Pre-fishery abundances of MSW and 1SW wild salmon and wild and reared salmon together based on scenario 6 (zero fishing) (medians with 90% probability intervals). PFAs reflect the abundance that is available to the fisheries. In case of MSW salmon natural mortality is taken into account until end of June of the fishing year and in case of post-smolts, until end of August (four months after post-smolt mortality phase). See text for details.

272 266 ICES WGBAST REPORT 2018 Sea catches Catch (1000's) Year Figure Estimates of reported commercial sea catches (all gears, black boxplots) and recreational sea catches (all gears, grey boxplots) based on scenarios 1 6. Boxplots show medians with 5%, 25%, 75% and 95% quantiles.

273 ICES WGBAST REPORT Probability of meeting 75% Tornionjoki Probability of meeting 75% Simojoki Probability of meeting 75% Kalixälven Probability of meeting 75% Råneälven Figure a. Probabilities for different stocks to meet an objective of 75% of potential smolt production capacity under scenarios 1 6. Fishing in 2019 affects mostly years

274 268 ICES WGBAST REPORT 2018 Probability of meeting 75% Piteälven Probability of meeting 75% Åbyälven Probability of meeting 75% Byskeälven Probability of meeting 75% Rickleån Figure b. Probabilities for different stocks to meet an objective of 75% of potential smolt production capacity under scenarios 1 6. Fishing in 2019 affects mostly years

275 ICES WGBAST REPORT Probability of meeting 75% Sävåran Probability of meeting 75% Vindelälven Probability of meeting 75% Öreälven Probability of meeting 75% Lögdeälven Figure c. Probabilities for different stocks to meet an objective of 75% of potential smolt production capacity under scenarios 1 6. Fishing in 2019 affects mostly years

276 270 ICES WGBAST REPORT 2018 Probability of meeting 75% Ljungan Probability of meeting 75% Mörrumsån Probability of meeting 75% Emån Probability of meeting 75% Kågeälven Figure d. Probabilities for different stocks to meet an objective of 75% of potential smolt production capacity under scenarios 1 6. Fishing in 2019 affects mostly years

277 ICES WGBAST REPORT Tornio Simo Scen1 Scen2 Scen3 Scen4 Scen5 Scen Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Kalix Råne Scen1 Scen2 Scen3 Scen4 Scen5 Scen Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Pite Åby Scen1 Scen2 Scen3 Scen4 Scen5 Scen Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Byske 2017 Scen1 Scen2 Scen3 Scen4 Scen5 Scen Rickleån 2017 Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Figure a. Predicted smolt production in 2024 (or 2023 for Emån and Mörrumsån) under fishing scenarios 1 6 (thin lines) compared to estimated production in 2017 (bold line). Vertical lines illustrate medians of the distributions.

278 272 ICES WGBAST REPORT Sävarån 2017 Scen1 Scen2 Scen3 Scen4 Scen5 Scen Ume/Vindel 2017 Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Öre Lögde Scen1 Scen2 Scen3 Scen4 Scen5 Scen Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Ljungan Mörrumsån Scen1 Scen2 Scen3 Scen4 Scen5 Scen Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Emån 2017 Scen1 Scen2 Scen3 Scen4 Scen5 Scen Kåge 2017 Scen1 Scen2 Scen3 Scen4 Scen5 Scen Smolt production Smolt production Figure b. Predicted smolt production in 2024 (or 2023 for Emån and Mörrumsån) under fishing scenarios 1 6 (thin lines) compared to estimated production in 2017 (bold line). Vertical lines illustrate medians of the distributions.

279 ICES WGBAST REPORT Figure a. Median values and 90% probability intervals for smolt and spawner abundances for rivers Tornionjoki, Simojoki, Kalixälven and Råneälven in scenarios 1 (black), 4 (red) and 6 (blue).

280 274 ICES WGBAST REPORT 2018 Figure b. Median values and 90% probability intervals for smolt and spawner abundances for rivers Piteälven, Åbyälven, Byskeälven and Rickleån in scenarios 1 (black), 4 (red) and 6 (blue).

281 ICES WGBAST REPORT Figure c. Median values and 90% probability intervals for smolt and spawner abundances for rivers Sävarån, Ume/Vindelälven, Öreälven and Lögdeälven in scenarios 1 (black), 4 (red) and 6 (blue).

282 276 ICES WGBAST REPORT 2018 Figure d. Median values and 90% probability intervals for smolt and spawner abundances for rivers Ljungan, Mörrumsån, Emån and Kågeälven in scenarios 1 (black), 4 (red) and 6 (blue).

283 ICES WGBAST REPORT Figure Share of commercial and recreational catches at sea, river catches (including unreporting and also some commercial fishing), and discard/unreporting/misreporting of total sea catches in subdivisions in years Commercial sea catch also includes recreational sea catch in Recreational sea catch is presented separately from 2001 onwards. Note that updated expert estimates of recreational trolling catches (Section 2.1.2) are included.

284 278 ICES WGBAST REPORT Sea trout The assessment of sea trout populations in the Baltic is based on a model developed by the Study Group on Data Requirements and Assessment Needs for Baltic Sea Trout, SGBALANST (ICES, 2011), first implemented at the assessment in 2012 (ICES, 2012). For the evaluation of model results, other basic observations such as tagging data, spawner counts and catch statistics are also taken into account. Below follows sections on sea trout catches, fisheries, and biological monitoring data followed by descriptions of assessment methods and results. 5.1 Baltic Sea trout catches Commercial fisheries Nominal commercial catches of sea trout in the Baltic Sea are presented in Table The total catch increased slightly, from 232 tonnes in 2016 to 244 tonnes in A majority (75%) of this catch was caught in the Main Basin. In the Main Basin, the catch has decreased from 954 tonnes in 2002 to 236 tonnes in After two years ( ) of somewhat higher catches, around 450 tonnes, the total commercial catch again fell, reaching a minimum of 145 tonnes in In 2016 and 2017, the total Main basin catches again increased a little (to 184 tonnes). About 83% of the commercial catch of sea trout in the Main Basin was taken by Polish vessels. In 2017 they reported 153 tonnes, which is similar to the catch reported in 2016 (151 tonnes) but clearly below the ten year average (246 tonnes). Out of the total Polish commercial catch in 2017, 27% was taken by the coastal and 73% by the offshore fishery. The total nominal commercial catch of trout in the Gulf of Bothnia was 41 tonnes in 2017, which is somewhat higher than in 2016 (29 tonnes), but below the ten year average catch (48 tonnes). About 58% of the commercial catch in Gulf of Bothnia was from coastal fisheries. In the Gulf of Finland, the total commercial sea trout catch has been around 20 tonnes in the last three years (Table ). The catch of sea trout in the Gulf of Finland decreased a little from 2016 to 2017 (from 20 to 19 tonnes) Recreational fisheries Recreational sea trout catches (landed) in the Baltic Sea are presented in Table In 2017, the total catch decreased to 262 tonnes, from 592 tonnes in However, it should be mentioned that the figure for 2017 is preliminary because the Danish catches, that in recent years constituted a major part of the total, were not yet available. Recreational river catches in 2017 were 20 tonnes, taken mainly in Swedish Gulf of Bothnia rivers. This is a much smaller river catch than the ten years average (47 tonnes; Table ). Most (98%) of the recreational catch in the coastal zones of the Gulf of Bothnia and the Gulf of Finland was taken by Finnish fishermen (232 tonnes). Data on recreational coastal catches from the Main Basin in 2017 were available from Estonia, Latvia, Finland, Sweden, amounting to 6 tonnes (Table ). However, the catch estimates from Sweden are uncertain and likely underestimated. From the last few years, there are also results from questionnaires on Danish coastal recreational catches; those catches increased from 224 tonnes in 2011 to 521 tonnes in Until 2016, they decreased to 323 tonnes, which constitutes about 55% of the total Baltic Sea recreational catch of sea trout.

285 ICES WGBAST REPORT Total nominal catches The highest combined commercial and recreational nominal catches, above 1300 tonnes, were taken in the early and late 1990s (Table ). Since 2001 they have been decreasing to the level of tonnes in recent years, and even 506 tonnes in 2017 (but without data on Danish recreational catches in 2017) (Tables and ) Biological catch sampling Strategies for biological sampling of sea trout and procedures are very similar to those for salmon (Section 2.5). In total, 1379 sea trout were sampled in 2017 (Table ), about 20% less than in the Most samples were collected from Latvian (n=474) and Swedish (n=436) catches. In addition, 150 samples were collected from Estonian catches in the Gulf of Finland (SD 32), and 123 from Finnish catches in SD Polish samples originated mainly from river catches (n=175) in three rives: Vistula, Słupia and Rega. Only 21 Polish samples have been taken in the sea (Table ). 5.2 Data collection and methods Monitoring methods Monitoring of sea trout populations is carried out in all Baltic Sea countries. The intensity and period during which monitoring has been going on varies (ICES, 2008c). Some countries started their monitoring in recent years, while very long dataseries exist for a few streams in others (ICES, 2008c). From 2016, a new European Union (EU) regulation (2016/1251) adopting a multiannual program for the collection, management and use of data in the fisheries and aquaculture, obligated EU countries to collect sea trout catch data. Most monitoring of sea trout is carried out by surveying densities of trout parr in nursery streams by electrofishing. In Denmark, only a few sites in Baltic streams are monitored annually. In addition, a rolling scheme is used for electrofishing-monitoring of sea trout on the national level. Due to the large time lap between fishing separate rivers these are not directly useable for assessment, but results from these are used as background information on the status of populations as such. In a couple of countries, sampling of parr densities are used to calculate smolt production by a relation of parr to smolt survival, either developed in the same stream or in some other (ICES, 2008). In most countries (but not in Denmark and Poland) electrofishing is supplemented with annual monitoring of smolt escapement by trapping and counting in one or more streams. In total, smolt production estimates exist for rivers in the entire Baltic area, but the length of the time-series varies very much. In only four streams/rivers (Mörrumsån, Åvaån, Testeboån in Sweden and Pirita in Estonia) both numbers of spawners and smolts are monitored. Adult counts are determined by trapping or recording of the ascending sea trout using automatic counters. In Lithuania, the spawning runs are estimated by test fishing. In 24 rivers (ten in Sweden, three in Poland, six in Germany, two in Estonia and three in Finland) the numbers of spawners are monitored by automatic fish counters or video systems. In three rivers, the total run of salmonids is determined using echosounder systems. However, this technique does not allow discrimination between sea trout and salmon (or other fish species of similar size). An indication of the spawning intensity can also be obtained by counting of redds. Such information is collected from a number of sea trout streams in Poland, Lithuania

286 280 ICES WGBAST REPORT 2018 and Germany (ICES, 2008). In a couple of streams in Denmark, the catch in sport fisheries has been used to estimate the development in the spawning run. Catch numbers are also available from some Swedish rivers. Tagging and marking are furthermore used as methods to obtain quantitative and qualitative information on trout populations (see below). Evaluation of sea trout status in rivers is done based on national expert opinions, as well as on factors influencing status. Such evaluations are updated irregularly Assessment of recreational sea trout fisheries There is a highly developed recreational fishery targeting sea trout in many countries. Angling (rod-and-line fishing) accounts for the majority of the catches. The most common methods are spin and fly fishing from the shore or in rivers, and trolling with small boats at sea (see Section for a general description of the trolling fishery). The shore-based fishery along coasts and in rivers is highly diffuse and variable with strong local and regional variations depending on weather conditions and season. In the southern Baltic Sea, recreational fishing on sea trout takes places during the whole year with distinct activity peaks in spring and autumn. Fishing times vary between seasons, but most anglers fish a few hours around dawn and dusk. In winter and early spring, there is also an activity peak during noontime due to higher water temperatures. Some night fishing occurs in summer. While the recreational catches of sea trout is largely dominated by rod-and-line fisheries, there are other types of fisheries carried out in some countries. To a smaller extent passive gears such as trapnets, gillnets or longlines are being used for catching sea trout in the Baltic Sea, either as a target species or as bycatch in other coastal recreational fisheries. The catches from this type of fishing is estimated to be of minor importance in terms of impact on the stocks, i.e. removals. Monitoring of the recreational fisheries is carried out in different ways. Bellow follows a description of methods and activities in the Baltic countries. Since 2009, recreational catches of sea trout in Denmark have been estimated based on an interview-based recall survey, which is conducted by DTU Aqua in cooperation with Statistics Denmark. In addition, during spring 2017 a project on the recreational sea trout coastal rod-and-line fishery was carried out on the island Funen in SD 22. Two different approaches were applied: 1) on-site interviews (rowing creel) collected information on i.a. catch, release rates and effort, and 2) by aerial survey, information on effort was obtained. Furthermore, information on motivation and satisfaction was collected. In Estonia, catch reporting has been mandatory since The data are reported to and stored in the Estonian Fisheries Information System (EFIS) for passive gears (gillnets, longlines) and salmon and sea trout rod-and-line fishing in rivers. The latest recreational fishery survey was carried out in 2016, based on a phone call approach. The next recreational fishery survey is planned to be carried out in Since 2002, the official catch estimates of the recreational sea trout fishery in Finland is based on a national recreational fisheries survey. Biannual surveys are conducted to estimate participation, fishing effort and catches of the recreational fishery ( A stratified sample of about 7500 household-dwellings is contacted with response rates of around 40 45% after a maximum of three contacts. Afterwards, a telephone interview is done for a sample of the non-respondents. Harvested and released catch is measured separately by species. The last survey covering year 2016 was conducted in 2017.

287 ICES WGBAST REPORT In Germany, a nationwide telephone-diary survey with quarterly follow-ups was conducted in 2014/2015, contacting German households to collect representative data on catch and effort, and social, economic and demographic parameters for the German marine recreational fishery covering also the recreational sea trout fishery. However, to collect more detailed information on the recreational sea trout fishery an additional pilot study (diary recall survey) was conducted. During this study a bus route intercept survey was used to recruit diarists, collect biological samples (length, weight, scales, and tissue samples), and socio-economic data. The ongoing analyses aim to combine both studies to provide a full picture of the recreational sea trout fishery in Germany. Anecdotal information showed that recreational sea trout catches in freshwater are small and probably insignificant compared to marine catches. However, a literature study including expert interviews will be conducted in 2018/2019 to gather more information on recreational sea trout fisheries in freshwater of the Baltic Sea catchment area. Beginning in 2018, the recreational fishery in Latvia on sea trout (catches and releases) will be estimated. Recreational fishery (angling) catches of sea trout will be estimated by contracting a company that offers recreational trolling trips in the Baltic Sea. Catch and biological information will be collected and, by applying snowball sampling, total landings will be estimated. Information from licensed fisheries in the rivers will be used to estimate the freshwater recreational fishery. Recreational fishery in the Latvian coastal zone is performed by subsistence fishermen. Only limited number of gillnets and longlines are allowed, and it is forbidden to sell any fish (only personal consumption). Every fisherman is reporting all fishing activities in logbooks, and those detailed data are available to the national institute (BIOR). In Lithuania, recreational sea trout fishing is mainly conducted in rivers. Since 2015 recreational (anglers) sea trout catches are estimated by an online survey, a face-to-face interview survey, and individual interviews and catch reporting with diaries of selected anglers and experts. Catch-per-unit-of-effort data (ind/person/day) is estimated from survey data, and combined with number of licences sold to anglers to calculate the total catch. In 2015 the online survey, face-to-face interview survey, and individual angler interviews were conducted, in 2016 and 2017 only online surveys were carried out. A pilot study in Poland has been initiated to monitor the coastal recreational fishery for sea trout from the shore with rod and line. The study covers the period from early summer 2017 to winter The main methods applied to monitor this segment of the recreational fishery are on-site and off-site questionnaire interviews and field observations by observers from the national institute (NMFRI). The estimated catches declared in the off-site questionnaire interviews will be verified using direct on-site observations. Polish sea trout rivers are mostly ruled by the Polish Angling Association ( members). All anglers are obligated to complete a catch diary before fishing and after a fish has been caught. In theory, the catch diary must be returned at the end of the year and before paying the fishing fee for the next year. However, the return rate of diaries is insufficient (approximately 30%) and some reliability issues exist. To test recreational fishing diary trustiness, a pilot study was started in 2017; verifications based on correlation with on-site survey data, fish counter records and spawner collection has been applied. Three Pomeranian rivers were involved, including Słupia, Rega, and Ina. Survey questionnaires were collected from January to September 2017 with 322 anglers responding. The survey will be continued in 2018.

