Co-Financed Under European Integrated Maritime Policy

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1 Co-Financed Under European Integrated Maritime Policy PLAN BOTHNIA MSP 3/2011 PLAN BOTHNIA MSP 3 Helsinki, Finland, October 19-20, 2011 Agenda Item 3 The PLAN BOTHNIA MSP Assessment Document code: 3/4 Date: 12 October 2011 Submitted by: Swedish University of Agricultural Sciences (SLU) FISHERIES BACKGROUND DOCUMENT This document includes background information regarding fisheries in the Bothnian Sea. The meeting is invited to: -take note of the information as a basis for work

2 PLAN BOTHNIA MSP 3 Meeting Helsinki October 2011 FISHERIES-Background Document Swedish University of Agricultural Sciences (SLU) Coastal laboratory team [Ronny Fredriksson, Ulf Bergström et al] Introduction... 1 Methods... 2 Results... 3 Fish and fisheries in relation to other activities... 8 References Introduction Compared to the Baltic Proper, fewer fish species have been able to adapt to the conditions of the Bothnian Sea, mainly because the salinity is too low for some marine species. The commercial fishing activity in offshore areas of the Bothnian Sea is mainly directed towards herring (Clupea harrengus), and to some extent sprat (Sprattus sprattus). Here fishing is almost exclusively done with midwater and bottom trawls. In coastal areas, herring is caught by gillnets and traps, but these catches are small compared to the trawl catches. The Bothnian Sea constitutes the most important area for herring fishery in the Baltic Sea, providing 30% of the total catches according to catch data from 2009 (ICES 2010). For sprat, the corresponding figure is only 1%. Fishing is most intense in January to June, when over 70% of the catches are taken. During the past 30 years the estimated biomass of herring in the Bothnian Sea has increased from 100 thousand tonnes in the early 1980s to the current size of 400 to 500 thousand tonnes, which has mainly been connected to an increase in zooplankton, which is the main food for herring. The increase in zooplankton availability, in turn, has been related to changes in the physical environment favouring important prey species of herring (Lindegren et al 2011). During the same period of time, the commercial catches of herring have increased from about 20 thousand tonnes to 70 thousand tonnes a year (Fiskeriverket 2011). However, the growth rate and the proportion of larger herring, which is important for the fishery, have decreased in the Bothnian Sea (ICES 2010). This may probably be attributed to the increasing predation from seals in combination with mortality from fishing (Lindegren et al. 2011). Commercial fishery is only conducted by Finland and Sweden in the Bothnian Sea. The fishery is truly transboundary since fishing is allowed into four nautical miles from the other country s baseline (the inner border of the territorial sea). About 90 % of the herring catches are taken by Finnish vessels. The trawl fishery also catches significant amounts of sprat, 4 thousand tonnes in 2009 (WGBFAS 2010). Other species are scarce in the offshore fishery of the Bothnian Sea. For the coastal fishery, herring is the most important species as well (Fiskeriverket 2011). Other important target species for the coastal fishery are whitefish, salmon (Salmo salar) and perch (Perca fluviatilis). Gillnet fishery is most common. When performing multi-sectoral and multi-disciplinary marine spatial planning, it is important to have high resolution maps of activities using the sea as a resource in different forms. Commercial fishery is one of those activities. However, in most countries, fishing efforts are reported at a 1

3 spatial scale of the ICES statistical rectangles, which are approximately 50*50 km large. In Sweden, logbooks are kept at a higher spatial resolution, by recording set positions in degrees for each fishing effort. The ICES rectangle resolution is obviously not high enough for most spatial planning purposes. The VMS (vessel Monitoring System) data, on the other hand, provides a high spatial resolution of fishing activities, but does not provide any information on gear types or catches. VMS is a satellite based surveillance system that identifies the position and speed of the vessel. In EU Community waters, all fishing vessels exceeding 15 meters in length must have installed VMS and transmit information at a minimum of once every two hours. In both Finland and Sweden, information is transmitted every hour. In addition to VMS, all vessels are also obliged to keep record of fishing operations in a fishing logbook. By combining the two data sources, high resolution data on gear-specific fishing activity as well as catches of commercial fisheries can be obtained (Bastardie et al, 2010). The fishery in the Bothnian Sea is transboundary since fishing by Finnish and Swedish vessels is allowed into four nautical miles from the other country s baseline (defining the inner limit of a state's territorial sea). Inside this four nautical mile border each country determines its own form of regulations. Between 4 nautical miles from the baseline and the outer border of the territorial sea (i.e. the zone lying 4-12 nautical miles from the baseline) national and foreign vessels from countries that reached a special agreement are allowed to fish, in the case of the Bothnian Sea this concerns only Swedish and Finnish vessels. In this zone each country are free to regulate the fishery of national vessels in the same way as inside the trawling border. However, in order to include foreign vessels in the regulations it is required that each country has the same regulations in their national legislation. In the Exclusive Economic Zone (EEZ), outside the 12 nautical mile border, all European countries are theoretically allowed to fish. However, in practise it is only a Swedish and Finish fishery in the Botnian Sea, since herring here has an TAC (total allowable catch) that is shared between Sweden and Finland only. According to the common fisheries policy, within the EEZ it is not possible to institute new regulations on a national basis. Since the fishery in the Botnian sea only are conducted by Sweden and Finland the most convenient way to institute new regulations are to reach bilateral agreements and request for a decision within the EU. Methods In this study records from VMS were merged with catch and gear type data in logbooks with the purpose to analyse the spatial distribution of fishing efforts and catches in the Bothnian Sea. For the analysis, Swedish and Finnish VMS records and logbook data from were used. Since vessels less then 15 meters in length do not have VMS equipment installed they were not included in this analysis. However, overall, fishing activity with smaller vessels is negligible in the offshore areas included in the PlanBothnia planning area. In total, 45 Finnish vessels, with an average engine power of 540 kw, and 10 Swedish boats, with an average engine power of 1050 kw, were included in the analysis. The first step of the analysis was to clean the VMS dataset so it only contained signals when fishing occurred, by removing signals when vessels were in port or steaming. In this work, a speed-based approach was used to separate fishing from non-fishing signals. The speed interval of fishing activity was set using speed-frequency histograms. The pattern of midwater and bottom trawl fisheries was similar and the maximum fishing speed was defined to four knots. VMS positions near harbours and close to land were classified as non- 2

