4 Celtic Sea and Division VIIj Herring

Transcription

1 ICESHAWG Report Celtic Sea and Division VIIj Herring 4.1 The Fishery The herring fisheries to the south of Ireland in the Celtic Sea and in Division VIIj exploit autumn and winter spawning components. For the purpose of stock assessment and management, these areas have been combined since The management unit covers all of Divisions VIIg,h,j and k and the southern part of Division VIIa (Figure 1.5.1) Advice and management applicable to The TAC in 25 was 13 t, and in 26 is In 25, ACFM considered the current level of SSB to be uncertain, but maybe below B pa and possibly even below B lim. Though there was no short term forecast, ACFM advised that, given the risk to the stock indicated by the poor recruitment of the 21 year class, exploitation should be significantly reduced in 26. ACFM suggested that such a reduction should result in catches of 6 7 t corresponding to 6% of the average catch in In addition, ACFM recommended supplementary measures such as the re-closure of the eastern section of the Celtic Sea (Spawning Box C), see Figure a.. ICES considered that this would be an effective measure to reduce exploitation as most of the herring catches have been taken in this area since the voluntary closure was removed in December 23. Ad hoc requests In October 25, ICES was asked by Ireland to answer the following requests on this stock: 1 ) Comment on the benefit to the stock of an indefinite closure of Spawning Box C in Division VIIa as an alternative to reduction of the advised catches by 4% in ) Since this stock is characterised by variable recruitment, to comment on whether the advised reduction of 4% in catches for 26 was too severe, given that it is driven by recent low recruitments and bearing in mind that similarly low recruitments have been recorded in the past, most recently in ICES response to point one was that the box closure was intended as a supplementary measure intended to support the main advice to reduce catch in 26. The closure of Box C is not an alternative to the reduction in TAC. ICES response to point 2 was that in 1991 the SSB was larger (>B pa ) than in 25. Although current SSB is uncertain, it seems low, below B pa and maybe even below B lim. Hence, the more conservative advice was based on the current perception of SSB being low. The TAC is set by calendar year, whilst the assessment of the stock is conducted on a seasonal basis (1 st April to 31 st March). In the past three seasons, a fishery was permitted during the summer months. In 23 it opened in July, and in subsequent years in August. This was to allow vessels to target fish outside the spawning seasons when the fish are of better quality, marketability and constituting less fish per tonne landed. Spawning Box Closures The spawning box closures implemented under EU legislation continued. In the 25/26 season, Spawning Box C was closed in the second two weeks of January (Fig a). In 26/27, Box A will be closed. However, Spawning Box C was not closed entirely in 26.

2 296 ICESHAWG Report 26 In addition to these, Box A was voluntarily closed in the recent seasons, being finally reopened in December 23. This initiative was put in place by the Irish Celtic Sea Herring Management Advisory Committee to afford extra protection to first time spawners. Areas mentioned in the text are shown in Figure b. Management Plan The Irish Celtic Sea Herring Management Advisory Committee was established to manage the Irish fishery for this herring stock, having been constituted in law in 25. This committee, therefore, has responsibility for management of the entire fishery for this stock at present. The committee has the following objectives: To build the stock to a level whereby it can sustain annual catches of around 2, t. In the event of the stock falling below the level at which these catches can be sustained the Committee will take appropriate rebuilding measures. To introduce measures to prevent landings of small and juvenile herring including closed areas, and or appropriate time closures. To ensure that all landings of herring should contain at least 5% of individual fish above 23 cm. To maintain and if necessary expand, the spawning box closures in time and area. To ensure that adequate scientific resources are available to assess the state of the stock. To participate in the collection of data and to play an active part in the stock assessment procedure. Local management of the fishery In 25 the Irish quota was t and in 26, is t. The Irish quota is managed by allocating individual quotas to vessels on a weekly basis. Participation in the fishery is restricted to licensed vessels. The licensing requirements have been changed. Previously, vessels had to participate in the fishery each year to maintain their licence. Now this requirement has been lifted. This has been one of the contributing factors to the reduction in number of vessels participating in the fishery in recent seasons. The efficiency of these vessels has improved, however. Fishing is restricted to the period Monday to Friday each week, and vessels must apply a week in advance before they are allowed to fish in the following week The fishery in 24/25 The landings in this fishery since 1958 are shown in Figure Prices for Celtic Sea herring were better in the current season. In 25/26, 34 vessels participated in the fishery, as follows: 12 RSW trawlers of 23-4m, using pair trawls 6 dry hold trawlers of 2-24m, using pair trawls 16 dry hold trawlers < 2m. Most vessels under 2 m reported landings of less than 1 t for the assessment period while a number of RSW vessels reported landings greater than 1 t. In addition small incidental landings, typically less than a tonne were reported by a number of other vessels. Gillnets are a minor component of the fishery in recent years. The fishing season is divided into three periods. In quarter 3, 25 about 3 t were landed. These fish were targeted in offshore feeding aggregations to the north of the Labadie Bank