288 282 ICES WGBAST REPORT 2018 In Russia, sea trout is a protected species in the Baltic Sea, and recreational fishers are not allowed to target sea trout in the sea nor in rivers. In Sweden, recreational fishery for sea trout is very popular. Since there is no commercial fishing specifically targeting the species, commercial catches are low and most catches are from recreational fisheries in rivers and the sea. A major part of the Swedish recreational catch is taken along the Baltic coast (>2400 km, including islands of Öland and Gotland), in particular by angling from shore or small boats, and from use of gillnets. Offshore recreational fisheries is in most cases done by trolling targeting salmon, with sea trout caught only occasionally. However, trolling closer to the coast targeting sea trout is starting to be popular in some areas. Swedish data on recreational sea trout river catches are only collected from larger salmon rivers, and therefore river catch statistics are far from complete. However, as mentioned above, the largest proportion of the catch is assumed to be taken in coastal waters where no surveys specifically targeting sea trout are in place so far. Currently the best source for catch statistics comes from an annual national mail survey conducted by the Swedish Agency for Marine and Water Management (SWaM), the authority responsible for fisheries management. The survey is sent to about randomly selected persons each year, and it collects statistics on different aspects of recreational fishing (catches, expenditures, fishing days, etc.) for all species. However, this survey can neither estimate trout catches with good precision nor on the geographic scale needed for effective management. To obtain catch statistics with better precision and finer geographic resolution, a specific survey programme needs to be developed Marking and tagging The total number of finclipped sea trout released 2017 in the Baltic Sea area was smolts, equal to approximately 35% of all released (Table ). Finclipping of hatchery-reared smolts is mandatory in Sweden, Finland and Estonia. The largest number of finclipped smolts was released in Sweden ( ) and Finland ( ). All released sea trout smolts have been finclipped in the Gulf of Finland since 2014 and in the Gulf of Bothnia since Finclipping was not performed in Poland in 2017, and there was also no stocking of finclipped sea trout smolts in Denmark, Germany, Russia, Latvia or Lithuania. However, in Germany and Denmark (SD 22) a small number of ca sea trout smolts were finclipped, because those fish carry internal (PIT) tags. In Germany and Finland, a total of alizarin red S solution (ARS) marked sea trout larvae/fry were released. The releases in Germany were project-based to estimate fry survival. In Finland, similarly marked individuals were released in SD 31 rivers (Table ). In 2017, the total number of Carlin tagged sea trout was Most of the tagged trout were released in SD 28 and (Table ). In addition, 6904 sea trout were tagged with T-bar (T-Anch) tags. Out of those, 706 adults and kelts (post-spawners) were released in Germany (SD 22) and 50 kelts in Poland (SD 25). In Finland, and partly also in Estonia, 6148 juveniles were tagged with T-bars, mostly in SD 29, 31 & 32 (Table ). Additionally reared and wild juveniles (mainly smolts) were tagged internally with passive integrated transponders (PIT); the vast majority was tagged by Sweden as reared and wild smolts in SD 30 (19 860), in SD 31 (4120) and in SD 25 (406). In SD 25, 38 adults were also PIT-tagged in Poland. In SD 22, smolts were PIT-tagged in Denmark (1100) and in Germany (980) (Table ).

289 ICES WGBAST REPORT Assessment of recruitment status Methods Recruitment status The SGBALANST (ICES, 2008c; 2009b) screened available data on sea trout populations around the Baltic Sea, and proposed an assessment method (ICES, 2011). The basic method, theory and development is fully described in ICES (2011; 2012), and the slightly adjusted method applied since the assessment in 2012 is briefly summarized below, together with modifications applied in the present assessment. Through screening of data availability (ICES, 2008; 2009; 2011) it was found that only abundance of trout from electrofishing were available from all countries. Together with habitat data, trout densities are collected annually from specific sites every year in most countries. However, at the time of the screening, the number of sites was highly variable and mostly sparse in many parts of the Baltic. From a few countries, directly useable data were not available, either because there was no electrofishing program at all, or because the information collected was not sufficiently detailed. It was also found that only little and scattered information existed on other life stages (sea migration, abundance of spawners, smolt production and survival). Likewise, information on human influence, such as sea and river catches (especially recreational ones), was sparse. An assessment model using electrofishing data together with habitat information collected at the same sites was proposed focusing on recruitment status as the basic assessment tool (reference point). Recruitment status was defined as the observed recruitment (observed densities) relative to the potential maximal recruitment (maximal densities that could be expected under the given habitat conditions, i.e. the predicted densities, see below) of the individual sea trout populations. Due to the significant climatic (e.g. temperature and precipitation) and geological differences found across the Baltic area, as well as the huge variation in stream sizes, the model proposed is constructed to take variables quantifying such differences into account. Differences in habitat qualities (suitability for trout) influence trout parr abundance, given that stock status is below carrying capacity and spawning success is not limited by environmental factors such as migration obstacles downstream to monitored sites. To allow comparison of trout abundances between sites with different habitat quality, a submodel was used, i.e. the Trout Habitat Score (THS). THS is calculated by first assigning values (scores) for the following relevant (and available) habitat parameters for 0+ trout: average/dominating depth, water velocity, dominating substrate, stream wetted width, slope (where available) and shade. Scores assigned range between 0 for sites with poor conditions and 2 for best conditions (assessed from suitability curves and in part by expert estimates; see details in ICES, 2011). THS is then calculated by addition of score values resulting in a total score that can vary between 0 (very poor conditions) and 12 (10 if slope is omitted) for sites with very good habitat conditions. Finally, the THS values obtained were grouped in four Habitat Classes ranging between 0 (poorest) and 3 (best) (Table ) (ICES, 2011). In calculations, observed parr abundance was transformed using Log10 (x+1) to minimize variation and improve fit to a normal distribution. The potential maximum recruitment for sites with a given habitat quality used in this year s assessment was the same as in 2015 (ICES, 2015). Predicted maximum densities

290 284 ICES WGBAST REPORT 2018 were determined by a multiple linear regression analysis based on select sites displaying expected optimal densities (see Section in ICES, 2015). The analysis found the variables log (width), average annual air temperature, latitude, longitude and THS to be significant in determining optimal densities of 0+ trout (r 2 =0.5, Anova; F2,254=51.8, p<0.001) according to the following relation: 1 ) Log10 (0+optimal density) = (0.906*logwidth) + (0.045*airtemp) - (0.037*longitude) + (0.027*latitude) + (THS*0.033). This multiple regression relation (1) was used for calculating the potential maximal densities at the individual fishing occasions, with current Recruitment Status (2) calculated as: 2 ) Recruitment status = (Observed density / Predicted maximal density) * 100. As described above, predicted maximal densities are calculated using multiple regression based on observations that show variation around the mean. In addition, the calculation of predicted maximal densities have not been updated since the construction of the model in 2015, taking more recent observations into account. For these two reasons, it is possible that single observed densities can sometimes by higher than the predicted mean, resulting in a recruitment status somewhat above 100%. Mean recruitment status was calculated for each Assessment Area (see below and Figure ), each ICES subdivision (SD) and by SD and country combined. Recruitment status was calculated for 2017 and for the years separately. Assessment Areas were defined according to the table below: Assessment Area SD Gulf of Bothnia (GoB) Gulf of Finland (GoF) 32 Western Baltic Sea (West) 27 & 29 Eastern Baltic Sea (East) 26 & 28 Southern Baltic Sea (South) Recruitment trends An indicator of Recruitment Trend was calculated as the bivariate correlation between annual recruitment status (see above) and sampling year, illustrated using Pearson s r (resulting in possible values ranging from -1 to +1). Recruitment over time was assessed for the last five year period ( ) in order to illustrate the most recent development in change of status. Only sites where a calculated status was available for all years in the last five year period were used when trends were calculated (Figure ). Both recruitment status and trend were calculated as average values for each of the following units of analysis: Assessment Area, ICES subdivision (SDs) and, where more countries have streams in one SD, for individual countries. For a final assessment, the results from the above status and trend analyses were combined with additional information gathered, most markedly from fisheries and count of spawners (where available).

291 ICES WGBAST REPORT Data availability for status assessment Information on densities of 0+ trout from 612 fishing occasions in 2017, at sites with good or intermediate water quality and without stocking, was available for calculation of recruitment status. For the trend analysis only 130 sites that had been fished continuously in the latest five years period ( ) were included (Table ). The geographical distribution of fishing occasions used tor evaluation of status is shown in Figure , whereas the corresponding distribution of sites for trend analysis is shown in Figure Note that new, previously not available electrofishing data have been included in the assessment over time. This is i.a. the case for Germany, where many sites have now been included. In Russia, no data for 2016 were available, and only from a few sites in 2017 due to flow conditions. 5.4 Data presentation Trout in Gulf of Bothnia (SD 30 and 31) Sea trout populations are found in a total of 57 Gulf of Bothnia rivers, of which 28 have wild and 29 have mixed populations (Table ). The status of sea trout populations in Swedish rivers is in general considered to be uncertain (Table ). Populations are affected by human activities influencing freshwater habitats, mostly through overexploitation, damming, dredging, pollution and siltation of rivers (Table ). Average 0+ parr densities for Swedish and Finnish rivers in the area are presented in Figure For Sweden, the densities presented in this figure are from sites in larger rivers were also salmon are found. In the Swedish sites densities dropped after 2005, from 8 16 to parr per 100 m 2, and they have remained stable at this low level since then, although with a slight increase since 2015 (Figure ). The SD electrofishing results from Finland include three rivers (Lestijoki, Isojoki, and Torne River with two tributaries). Densities of 0+ parr have remained low in Lestijoki, higher in Isojoki while they have been variable in the tributaries to Torne River, resulting in an overall average of 2 6 parr per 100 m 2 in most years, but with an increase to more than ten in again followed by a decrease in (Figure ). Estimated sea trout smolt production in Baltic Sea rivers in the period is presented in Table In addition, exact numbers of caught individuals and details on methods and catchability coefficients for some of the traps are given. In river Tornionjoki (SD 31) smolt trapping during the whole migration period for sea trout has only been possible in some years, because the trout smolt run is earlier than for salmon, and in most years the trout smolt run is already ongoing when river conditions allow start smolt-trapping; the five annual estimates available for Tornionjoki range between about and sea trout smolts. In the two smaller SD 31 rivers Sävarån and Rickleån, yearly production estimates vary from c and smolts, respectively (Table ). The number of sea trout spawners recorded by fish counters is low in most larger salmon rivers in Sweden (Figure ). The average number of sea trout counted in River Kalixälven increased somewhat after 2006, from about 100 to , with a further increase in 2014 to over 300 fish. In River Byskeälven, the number decreased after 2005, from approximately 100 sea trout to very low levels (ca. 25 sea trout per year), again increasing in to almost 300 fish. From 2001, the annual number of ascending sea trout in River Vindeläven has varied within the range However, the number increased considerably in 2015 to more than 500 fish, but again decreased in 2016 to 250. In all the above three rivers a drop to ca. 200 fish was observed

292 286 ICES WGBAST REPORT 2018 in In contrast, River Piteälven has showed a positive trend that has lasted since the beginning of the century, with 1600 sea trout spawners recorded in 2017 (Figure ). Catches of wild sea trout in SD have declined considerably over a long time period (Figure ), possibly indicating large overall reductions in population size. Although catches from 2013 and forward do not reflect actual runs, because of implemented restrictions (size and catch limits, in R. Torne a complete ban on harvest of sea trout, etc.) catches have declined considerably after the late 1970s and remained low until present. As an example, the catch in River Kalixälven dropped to zero in 2017 (Figure ). However, in 2017 the overall catch of wild sea trout from sport fishing increased somewhat in Swedish SD 31 rivers whereas it decreased in SD 30 (Figure ). Returns from Carlin tagged sea trout have showed a rapid decrease since the 1990s, and after 2003 the average return rate has been below 1% (Figure ). Results from rivers in the Gulf of Bothnia show a large and increasing proportion of the tagged sea trout, often a majority, to be caught already as post-smolts during their first year in sea. Sea trout are mainly caught as bycatch in the whitefish fisheries by gillnets and fykenets. Based on tagging data, the proportion of fish caught as undersized fish during the first sea year has been fluctuating around 50% in the last decades (Figure ), and the proportional distribution of recaptures in different fishing gears has also been relatively stable (Figure ). According to tagging results, the survival of the released smolt is at present lower than the long-term average. Furthermore, tagging data show that Finnish sea trout migrate partly to the Swedish side of the Gulf of Bothnia (ICES, 2009), whereas Swedish sea trout have been caught at the Finnish coast. There are no more recent information available. A Bayesian mark recapture analysis (Whitlock et al., 2017) has recently been conducted for tagging data from reared sea trout in two Finnish rivers in SD 30 and 31 (Isojoki and Lestijoki, ). The results of this study indicate substantial fishing mortality for sea trout aged three years and older from both stocks, but particularly in the case of Isojoki (Figure ). Annual total fishing mortality rate estimates ranged from 1 to 3 in most years for sea trout aged 3 and older in both rivers, corresponding to harvest rates between 0.63 and Total fishing mortality for the Isojoki stock showed a decreasing pattern over time, while the temporal pattern was fairly stable for Lestijoki sea trout. Fishing mortality was considerably higher for sea trout of age 3 compared with fish of age 2 in both stocks (Figure ). A decreasing pattern of survival in the first year at sea was also estimated (results not shown). Sustained high rates of fishing mortality have likely contributed to the poor status and limited reproduction of wild sea-trout stocks in the Isojoki and Lestijoki rivers (Whitlock et al., 2017) Trout in Gulf of Finland (SD 32) The number of streams with sea trout in Gulf of Finland was partly updated in It is now estimated that there are 100 rivers and brooks with sea trout in this region; out of these 92 have wild stocks (Tables and ). The rest are supported by releases. The situation for populations is uncertain in 36 rivers and very poor in 20 (with current smolt production below 5% of the potential). In Estonia, sea trout populations are found in 40 rivers and brooks in the Gulf of Finland region, of which 38 have wild populations (Table ). Electrofishing data from Estonian rivers show densities of up to parr per 100 m 2 in the 1980s. In more

293 ICES WGBAST REPORT recent years, densities have in general been below parr per 100 m 2. Average densities from 1992 and onwards are presented in Figure Estonian rivers with higher smolt production are situated in the central part of the north coast. Smolt runs in River Pirita during the period have varied between around 100 and 4000, and after a drastic drop in 2014 it attained its record value in 2016 (Table ). The number of spawners recorded by a fish counter in this river during has been 26, 125, 76 and 43 (only half of the run counted in 2017). Parr densities for sea trout in the Finnish rivers in the Gulf of Finland have been highly variable, with densities varying between 0 and parr per 100 m 2 in the period , as shown in Figure The recapture rate of sea trout Carlin tagged in Gulf of Finland shows a continued decreasing trend for more than 20 years; in recent years, it has been close to zero (Figure ). Finnish tagging results have shown that in Finnish catches in general about 5 10% of the tag recoveries are from Estonia and some also from Russia. These migration patterns have been confirmed in a genetic mixed-stock analysis (Koljonen et al., 2014). In Russia, wild sea trout populations are found in at least 46 rivers and brooks, including the main tributaries (Table and ). A majority of these populations are situated in rivers or streams along the Russian north coast of Gulf of Finland, but the rivers with highest smolt production are located along the south coast. In most recent years, average 0+ parr densities have in general been below ten individuals per 100 m 2 (Figure ). The highest Russian 0+ parr densities have been observed in a few small streams and two of the River Luga tributaries. In the Lemovzha tributary densities increased up to 100 individuals of 0+ parr per 100 m 2 in 2014 and 56 individuals in In Solka (the second tributary of Luga River) numbers of 0+ parr per 100 m 2 have increased since 2011 to 56 in 2014, but in 2015 the densities were 0. This lack of 0+ parr was due to reconstruction of the dam situated upstream near the main spawning grounds, which prevented the spawning migration in The smolt run in River Luga during the period varied between 2000 and 8000 wild trout smolts (Table ). After increasing to a record level of smolts in 2015, almost three times higher than the average for the total monitoring period (ca smolts), it again decreased to 2600 in 2016 and 3500 in Total smolt production in the Russian part of Gulf of Finland has been estimated to about Genetic studies have shown that 6 9% of the sea trout caught along the southern Finnish coast was of Russian origin (Koljonen et al., 2014) Trout in Main Basin (SD 22 29) In the Main Basin, when including tributaries in larger water systems (Odra, Vistula and Nemunas), there are 493 rivers and streams with sea trout populations, out of which 404 are wild (Tables and ). These figures do not include Germany; however, the actual number of sea trout streams/rivers has not yet been evaluated, although it has been estimated that it could be approximately 95. In Sweden, 207 sea trout rivers are found in the entire Main Basin. Out of these, 200 have wild sea trout populations whereas seven are supported by releases. In Denmark, 139 out of 173 trout rivers are wild, and majority of them as classified as in good condition. In Poland, the number of populations was revised in 2018; sea trout are found in 26 rivers (whereof 12 in SD 26), mainly in Pomeranian rivers (eleven) but also in the Vistula (six) and Odra (six) systems (including the main rivers). All Polish sea trout populations but two are mixed due to supplemental stocking since many years. There

294 288 ICES WGBAST REPORT 2018 are three Russian sea trout rivers flowing into the Main Basin (in the Kaliningrad Oblast). All are wild and their status is uncertain. In Lithuania, sea trout are found in 19 rivers, whereof eight belonging to the Nemunas drainage basin. In eight Lithuanian rivers there are wild populations while the rest are supported by releases. In Latvia, sea trout populations are found in 28 rivers, about half of them wild. In Estonia, sea trout occurs in 36 rivers and brooks discharging into the Main Basin. All of them are small with wild populations. The situation for sea trout populations in the Main Basin was partially revised in 2018, and it was found to be uncertain in 222 rivers with wild populations. Status of 25 populations (wild and mixed, including tributaries in large systems) are poor with an estimated production <5% (Table and ), mainly due to habitat degradation, dam buildings and overexploitation (Tables and ). Eastern Main Basin Average 0+ parr densities in eastern Estonian rivers (SD 29) have in recent years been up to approximately 40 parr per 100 m 2 and increasing in recent years (Figure ). However, densities tend to fluctuate much between years, partly because of changing water flow. In Latvia, average densities of 0+ parr have varied from 4 12 per 100 m 2 (Figure ). Rivers Salaca, Gauja and Venta show the highest estimated wild sea trout smolt production in Latvia. In Salaca estimated smolt numbers from smolt-trapping have varied between 2500 and in the period In 2017 it dropped to 5400 from 2 3 times higher levels in 2015 and 2016 (Table ). Estimated smolt production in 2017 for all Latvian rivers combined was about smolts, above the five year average (57 700). In Lithuania average parr densities for 0+ trout have varied from 6 12 individuals per 100 m 2 during the past few years (Figure ). The estimated total natural smolt production in 2017 was , very similar to in The estimated overall number of spawners has for a number of years been relatively stable, varying between 5500 and 8000 individuals (Kesminas and Kontautas, in Pedersen et al., 2012). In Poland, average densities of 0+ parr in SD 26 rivers have been generally high but variable, with densities of up to more than 90 individuals per 100 m 2 in some years. After four years ( ) with high (70 90) and stable densities the average 0+ density dropped to only 32 in 2017 (Figure ). Number of adult sea trout migrating upstream recorded by an electronic counter (VAKI) in a newly rebuilt fish-pass at the Wloclawek dam in Vistula River decreased from 1554 in 2015 to only 173 in 2017 (Figure ). Western Main Basin Average parr densities in Swedish rivers (SD 25 and 27) have been low in the period (Figure ). In River Emån, the average 0+ parr density has varied between 0.2 and eleven individuals per 100 m 2, whereas in Mörrumsån it has been below 15 since the mid-1990s, although it increased to 20 in Results from smolt trapping in Mörrumsån shows that the production in the upper half of the river (the smolt trap is located approximately 15 km from the outlet) has varied between 3500 and smolts during the last six years, with the smallest number seen in 2017 (Table ).

295 ICES WGBAST REPORT Nominal (landed) river catches of sea trout in Swedish Emån (SD 27) and Mörrumsån (SD 25) are presented in Figure The sport fishing harvest of sea trout in Emån has been declining, and in 2017 is was zero. However, since catch and release is not included, this does not give a correct picture of the total catch which comprised 673 individuals in In Mörrumsån the nominal (landed) 2017 catch has also declined markedly in the past decade, and in 2017 it was 41 fish (out of a total catch of 293). The total number of wild sea trout smolts produced in Danish rivers (SD 22 25) is at present estimated to around per year. Electrofishing data from Danish streams used to show average 0+ parr densities of between 50 and just below 200 per 100 m 2 since around year 2000, decreasing in the last five years (Figure ). Annual smolt migration in one stream on the Island of Bornholm (Læså, length 17 km, productive area 2.46 ha) was on average 6300 individuals in the period ; however, with very high variation among years ( ) probably due to varying water levels (Table ). Smolt-trapping in Læså has not continued after The average parr abundance in Germany 2017 was lower than in 2016 (Figure ). Since 2002, a monitoring programme has been established in Mecklenburg Western Pomerania (Germany) based on electrofishing, to evaluate recruitment and stocking success. From initially about 25 rivers and tributaries in 2002, 14 rivers remain to date in the Mecklenburg Western Pomerania stocking programme. No specific monitoring or assessment of stocking survival was performed in Schleswig-Holstein (the second German state at the Baltic Sea) before in Recently, an electrofishing survey for 0+ and 1+ parr, based on the Trout Habitat Parr Index method (THS) used by ICES, WGBAST was initiated in Schleswig-Holstein. Since 2014 the same approach has been used also in the Mecklenburg Western Pomerania parr monitoring. In 2017, nine rivers flowing into the Baltic Sea have been analysed by electrofishing at 55 stations. Spawner numbers have been collected by video counting in four German streams in SD 22 and 24 with wild populations (Figure ). In Peezer Bach (SD 24) the number of spawners has remained almost identical (ca. 650) over the last three years. Hellbach (SD 22) showed the highest count in 2013 with 2300 adult trout, whereas in 2015 the count was In Tarnewitz (SD 22) counts have varied between 140 and 380 adults in the period There was a decrease in all monitored rivers in Data for 2016 and 2017 are yet not available. Average densities of 0+ parr on spawning sites in Polish rivers in SD 25 have varied between 22 and 114 individuals per 100 m 2 in the period (Figure ). Spawning runs have been monitored by fish counting in the Slupia River since 2006; the number of migrants during the last four years has decreased from more than 7000 to below 500 (Figure ). A dermatological disease affecting sea trout spawners in most Polish Pomeranian rivers has continued (outbreak in 2007; Section 3.4.3). In summary, parr densities in southwestern Baltic rivers (SD 22 25) were mostly on average levels or slightly decreasing in Notably, the observed numbers of spawners in some southern Baltic rivers are higher than in larger northern ones, even if some of these southern rivers are very small. In most rivers with spawner counts, the timeseries (number of years) are still too short to evaluate trends. However, in rivers with the largest numbers of spawners (Słupia R., Hellbachsystem) there was a decrease in the spawning run in 2017 (Figure ). 5.5 Recruitment status and trends Results from the updated analyses of recruitment status and trends for sea trout in rivers and streams around the Baltic Sea are shown in Figures to

296 290 ICES WGBAST REPORT Recruitment status In the Gulf of Bothnia assessment area (SD 30 31) the recruitment status is modest, on average just above 60% (Figures to 5.5.3). Status in SD 30 is slightly better in Finland compared to in Sweden (Figure 5.5.3). However, the results for SD 30 are based on a very limited number of sites (only one stream in Finland and six in Sweden). In SD 31 status was similar in both countries (Figure 5.5.3). In the Gulf of Finland assessment area (SD 32) the overall status is good (Figure 5.5.1), but with clear differences between the three countries in the area; the situation is best in Estonia, where status in general is close to optimal, being much better than in both Finland and Russia (Figure 5.5.3). In assessment area East (SD 26 and 28; Figure ) the overall status is low, but at the same time much higher in SD 28 compared to in SD 26. (Figures to 5.5.3). In SD 26 status is only approximately 50% in both Poland and Lithuania. In SD 28 status is approximately equal in the three countries with streams in this SD (Estonia, Latvia, Sweden). In assessment area West (SD 27 and 29; Figure ) overall status is much higher in SD 29 than in SD 27 (Figure 5.5.2) However, in should be noted that only two sites are found in SD 29 (one Swedish and one Estonian). The site in Estonia is only fished every other year. In assessment area South (SD 22 25; Figure ) overall status is reasonable; it is highest in SD 23 and 25 (close to or above 80%), while it is much lower in SD 22 and 24 (Figure 5.5.2). In SD 22 status was low in both Denmark and Germany, while the low average status in SD 24 is mainly reflects sites with poor status in Germany (Figure 5.5.3). Recruitment status for year 2017 compared to an average computed for the three-year period shows differences in some assessment units, indicating interannual variation. But in most comparisons the overall situation has been relatively stable (Figures to 5.5.3) Recruitment trends The trend in the development of recruitment status has been positive in all assessment areas except in the assessment area West (SD 27 and 29) (Figure 5.5.4). A positive trend is especially evident in the assessment area East (SD 26 and 28) and the northern Gulf of Bothnia (GoB). However, the overall trends in the larger assessment areas covers large variations between both subdivisions and countries (Figures and 5.5.6). Especially in the assessment area South (SD 22 25), variation between SDs are large, with little or no change in SD 22 and 23, and a clear positive trend in SD 24 and 25 (Figure 5.5.5). In SD 26 the overall positive trend (Figure 5.5.5) covers a very positive trend in Lithuania but a negative trend in Poland (Figure 5.5.6). Also in SD 28 the positive trend covers a difference between countries, with a negative trend in Sweden and a positive in both Estonia and Latvia. However, it should be noted that in most of the units only a very limited number of sites were available for the analysis, and that two countries (Germany and Russia) did not have any sites at all with data from all of the five years ( ) and for this reason were not included in the trend analysis.

297 ICES WGBAST REPORT Reared smolt production Total number of reared sea trout smolts released 2017 in the Baltic Sea (SD 22 32) was , which is little more than last year ( ) and above the ten year average ( ). Out of this total, smolts were released into the Main Basin, into the Gulf of Bothnia and into the Gulf of Finland (Table 5.6.1). In Finland, trout smolt production is mainly based on reared broodstocks supplemented by spawners caught in rivers. In the past ten years the average number of smolts released has been In 2017, the number of smolts was , whereof 60% were stocked into the Gulf of Bothnia and 25% into the Gulf of Finland. In Sweden, the number of trout smolts stocked in 2017 was , close to the average level in the last few years. A majority of the Swedish smolts were released into Gulf of Bothnia (72%). Estonia released 2500 smolts into the Gulf of Finland in In Poland, juvenile fish are reared from spawners caught in each river separately; only a part of the Vistula stocking is of reared broodstock origin. A total of smolts were released into Polish rivers in 2017, close to the ten years average of Denmark released smolts in 2017, substantially less than in 2016 ( ). Latvia released smolts in 2017, somewhat less than in 2016 ( ) but more than the last ten year average ( ). Russia released smolts in 2017 into the Gulf of Finland, similar to in The German level of stocking has been smolts per year since In addition to direct smolt releases, trout are also released as eggs, alevins, fry and parr (Table 5.6.2). The estimated number of smolts originating in these releases of younger life stages over time ( smolt equivalents, calculated as in Table 5.6.2) is presented in Table In 2017, the estimated smolt number expected from releases of younger life stages in previous years was around , mainly in Main Basin rivers. The prediction for 2018 is approximately smolts for the whole Baltic, of which will migrate into the Main Basin. Total number of smolt equivalents from enhancement releases in recent years has been lower than in the very beginning of the 20th century (Table 5.6.3). 5.7 Recent management changes and additional information Management changes In Estonia, in the Gulf of Finland (SD 32), a ban of fishing with gillnets with a mesh size smaller than 55 mm (knot to knot) at a water depth of less than 3 meters during the periods 1 December 31 March was enforced in 2017, in order to decrease the bycatch of undersized trout in coastal fisheries. See last year s report (ICES, 2017 Section 5.7.1) for additional management changes for Baltic Sea trout in recent years (until 2016).

298 292 ICES WGBAST REPORT Additional information In recent years, predators on sea trout such as cormorants (Phalacrocorax carbo) have increased dramatically in the Baltic area. Studies have shown that cormorants can have severe effects on fish stocks (Bzoma, 2004; Leopold et al., 1998; Koed et al., 2006; Skov et al., 2014). Where large cormorant colonies occur in the vicinity of important salmonid rivers, there are good reasons to investigate whether cormorants have a significant negative impact on the stock. In Poland, research focused on investigation of genetic polymorphism in order to support fisheries resources management and biodiversity protection was initiated at NMFRI in the 1990s. Differentiation between and within sea trout populations inhabiting Polish rivers was analysed with various methods, first with RFLP analysis of mtdna and later using more selective methods like nuclear microsatellite and SNP analyses. Recent results have shown that the genetic composition of sea trout sampled in the Vistula river system resembled the non-admixed hatchery population that is composed of descendants of the winter-run stock with origin from the Vistula River. Trout parr otolith core strontium/calcium (Sr:Ca) ratios have been used to determine whether parr has an anadromous or resident maternal parent. Trout parr were sampled from 21 Estonian and three Finnish short, coastal streams. In Estonia, 92% of the analysed parr were of anadromous and 8% of resident maternal origin. In Finland, the respective proportions were 79% and 21%. It could be concluded that easily accessible spawning areas, situated up to 30 km from the sea, largely contained progeny of sea trout. This study demonstrated that the Sr:Ca-method provides an effective means to distinguish between the progeny of sea trout and resident brown trout (Rohtla et al., 2017). However, if an anadromous female enters into freshwater several months prior to spawning, a dilution effect (i.e. marine Sr:Ca ratio is diluted with low freshwater Sr:Ca ratio in the developing eggs) can lower the Sr:Ca core otolith values, and the anadromic mark among the offspring may become unnoticeable. High freshwater Sr:Ca values may also make the initial core Sr:Ca value undistinguishable between marine and freshwater phases. Therefore additional studies are needed to clarify regional characteristics. In recent years, significant progress has been made in Germany with respect to research on Baltic Sea trout. This has included (i) monitoring of spawners and smolt runs with video camera systems, traps and tagging (PIT, t-bar), (ii) detection of before unknown trout rivers after a census of more systems, as well as (iii) measures of parr abundance and stocking efficiency, while combining electrofishing with subsequent genetic parental assignment techniques and internal marking (Alizarin). A model (iv) of the spawning stock biomass, based on spawners video counting and quality and quantity of spawning habitat structure, was also developed in references streams and it resulted in an index that has been used to estimate the potential spawning population size in other suitable rivers, which can finally be extrapolated to specific areas. Finally, (v) redd counting was used as an independent method to calibrate the calculated spawning population size in specific German rivers, given the assumed sex ratio of 1 female: 1 male per spawning redd. In 2014/2015, a national probability-based telephone-diary survey was conducted aimed at providing information on the marine recreational fishery in Germany, covering also sea trout. To collect more detailed information on the recreational sea trout fishery, an additional pilot study (diary recall survey) was conducted. During this study a bus route intercept survey was used to recruit diarists, collect biological samples (length, weight, scales, and tissue samples), and socio-economic data. The ongoing

299 ICES WGBAST REPORT analyses aim to combine both these studies to provide a full picture of the recreational sea trout fishery in Germany. The majority of research activities was, and still is, short or medium-term projects, mostly funded on federal state authority level or externally through angling licence funds. For the assessment in the coming years there is concern about data availability from Schleswig-Holstein (S-H), Germany. In S-H, information has in recent years been provided from a time-limited project. The working group was informed that this project is likely to be discontinued, resulting in a regrettable lack of information on sea trout in western Germany. In contrast, it is very positive that a new initiative should be able to provide information in future years for sea trout in Mecklenburg-Vorpommern, Germany. 5.8 Assessment result In general, a positive development is observed in sea trout populations around most of the Baltic Sea. Despite this general result, populations in some areas are still considered fragile, and many uncertainties remain. In the Gulf of Bothnia, counts of spawners shows a continued increase, especially in the river Pite, where the increase is believed to be partly the result of habitat improvements, whereas increases are modest in other rivers. Also, the absolute spawner numbers are still very low considering the size of the rivers, and the same is the case for the number of smolt in both Säverån and Rickleån examined in recent years. Parr densities in the Gulf of Bothnia have improved, as has the calculated recruitment status, also reflected in a positive trend. The restrictions in the Swedish sea fishery, that have now been in effect for a number of years, and more recent restrictions in the Finnish sea fishery, are likely to be the main reason for this development. Also the ban on catch of sea trout in the River Torne is believed to have contributed positively to the development in this river. The complete ban of harvest of wild (not finclipped) sea trout in Finnish waters (that will come into effect 2019) is expected to contribute further to the positive development. However, the continued fishery for other species (e.g. whitefish) with fine meshed gillnets that also catch post-smolts and young sea trout is still problematic, and can be expected to either limit the level of wild sea trout populations in the area, or at least delay their recovery. The high recruitment status for sea trout in Finnish SD 30 is currently based on data from only one river (Isojoki). The expert opinion, based on local knowledge, is that the assessment model currently overestimates the actual status in Isojoki, but that the trend in recruitment status is correct. Similar opinions have also been expressed regarding Swedish Gulf of Bothnia populations. It is possible that the predicted maximum densities used as reference when assessing sea trout status are at present yielding a generally too optimistic view of the situation, and there is a particular need to update the underlying submodel (i.e. THS; ICES, 2015) with additional data from the northern Baltic Sea. For this reason, sea trout in SD 30 and 31 should still be considered vulnerable. It is recommended to further reduce the fishing mortality in the fishery targeting other species, and to maintain the present restrictions. In the Gulf of Finland, a positive development is observed in Estonia, where trout populations in general seem to be in a good shape, however with a relatively low (but increasing) smolt run in the Pirita. In contrast, sea trout populations in Russia are still relatively weak with a modest smolt run in the Luga, taking the size of this river into account. Recent catch restrictions for wild sea trout in Finland are expected to improve the sea survival of trout from all countries in the area. It is recommended to continue

300 294 ICES WGBAST REPORT 2018 with the present management restrictions in both Finland and Estonia. In Finland catch restrictions of wild sea trout in private waters should also be established. In Russia illegal catch of sea trout may be the reason for the continued poor status for the populations in this area. In the Western Main Basin (assessment area West, SD 27 and 29), the recruitment status has, for unknown reasons, decreased considerably in SD 27 (Sweden) in recent years, while it has been positive in the only included Swedish SD 29 site. In both Sweden and Estonia the recruitment status over the last three year period has been good in both countries (in Sweden four sites were fished in 2015, one in 2016). In Estonia it is believed that the good status is, at least in part, the result of enforcement of fisheries restrictions. The reason for the negative trend and low status in the Swedish streams should be investigated. In the Eastern Main Basin (assessment area East, SD 26, 28 and eastern part of SD 29) the recruitment status is low in both Lithuania and Poland (SD 26), where the trend in the last five years has also been negative. In Latvia and Estonia (SD 28) the status is better, and the trend positive. The smolt run in the Latvian river Salaca has in recent years been variable, but without signs of any significant change. In Lithuania, where smolt counts are low in most rivers with trapping (however increasing in R. Mera) a possible reason for the low status is believed to be low water flows during the spawning period in recent years. In addition, it is uncertain if there are sufficient spawning possibilities in all areas. The recruitment status in Lithuania could also be influenced by the long distance from most spawning areas to the sea. In Poland, the number of spawners in the river Vistula has been declining, but the change in status is believed to be due to natural causes. The same trend in status is found also in other parts of Poland, and at present the situation does not raise concerns. In the Southern Baltic Sea (SD 22, 23, 24 and 25) the status is far from optimal in the Danish and German populations in SD 22. However, this is not believed to represent the general situation for Danish sea trout populations, and currently it does not raise concern. In Germany (SD 22), the reason for the low status is unknown. In SD 24 the population status is highly variable between countries, being low in German streams in the area. With a relatively stable count of spawners in two rivers in the SD, reasons for this is unknown. However, high water during fishing is likely to have influenced the precision of the density estimates, and in addition it is unknown if sufficient spawning possibilities are available. In some rivers, where both post-smolt and adult fish need to pass through a long and narrow lagoon, mortality could be high due to both fisheries and natural predation. In Poland (SD 25) a continuous decrease in count of spawners in river Slupia, is believed to be related to cessation of stocking of smolt. In Sweden the status in the streams included is good or reasonably good, having a positive trend. In the River Mörrum the number of smolt counted (upper part of the river only) has decreased during the last few years, being lower than what could be expected considering the size of the river Future development of model and data improvement In 2017, the ICES Working Group WGTRUTTA (Working Group with the Aim to Develop Assessment Models and Establish Biological Reference Points for Sea Trout (Anadromous Salmo trutta) Populations) was established. In this group, one modelling approach for sea trout populations being evaluated is similar to the one employed in WGBAST. It is expected that the outcome from this ongoing work can be used in future