3 ICESHAWG Report and around the Kinsale Gas Field. This fishery opened on the 7 th August and closed on 1 st September. These catches consisted of about 7 fish per tonne. These catches were taken by pair trawl vessels using RSW or modified RSW fish storage. Vessels without RSW storage cannot participate in the summer fishery. In quarter 4, 25 about 3 t were landed. The fishery opened on the 13 th November and closed on the 2 nd December 26. Most of the catch came from the traditional fishing grounds in Division VIIaS. About 2 t were taken from within Waterford Estuary, using single trawls by small inshore vessels. Small catches were taken from VIIj in quarter 4 only. In quarter 1, 26, about 3 5 t were landed. The fishery was opened in the beginning of January 26 and was closed on the 2 th January. From the 15 th January, Spawning Box C was closed, and effort was diverted to the inshore grounds of VIIg, around Ballycotton and off the Daunt Rock (Figure b). Again, about 2 t were taken from within Waterford Estuary, using single trawls by small inshore vessels. These small vessels also fished outside Waterford Estuary The catches in 25/26 The estimated national catches from for the combined areas by year and by season (1 April 31 March) are given in Table and Table respectively. The total catches for the fishery over the longer period from 1958 to 24 are shown in Figure The catch, taken during the 25/26 season was under 1 t having declined from almost 13 t during the previous season. There are no estimates of discards for this fishery. Anecdotal reports from fishermen suggest that discarding is not a feature of this fishery at present. 4.2 Biological composition of the catch Catches in numbers-at-age Catch numbers at age are available for the period 1958/1959 to 24/25. These data include discards, when estimates were produced (until 1997). In 25/26, the 1-ringers were a higher proportion of the catch than at any season since 1982/1983 (Figure and Table ). The absolute numbers of 1-ringers were among the highest in recent years, along with those in 1999/2 and 21/22. The proportion of 2-ringers (38%) was about average for recent seasons. The 3-ringers were very low (7%) confirming the weakness of the 2-ringers last season. It is important to note that the weakness of 3-ringers tends to inflate the proportions of the other important age groups in the catches. The overall proportions at age were largely similar in the 4 th and 1 st quarter in VIIg and VIIaS. However, the catches in VIIaS (Waterford Harbour) in the 1 st quarter were very different, being over 7% 1-ringer. This large proportion of 1-ringers contributed to their overall high contribution in the catches. In VIIj, the proportion at age did not differ from elsewhere, in contrast to last season Movements of fish Juveniles It is known that fish spawned in the Celtic Sea are present as juveniles in the Irish Sea along with native fish, especially the western part (Brophy and Danilowicz, 22). Their results show that fish spawned in the eastern Celtic Sea are present as juveniles in the Irish Sea, where fish of local origin are also found. The fish of Celtic Sea origin then return as 1- and 2- ringers (Molloy et al. 1993).

4 298 ICESHAWG Report 26 Small fish (1-ringer) predominated in quarter 1, 26 though not in quarter 4, 25, in Waterford Estuary. As these fish were smaller, it seems likely that these fish migrated to the Celtic Sea from the Irish Sea. Further work, redrawing historic larval survey data from the 198s shows that autumn and winter spawning was taking place in the eastern Celtic Sea (Figure ). Thus juveniles of Celtic Sea origin present in the Irish Sea cannot be distinguished on the basis of spawner type alone. Therefore further work is required to allow for splitting Irish and Celtic Sea origin fish. Adults The quarter 3 fishery targets offshore feeding aggregations of herring in VIIg. It is not known where these fish spawn. However a combination of positional data from the commercial fishery (August) and acoustic surveys (September to December) in this area displays a seasonally progressive movement towards the traditional spawning grounds inshore (Figure ). Spatial data from all groundfish surveys using the Portuguese high headline net and the GOV trawl were presented by WGFISHECO (ICES, 26) show that herring display a continuous distribution throughout the Celtic Sea and Division VIIf. However abundance is very low in the middle area between VIIf and VIIg. However there appears to be a hiatus between VIIe and VIId, though there is little survey effort in that area. It seems possible that the summer feeding aggregations are a mixture of VIIg, VIIaS, and VIIe fish, though information is scarce Quality of catch and biological data Since 1997 there has been a major increase in the monitoring of landings from this fishery and the management measures were again tightly enforced throughout the season. There is no information on misreporting in this fishery in recent years, but it is thought to have decreased. Biological sampling of the catches throughout the region was comprehensive, except in VIIj. The spasmodic nature of the fishery in that area makes sample acquisition difficult, (Table ). Under the Data Collection Programme the sampling of this stock is well above that required by the Minimum Programme (Section 1.5). 4.3 Fishery Independent Information Acoustic Surveys Acoustic surveys of this stock have been carried out since 199, with the exception of Up until 1996, two acoustic surveys were carried out annually. In 1997 there was no research vessel available to do the survey. Since 1998, usually only one winter survey was conducted (Table ). The survey conducted in 25/26, was conducted on the Celtic Explorer, for the second time. Revision of acoustic time series The problems with the acoustic survey have been documented in previous reports. In order to improve the series a review was conducted and the series has been revised (Clarke et al. in prep.). This review had two main aims with these being to check the internal consistency of the previous surveys and produce a new refined series for tuning the assessment. The surveys were divided into two series, early and late, based on how far from the south coast they went. The early group, to , extended to about 15 nautical miles offshore with two surveys, one in autumn (before Christmas) and another in winter (after Christmas). This design aimed to survey spawning fish close inshore with two surveys, the results of which could be added, the two legs covering the two main spawning seasons. The

5 ICESHAWG Report off shore limits were extended in 1995 and some of these surveys had more fish off shore than close inshore. This changed the catchability, suggesting the later series should be separated from the earlier one. Consequently the years before 1995 were removed. This is not considered to be a problem because the earlier series would contribute little to the ICA anyway. Winter surveys were not always conducted in the later series, not being done in 1998 and not at all after 2 so these were dropped too. The autumn surveys did not cover the southwest Irish coast of VIIj in all years (3 years missing). In order to correct for this, the missing values were substituted with the mean of the available western bays SSB estimates, 7 8 t (11 values, range from to 16 t). Numbersat-age in these surveys were adjusted upwards by the ratio of the adjusted SSB in the SW to the south coast SSB. The abundance estimates produced are presented in Table Analysis errors were found in the surveys from 1998 onwards. The 23 biomass (SSB, 85 5 t) was re-analysed after the discovery of errors in the spreadsheets used to estimate biomass. The errors affected the calculation of the weighted mean of the integrated backscatter when positive samples had lengths shorter than the base one (here, 15 minutes) and the partitioning of the backscatter for a mixture of species. Also, no account was taken of different sampling frequencies within a 1x2 minute cell (the analysis unit). The 23 SSB came mainly from two cells that included an intensive survey in Waterford Harbour and these cells had a SSB of about 68 t, which was reduced to 7 3 t when all errors were corrected. There were some minor corrections in three other cells. The revised total biomass was 24 t and the revised spawning biomass was 22 7 t. In addition, the cell means took no account of the implicit sampling area of transects so that the biomass coming from a large sample value depended on the number of transects passing through the cell. The data were re-analysed using mean herring density by transect as the sample unit and dividing the area into strata based on transect spacing. Areas with no positive samples were excluded from the analysis (since they have zero estimates). Zigzags in bays were analysed as before. For each stratum, a mean density was obtained from the transect data (weighted by transect length) and this was multiplied by the stratum area to obtain a biomass and numbers-at-age. The overall total was the sum of the strata estimates. The same haul assignments as in the original analysis were used. At the same time, a CV was obtained based on the transect mean densities, i.e. a survey sample error. For surveys before 1998 and the western part survey in 22, a cv was estimated using; 2 log(1.3 ) n where n is the number of positive sample values (15 minute of survey track) from Definite and Probably Herring categories. This was based on the data from the autumn surveys in 1998, 2, 21, 22, and 25. Results are shown in Table Survey The acoustic survey of the 25/26 season was carried in October 25 (Doonan, presentation to HAWG). The survey track was begun at the northern boundary of VIIj, covering the SW bays in zig-zags and parallel transects. The main traditional grounds on the south Irish coast (VIIg and VIIaS) were covered using transects of 2nmi spacing, extending 67 nmi offshore (Figure a). In total the combined survey transect length was in the order of nmi. To check that the research vessel was adequate in shallower waters, another localised survey was done along parts of the south coast during October by a smaller commercial fishing