301 ICES WGBAST REPORT as a basis for development of the current sea trout assessment. Consequently, a separate update of the sea trout model used in WGBAST is not planned. 5.9 Compatibility of the EU-MAP with the data needs for WGBAST A better geographical coverage than hitherto is needed, with a sufficient number of electrofishing sites from typical trout streams. This is especially relevant in the northern parts of the Baltic, where most present electrofishing sites are situated in larger rivers, fished primarily for monitoring of salmon populations. This is relevant both for the actual assessment as such, and in order to evaluate how well the application of the assessment model employed work in these areas. Also, in the southwest Baltic (Denmark) there is currently a lack of sites being collected annually. The concept of the current assessment model builds on a comparison of observed densities with estimated maximum densities at sites with good conditions, no migration obstacles and no or low impact from fishing. This is to a large extent depending on expert judgment. If an array of trout index-rivers, with counts of both smolt and returning adults, was established it would, from recruitment at MSY (i.e. with spawning targets reached), be possible to express both the recruitment as a proportion of the maximum density and to include spawning targets in this approach Recommendations Sufficient data coverage of sea trout parr densities from typical trout streams should be collected in all countries. Continued (annual) sampling from these sites for longer time periods is required. Sea trout index-rivers should be established to fulfil assessment requirements with respect to geographical coverage and data collection needs. Data on recreational sea trout catches should be consistently collected, taking into account the potentially high impact of recreational fisheries on sea trout stocks and the lack of these data in several countries. The model used for assessment of recruitment status should be re-evaluated with the currently used and additional variables, both within the Baltic Sea and outside. This should also be done in separate geographical areas within the Baltic, to determine if the model adequately evaluates status also in e.g. northern areas where increasingly more data are becoming available.

302 296 ICES WGBAST REPORT 2018 Table Nominal commercial catches (in tonnes round fresh weight) of sea trout in the Baltic Sea ( ). S=Sea, C=Coast and R=River. Main Basin Total Gulf of Bothnia Total Gulf of Finland Total Grand Year Denmark Estonia Finland Germany Latvia Lithuania Poland Sweden Main Finland Sweden Gulf of Estonia Finland Russia Gulf of Total S C S C S C S C R S C R S C R S C R Basin S C C R Bothnia C S C R Finland

303 ICES WGBAST REPORT Table Nominal landed recreational catch (in tonnes round fresh weight) of sea trout in the Baltic Sea ( ). S=Sea, C=Coast and R=River. N.a. data not available. Main Basin Total Gulf of Bothnia Total Gulf of Finland Total Whole of the Baltic Grand Denmark Estonia Finland Latvia Poland Sweden Main Finland Sweden Gulf of Estonia Finland Gulf of Finland Total Year C+R C R C R R R Basin R C R Bothnia C R Finland C 2001 n.a n.a n.a n.a n.a n.a n.a n.a n.a n.a n.a n.a n.a n.a n.a

304 298 ICES WGBAST REPORT 2018 Table Nominal catches (commercial + recreational; in tonnes round fresh weight) of sea trout in the Baltic Sea in years Commercial and recreational catches after year 2000 are presented in Tables and S=Sea, C=Coast and R=River. Year Main Basin Total Gulf of Bothnia Total Gulf of Finland Total Grand Denmark 1,4 Estonia Finland 2 Germany 4 Latvia Lithuania Poland Sweden 4 Main Finland 2 Sweden Gulf of Estonia Finland 2 Gulf of Total S + C C S S + C R C S + C R C R S 9 S + C R S 6 C 6 R Basin S C R S 6 C 6 R Bothnia C S C R Finland na 10 na na na na na na na na na na 6 na na 11 na na na na na na na na na na 87 na na 51 na 5 na na na na na na na na na na na na na na na na na na 50 na 14 na na na na na na na na na 66 na 9 na na na na na na na na na 62 na 9 na na na na na na na na na 53 na 8 na na na 1 24 na na 66 na 2 na na na 1 26 na 150 na na 99 na 8 na na na na na na na na , na na na na na , na na na na , na 6 na na na na , na na na na , , na na na , , na na na , na na , na na na , , , , ,339 1 Additional sea trout catches are included in the salmon statistics for Denmark until 1982 (table 3.1.2). 2 Finnish catches include about 70 % non-commercial catches in , 50 % in , 75% in Rainbow trout included. 4 Sea trout are also caught in the Western Baltic in Sub-divisions 22 and 23 by Denmark, Germany and Sweden. 5 Preliminary data. 6 Catches reported by licensed fishermen and from 1985 also catches in trapnets used by nonlicensed fishermen. 7 Finnish catches include about 85 % non-commercial catches in ICES Sub-div. 22 and Catches in included sea and coastal catches,since 1998 costal (C) and sea (S) catches are registered separately na=data not available + Catch less than 1 tonne.

305 ICES WGBAST REPORT Table Biological sea trout samples collected in NUMBER OF SAMPLED FISH BY SUBDIVISION COUNTRY MONTH (NUMBER) FISHERIES GEAR TOTAL Estonia 1 12 Coastal Gillnet Finland 4 9 Coastal All gears Latvia 3 11 Coastal, River Gillnet, trapnet Poland 1 12 River, Offshore,Coastal, All gears Sweden 6 9 River All gears TOTAL 1379

306 300 ICES WGBAST REPORT 2018 Table Adipose finclipped and tagged sea trout released in the Baltic Sea area in Country Sub- River Age Number Tagging Other Methods division fry parr smolt Carlin T-bar Anch PIT ARS (1) n.n Denmark 22 Gudsoe Mollebak 1 n.a. n.a. Denmark 22 Egåen 1 1,100 1,100 Germany 22 Habernisser Au fry 11,000 * Germany 22 Lipping Au fry 11,000 * Germany 22 Lipping Au 1 and 2 wild Germany 22 Lipping Au 1 hatchery Germany 22 Farver Au spawners 425 Germany 22 Lipping Au spawners 180 Germany 22 Loiter Au spawners 43 Germany 22 Jevenau Au spawners 58 Poland 25 Parsęta spawners 38 Poland 25 Łeba spawners 50 Sweden 25 Listerbyån Sweden 25 Ronnebyån 1 1,500 Sweden 25 Lyckebyån 1 5,000 Sweden 25 Mieån 1 1,500 Sweden 25 Mörrumsån 1 15,000 Sweden 25 Mörrumsån wild smolts Sweden 27 Åvaån 1 1, Sweden 27 Åvaån 1 132,300 Sweden 27 Åvaån 2 10,023 Sweden 27 Åvaån 2 7,000 Sweden 27 Gullspång (Lake Vänern) 2 16,000 Latvia 28 Venta 1 2,000 Finland 29 at sea 2 27,240 Finland 29 at sea 3s 2,500 1,186 Finland 29 Mynäjoki 2 3,202 Finland 29 Laajoki 2 1,602 Finland 30 at sea 2 23,000 Finland 30 Lapväärtinjoki/Isojoki 1 29,285 Finland 30 Lapväärtinjoki/Isojoki 2 17, Finland 30 Karvianjoki/Merikarvianjoki 1 5,800 Finland 30 Karvianjoki/Merikarvianjoki 2 18,377 1,000 Finland 30 Kokemäenjoki 2 22,000 Sweden 30 Gideälven 1 7,430 Sweden 30 Ångermanälven 2 51,043 Sweden 30 Indalsälven 2 98,200 Sweden 30 Ljungan 2 36,000 Sweden 30 Ljusnan 1s 3,177 Sweden 30 Ljusnan 1 12,799 Sweden 30 Ljusnan 2 46,907 Sweden 30 Dalälven 2 2,237 Sweden 30 Dalälven 1 75,982 18,000 Sweden 30 Dalälven 2 78,136 1,499 Sweden 30 Testeboån Wild smolts Finland 31 Lestijoki 1 22,050 Finland 31 Lestijoki 2 11, Finland 31 Perhonjoki 1 13,625 Finland 31 Perhonjoki 2 2, Finland 31 Siikajoki 2 1,000 Finland 31 Oulujoki 1 5,500 Finland 31 Oulujoki 2 72,344 1,984 Finland 31 Kiiminkijoki 1 18,018 Finland 31 Kiiminkijoki 2 37,076 37,076 Finland 31 Iijoki 2 1,441 62, ,911 Finland 31 Kuivajoki Finland 31 Kemijoki 2 11, , ,055 Finland 31 Tornionjoki 2 4,500 Finland 31 Tornionjoki wild smolts Sweden 31 Luleälven 1 34,758 Sweden 31 Luleälven 2 50,528 2,000 Sweden 31 Skellefteälven 1 26,219 Sweden 31 Umeälven 1 16,779 1,000 Sweden 31 Umeälven 2 5,019 1,000 Sweden 31 Umeälven Sweden 31 Umeälven 1 summer 4,997 Sweden 31 Vindelälven Wild smolts Sweden 31 Rickleån wild smolts Estonia 32 Pudisoo 2 2, Finland 32 at sea 2 121, Finland 32 Kymijoki 2 57, Total sea trout - 116,614 1,351,338 8,723 6,904 26, ,042 - (1) ARS = Alizarin Red Staining, *single marked, released as f ry Table Number of Carlin-tagged sea trout released into the Baltic Sea in Country Total Latvia 2, Finland 1,999 3, Sweden Poland 0 0 Total , ,999 3, ,823

307 ICES WGBAST REPORT Table Habitat classes and corresponding Trout Habitat Scores (THS). See text for details. Habitat Class THS including slope THS omitting Slope 0 <6 < Table Number of fishing occasions/sites in 2017 available for assessment of trout recruitment status, distributed on ICES subdivisions (SD), and number of sites available for trend analysis (sites fishes all years ). Number fishing occasions ICES SD Recruitment Trend Total

308 302 ICES WGBAST REPORT 2018 Table Status of wild and mixed sea trout populations. Partial update in Potential Smolt production (% of potential production) Area Country smolt <5 % 5-50 % > 50 % Uncertain Total production (x1000) wild mixed wild mixed wild mixed wild mixed wild mixed Gulf Finland < of Bothnia * > Uncertain 0 0 Total Sweden < > Uncertain Total Total Gulf Estonia < of Finland > Uncertain 0 0 Total Finland** < > Uncertain 0 0 Total Russia < * > Uncertain Total Total

309 ICES WGBAST REPORT Table Continued. Main BasinDenmark < > Uncertain 0 0 Total Finland < > Uncertain 0 0 Total Estonia < > Uncertain 0 0 Total Latvia < > Uncertain Total Lithuania < > 100* 0 0 Uncertain 0 0 Total Poland < > Uncertain 0 0 Total Russia < > Uncertain Total Sweden < > Uncertain Total Total Grand total * includes data from large river systems ** in 7 wild rivers it is not known if releases are carried out

310 304 ICES WGBAST REPORT 2018 Table Factors influencing status of sea trout populations. Partial update in Country Potential Number of populations Area smolt Over Habitat Dam Pollution Other Uncertain production exploitation degradation building Gulf of Finland < Bothnia* > Uncertain Total Total Gulf of Finland < Finland > Uncertain Total Russia < > Uncertain Total Estonia < > Uncertain Total Total

311 ICES WGBAST REPORT Table Continued. Main Finland < Basin* > Uncertain Total Estonia < > Uncertain Total Latvia < > Uncertain Total Lithuania < > Uncertain Total Poland < > Uncertain Total Russia < > Uncertain Total Denmark < > Uncertain Total Total Grand total * data from Sweden were unavailable

312 306 ICES WGBAST REPORT 2018 Table Sea trout smolt estimates for the period SD Country DK SE LV LV LT LT LT LT SE SE FIN RU RU EE EE River name Læså Mörrum Salaca Salaca R. Mera R. Mera R. Siesartis R. Siesartis Sävarån Rickleån Tornionjoki Luga Luga Pirita Pirita Method 1) 2) 3) 4) 5) 6) 5) 6) 7) 8) 9) 10) 11) 12) 13) n.d. 243 n.d n.d n.d. trap moved 348 n.d n.d * 23* n.d. trap moved n.d. n.d n.d n.d. trap moved n.d n.d. trap moved 470 n.d n.d. = no data 1) based on smoltrap - directly counted number of smolts, varying efficiency over years due to water level (probability level data available) 2) Median values of Bayesian estimates are only for the upper part of the river! 3) estimated smolt output on the base of counted smolts and mean trap efficiency (2014=8.5%; 2015=5.9%; 2016=9.5) 4) directly counted number of smolts during trapping season 5) estimated output derived by electrofishing data. (assumed surval probabilities to smolts: 0+ --> 40%; >0+ --> 60%) 6) counted number of individuals smolts in trap. Assumed trap efficiency almost 100% 7) simple Peterson estimates - trap moved to river Rickleån in Year ) Trap located close to river mouth, so this is the total estimated production 9) estimated smolt output. Trap efficiency in 2016 from efficiency for salmon smolt 10) estimated number of smolt output based on results of floating trap-netting- 2.9 % in 2016, due to high water only part of migration period covered 11) directly counted number of smolts in trap 12) Original estimates based on smolt trapping 13) Estimates based on a Bayesian model *) due to high waterlevel counts individual numbers presumably too low

313 ICES WGBAST REPORT Table Status of wild and mixed sea trout populations in large river systems. Country River Potential Smolt production (% of potential production) (Area) smolt <5 % 5-50 % > 50 % Uncertain Total production wild mixed wild mixed wild mixed wild mixed wild mixed Lithuania Nemunas < (Main Basin) > Uncertain 0 0 Total Poland Odra < (Main Basin) > Uncertain 0 0 Total Poland Vistula < (Main Basin) > Uncertain 0 0 Total Russia Luga < (Gulf of Finland) > Uncertain Total Finland Tornion- < joki (Gulf of Bothnia) > Uncertain 0 0 Total

314 308 ICES WGBAST REPORT 2018 Table Factors influencing status of sea trout populations in large river systems. Partial update in Country River Potential Number of populations smolt production Overexploitation Habitat degradation Dam building Pollution Other No influence Lithuania Nemunas < (Main Basin) > Uncertain Total Poland Odra < (Main Basin) > Uncertain Total Poland Vistula < (Main Basin) > Uncertain Total Russia Luga < (Gulf of Finland) > Uncertain Total Finland Tornion- < joki (Gulf of Bothnia) > Uncertain Total

315 ICES WGBAST REPORT Table Sea trout smolt releases (x1000) into the Baltic Sea by country and subdivision in Note that project based fisheries enhancement releases included. yea r country age M ain DE 1yr Basin 22-2yr DK 1yr yr EE 1yr yr FI 1yr yr yr LT 1yr yr LV 1yr yr PL 1yr yr SE 1yr yr Main Basin Total Gulf of FI 1yr Bothnia 30-2yr yr SE 1yr yr Gulf of Bothnia Total Gulf of Finland 32 EE 2yr FI 1yr yr yr RU 1yr yr Gulf of Finland Total Grand Total

316 310 ICES WGBAST REPORT 2018 Table Release of sea trout eggs, alevins, fry and parr into Baltic rivers in 2017 with correponding smolt equivalents (calculated according to survival rates and smolt ages below the table). The smolt equivalents from releases in 2017 have been added in Table (summed to values calculated for releases in previous years). Parr Smolt equivalents Region Egg Alevin Fry 1- s old 1- y old 2- s old 3-s old Total Sub-divs (1) (1) (4) (6) (9) (10) (10) Denmark - - 3,639 6, Estonia Finland 22,500 1, ,600 85,300-13, ,707 Germany , ,129-24,129 Latvia Poland - 2,300,000 4,816, , ,504 Sweden , ,226-2,226 Lituania , ,120-6,120 Total 22,500 2,301,500 5,902,943 6,815 5,600 85,300-13, , ,204 Sub-divs (2) (3) (5) (7) (8) (8) (10) Finland 6,900 10, , , ,489 Sweden 288, ,200 9,000 15, ,896 6,564 8,460 Total 294,900 10, ,200 9, , ,200 6,749 19,949 Sub-div. 32 (1) (1) (4) (6) (9) (10) (10) - Estonia Finland 117,000 1, , ,968 1,180-3,148 Russia Total 117,000 1, , ,968 1,180-3,148 Grand total Sub-divs ,400 2,312,500 6,132,143 15, ,000 85,300-15, ,117 6, ,301 Rate of survival Time to Rate of survival Time to to smolt smoltification to smolt smoltification (1) = 1.0% 2 years (6) = 6.0% 2 years (2) = 0.5% 3 years (7) = 6.0% 3 years (3) = 1.5% 3 years (8) = 12.0% 2 years (4) = 3.0% 2 years (9) = 12.0% 1 year (5) = 2.0% 3 years (10) = 15.0% 1 year