6 3 ICESHAWG Report 26 vessel. This main survey was aimed at pre-spawners as they moved inshore to spawn. The main survey area was based on an analysis of results from previous autumn surveys to make sure that it covered the likely extent of the stock at this time. The survey started at the northern boundary of VIIj, moving through it in a southerly direction, before moving eastwards through the Celtic Sea (Figure a). No substantial echo traces of adult herring were encountered in the bays and inlets of VIIj, but there were some from juveniles (Figure b). In VIIg, most herring shoals were encountered offshore, but one or two were seen inshore. Nearly all large schools were successfully fished on. The localised inshore survey also found very few herring schools indicating that the research vessel was adequate in shallower waters. It was concluded from this information that the survey estimated the stock size in these areas in 25/26. The age structured index of biomass and catch numbers from acoustic surveys in this area, is shown in Table , and the revised series in Table In 25/26 the SSB estimate was 3 t. The percentage age composition in the survey and the commercial fishery are compared in Figure The survey displayed the same age distribution as the commercial fishery, both showing a strong predominance of 2-ringers and the very low abundance of 3-ringers. However the survey picked up somewhat lower numbers of 4-ringers and older Other surveys The working group has sought alternative tuning series for this stock. In 25, an investigation of the utility of the Irish segment of the western IBTS survey was made (Johnston and Clarke, WD 25). This survey displayed strong year effects and only those surveys from 23 onwards are directly comparable because they use the same research vessel. Herring distribution in quarter 4 is very contagious, with fish being caught in large aggregations, or not at all. Consequently the signal from the survey is noisy, but when a longer time series is developed, it will at least provide qualitative information. This survey did highlight the absence of the 21 year-class in 24. In 26, the working group had access to data from the French EVHOE quarter 4 western IBTS survey (GOV trawl) and the CEFAS UK (E&W) quarter 1 survey (Portuguese high headline trawl) (Johnston et al. WD 26). The French survey series is from 1997 to 25 and displayed very variable observed numbers at age between years. Consequently, further exploration of the series was not perfomed. The UK quarter 1 survey was explored further (Figure ). There are strong year and age effects in the survey, particularly at 2- and 5-ringer. Total numbers per year vary widely. Because of strong year and age effects and because it was discontinued in 22 this survey is considered unsuitable as a recruit index. However the survey does display a truncation of older age groups throughout the series, but particularly in the 199 s (Figure ). This trend is displayed in the catch numbers at age, the acoustic series and the UK quarter 1 survey. In all three cases, this trend seems progressive with time. Other surveys that may have utility for tuning the assessment are the DARDNI Groundfish Survey of the Irish Sea, Northern Ireland and the UK quarter 4 western GFS. It is known that juveniles from the Celtic Sea are present in the Irish Sea. If it is possible to distinguish these fish from native Irish Sea herring, in the DARDNI survey then this survey could offer potential for a recruit index for Celtic Sea herring. 4.4 Mean weights-at-age and maturity-at-age The mean weights in the catch over time are presented in Figure 4.4.1, with stock weights displayed in Figure There has been an overall downward trend in mean weights at age since the mid-198 s. The values for 25/26 for the important age groups are among the

7 ICESHAWG Report lowest in the series. This trend in mean weights at age is similar to those seen in VI an, the Irish Sea and to a lesser extent, the North Sea. For the past three seasons substantial catches were taken outside the spawning season. For 25/26, the mean weights in the spawning stock were calculated from samples taken in VIIg, VIIj and VIIaS from October 25 to February 26. Samples from quarter 3 were not used in these calculations. No data for 8- or 9-ringers were available this year to calculate stock weights. Therefore values were calculated by linear extrapolation of the 1- to 7-ringer mean weights for these year classes. While the maturity-at-age for this stock has been assumed to be constant throughout the whole time period (5% of 1 ring fish are assumed to be mature at age 1 and 1% mature at 2 ring), it may not be stable. A new project to develop maturity ogives for this stock from catch and survey data is being started in 26. This project will also examine long term changes in biological parameters. 4.5 Recruitment At present there are no recruitment estimates for this stock that can be used for predictive purposes. The 23 recruitment was estimated as weak in the 24 assessments, and appears to be the weakest in the series. There is little information in the assessment on the strength of recruitment in 25, because these 1-ringers are poorly represented in the catches, though they were high. In this stock a proportion of juvenile fish are present in the Irish Sea and do not recruit to the Celtic Sea and Division VIIj until they are mature. Therefore neither the numbers of 1-ringers in the stock as estimated from the acoustic surveys nor the numbers in the catches give a reliable indication of year class strength. The relationship between the numbers of 1-ringers taken per hour in the ground fish surveys in the Irish Sea and the numbers of 1- ringers estimated by ICA for the Celtic Sea and Division VIIj was examined in a working document presented to the 1999 WG (Armstrong et al., WD 1999) and the results suggest that these surveys may become a useful indicator of recruitment to the Celtic Sea and Division VIIj when a longer time-series is established. 4.6 Assessment This stock is scheduled for benchmark assessment in 27. The last time the assessment of this stock was accepted by ACFM as a basis for management advice was 21. In 25, the working group did not present a final assessment, but rather presented two exploratory assessments. These assessments were based on the inclusion or exclusion of the acoustic survey conducted in 24. This survey produced the lowest abundance estimate in the series, and was not considered by the group to have measured the stock. The most important information considered by the 25 working group was weakness of the 21 year class. In 26, the working group continued to conduct exploratory assessments and no final assessment was put forward by the group in Data exploration Considerable data exploration was conducted in 25. In 26, only exploration of the revised acoustic series was conducted. The revised acoustic series displays the same age structure as the old one over comparable years. Therefore the series was considered only to be used for tuning over 2- to 5-ringer. The series displays the same truncation of older age groups as seen in the catch at age data (Figure and Figure ). The revised acoustic series and the catch at age data display similar proportions at age (Figure ).

8 32 ICESHAWG Report 26 Both acoustic series and the catch at age data displayed similar mortality signals (Figure ) Exploratory Assessments In 26, exploratory assessments were conducted to investigate: Behaviour of the revised acoustic series Inclusion of 2 and 21 surveys which had very high CVs. Change of the separable period to accommodate the new quarter 3 fishery. Shape of the exploitation pattern In each case, the same procedure as previous years was used to deal with the assumption that 5% of 1-ringers are mature. Therefore recruitment at 1-ring was replaced with geometric mean ( ), 39 million fish, and the SSB was recalculated based on the stock weights and population numbers in the final year. In order to compare the old and revised series, two runs of ICA were conducted using the same procedure as last year s assessment (SPALY), which did not use the 24 survey estimates. The separable period was 6 years and no shrinkage was used. The results of this analysis are presented in Figure Patterns of SSB and recruitment were the same, but slight differences in F were observed, with the old series scaling F up slightly in the final two years. Residual patterns in the tuning series are presented for these runs in Figure The revised series does not represent an appreciable better model fit. Strong age year effects are still present. However, because CVs are available for this series, it is possible to identify years were the survey is particularly noisy. Further diagnostics for comparing these runs are presented in Figures and Figure for the old and revised series respectively. Figure shows q-q plots for the runs with the old and revised surveys. These plots show ranked percentiles of the residuals, and provide a quantitative means to compare residual patterns. This analysis shows that catch numbers-at-age distributions are similar, but with about 2% larger standard deviation (slope of the line fit) when using the new series. The distributions of the survey residuals are not quite the same and the new series standard deviation is much higher. Surveys with particularly high CVs were those in 2 and 21. Exploration of their exclusion was performed in ICA using SPALY. Summary plots for these runs are shown in Figure and residual patterns in the survey series in Figure , and q-q plots in Figure Their exclusion did not change the perception of stock dynamics. However, the q q plot shows that both distributions are similar, but there is a reduction in the standard deviation when dropping the two surveys. A priori assumptions that the new quarter 3 fishery in the last three years changed the exploitation pattern were tested by running exploratory assessments with 6 year (both using the new survey series with the 2 and 21 surveys excluded) and a 4 year separable period. Summary plots are presented in Figure , residuals in Table and q-q plots in Figure Stock perception did not change substantially, but the residual pattern did improve. When a 4 year separable period is used (both using the new survey series with the 2 and 21 surveys excluded), the qq plots show the same distribution, with no change in standard deviation for the survey. In order to investigate the shape of the selection pattern, selection on at oldest age relative to reference age (3-ring) was set at 1.5 in comparison to the base case run using the revised acoustic series (Figure ). Comparative runs are shown in Figure and residual patterns in Figure Clearly the model fit is somewhat better when selection at the oldest age is set at 1.5 and the model seems to behave better with an increase in selection at

9 ICESHAWG Report the oldest age, compared to setting oldest age selection = 1.. It is also clear that using a higher S at oldest age applies a scaling factor to the SSB throughout the time series. Figure shows the q-q plot of comparison of these exploitation patterns. The choice of 1.5 appears to improve the residual pattern. 4.7 Short term projections There was no final assessment and consequently no short term projections. 4.8 Medium term projections No medium term projections were conducted in Precautionary and yield based reference points Biological reference points were discussed in detail in the 2 WG report (ICES 2/ACFM:1) and in the report of the previous years (ICES 1999/ACFM:12, ICES 1998/ACFM:14). A summary of this discussion was presented in the 23 HAWG report. B pa is currently at 44,t and B lim at 26, t for this stock F pa and F lim are not defined. The SGPRP (ICES 23 ACFM 15) has reviewed the methodology for the calculation of biological reference points, and applying a segmented regression to the stock and recruit data from the 22 HAWG assessment gave a breakpoint at 61,36 t. This change point appears to be very high with respect to the historical exploitation of the stock. Given that there is a cluster of observations just above this value the sensitivity of the method to these data needs to be further investigated. The HAWG decided that the first priority for this stock should be to achieve a stable assessment and that once this was done the reference points would be reinvestigated. There is still considerable instability in the assessment, so there is no basis for a revision of reference points at this point. 4.1 Quality of the Assessment No assessment was conducted Management Considerations There is no new assessment in 26 upon which to base management advice. However preparations are being made for benchmark assessment next year. There are certain pieces of information that can be obtained from the available data. The revision of the acoustic survey, though not substantially improving the model fit does show the noise in the individual survey estimates. The revision of the series shows evidence of declining stock abundance. A period of high abundance is evident with reasonable CVs, a period of very fluctuating abundance with high CVs and then a period of low stock abundance with lower CVs. In 25, ICES based advice on the poor recruitment of the 21 year class. In 26, this year class weakness was further confirmed. The 22 year class appears stronger in the catches. Although the 23 year class (1-ringers) are considered to contribute to SSB there is insufficient information in the data available to state if this cohort is stronger than average. In recent years the fishery has been tightly managed and it is now restricted in time and area. In 25/26 fishing was concentrated in the feeding area and also in a few of the traditional inshore areas. Little fishing took place in VIIj. Though the data available are not informative as to stock status at present., and the exploratory assessments are uncertain The weak 21-year class means that the stock is more dependent