317 ICES WGBAST REPORT Table Estimated number of sea trout smolts ('smolt equivalents', see Table 5.6.2) originating in releases of eggs, alevins, fry and parr in Subdivs Denmark 30,858 25,555 45,759 7,912 17,790 17,508 13,695 13,695 13,704 12,540 12,540 10,737 9,177 9,606 9,240 9,246 9, Estonia - - 2,100 1, , Finland ,670 33,965 19,550 18, ,445 13,815 10,350 8,100 14,375 16,260 17,787 14,349 18,313 16, Germany 25,500 24,900 61,200 72,240 27,240 36,900 32,550 38,400 29,640 29,910 40,800 34,500 29,400 34,650 32,700 32,580 31,860 35,874 29,550 24,129 - Latvia 13,815 8,644 11, ,340 15,227 6,462 3,189 19,015 6,840 17,664 30,595 5,987 15,300 28,913 7,787 11,621 6,000 6, Poland 167, ,500 84,240 68,400 91,000 63,236 77,690 61, ,686 84, , ,982 95, , , , , , , ,504 - Sweden 13,129 39,333 42,690 5,320 29,335 2,055 27,700 4,425 1,623 2, ,385 1,737 2,940 3,258 1,368 1,380 2,379 2,226 - Lituania ,670 2,400 4,350 7,440 18,180 12,990 8,040 6,750 5,370 10,935 8,580 6,300 4,560 4,680 3,840 6,120 - Total 251, , , , , , , , , , , , , , , , , , , ,737 - Subdivs Finland 54,268 80,662 26,523 42,828 36,670 1,890 31,362 11,787 22,704 29,892 32,550 46,753 39,285 25,881 22,595 18,782 12,878 12,879 21,328 16, Sweden 84,237 78,440 43,614 24,092 22,921 36,170 20,207 22,756 24,561 16,690 16,497 12,811 13,026 5,456 21,906 9,073 25,850 12,996 17,203 11,003 6,564 Total 138, ,102 70,137 66,920 59,591 38,060 51,569 34,543 47,265 46,582 49,047 59,564 52,311 31,337 44,501 27,855 38,728 25,875 38,531 27,287 6,749 Subdiv Estonia ,412 2,532 4,407 2, ,536 2,098 6,552 9,486 3, , Finland 20,910 5,500 2, , ,574 8,997 4,353 5,919 5, ,747 1,632 1,050 7,716 2,409 2,722 1,180 - Russia 3,882 3,630 7, ,630 1,281 6,690 3, , ,441 1, , Total 24,792 9,130 9,849 3,031 4,502 9,117 9,135 15,918 8,997 4,665 16,836 7,457 10,284 12,979 5,154 4,800 8,736 3, ,180 - Grand total Subdivs , , , , , , , , , , , , , , , , , , , ,204 6,749

318 312 ICES WGBAST REPORT 2018 Figure Electrofishing site is subdivisions used for assessment of sea trout recruitment status (2018).

319 ICES WGBAST REPORT Figure Electrofishing site is subdivisions used for trend analysis of sea trout recruitment status (2018).

320 314 ICES WGBAST REPORT ; SD: FI SE Figure Average densities of 0+ trout in Finnish (FI) and Swedish (SE) rivers in ICES SD Number of acending sea trout spawners R. Kalixälv R. Vindelälv R. Piteälv R Byskeälv 0 Figure Number of ascending sea trout spawners from fish counters in four Swedish rivers debouching in the Bothnian Bay.

321 ICES WGBAST REPORT Catch in kg Torneälven river Kalixälven river Figure Swedish sea trout catches (landed, in kilos) in rivers Kalixälven and Torneälven (SD 31). Note that since 2013 there is a ban for landing of sea trout in Torneälven Figure Nominal catches (in numbers) of sea trout in Swedish wild rivers (ICES SD 25, 27, 30 and 31). Only landed catches are included (no catch and release).

322 316 ICES WGBAST REPORT % 12 % 10 % 8 % 6 % GoB GoF 4 % 2 % 0 % Figure Return rates of Carlin tagged sea trout released in Gulf of Bothnia and Gulf of Finland in Figure Age distribution of recaptured Carlin-tagged sea trout released in the Bothnian Bay (Subdivision 31) area in Finland, (updated for ICES, WGBAST 2018).

323 ICES WGBAST REPORT Figure Proportional distribution of fishing gear used for recaptures of Carlin-tagged sea trout in the Bothnian Bay (SD 31) in Finland, (updated for ICES, WGBAST 2018). Figure Posterior estimates of total annual instantaneous fishing mortality (F, summed over gear types/fleets) for sea trout from the Isojoki (top panels) and Lestijoki (lower panels) stocks with a time-invariant recreational tag reporting rate (left-hand panels) and time-varying recreational tag reporting rate (right-hand panels). Survival from fishing =exp(-f) and harvest rate=1-exp(- F). Black boxes, age 2; grey boxes, ages 3+. The horizontal line in the centre of each box denotes the median, the ends of the box denote the interquartile range and the whiskers extend to the 2.5th and 97.5th percentiles.

324 318 ICES WGBAST REPORT ; SD: EE FI RU Figure Average densities of 0+ trout in Estonian (EE), Finnish (FI) and Russian (RU) rivers in the Gulf of Finland (ICES SD 32) ; SD: EE LT LV PL SE Figure Average densities of 0+ trout in Estonian (EE), Lithuanian (LT), Latvian (LV) Polish (PL) and Swedish (SE) rivers in ICES SD

325 ICES WGBAST REPORT Figure Video monitoring based spawners counts in four German small river systems (SD 22 and 24; left panel), and Vaki counter numbers from Polish rivers (SD 25 and 26, right panel).

326 320 ICES WGBAST REPORT ; SD: DK PL SE GER Figure Average densities of 0+ trout in Danish (DK), Polish (PL), Swedish (SE) and German (GER) rivers in ICES SD

327 ICES WGBAST REPORT year avg East GoB GoF South West Figure Recruitment status for 0+ trout by Assessment Area Division (95% CL, only positive value displayed) in 2017 and the last three years ( ) year avg Figure Recruitment status for 0+ trout by ICES SD (95% CL, only positive value displayed) in 2017 and the last three years ( ).

328 322 ICES WGBAST REPORT 2018 Recruitment Status DK 22 DE 23 SE 24 DK 24 DE 24 PL 24 SE 25 PL 25 SE 26 LT 26 PL 27 SE 28 EE 28 LV 28 SE 29 EE 29 SE 30 FI 30 SE 31 FI 31 SE 32 EE 32 FI 32 RU year avg Figure Recruitment status for 0+ trout by ICES SD and individual countries within SD (95% CL, only positive value displayed) in 2017 and the last three years ( ) pearsons r GoB GoF East West South Figure Average trend (Pearsons r) in 0+ trout recruitment status in the last five years by Assessment Area Division.

329 ICES WGBAST REPORT Figure Average trend (Pearsons r) in 0+ trout recruitment status in the last five years by ICES SD pearson r DK 23 SE 24 DK 24 SE 25 PL 25 SE 26 LT 26 PL 27 SE 28 EE 28 LV 28 SE 29 SE 30 FI 30 SE 31 FI 31 SE 32 EE -1 Figure Average trend (Pearsons r) in 0+ trout recruitment status in the last five years by ICES SD and country (within SD:s shared by several countries).

330 324 ICES WGBAST REPORT References 6.1 Literature Alm, G The salmon catch and the salmon stock in the Baltic during recent years. Svenska vattenkraftföreningens publikationer 441 (1954:5). Backman, J Itämeren hydrologisten vaihteluiden sekä biologisten tekijöiden yhteys lohen M74-oireyhtymään. Helsingin yliopisto, Bio- ja ympäristötieteiden laitos, Akvaattiset tieteet/hydrobiologia, Toukokuu 2004, 53 pp. (In Finnish). Bartel, R., Bernaś, R., Grudniewska, J., Jesiołowski, M., Kacperska, B., Marczyński, A., Pazda, R., Pender, R., Połomski, S., Skóra, M., Sobocki, M., Terech-Majewska, E. and Wołyński, P Wrzodzienica u łososi Salmo salar i troci Salmo trutta trutta w Polsce w latach (Furunculosis in salmon Salmo salar and sea trout Salmo trutta trutta in Poland in ). Komunikaty Rybackie, 3: 7 12 (in Polish with English summary). Butler, J.A. and Loeffel, R.E Experimental use of barbeless hooks in Oregon's troll salmon fishery. Pacific Marine Fisheries Commission Bulletin, 8. Bylund, G. and Lerche, O Thiamine therapy of M74 affected fry of Atlantic salmon Salmo salar. Bulletin of the European Association of Fish Pathologists 15: Bzoma, S Kormoran Phalacrocorax carbo (L.) w strukturze troficznej ekosystemu Zatoki Gdańskiej (Cormorant in the trophic structure and ecosystem of Gulf of Gdańsk, PhD Thesis). Praca doktorska (maszynopis) w Katedrze Ekologii i Zoologii Kręgowców, Uniwersytet Gdański, Gdynia. Börjeson, H Redovisning av M74-förekomsten i svenska kompensationsodlade laxstammar från Östersjön för kläckårgång pp. Börjeson, H Redovisning av M74-förekomsten i svenska kompensationsodlade laxstammar från Östersjön för kläckårgång pp. Börjeson, H Redovisning av M74-förekomsten i svenska kompensationsodlade laxstammar från Östersjön för 2015 (in Swedish). 5 pp. Börjeson, H Redovisning av M74-förekomsten i svenska kompensationsodlade laxstammar från Östersjön för 2017 (in Swedish). 5 pp Börjeson, H., Amcoff, P., Ragnarsson, B. and Norrgren, L Reconditioning of sea-run Baltic salmon (Salmo salar) that have produced progeny with the M74 syndrome. Ambio, 28: Casini, M., Hjelm, J., Molinero, J.C., Lovgren, J., Cardinale, M., Bartolino, V., Belgrano, A. and Kornilovs, G Trophic cascades promote threshold-like shifts in pelagic marine ecosystems. Proceedings of the National Academy of Sciences of the United States of America, 106: Denwood, M.J runjags: An R Package Providing Interface Utilities, Model Templates, Parallel Computing Methods and Additional Distributions for MCMC Models in JAGS. Journal of Statistical Software, 71(9): European Commission Proposal for a Regulation of the European Parliament and of the Council establishing a multiannual plan for the Baltic salmon stock and the fisheries exploiting that stock. COM/2011/0470. Fiskhälsan Produktion av lax och havsöring baserad på vildfisk från Östersjön och Västerhavet: Kontrollprogram för vissa smittsamma sjukdomar samt utfallet av M74, Fiskhälsan FH AB, Älvkarleby. 10 pp. Fohgelberg, P. and Wretling, S Kontroll av främmande ämnen i livsmedel National Food Agency s report pp (in Swedish with English Abstract).

331 ICES WGBAST REPORT Gelman, A., and Rubin, D.B Inference from iterative simulation using multiple sequences. Statistical Science, 7: Gjernes, T., Kronlund, A.R. and Mulligan, T.J Mortality of Chinook and Coho Salmon in their first year of ocean life following catch and release by Aanglers. North American Journal of Fisheries Management, 13: Hansson, S., Karlsson, L., Ikonen, E., Christensen, O., Mitans, A., Uzars, D., Petersson, E. and Ragnarsson, B Stomach analyses of Baltic salmon from and : possible relations between diet and yolk-sac-fry mortality (M74). Journal of Fish Biology, 58: Hansson, S., Bergström, U., Bonsdorff, E., Härkönen, T., Jepsen, N., Kautsky, L., Lundström, K., Lunneryd, S.-G., Ovegård, M., Salmi, J., Sendek, D., and Vetemaa, M Competition for the fish fish extraction from the Baltic Sea by humans, aquatic mammals, and birds. ICES Journal of Marine Science, doi: /icesjms/fsx207. In press. Hasselborg, T Kartering av fasta redskap inom Bottniska viken samt fångstuppskattning för fritidsfiskets fångster av lax med fasta redskap inom områden 30 och 31 under 2015 (in Swedish, preliminary report), 24 pp. HELCOM Salmon and Sea Trout Populations and Rivers in the Baltic Sea Helcom assessment of salmon (Salmo salar) and sea trout (Salmo trutta) populations and habitats in rivers flowing to the Baltic Sea. Baltic Sea Environment Proceedings, 126A: 79 pp. HELCOM Climate change in the Baltic Sea Area: HELCOM thematic assessment in Baltic Sea Environment Proceedings, 137: 66 pp. HELCOM. 2011b. Salmon and Sea Trout Populations and Rivers in Finland HELCOM assessment of salmon (Salmo salar) and sea trout (Salmo trutta) populations and habitats in rivers flowing to the Baltic Sea. Baltic Sea Environment Proceedings, 126B: 97 pp. ICES Report of the Baltic Salmon and Trout Working Group ICES Doc. CM 2000/ACFM:12. ICES ACFM:12. Report of the Workshop on Catch Control, Gear Description and Tag Reporting in Baltic Salmon (WKCGTS), Svaneke, Denmark January ICES. 2003b. Report of the Baltic salmon and trout assessment working group. ICES CM 2003/ACFM:20. ICES Report of the Working Group on Baltic Salmon and Trout (WGBAST), April 2004, Tartu, Estonia. ICES CM 2004/ACFM:23, Ref: I. 163 pp. ICES Report of the Baltic Salmon and Trout Working Group (WGBAST) 5 14 April 2005, Helsinki, Finland. ICES CM 2005/ACFM:18. ICES Report of the Baltic Salmon and Trout Working Group (WGBAST), April 2007, Vilnius, Lithuania.ICES CM 2007/ACFM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST). ICES CM 2008/ACOM:05. ICES. 2008b. Report of the ICES Advisory Committee, ICES Advice, Book 8, 133 pp. ICES. 2008c. Report of the Study Group on data requirements and assessment needs for Baltic Sea trout [SGBALANST], by correspondence, December 2007 February ICES CM 2008/DFC: pp. ICES. 2008d. Report of the Workshop on Baltic Salmon Management Plan Request (WKBALSAL), May 2008, ICES, Copenhagen, Denmark. ICES CM 2008/ACOM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), March 2009, Oulu, Finland. ICES CM 2009/ACOM: pp.

332 326 ICES WGBAST REPORT 2018 ICES. 2009b. Report of the Study Group on data requirements and assessment needs for Baltic Sea trout [SGBALANST], 3 5 February 2009, Copenhagen, Denmark, ICES 2009/DFC: pp. ICES Report of the Working Group on Baltic Salmon and Trout (WGBAST), March 2010, St Petersburg, Russia. ICES CM 2010/ACOM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), March 2011, Riga, Latvia. ICES 2011/ACOM: pp. ICES. 2011b. Study Group on data requirements and assessment needs for Baltic Sea trout (SGBALANST), 23 March 2010, St Petersburg, Russia, By correspondence in ICES CM 2011/SSGEF: pp. ICES. 2011c. Report of the ICES Advisory Committee, ICES Advice, Book 8, pp ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), March 2012, Uppsala, Sweden. ICES 2012/ACOM: pp. ICES. 2012b. Report of the Inter-Benchmark Protocol on Baltic Salmon (IBPSalmon). ICES 2012/ACOM: pp. ICES. 2012c. Report of the Baltic Fisheries Assessment Working Group 2012 (WGBFAS). ICES Document CM 2012/ACOM: pp. ICES. 2012d. Report of the Workshop on Eel and Salmon DCF Data (WKESDCF), 3 6 July 2012, ICES HQ, Copenhagen, Denmark. ICES CM/ACOM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), 3 12 April 2013, Tallinn, Estonia. ICES CM 2013/ACOM: pp. ICES. 2013b. Report of the ICES Working Group on Recreational Fisheries Surveys 2013 (WGRFS), April 2013, Esporles, Spain. ICES CM 2013/ACOM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), 26 March 2 April 2014, Aarhus, Denmark. ICES CM 2014/ACOM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), March 2015, Rostock, Germany. ICES CM 2015/ACOM: pp. ICES. 2015b. ICES special request advice Northeast Atlantic on data needs for monitoring of recreational fisheries. Published 21 August ICES Advice 2015, Book 1. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), 30 March 6 April 2016, Klaipeda, Lithuania. ICES CM 2016/ACOM: pp. ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), 27 March 4 April 2017, Gdańsk, Poland. ICES CM 2017/ACOM: pp. ICES. 2017b. Report of the Workshop on Potential Impacts of Climate Change on Atlantic Salmon Stock Dynamics (WKCCISAL), March 2017, Copenhagen, Denmark. ICES CM 2017/ACOM: pp. ICES. 2017c. Report of the Baltic fisheries assessment working group (WGBFAS), April 2017, Copenhagen, Denmark. ICES CM 2017/ACOM: pp. ICES. 2017d. Report of the Benchmark Workshop on Baltic Salmon (WKBALTSalmon), 30 January 3 February 2017, Copenhagen, Denmark. ICES CM 2017/ACOM: pp. Ikonen, E The role of the feeding migration and diet of Atlantic salmon (Salmo salar L.) in yolk-sac fry mortality (M74) in the Baltic Sea. PhD Thesis, Department of Biological and Environmental Sciences, Faculty of Biosciences, University of Helsinki, and Finnish Game and Fisheries Research Institute, Finland. 34 pp. IPCC Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change