10 34 ICESHAWG Report 26 on subsequent cohorts and also 4-ringers. The truncation of age groups in the catches in recent years along with the spatially small area of the fishery are causes for concern. The stock is probably at as low a level as when it previously collapsed. It would seem prudent to proceed with caution.

11 ICESHAWG Report Table Celtic Sea and Division VIIh, j and k herring landings by quota year (t), (Data provided by Working Group members.) These figures may not in all cases correspond to the official statistics and cannot be used for management purposes. Year France Germany Ireland Netherlands U.K. Unallocated Discards Total , 1,9-1,3 3,5 22, ,8 1, 2 7 2,5 2, ,4 1,6-6 1,9 23, , 1 + 2,3 2,1 23, , 1,3 + -1,1 1,9 21, ,4 1,3 + -1,5 1,7 19, , , , 18,6 1, - -1,8 3, 21, ,3 18, 1,4 - -2,6 7 18, ,3 1, , , , , , , , , , , , ,56-1, , , ,452 Table Celtic Sea & Division VIIj herring landings (t) by assessment year (1st April 31 st March) 1988/ /25. (Data provided by Working Group members.) These figures may not in all cases correspond to the official statistics and cannot be used for management purposes. Year France Germany Ireland Netherlands U.K. Unallocated Discards Total 1989/ , 1,9-2,6 3,6 23,1 199/ , 1, 2 7 1,7 18,6 1991/ ,4 1, ,1 25,6 1992/ , 1, , 21,2 1993/ ,6 1,3 + -1,1 1,8 18,6 1994/ ,4 1,3 + -1,5 1,9 19,3 1995/ , , 23,3 1996/1997 1, - 17,9 1, - -1, ,8 1997/1998 1,3-19,9 1, ,5 1998/ ,7 1, ,2 1999/2 2 18, ,5 2/ , ,191 21/ , ,236 22/ , ,465 23/ , ,424-11,536 24/ , ,743 25/ , ,494

12 36 ICESHAWG Report 26 Table Celtic Sea & Division VIIj herring. Comparison of age distributions (percentages) in the catches of Celtic Sea and VIIj herring over recent seasons. Rings Mean (58-5)

13 ICESHAWG Report Table Celtic Sea & Division VIIj herring. Length frequency distributions of the Irish catches (raised numbers in s) in the 24/25 season in the Celtic Sea and VIIj fishery. Length cm Quarter 3 Quarter 4 Quarter 4 Quarter 4 Quarter 4 Quarter 1 Quarter 1 Quarter 1 Total Celtic Sea and VIIg VIIaS River VIIaS C.S. VIIg VIIj VIIg VIIaS River VIIaS C.S. VIIj Nos./t

14 38 ICESHAWG Report 26 Table catches. Celtic Sea & Division VIIj (24/25). Sampling intensity of commercial ICES area Year Quarter Landings (t) No. Samples No. aged No. Measured Aged/1 t VIIa south VIIg VIIj Overall Table Celtic Sea & Division VIIj herring. Acoustic surveys of Celtic Sea and VIIj herring, by season. Number of surveys per season and type indicated along with biomass and SSB estimates. Shaded sections show surveys not used in tuning. Old Revised Season No. Type SSB Abundance 1 6 SSB 199/ Autumn and winter spawners / Autumn and winter spawners / Autumn and winter spawners / Autumn and winter spawners / Autumn and winter spawners / Autumn and winter spawners / Autumn spawners / No survey / Autumn spawners /2 1 Feeding phase /2 1 Winter-spawners /21 2 Autumn and winter spawners /22 2 Pre-spawning /23 1 Pre-spawning /24 1 Pre-spawning /25 1 Pre-spawning /26 1 Pre-spawning

15 ICESHAWG Report Table Celtic Sea & Division VIIj herring. Total stock numbers-at-age (1 6 ) estimated using combined acoustic surveys (age refers in winter rings, biomass and SSB in s tonnes). Bold text denotes the years used as inputs to assessment input files Total Biomass ( t) SSB ( t) Table Celtic Sea & Division VIIj herring. Revised acoustic index of abundance. Total stock numbers-at-age (1 6 ) estimated using combined acoustic surveys (age refers in winter rings, biomass and SSB in s tonnes) Abundance SSB ( t) CV (%)

16 31 ICESHAWG Report 26 Table Celtic Sea and VIIj herring. Separable model residuals from exploratory ICA runs for 4 year and 6 year separable periods. High residuals indicated. 4 year year

17 ICESHAWG Report C A B Figure a. Celtic Sea and VIIj herring, areas mentioned in the text and spawning boxes A, B and C, south of Ireland. One of these boxes is closed each season, under EU legislation. 1 Courtmacsherry, 2 Cork Harbour, 3 Daunt Rock, 4 Kinsale Gas Field (Rigs), 5 Labadie Bank, 6 Kinsale, 8 Waterford Harbour, 9, Baginbun Bay, 1, Tramore Bay/ Dunmore East, 11, Ballycotton Bay, 12, Valentia Island, 13 Kerry Head to Loop Head, 14, The Smalls. Figure b. Celtic Sea and VIIj herring, Location of non-spawning (open symbol) and spawning (closed symbol) herring in the Celtic Sea and SW of Ireland. Based on expert fishermens personal information.

18 312 ICESHAWG Report 26 5 Herring in the Celtic Sea, VIIj and VIIh, catches by season Figure Celtic Sea and Division VIIj working group estimates of herring landings per season. % % canum by division and quarter VIIg q3 VIIg q4 VIIaS q4 W. Harbour VIIaS q4 open sea VIIg q1 VIIj q4 VIIaS q1 W. Harbour VIIaS q1 open sea Winter rings Figure Celtic Sea and Division VIIj percentage age composition by metier (ICES Division and quarter).

19 ICESHAWG Report Quarter 1 25 Quarter '"W 1 '"W Legend IVa Land IVa ICES Division VIb VIa VIa North IVb Legend Land ICES Division VIb VIa North VIa IVb Herring 26 Qtr3_ Herring 26 VIa South VIa South Qtr1_ VIIc VIIb VIIa VIIc VIIb VIIa VIIa North VIIa South ICES Statistical Rectangles VIIg VIIf VIIg VIIf VIIk VIIj ICES Statistical Rectangles 5 '"N VIIk VIIj 5 '"N 5 '"N 5 '"N VIIe VIIe VIIh VIIh 1 '"W VIIIe VIIId VIIIa 1 '"W Quarter 4 25 Quarter '"W 1 '"W 6 '"N Vb1 Vb2 Vb1 IVa 6 '"N Legend Land ICES Division Herring 26 Qtr4_5 VIb VIa North VIa IVa IVb Legend Land ICES Division Herring 26 Qtr1_6 VIb VIa VIa South VIa North IVb VIa South VIIc VIIb VIIa ICES Statistical Rectangles VIIa North VIIa South ICES Statistical Rectangles VIIc VIIb VIIa VIIg VIIf VIIa North 5 '"N VIIk VIIj 5 '"N VIIa South VIIe VIIk VIIj VIIg VIIf VIIh 1 '"W VIIe VIIIe 1 '"W VIIId VIIIa Figure Herring catches by statistical rectangle in the first, third and fourth quarters of 25 and the first quarter of 25. Catches in ICES division V11a south, VIIg and VIIj are those in the 33 series of statistical rectangles and lower. Quarter 1 catches for VIaS only are indicated.

20 314 ICESHAWG Report N 9 W - 53 N 9 W N N N October November December January February March 51 N October November December January February March 53 N 1 W 9 W 9 W 8 W 7 W 6 W - 53 N 1 W 9 W 9 W 8 W 7 W 6 W N N N 53 N 9 W 1 W 9 W 8 W 7 W 6 W - October November December January February March 51 N 53 N 9 W 1 W 9 W 8 W 7 W 6 W - October November December January February March N N N 53 N 9 W 1 W 9 W 8 W 7 W 6 W - October November December January February March 51 N 53 N 9 W 1 W 9 W 8 W 7 W 6 W - October November December January February March N N N October November December January February March 51 N October November December January February March 53 N 1 W 9 W 9 W 8 W 7 W 6 W N 1 W 9 W 9 W 8 W 7 W 6 W N N N 1 W 9 W 8 W 7 W 6 W October November December January 51 N February March 1 W 9 W 8 W 7 W 6 W Figure Celtic Sea and Division VIIj. Summary of larval distributions by month in 198 s from Irish surveys. October November December January February March

21 ICESHAWG Report Figure Celtic Sea and Division VIIj. Progressive movement of main aggregations of herring inshore in quarter 3 and 4. Data are from acoustic surveys 1998 to 25 and the summer fishery in 25.