333 ICES WGBAST REPORT [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. Jacobson, P., Gårdmark, A., Östergren, J., Casini, M. and Huss, M., Size-dependent prey availability affects diet and performance of predatory fish at sea: a case study of Atlantic salmon. Ecosphere 9: Jonsson, B. and Jonsson, N A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flow. Journal of Fish Biology, 75: Jutila, E., Jokikokko, E., Kallio-Nyberg, I., Saloniemi, I. and Pasanen, P Differences in sea migration between wild and reared Atlantic salmon (Salmo salar L.) in the Baltic Sea. Fisheries Research, 60: Järvi, T.H Vaihtelut Itämeren lohikannassa. Suomen kalatalous Kaiser, F Estimating German recreational salmon catches in the Baltic Sea. M.Sc. thesis, University of Rostock, Rostock, Germany. 68 pp. Karlsson, L., Ikonen, E., Mitans, A. and Hansson, S The diet of salmon (Salmo salar) in the Baltic Sea and connections with the M74 syndrome. Ambio, 28: Karlström, Ö Development of the M74 syndrome in wild populations of Baltic salmon (Salmo salar) in Swedish rivers. Ambio, 28: Keinänen, M., Tolonen, T., Ikonen, E., Parmanne, R., Tigerstedt, C., Rytilahti, J., Soivio, A. and Vuorinen, P. J Itämeren lohen lisääntymishäiriö - M74 (English abstract: Reproduction disorder of Baltic salmon (the M74 syndrome): research and monitoring.). In Riista- ja kalatalouden tutkimuslaitos, Kalatutkimuksia - Fiskundersökningar 165, 38 pp. Keinänen, M., Uddström, A., Mikkonen, J., Rytilahti, J., Juntunen, E.-P., Nikonen, S. and Vuorinen, P. J Itämeren lohen M74-oireyhtymä: Suomen jokien seurantatulokset kevääseen 2007 saakka. (English abstract: The M74 syndrome of Baltic salmon: the monitoring results from Finnish rivers up until 2007). Riista- ja kalatalous - Selvityksiä 4/2008, 21 pp. Keinänen, M., Uddström, A., Mikkonen, J., Casini, M., Pönni, J., Myllylä, T., Aro, E. and Vuorinen, P. J The thiamine deficiency syndrome M74, a reproductive disorder of Atlantic salmon (Salmo salar) feeding in the Baltic Sea, is related to the fat and thiamine content of prey fish. ICES Journal of Marine Science, 69: Keinänen, M., Iivari, J., Juntunen, E.-P., Kannel, R., Heinimaa, P., Nikonen, S., Pakarinen, T., Romakkaniemi, A. and Vuorinen, P. J Thiamine deficiency M74 of salmon can be prevented. Riista- ja kalatalous - Tutkimuksia ja selvityksiä 14/2014, 41 pp. (In Finnish with English abstract). Keinänen, M., Käkelä, R., Ritvanen, T., Myllylä, T., Pönni, J. and Vuorinen, P.J Fatty acid composition of sprat (Sprattus sprattus) and herring (Clupea harengus) in the Baltic Sea as potential prey for salmon (Salmo salar). Helgoland Marine Research, 71: 4. (doi: /s ). Kesminas, V. Virbickas and T., Repečka, R The present state of salmon (Salmo salar L.) in Lithuania. Acta Zoologica Lituanica, V. 13, N 2, Vilnius p Kesminas, V. and Kontautas, A Sea trout in Lithuania, Country report. Workshop on Baltic sea trout, Helsinki, Finland, October DTU Aqua Report No National Institute of Aquatic resources, Technical University of Denmark. 95pp. Eds. S. Pedersen, P. Heinimaa and T. Pakarinen. Koed, A., Baktoft, H. and Bak, B.D Causes of mortality of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) smolts in a restored river and its estuary. River Research and Applications, 22:

334 328 ICES WGBAST REPORT 2018 Koljonen, M-L Annual changes in the proportions of wild and hatchery Atlantic salmon (Salmo salar) caught in the Baltic Sea. ICES Journal of Marine Science, 63: Koljonen, M.L., Gross, R. and Koskiniemi, J Wild Estonian and Russian sea trout (Salmo trutta) in Finnish coastal sea trout catches: results of genetic mixed-stock analysis. Hereditas, 151: Koski, P., Pakarinen, M., Nakari, T., Soivio, A. and Hartikainen, K Treatment with thiamine hydrochloride and astaxanthine for the prevention of yolk-sac mortality in Baltic salmon fry (M74 syndrome). Diseases of Aquatic Organisms, 37: Koski, P., Soivio, A., Hartikainen, K., Hirvi, T. and Myllylä, T M74 syndrome and thiamine in salmon broodfish and offspring. Boreal Environment Research, 6: Kulmala S., Haapasaari P., Karjalainen T.P., Kuikka S., Pakarinen T., Parkkila K., Romakkaniemi A. and Vuorinen P.J TEEB Nordic case: Ecosystem services provided by the Baltic salmon - a regional perspective to the socio-economic benefits associated with a keystone species. In: Kettunen et al. Socio-economic importance of ecosystem services in the Nordic Countries - Scoping assessment in the context of The Economics of Ecosystems and Biodiversity (TEEB). Nordic Council of Ministers, Copenhagen. Available also at: Larsson, P-O Growth of Baltic salmon Salmo salar in the sea. Marine Ecology Progress Series, 17: Leopold, M.F., Van Damme, C.J.G. and Van der Veer, H.W Diet of cormorants and the impact of cormorant predation on juvenile flatfish in the Dutch Wadden Sea. Journal of Sea Research, 40: Lilja, J., Romakkaniemi, A., Stridsman, S., and Karlsson, L Monitoring of the 2009 salmon spawning run in River Tornionjoki/Torneälven using Dual-frequency IDentification SONar (DIDSON). A Finnish-Swedish collaborative research report. 43 pp. Lindroth, A The smolt migration in the river Mörrumsån (Sweden) Anadromous and Catadromous Fish Committee, CM 1977/M:8. 11 pp. Lundström, J., Carney, B., Amcoff, P., Pettersson, A., Börjeson, H., Förlin, L. and Norrgren, L Antioxidative systems, detoxifying enzymes and thiamine levels in Baltic salmon (Salmo salar) that develop M74. Ambio, 28: MacKenzie, B., Gislason, H., Möllmann, C. and Köster, F Impact of 21st century climate change on the Baltic Sea fish community and fisheries. Global Change Biology, 13: Mikkonen, J., Keinänen, M., Casini, M., Pönni, J., and Vuorinen, P. J Relationships between fish stock changes in the Baltic Sea and the M74 syndrome, a reproductive disorder of Atlantic salmon (Salmo salar). ICES Journal of Marine Science 68: Niva, T Perämeren ja sen jokien lohi-istutusten tuloksellisuus vuosina Results of salmon smolt releases in the Bothnian Bay from Riista- ja kalatalouden tutkimuslaitos, Kalatutkimuksia - Fiskundersökningar 179, 67 pp. (In Finnish with English abstract). Orsi, J.A., Wertheimer, A.C. and Jaenicke, H.W Influence of selected hook and lure types on catch, size, and mortality of commercially troll-caught Chinook salmon. North American Journal of Fisheries Management, 13: Otero, J., L Abée-Lund, J.H., Castro-Santos, T., Leonardsson, K., Storvik, G.O., Jonsson, B., Dempson, J.B., Russell, I., Jensen, A.J., Baglinière, J-L., Dionne, M., Armstrong, J.D., Romakkaniemi, A., Letcher, B.H., Kocik, J.F., Erkinaro, J., Poole, R., Rogan, G., Lundqvist, H., MacLean, J.C., Jokikokko, E., Arnekleiv, J.V., Kennedy, R.J., Niemelä, E., Caballero, P., Music, P.A., Antonsson, T., Gudjonsson, S., Veselov, A.J., Lamberg, A., Groom, S., Taylor, B.H., Taberner, M., Dillane, M., Arnason, F., Horton, G., Hvidsten, N.A., Jonsson, I., Jonsson, N., McKelvey, S., Naesje, T.F., Skaala, Ø., Smith, G.W., Saegrov, H., Stenseth,

335 ICES WGBAST REPORT N.C., and Vøllestad, L.A Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar). Global Change Biology, 20: doi: /gcb Östergren, J., Lind, E., Palm, S., Tärnlund, S., Prestegaard, T., Dannewitz, J Stamsammansättning av lax i det svenska kustfisket 2013 & genetisk provtagning och analys. Rapport till Havs- och vattenmyndigheten (In Swedish), 30 pp. Parker, R.R., Black, E. C. and Larkin, P.A Fatigue and mortality in troll-caught Pacific salmon (Oncorhynchus). Journal Fisheries Research Board of Canada, 16: 4. Pella, J., and Masuda, M Bayesian method for analysis of stock mixtures from genetic characters. Fishery Bulletin, 99: Persson, M.E., Larsson, P., Holmqvist, N. and Stenroth P Large variation in lipid content, sigma PCB and delta c-13 within individual Atlantic salmon (Salmo salar). Environmental Pollution, 145: Pettersson, A. and Lignell, Å Astaxanthin deficiency in eggs and fry of Baltic salmon (Salmo salar) with the M74 syndrome. Ambio, 28: Plummer, M JAGS: A program for analysis of Bayesian graphical models using Gibbs sampling. In proceedings of the 3rd International Workshop on Distributed Statistical Computing (DSC 2003), March, Vienna, Austria. ISSN X. Raitaniemi, J. and Manninen, K. (Eds.) Kalakantojen tila vuonna 2016 sekä ennuste vuosille 2017 ja Luonnonvara- ja biotalouden tutkimus 77/2017, 92 pp. (In Finnish with table and figure texts in English). Rohtla, M., Matetski, L., Svirgsden, R., Kesler, M., Taal, I., Saura, A., Vaittinen, M. and Vetemaa, M Do sea trout Salmo trutta parr surveys monitor the densities of anadromous or resident maternal origin parr, or both. Fisheries Mangement and Ecology, 24: Romakkaniemi, A., Perä, I., Karlsson, L., Jutila, E., Carlsson, U., and Pakarinen, T Development of wild Atlantic salmon stocks in the rivers of the northern Baltic Sea in response to management measures. ICES Journal of Marine Science, 60: Romakkaniemi, A., Jutila, E., Pakarinen, T., Saura, A., Ahola, M., Erkinaro, J., Heinimaa, P., Karjalainen, T. P., Keinänen, M., Oinonen, S., Moilanen, P., Pulkkinen, H., Rahkonen, R., Setälä, J. and Söderkultalahti, P Background studies for the national salmon strategy. Kala- ja riistahallinnon julkaisuja 91 (1/2014), 58 pp. (In Finnish with English abstract). Skov, C., Jepsen, N., Baktoft, H., Jansen, T., Pedersen, S. and Koed, A Cormorant predation on PIT-tagged lake fish. Journal of Limnology, 73: Sundt-Hansen, L.E., Hedger, R.D., Ugedal, O., Diseruda, O.H., Finstad, A.G., Sauterleute, J.F., Tøfte, L., Alfredson, K. and Forseth, T Modelling climate change effects on Atlantic salmon: Implications for mitigation in regulated rivers. Science of the Total Environment, : SVA (Statens veterinärmedicinska anstalt.) Sjuklighet och dödlighet i svenska laxälvar under : Slutrapport avseende utredning genomförd 2016 Dnr 2017/ pp. (In Swedish with English abstract). Vuorinen, P.J. and Keinänen, M Environmental toxicants and thiamine in connection with the M74 syndrome in Baltic salmon (Salmo salar). In: B.-E. Bengtsson, C. Hill and S. Nellbring (Eds.), Nordic Research Cooperation on Reproductive Disturbances in Fish. Report from the Redfish project. TemaNord 1999:530, pp Vuorinen, P.J., Parmanne, R., Vartiainen, T., Keinänen, M., Kiviranta, H., Kotovuori, O. and Halling, F PCDD, PCDF, PCB and thiamine in Baltic herring (Clupea harengus L.) and sprat (Sprattus sprattus (L.)) as a background to the M74 syndrome of Baltic salmon (Salmo salar L.). ICES Journal of Marine. Science, 59:

336 330 ICES WGBAST REPORT 2018 Vuorinen, P.J., Keinänen, M., Kiviranta, H., Koistinen, J., Kiljunen, M., Myllylä, T., Pönni, J., Peltonen, H., Verta, M. and Karjalainen, J Biomagnification of organohalogens in Atlantic salmon (Salmo salar) from its main prey species in three areas of the Baltic Sea. Science of the Total Environment, : Vuorinen, P.J., Keinänen, M., Heinimaa, P., Iivari, J., Juntunen, E.-P., Kannel, R., Pakarinen, T. and Romakkaniemi, A. 2014a. M74-oireyhtymän seuranta Itämeren lohikannoissa. RKTL:n työraportteja 41/2014, 24 pp. (In Finnish). Vuorinen, P.J., Kiviranta, H., Koistinen, J., Pöyhönen, O., Ikonen, E. and Keinänen, M. 2014b. Organohalogen concentrations and feeding status in Atlantic salmon (Salmo salar L.) of the Baltic Sea during the spawning run. Science of the Total Environment, : Walters, C. and Korman, J Analysis of stock recruitment data for deriving escapement reference points. In Stock, recruitment and reference points - assessment and management of Atlantic salmon, pp Ed. by É. Prévost and G. Chaput. INRA editions, Fisheries and Oceans Canada. Wertheimer, A Hooking Mortality of Chinook Salmon Released by Commercial Trollers. North American Journal of Fisheries Management, 8: Wertheimer, A., Celewycz, A., Jaenicke, H., Mortensen, D. and Orsi, J.A Size-related Hooking Mortality of Incidentally Caught Chinook Salmon, Oncorhynchus tshawytscha. Marine Fisheries Review, 51: Whitlock, R., Mäntyniemi, S., Palm, S., Koljonen, M.-L., Dannewitz, J. and Östergren, J Integrating genetic analysis of mixed populations with a spatially-explicit population dynamics model. Methods in Ecology and Evolution. 9:

337 ICES WGBAST REPORT Annex 1: List of Participants NAME ADDRESS PHONE/FAX Rafal Bernas Inland Fisheries Institute Department of Migratory Fishes Phone Rutki Żukowo Poland Jānis Bajinskis (part of meeting) Institute of Food Safety, Animal Health and Environment (BIOR) Fish Resources Research Department Inland Waters Division 8 Daugavgrivas Str Riga Latvia Johan Dannewitz (part of meeting) Swedish University of Agricultural Sciences Department of Aquatic Resources (SLU Aqua) Phone , mobile johan.dannewitz@slu.se Stångholmsvägen Drottningholm Sweden Piotr Debowski Inland Fisheries Institute Department of Migratory Fishes p.debowski@infish.com.pl Rutki Żukowo Poland Harry Hantke (part of meeting) Landesforschungsanstalt für Landwirtschaft und Fischerei Institut für Fischerei h.hantke@lfa.mvnet.de Fischerweg Rostock Germany Anders Kagervall (by correspondence) Swedish University of Agricultural Sciences Department of Aquatic Resources (SLU Aqua) anders.kagervall@slu.se Stångholmsvägen Drottningholm Sweden Kelsey Hartikainen (part of meeting) Ecosystems and Environment Research Programme Faculty of Biological and Environmental Sciences and Helsinki Institute of Sustainability Science (HELSUS) University of Helsinki PO Box 65 Helsinki kelsey.hartikainen@helsinki.fi Finland

338 332 ICES WGBAST REPORT 2018 NAME ADDRESS PHONE/FAX Martin Kesler Vytautas Kesminas (part of meeting) Marja-Liisa Koljonen (by correspondence) Antanas Kontautas (part of meeting) Adam Lejk Katarina Magnusson (by correspondence) Hans Jakob Olesen Tapani Pakarinen Stefan Palm Chair University of Tartu Estonian Marine Institute Ülikooli Tartu Estonia Institute of Ecology Nature Research Centre Akademijos str Vilnius 12 Lithuania Natural Resources Institute Finland (Luke) Production systems Animal genetics Latokartanonkaari Helsinki Finland Marine research Institute Klaipeda University H. Manto 84 LT Lithuania National Marine Fisheries Research Institute ul. Kollataja Gdynia Poland Institute of Freshwater Research Drottningholm Stångholmsvägen Drottningholm Sweden Technical University of Denmark National Institute of Aquatic Resources Kemitorvet Building 201, room Kgs. Lyngby Denmark Natural Resources Institute Finland (Luke) Latokartanonkaari 9 PO Box Helsinki Finland Swedish University of Agricultural Sciences Department of Aquatic Resources (SLU Aqua) Stångholmsvägen Drottningholm Sweden Phone Phone Fax Tel martin.kesler@ut.ee v.kesminas1@gmail.com marja-liisa.koljonen@luke.fi antanas.kontautas@ku.lt Cell adam.lejk@mir.gdynia.pl katarina.magnusson@slu.se Cell Phone Phone hjo@aqua.dtu.dk tapani.pakarinen@luke.fi stefan.palm@slu.se