22 316 ICESHAWG Report Latitude Trawl Haul Longitude CTD Cast Figure a Celtic Sea and Division VIIj acoustic survey track and haul positions from acoustic survey, October D 8 D 9 E E 1 E 2 E Latitude to 1 1 to 1 1 to 1 1 to Longitude Figure b Celtic Sea and Division VIIj acoustic survey, total Sa values for herring obtained in October 25. 3

23 ICESHAWG Report Overall VIIg q3 VIIaS q1 W. Harbour Acoustic survey Oct Figure Celtic Sea & Division VIIj herring, comparison of percentage catches-at-age from the commercial fishery and from the acoustic survey. -1 UK Q1 Mean standardised numbers Figure Celtic Sea & Division VIIj herring, mean standardised abundance estimate from UK quarter 1 groundfish survey 1987 to 22.

24 318 ICESHAWG Report Mean weight in the catch.3 Kg Figure Celtic Sea and VIIj herring, trends over time in mean weights in the catch..35 Mean weight in the spawning stock.3 Kg Figure Celtic Sea and VIIj herring, trends over time in mean weights in the stock at spawning time.

25 ICESHAWG Report Figure Celtic Sea and VIIj herring. Catch numbers at age in the time series, standardised by year mean Figure Celtic Sea and VIIj herring. Acoustic estimates of abundance at age in the revised time series, standardised by year mean.

26 32 ICESHAWG Report 26 Figure Celtic Sea and VIIj herring. Comparison of proportions at age in the commercial catch and in the revised acoustic survey abundance estimates Old total Revised old ( ) Revised Z =.87 Old all years Z =.82 Old Z = Figure Celtic Sea and VIIj herring. Catch curves based on acoustic abundance estimates from revised and old acoustic survey series.

27 ICESHAWG Report SPALY,: recruits revised old series 8 Millions SPALY: SSB revised old B lim B pa SSB ' t F per year SPALY_ mean F revised old Figure Celtic Sea and VIIj herring. Results of exploratory ICA assessments using SPALY and comparing the revised and the old acoustic sureys.

28 322 ICESHAWG Report 26 1 SPALY: Revised SPALY: Old Figure Celtic Sea and VIIj herring. Survey series residuals of exploratory ICA assessments using SPALY and comparing the revised and the old acoustic surveys.

29 ICESHAWG Report ringer 3 ringer 4 ringer 5 ringer Figure Herring in the Celtic Sea and Division VIIj. Exploratory assessment using updated catch data, excluding the 24 survey data. Diagnostics of the fit of the old acoustic survey index at age 5 against the estimated spawning biomass. Top left, spawning biomass from the fitted populations (line), and predictions of spawning biomass in each year made from the index observations and estimated catchability (triangles +/- standard deviation), plotted by year. Top right, scatter plot and fitted relationship of spawning biomass from the fitted populations and larvae survey index observations. Bottom, residuals, as ln(observed index) ln(expected index) plotted against expected values and time.

30 324 ICESHAWG Report 26 2 ringer 3 ringer 4ringer 5 ringer Figure Herring in the Celtic Sea and Division VIIj. Exploratory assessment using updated catch data, excluding the 24 survey data. Diagnostics of the fit of the revised acoustic survey index at age 5 against the estimated spawning biomass. Top left, spawning biomass from the fitted populations (line), and predictions of spawning biomass in each year made from the index observations and estimated catchability (triangles +/- standard deviation), plotted by year. Top right, scatter plot and fitted relationship of spawning biomass from the fitted populations and larvae survey index observations. Bottom, residuals, as ln(observed index) ln(expected index) plotted against expected values and time.

31 ICESHAWG Report Figure Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessments using SPALY and comparing the revised and the old acoustic surveys.

32 326 ICESHAWG Report Recruits In Out 8 Millions SSB In Out Blim Bpa 's IN OUT F F per year Figure Celtic Sea and VIIj herring. Comparison of performance of revised acoustic series including and excluding surveys with high CVs (2 and 21).

33 ICESHAWG Report , 21 out , 21 in Figure Celtic Sea and VIIj herring. Survey series residuals of exploratory ICA assessments including or excluding the 2 and 21 points.

34 328 ICESHAWG Report 26 Figure Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessments including or excluding the 2 and 21 points.

35 ICESHAWG Report Recruits 6 year 4 year 8 Millions SSB year 4 year Blim Bpa 1 's t F per year year 4 year F Figure Celtic Sea and VIIj herring. Exploratory runs with 4 and 8 year separable period.

36 33 ICESHAWG Report 26 Figure Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessment comparing 6 year and 4 year separable periods.

37 ICESHAWG Report Recruits Millions SSB Blim Bpa 's F F per year Figure Celtic Sea and VIIj herring. Exploratory runs with terminal S = 1. and = 1.5.

38 332 ICESHAWG Report 26 1 S = S = Figure Celtic Sea and VIIj herring. Survey series residuals of exploratory ICA assessments including or excluding the 2 and 21 points.