339 ICES WGBAST REPORT NAME ADDRESS PHONE/FAX Stig Pedersen DTU Aqua - National Institute of Aquatic Resources Department of Inland Fisheries Vejlsøvej Silkeborg Denmark Phone Cell sp@aqua.dtu.dk Wojciech Pelczarski National Marine Fisheries Research Institute ul. Kollataja Gdynia Poland Phone Fax wpelczarski@mir.gdynia.pl Christoph Petereit (part of meeting) GEOMAR Helmholtz Centre for Ocean Research Düsternbrooker Weg Kiel Germany Phone: Fax: cpetereit@geomar.de Henni Pulkkinen (part of meeting and by correspondence) Natural Resources Institute Finland (Luke) Paavo Havaksentie Oulun Yliopisto Finland Phone henni.pulkkinen@luke.fi Atso Romakkaniemi Natural Resources Institute Finland (Luke) Paavo Havaksentie Oulun Yliopisto Finland Phone atso.romakkaniemi@luke.fi Stefan Stridsman County Administrative Board of Norrbotten Waters and Fisheries Unit Stationsgatan Luleå Sweden Phone Fax stefan.stridsman@lansstyrelsen.se Susanne Tärnlund Swedish University of Agricultural Sciences Department of Aquatic Resources (SLU Aqua) Stångholmsvägen Drottningholm Sweden Phone , mobile susanne.tarnlund@slu.se Sergey Titov State Research Institute of Lake and River Fisheries Makarova emb St Petersburg Russia Phone: Fax: sergtitov_54@mail.ru

340 334 ICES WGBAST REPORT 2018 NAME ADDRESS PHONE/FAX Oula Tolvanen (part of meeting) Ecosystems and Environment Research Programme Faculty of Biological and Environmental Sciences and Helsinki Institute of Sustainability Science (HELSUS) University of Helsinki PO Box 65 Helsinki Finland Phone Didzis Ustups (part of meeting) Institute of Food Safety, Animal Health and Environment (BIOR) Fish Resources Research Department Tel Mob Inland Waters Division 8 Daugavgrivas Str Riga Latvia Simon Weltersbach Thünen-Institute of Baltic Sea Fisheries Phone simon.weltersbach@thuenen.de (part of meeting) Alter Hafen Süd Rostock Fax Germany Rebecca Whitlock Swedish University of Agricultural Sciences Phone: rebecca.whitlock@slu.se (by correspondence) Department of Aquatic Resources (SLU Aqua) Stångholmsvägen Drottningholm Sweden

341 ICES WGBAST REPORT Annex 2: Stock Annex for Salmon (Salmo salar) in subdivisions (Baltic Sea) The table below provides an overview of the WGBAST Stock Annex. Stock Annexes for other stocks are available on the ICES website Library under the Publication Type Stock Annexes. Use the search facility to find a particular Stock Annex, refining your search in the left-hand column to include the year, ecoregion, species, and acronym of the relevant ICES expert group. Stock ID Stock name Last updated Link sal Salmon (Salmo salar) in subdivisions (Baltic Sea and Gulf of Finland) May 2014 Baltic salmon

342 336 ICES WGBAST REPORT 2018 Annex 3: Recommendations The Working Group recommends following actions in order to fulfil the shortcomings in the present data and knowledge regarding the Baltic Sea salmon and sea trout to further improve the stock assessment and also, potentially support the management of Baltic salmon and sea trout. RECOMMENDATION 1. Catch estimates of recreational salmon and sea trout fisheries are uncertain, incomplete or totally missing for several countries. Studies to estimate these catches are needed. 2. Sufficient data coverage of sea trout parr densities from typical trout streams is needed from all countries. Continuing sampling for longer time-series is required for assessment. 3. There is suspected misreporting of salmon as sea trout in the Polish sea fishery. Data on proportions of sea trout and salmon in catches should be provided to the working group to facilitate more precise estimation of the rate of misreporting. Poland should provide representative catch composition data from coastal and offshore fisheries separately covering all main gears (longlines and surface gillnets). 4. Bycatch of salmon in the pelagic fishery for other species should be explored. 5. In Sweden and Finland in the coastal trapnet fishery salmon are released back to sea during part of fishing season because of quota fulfillment or fishing regulations. Amounts of these discarded salmon and their survival rate should be estimated. 6. Data on amounts and areal distribution of seal damaged salmon and other dead discards of salmon by fisheries should be collected in countries where these data are defective. 7. Sea trout index rivers should be established to fullfil assessment requirements with respect to geographical coverage and data collection needs. 8. The cause(s) of the increasing disease affecting salmon and trout in recent years needs to be investigated further, including increased cooperation between veterinarian authorities in countries with affected rivers. 9. Estimates of production areas are missing or uncertain for several salmon rivers in AU5. When reliable such estimates are available, it will be possible to apply the hierarchical smolt model that has recently been developed for southern rivers. Corresponding PSPC estimates are also needed for allowing future analytical stock assessment. 10. All countries should supply effort data per gear type from their main commercial salmon fisheries. 11. All countries need to deliver their data from the preceding calendar year until the deadlines set by WGBAST, to allow execution of stock assessment before the WG meeting. ADRESSED TO ICES Member States RCM Baltic Sea ICES Member States RCM Baltic Sea Poland National institutes (EU-MAP) RCM Baltic Sea Sweden, Finland Sweden, Denmark, Latvia, Estonia, Poland ICES Member States Sweden, Finland, Latvia, Poland, Germany ICES WGPDMO Latvia, Lithuania ICES Member States ICES Member States

343 ICES WGBAST REPORT Annex 4: Smolts and PSPC per Assessment Unit for HELCOM salmon indicator Table A4. The medians of total smolt production and potential smolt production capacity (PSPC) within assessment units 1 6 (AU1 2 combined) for the HELCOM salmon core indicator. In AU 1 4 estimates are based on the analytical assessment whereas in AU 5 AU 6 smolt production estimates are derived from parr densities with country specific unharmonised mortality parameter values and PSPS estimates are based on the expert evaluation. AU1-2 Year Smolts Q Q PSPC Q Q AU3 AU4 AU5 AU6 Smolts Q Q PSPC Q Q Smolts Q Q PSPC Q Q Smolts PSPC Smolts PSPC

344 338 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 Annex 5: Technical minutes from the Review Group on Baltic Salmon RGSalmon April Reviewer: Carrie Holt, Canada Working Group: WGBAST Overall The authors have completed a significant amount of work between last year s and this year s assessments, implementing revisions to analyses recommended at the Benchmarks Methods Meeting (January February 2017). The recommendations have mostly been adhered to, with a few minor changes identified in the text. The interpretation of results is generally justified, though I have highlighted a few areas where interpretation could be clarified or revised. As suggested in the report, it will be valuable to update the Report Annex including changes to methods from the Benchmark Meeting and others that have occurred prior and subsequent to the meeting (e.g. new time-series for trolling). In addition, the Annex should document justification for those changes, and where possible, assess impacts of changes to assessed status. It becomes increasing difficult to review assessments where descriptions of methods are scattered among numerous documents. In general for Baltic salmon, status of wild populations in AU 1 3 have shown increases, those in AU 4 and 5 have shown declines (especially Pärnu) or remained stable, and those in AU6 are highly uncertain because of large interannual variability of status (but small recent increases in 2 /3 wild populations). ToR: Review the list of Baltic Sea wild salmon rivers in Annex I of the EC Multiannual plan on Baltic Sea salmon. Review existing rivers in Annex I and identify if any other existing rivers with self-sustaining wild salmon populations with no or limited release of reared salmon not currently included on the list. The report identifies two potential salmon rivers in AU2 and 3 that were reclassified as wild after the 2011 assessment. The report further states that none of the other 22 potential rivers are close to achieving criteria for wild status, however, data to confirm this are not provided (only lists of rivers and restoration efforts in Table ). The report also identifies one river currently classified as mixed, Nemunas (AU 5, Lithuania), that could possibly be re-classified as wild. Further evaluation of available data is required before reclassifying this river. Also, the report suggests increased proportion of reared (vs wild) salmon in one wild river, Pärnu (AU5 Estonia) should be evaluated, possibly resulting in reclassification of this river as mixed. Increases in releases have occurred in recent years in response to depleted status. Although the suggestions to evaluate Nemunas and Pärnu are reasonable, a thorough review of additional rivers in the EC Multiannual Plan is not possible without river-specific proportions of reared and wild smolt production. For Sea Trout, status is stable in most regions especially for northern populations. Some declines are occurring in southern regions (within SD 27). However, large uncertainties in the data and assessment approaches, and conflicting patterns between types of data (0+ density estimatesvs.mark recapture studies in coastal waters) suggest caution in management approaches and the need for continuing conservation measures.

345 ICES WGBAST REPORT The comments below pertain to both methods/analysis and interpretation of results. I have highlighted in yellow those points that pertain to interpretation of results, which I will emphasize at the review meeting. Section 2. Salmon Fisheries Do regulations for recreational trolling prohibit barbs on hooks? This will affect post-release mortality rates. Because no estimates of post-release mortality from trolling are available for Atlantic or Baltic Salmon, estimate from Pacific salmon are used. However, several of the studies cited for Pacific salmon are quite dated (e.g. 1959, 1972 ). Historically, barbed hooks were allowed for Pacific salmon trolling, which would overestimate post-release mortality, if barbed hooks are currently prohibited in the recreational fishery for Baltic salmon (as they currently are for Pacific salmon) Clear documentation and justification for trolling catch estimates would help facilitate consistency in application of this expert driven approach among counties and over time. In particular, Swedish recreational fishery presumably represents a relatively large proportion of the total recreational fishery (Sweden represents a large proportion of total reported catch Table 2.2.1), yet there are very few data on those catch estimates. An upcoming Swedish study in 2019 may help inform these expert-derived time-series of troll fisheries for that country, and the study may also benefit from documentation from ICES (updated Annex) on how these are derived in other countries to facilitate consistencies in analyses were possible The text states that no official statistics on bycatches are available for Russia, but it also states that no salmon were caught in offshore and coastal fisheries. These statements are inconsistent, since salmon could be caught as bycatch but not recorded/available. In Table 2.2.3, how is sea catch defined (compared with coastal and river catch), and how does it differ from offshore catch? (Only Poland and Denmark currently have offshore fisheries in Table 2.4.3, yet numerous countries have sea catch) Clear rationale for changes in coefficient factors from experts on discarding over time would be valuable. The changes in 2013 in this coefficient are due in part to updated expert opinions; exact reasons for these changes should be documented (in an Annex) to ensure consistency across experts/analysts with subsequent assessment for a single country, and among countries. For example, in Denmark the proportion of seal-damaged fish reported by harvesters is 40 50%, but data based on on-board inspectors are much lower (4%). Which types of data do experts consider and why? Given the relatively large proportion of reportedly salmon-damaged fish (e.g. in Finland, Latvia and Poland), it may be valuable to include time-series of seal abundances. The text describes increases in seal abundances, but have they increased at the same rate, timing, and location as reported increases in seal-damaged catch? This additional information might increase credibility in seal-damaged catch time-series (if time-series corroborate each other). I suggest that this issue be emphasized in Section 1.3 on Ecosystem Considerations given its significant impact in Gulf of Finland. Currently, that section simply states: Discarding of seal-damaged salmon occurs mainly in the coastal trapnet and gillnet fishery, but also in the offshore longline fishery. Some specimens of seals drown in trapnets. Seal-safe trapnets have been developed, which has lately decreased seal damages, discarding and seal deaths in gear.

346 340 ICES WGBAST REPORT 2018ICES WGBAST REPORT Are finclips used to assess proportion of reared salmon spawning in natural rivers? If monitoring wild rivers is key, then monitoring the proportion of wildoriginvs.reared fish on spawning grounds is critical, but this is only possible if smolts can be differentiated, such as with finclips. This is especially important given difficulties differentiating wild and reared fish genetically in some cases The text states that the catch of undersized salmon in longline fishery may be noticeable; although data to evaluate this are not available, in part because survival rates of salmon released from hook are not known. Might survival rates of releases in longline fishery be similar to survival of trolling fish released from recreational fishery? Can the same assumptions be used here? (Section 2.1.2). Section 3. River data on salmon populations This section highlights the significant and often long-term use of rearing in many rivers. It s unclear to what extent the objectives of rearing are for conservation or to create fishing opportunities. If conservation is the goal, caution in the reliance on long-term rearing is warranted. As inferred in the report, domestication can cause risks to mixed, potential, and wild populations, when reared fish spawn in the natural environment as they can outcompete natural spawners and are often less reproductively successful (i.e. produce fewer returning adult fish) than natural-origin fish. Indeed, Jones et al. (2008) demonstrated that for one depleted salmon stock, productivity increased after supplementation from a hatchery was stopped, allowing further recovery. Recent work by the US Hatchery Science Reform Group, HSRG (a decade long-process involving 100s of analysts to review, model, and develop recommendations for hatcheries), suggested developing clear, specific measureable goals for conservation-based hatchery/rearing programmes, with the goal of reducing rearing/hatcheries as habitat is recolonized (i.e. using rearing as short-term measure only). When supplementation is required (e.g. Pärnu), care must be taken to minimize genetic impacts from domestication. Also, the thresholds specified in the Annex differentiating wild, mixed, and reared populations could perhaps be reconsidered. Recent work in Canada on Chinook Salmon (Withler et al., in press) has suggested that the degree of impact of reared fish on neighbouring wild populations is related to the proportion of out-of-basin strays to natural local-origin spawners. Modelling results indicate that fitness in the wild population may decline even when the proportion of out-of-basin strays is very low (<5%). Recent progress in our understanding fitness impacts (genetic and epigenetic effects, etc.) from rearing on natural spawning may warrant revisiting use of rearing for conservation purposes and the classification systems for wild, mixed, and reared fish. Also, is the management goal to recover mixed populations to wild status, or only potential rivers to wild status? 3.1. If one goal for wild rivers is to maintain wild status, I suggest including metrics of the impacts of rearing on these populations in the assessment (e.g. proportion of rearedvs.natural-origin fish in rivers, or Proportionate Natural Influence, PNI, as used by US and Canada). This would require marking and monitoring of reared fish in rivers Table is a useful way of examining restoration measures for potential rivers across Assessment Units. Because long-term rearing practices may have negative genetic impacts on the naturally spawning fish (and possibly likelihood of recovering to wild status), I suggest including length of time that rearing has occurred in the table.

347 ICES WGBAST REPORT As described in the text, restoration measures should address the numerous factors causing depleted status. However, this table highlights that this may not always be the case in practice. For example, in ten potential rivers, rearing is accompanied with only limited reduction in fishing pressure, failing to address habitat/pollution issues, possibly limiting recovery potential. Also, in the column on restoration measure, l and m are not defined Are there reports of disease in rearing facilities, in particular UDN-like diseases? The text states that disease has been documented in the returns of both wild rivers (Mörrumån) and reared (e.g. Indalsälven). Are there estimates of the proportion of diseased fish that die, directly and indirectly from the disease? 3.5. In AU5, the text suggests that implementation measures have stabilized the salmon populations in Lithuansian rivers, and the production is increasing very slowly. However Table shows that density of >0+ parr was 0 for 2/4 rivers in AU5 for 2017 (Mera and Žeimena), and 0 for parr of all ages in 1 river (Mera). I suggest specifying that production may be increasing for one river in particular (Neris), not in the others. For wild rivers of depleted status, a similar table as in (for potential rivers) may be of value to document ongoing measures to rebuilding those stocks. Section 4. Reference points and assessment of salmon New stock recruitment parameters Numerous changes to the Full Life-History Model (FLHM) have been implemented since the last successful run of the model. One of those changes was to include priors on maximum survival rates instead of eggsper-recruit (EPR), as discussed at the 2017 Benchmarks Meeting. Since the Benchmark Meeting, the alpha prior was subsequently updated to resemble that of Pulkkinen and Mäntyniemi (2012). Were these updated to match the posterior predictive distribution for an unknown stock in Pulkkinen and Mäntyniemi (2012)? Based on the peak egg survival of that distribution at ~25, the 2017 priors look like they match better than the 2018 priors. It s not clear what other transformations have been made to derive the new prior. More explanation would be helpful. Ensuring the proper prior for this parameter is quite important, as it has a significant impact on assessments against PSPC and stock projections. Any changes should be well justified and clearly documented. Figure Shows prior and posteriors on R0, but priors were implemented on K instead of R0 in the new model formulation, according to the 2017 Benchmarks Report (and also mentioned in subsection Effect of change son results and status evaluations p. 4). I assume these priors were transformed for the purposes of this plot, although priors on K were used? Effects of changes on results and status evaluations. Given the numerous changes to the model formulation and platform (WinBUGS to JAGS), and the propensity for unintended bugs to crop up (e.g. as shown historically in correction of errors section), a more thorough evaluation of the revised FLHM model would be of value. Quantifying the effects of individual changes in the model on estimated stock status is difficult due to long computing time (i.e. model cannot be re-run for each individual proposed change). However, as suggested at the Benchmarks meeting, an alternative approach is to run the model under a set of assumptions to generate predicted model outputs, and then re-run it using those model outputs as inputs. The idea of this simulation self-test is to evaluate if any unintended biases crop up in parameter estimates.

348 342 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 This type of analysis may not fit within the annual report, but could be included in a future benchmark meeting Several parameters in the FLHM did not converge, notably the alpha parameter for the stock recruitment model for three rivers (Torne, Simojoki, and Vindelälven). What is the impact on assessment results? Table shows that the posterior of alpha parameter for Ume/Vindelälven is extremely low (lowest among all rivers), and extremely high for Simojoki (highest among all rivers), thereby projecting production from those stocks to be very high and low, respectively (alpha=1/max egg survival). Results for these rivers should be interpreted with caution (and/or the observed patterns should be more fully explained). Indeed, the probability of achieving 75% of PSPC varies over time significantly (jumping frequently between 20% and 80%) for these two populations, likely due to the large uncertainty in alpha parameter (Figure ). Figure b. The large number of assumptions that are required for Piteälven are quite evident in the scatter of the poster distribution. The results for this river should also be interpreted with caution; small changes in those assumptions could have large impacts on the shape of the curve, especially at low abundances. Figure How is the trend in increasing proportion wild (vs reared fish) in the offshore catch interpreted? Is this due to reduced adult survival of reared salmon, resulting in increased pressure on salmon from wild rivers? (As suggested for Estonian coastal catches, page 12, Section and Figure ) The small increase in smolt production in 2017 in Pärnu is shown in 2017 in Table , but this increase is not visible in Figure If this stock does show small signs of improvement (page 10 bottom, last paragraph of Section 4.2.3), this should be visible in the time-trend (but appears to be at 0% of PSPC in 2017) The text states that the status of Estonian wild and mixed stocks [in AU 6] has improved in the past few years (Figures and ). However, the trends in mixed stocks show a steep drop in the last ~3 years. I suggest rewording to status of Estonian wild and mixed stocks has shown improvements since 2005, followed by recent declines for mixed stocks since 2015 OR followed by relatively low smolt production for mixed stocks I suggest removing (or rewording) This indicates that the total harvest rate in the sea fisheries in combination with established closed fishing area at the river mouth areas, can be considered sustainable, and that it may allow further recovery. All of the mixed-stock rivers in Estonia AU6 are below 50% PSPC (Figure ), and could be considered depleted If countries wish to target fishing mortality on salmon from particular rivers that are healthy, and avoid salmon from those that are depleted, a more through use of genitic mixed-stock analysis (MSA) data may be warranted, in order to understand which fish are being caught when and where. Although including those data quantitatively into the FLHM is listed on the work plan, I suggest moving to a higher priority if management intends to be more river-specific in future Is there evidence of compensation from M74 mortality, by reduced density-dependent mortality? Alternatively, could M74 (or other diseases) deplete components of the population in specific habitats, resulting in short-term relatively high densitydependence until those fish recolonize the newly available habitat? Without evidence either way, I suggest de-emphasizing the role of density-dependence reducing impacts of M74.

349 ICES WGBAST REPORT (Relates to comment on Section above.) Although wild stocks in AU6 have shown increases in recent years, the same is not true for mixed stocks. For the mixed rivers in AU6, and wild rivers in AU5, numerous additional factors are likely impacting recovery beyond fishing mortality (e.g. habitat, pollution, etc.). Section 5. Sea Trout I agree with the recommendation that more complex assessment methods which consider multiple sources of available data (like those for Baltic salmon) should be explored if possible. In the event that this is not possible (e.g. due to limited resources and/or data), I recommend that current production potential estimates be revised with updated data. Results show that recruitment status is >100% of production potential in many rivers, which seems implausible. In addition, for Lithuanian Rivers, the long distance for river migration was cited as a reason for poor status, but this variable (distance to sea) could be included in the regression model predicting production potential (Section 5.3) Catches include reported catches only. To what extent might unreporting, misreporting, and discarding of undersized or seal-damaged fish affect catch estimates? Table 5.4. Shows factors influencing status, presumably developed from expert opinion instead of quantitative analyses. Instead of individual factors, it s likely that the cumulative impacts drive status and that factors interact in often unpredictable ways (e.g. synergistically or antagonistically) The trend in recruitment status is based on correlation coefficients over the last five years of recruitment status. However, uncertainty in those coefficients is not provided, making them difficult to interpret. I suggest including credible intervals (if Bayesian) or statistical significance, that reflect the large interannual variability of recruitment trends. Although the correlation coefficients are positive for SD 30 and 31 indicating recovery, other data suggest caution for these stocks. For example, survival rates from tagging studies have declined over time to low levels for Finnish populations (Figure ), and a Bayesian mark recapture model of two Finnish populations suggests high fishing mortality has resulted in poor status (5.4.1). These additional pieces of information are not considered in the current conclusions.

350 344 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 Appendix 1: Results of an extended MCMC sampling Background As stated in the WG report (Section 4), by the time of the working group meeting MCMC sampling from the assessment model had not reached the level needed to properly approximate all the posterior distributions. The MCMC sample available for the WG-meeting contained two chains with burn-in periods of , after which next iterations (thinned by 150 to get a sample of 1000 from both chains) were used as posterior results. Poor mixing of the two chains and high level of autocorrelation indicated that some of the posteriors could not be approximated reliably from this sample. After the meeting an extended model was run until samples from both chains were obtained. From this sample the first iterations were regarded as burn-in period, and the remaining iterations were thinned to get a sample for the approximation of posterior distributions. In addition, an error in the code was located during the meeting and due to this error the last two years (2019 and 2020 in this year s assessment) of smolt priors (derived mostly from the river model) had been excluded from the model run. The input data used in the extended model run were therefore completed by correcting the piece of the model code, which reads in river-specific smolt priors. From Figure A1 (example showing trace plots for annual estimates of post-smolt survival of wild salmon) it is evident that posterior distributions were improved during the extended model run following the WG-meeting. Applying the Gelman-Rubin (G- R) diagnostics to the MCMC chains from the extended run supported convergence to the posterior distribution (>99% of G-R point estimates <=1.20). The maximum G-R estimate (1.48) was observed for the Beverton Holt alpha parameter in Torneälven/Tornionjoki. Updated model results The longer MCMC sampling resulted in some minor changes to the level of fishing mortality, the largest changes being an overall increase in the harvest rates of reared salmon (not shown). The estimates of the homing rates of grilse in improved considerably and became more accurate as a result of the extended MCMC sampling, especially for reared salmon (Figure A2). Minor changes were visible also in the homing rates of 2SW salmon, but otherwise no noticeable changes occurred in homing rates. Among the largest changes are the estimates of post-smolt survival (Mps) in a few years around The huge year-to-year variation ( ) seen in the results of the shorter model run decreased in the new results both among wild and reared postsmolts (Figure A3). The new results are more plausible considering that independent observations (e.g. sea-age structure in catch) support moderate (instead of drastic) variation in the smolt year-class strength during these years. The estimate of adult natural mortality rate of wild salmon decreased by about 2%, whereas adult mortality rate of reared salmon increased by about 1%. In the shorter model run, posterior probabilities for wild vs. reared proportions of salmon among offshore catches were very poorly converged for the years ; these estimates became much more accurate in the extended model run and now follow closely observations from scale analyses of catch samples (Figure A4).

351 ICES WGBAST REPORT Some posteriors of PSPC s (mostly those of Tornionjoki/Torneälven, Kalixälven and Ume/Vindelälven) have become poorly estimated in the last years assessments due to high autocorrelation (e.g. ICES, 2017). This is the case also in the current assessment. The longer MCMC sampling, however, was very useful for improving also these estimates. The long model run resulted in an increase of the PSPC estimate for Tornionjoki/Torneälven of about smolts (approximately 10% increase), while the estimate for Kalixälven decreased by about smolts (approximately 15%). A comparison of PSPC posteriors between the short and long model run can be seen in Figure A5. Generally the river-specific spawner estimates indicate a slightly more positive historic stock development according to the long model run, compared to the results of the short model run (results not shown). Only minor changes in river-specific smolt abundance estimates prior to 2019 smolt year were observed. However, the new estimates of smolt abundance in Kalixälven are somewhat lower overall. This is probably due to the lower PSPC estimate of Kalixälven in the longer model run which supresses the overall abundance of the salmon stock (smolts and spawners) from the period when the stock has been close to its PSPC (i.e. since the turn of the millennium). The smolt abundance estimates for the years have generally become more precise and the changes in the estimates are river specific, which apparently is a consequence of utilizing smolt priors of those years in the longer model run. Figure A6 (revised Figure ) shows time-series of smolt production on an AU-level in relation to the 75% objective. The same AU and corresponding river-specific estimates are also presented in Table A1 (revised Table ). Current status of wild salmon stocks was updated to some extent following the extended model run (Table A2; revised Table ). The status of Sävarån decreased and it is uncertain whether the river stock has reached even the 50% objective. Also Tornionjoki decreased somewhat in status, and according to results from the longer model run it is likely that the river stock has reached the 75% objective (previously it was very likely). For the other rivers only minor updates were observed and no changes in classification of status. The pre-fishery abundance (PFA) did not update much in the longer model run (Figure A7). Some minor changes can be seen in recent years but these updates have no significant effects on stock development and catches in the different fishing scenarios evaluated in stock projection analyses (see below). Updated stock projections The updates to certain model parameters from the extended run described above did not result in any significant change in overall perception of future stock status and development, as evaluated using projections for different catch scenarios. In Table A3 (revised Table ) estimates are presented of commercial and recreational removals, corresponding fishing mortalities (F) and expected numbers of spawners in 2019 for the six catch scenarios evaluated. In line with the small update of PFA in 2019 from the extended model run (Figure A7) the updates to this table are small. Table A4 (revised Table ) compares the probabilities of reaching 75% target around the years , which are approximately one full generation ahead from now. The largest change in expected stock status can be seen for Sävarån, having a lower probability than before of reaching the 75% target (e.g. 45% probability under Scenario 1 compared to 54% previously).

352 346 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 Figures A8a d (revised Figures a d) present river-specific annual probabilities to meet 75% of the PSPC under each scenario. The updated stock projections based on the extended model run are minor and similar to as for the shorter run; stocks show either stable or increased status over time, with Scenario 6 ( zero fishing ) deviating most clearly from the other five scenarios that all include various levels of fishing mortality. Corresponding longer term predictions in river-specific smolt and spawner abundances for three of the scenarios (1=removal which corresponds to ICES advice for 2018; 4=harvest rule of F0.1 for commercial catch; and 6=zero fishing) are shown in Figures A9a d (revised Figures a d). As before, updates from the extended model run are minor with the two most extreme scenarios included (4 and 6) illustrating the predicted effects of contrasting amounts of fishing. Reference ICES Report of the Baltic Salmon and Trout Assessment Working Group (WGBAST), 27 March 4 April 2017, Gdańsk, Poland. ICES CM 2017/ACOM: pp.

353 ICES WGBAST REPORT Table A1 (revised Table ). Wild smolt production in Baltic rivers with natural reproduction of salmon grouped by assessment units: posterior probability estimates derived from the Full Life-History Model (FLHM) for the AU 1 4 rivers (except Testeboån which is currently not included in the FLHM), and estimates derived by other means (inferred from parr densities, smolt trapping, etc.) for the rest of the rivers. Median estimates (x 1000) of smolts with the associated uncertainty (90% Probability interval) are shown. Also, the riverspecific reproductive areas and the potential smolt production capacities (PSPCs) are shown as medians and 90% PIs. Reprod. area (ha, median) Potential (*1000) Method of Pred Pred Pred estimation Pot. Pres. prod. prod. Assessment unit, subdivision, country Category Gulf of Bothnia, Sub-div : Finland Simojoki wild % PI Finland/Sweden Tornionjoki;Torneälven wild % PI Sweden Kalixälven wild % PI Råneälven wild % PI Assessment unit 1, total % PI Piteälven wild % PI ' Åbyälven wild % PI ' Byskeälven wild % PI Rickleån wild % PI Sävarån wild % PI Ume/Vindelälven wild % PI Öreälven wild % PI Lögdeälven wild % PI Kågeälven wild % PI Assessment unit 2, total % PI Ljungan wild % PI Testeboån wild % PI na Assessment unit 3, total % PI Total Gulf of B., Sub-divs % PI

354 348 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 Table A1 (revised Table ). Cont. Method of Pred Pred Pred estimation Assessment unit, subdivision, Reprod. area Potential Pot. Pres. country Category (ha, median) (*1000) prod. prod. Sweden Emån wild % PI Mörrumsån wild % PI Assessment unit 4, total % PI Estonia Pärnu mixed , 4 Latvia Salaca wild Vitrupe wild Peterupe wild , 5 Gauja mixed , 5 Daugava*** mixed , 6 Irbe wild Venta mixed , 5 Saka wild Uzava wild Barta wild Lithuania Nemunas river basin wild , 4 Assessment unit 5, total Total Main B., Sub-divs (AU's 4-5) Method of Pred Pred Pred estimation Assessment unit, subdivision, Reprod. area Potential Pot. Pres. country Category (ha, median) (*1000) prod. prod. Finland: Kymijoki mixed 15 1) +60 2) 20 1) +80 2) Russia: Neva mixed Luga mixed SE Estonia: Purtse mixed Kunda wild 2 2 (4) Selja mixed Loobu mixed Pirita mixed , 3 90% PI Vasalemma wild Keila wild 4 5 (12) Valgejõgi mixed Jägala mixed Vääna mixed Assessment unit 6, total Gulf of B.+Main B.+ Gulf of F., Sub-divs % PI = Low and uncertain production (not added Methods of estimating production Present production 7. Estimate inferred from stocking of reared fish in the river. into sub-totals or totals) Potential production 1. Bayesian full life history model (section 6.3.9) 8. Salmon catch, exploitation and survival estimate. ++ = Same method over time series; only the extension 1. Bayesian stock-recruit analysis 2. Sampling of smolts and estimate of total smolt run size. backwards preliminary 2. Accessible linear stream length and production capacity per area. 3. Estimate of smolt run from parr production by relation developed in the same river. Reared smolts *** = Tributaries 3. Expert opinion with associated uncertainty 4. Estimate of smolt run from parr production by relation developed in another river. *=Release river not specified **** = Only Latvian part, Lithuanian part of the river needs to be 4) Below the lovest dams 5. Inference of smolt production from data derived from similar rivers in the region. added 5) Above the lowest dams 6. Count of spawners. n/a No data available.

355 ICES WGBAST REPORT Table A2 (revised Table ). Overview of the status of the Gulf of Bothnia and Main Basin wild stocks (AU1-4) in terms of their probability to reach 50 and 75% of the smolt production capacity in Stocks are considered very likely to have reached this objective in case the probability is higher than 90%. They are likely to have reached the objective if the probability is between 70 and 90%, uncertain when the probability is between 30 and 70 % and unlikely if the probability is less than 30%. For all stocks except Testeboån, the results are based on the assessment model, whilst the categorization of Testeboån is based on expert judgments and therefore lacks precise probabilities (column 'Prob'). The extended model run resulted in changed status classification for Sävarån and Tornionjoki (old estimates in grey) whereas the other stocks only showed minor changes in probabilities to meet the objectives. Unit 1 Unit 2 Unit 3 Unit 4 Prob to reach 50% Prob to reach 75% Previous values Stock Category Prob V.likely Likely Uncert. Unlikely Prob V.likely Likely Uncert. Unlikely P50% P75% Tornionjoki wild 1.00 X 0.88 X X Simojoki wild 0.96 X 0.67 X Kalixälven wild 0.98 X 0.83 X Råneälven wild 0.95 X 0.72 X Piteälven wild 0.82 X 0.12 X Åbyälven wild 0.96 X 0.74 X Byskeälven wild 0.99 X 0.82 X Kågeälven wild 0.73 X 0.35 X Rickleån wild 0.45 X 0.11 X Sävarån wild 0.67 X X 0.33 X Ume/Vindelälven wild 1.00 X 0.89 X Öreälven wild 0.39 X 0.15 X Lögdeälven wild 0.27 X 0.12 X Ljungan wild 0.86 X 0.64 X Testeboån *) wild X X n.a. n.a. Emån wild 0.47 X 0.18 X Mörrumsån wild 0.99 X 0.79 X *) Preliminary evaluation, see section

356 350 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 Table A3 (revised Table ). Estimates (in thousands of fish) of total removal in the commercial fishery at sea by scenario, and the corresponding reported commercial catch in total and divided between these fisheries in Calculations about how the total catch is divided between reported commercial catch and discards/unreporting/misreporting are based on the situation prevailing in 2017 (see text). The table shows also the predicted total number of spawners in 2019 (in thousands). All values refer to medians unless stated otherwise. Commercial catches (thousands of fish) at sea in SD in 2019 Wanted Catch Unwanted Catch Total inst. F of Reported (Dead+Alive) commercial comm. Scenario catch at sea Catch (% of 2018 EU TAC) Undersized Seal damaged Wanted Catch Unreported Wanted Catch Misreported % % % % % % Scenario Total sea catch (comm. + recr.) 2019 inst. F of total catch at sea Recreational catch at sea 2019 River catch 2019 Spawners

357 ICES WGBAST REPORT Table A4 (revised Table ). River-specific probabilities in different scenarios to meet 75% of PSPC in 2023/2024 (depending on the assessment unit) Probabilities higher than 70% are presented in green. Probability to meet 75% of PSPC River Year of Scenario comparison Tornionjoki Simojoki Kalixälven Råneälven Piteälven Åbyälven Byskeälven Rickleån Sävarån Ume/Vindelälven Öreälven Lögdeälven Ljungan Mörrumsån Emån Kågeälven

358 352 ICES WGBAST REPORT 2018ICES WGBAST REPORT 2018 Figure A1. Traces of MCMC samples (two parallel chains, in red and black) of posterior estimates of annual wild salmon post-smolt survival (Mps) from the extended model run. Note in particular smolt years 2009 and 2011 that in the previous (shorter) run had not converged (cf. Figure A3).

359 ICES WGBAST REPORT Figure A2. Homing rates of reared salmon of different sea age. The largest updates can be found for grilse in years Black boxes=extended model run; grey boxes=short model run. Figure A3. Estimates of post-smolt survival for reared and wild salmon, and the ratio between them. The extended model run resulted in less variation in years Black boxes=extended model run; grey boxes=short model run.