4 fishing activity and were manually excluded from the dataset. In total, VMS positions from Finnish vessels and 6824 VMS positions from Swedish vessels were identified as fishing points and included in the analysis. The link between the VMS records and catch data from logbooks was obtained by assigning a unique identification number per vessel and fishing day in both the VMS- and logbook dataset. The VMS and logbook datasets were merged using an Access database. The merging process resulted in a dataset with information of gear type and catch of different species per VMS signal. Thus, it contained both the spatial information from the VMS-dataset and the information of gear type used and catches made from the logbook. The catches of each species were then distributed among the VMS signals, after adjusting for the fishing time, i.e. the elapsed time from the previous signal, in order to attain an estimate of catches at each position. The combined VMS and logbook dataset was converted from a point dataset to a raster layer by using the Point to raster function in the Spatial Analyst toolset in ArcGis 9.2. Fishing activity was analysed per gear type (midwater and bottom trawls only gears used) and species (herring and sprat) by calculating average yearly catch per square kilometre for The spatial resolution of the raster was set to 5 x 5 km to match the precision of the one hour interval of the VMS signals. To detect any seasonal spatial pattern the herring fishery was also analysed quarterly. To identify important areas for herring in the Bothnian Sea, maps of herring densities were produced by interpolating data from acoustic surveys from (ICES WGBIFS reports from ). Results Since the proportion of larger herring within the Plan Bothnia planning area has decreased during the past years it can be considered as a priority to identify important areas for larger herring from a conservational perspective. The result from the acoustic surveys is presented in figure 1 and indicates that coastal areas are of importance for larger herring. However, it must be remembered that this is only a snapshot from a limited part of the year. Adult herring migrate to the coast for spawning in spring/summer and then back to the open sea and therefore it can be expected that the location of important areas differ during the year. 3

5 Figure 1. Important areas for large herring identified by analysing densities of herring larger than 20 cm from acoustic surveys performed in October The important areas for herring larger than 20 cm are visualized by showing the 20 % proportion of the area that had the highest densities of herring. Shallow areas near the coastline are often important spawning and nursery grounds for many species of fish. Despite the fact that most spawning grounds are located outside the planning area they are included in this project due to their vital importance for the herring stock. Figure 2 shows spawning ground for herring, and also whitefish, identified by interviewing local fishermen. The map is based on two studies. Gunnarz et al. (2003) identified spawning grounds for herring and whitefish along the Swedish coast and the Regionplaneförbundet for the county of Vasa identifying spawning grounds for herring in the surroundings of Vasa, Finland in

6 Thousand tonnes Figure 2. Spawning grounds for herring (red) and whitefish (orange) identified by interviewing local fishermen. Spawning grounds for herring based on two studies, one from Sweden performed in 2003 by the Swedish Board of Fisheries (Gunnarz et al. 2011) and one from the surroundings of Vasa, Finland, in 1984 performed by Regionplaneförbundet för Vasa län. Spawning grounds for whitefish based on results from Gunnarz et al Please note that data from Finnish coast south of Ostrobothnia possibly available but not included here Sweden Finland Midwater trawl Bottom trawl Figure 3. Average catch of herring per year in thousands of tonnes, per gear type and country during the period

7 Figure 3 shows the average catch per year taken by Swedish and Finnish vessels with bottom and midwater trawls, respectively. About 65 % of the herring catches were by midwater trawls. A large part of the herring catches in the Bothnian Sea are taken by a few vessels only. During the period of time of this study ( ) five vessels accounted for 50 % of the catches. There was no major difference between Swedish and Finnish vessels regarding the gear type used. Figure 4 shows the areas where the largest herring catches were made during the time of this study. It gives an overall picture of the situation, since all data from three years has been used, regardless of the time of year. The results indicate that there are two major areas that could be regarded as being of main importance for the fishery. One large area in the southeast part of the study area and one in the north, outside Vasa. Figure 5 shows the seasonal pattern of the herring catches. The highest catches in the southeast area were made during January to June, while the highest catches in the northern area were made during July to September. The southeast area is used by both Finnish and Swedish vessels, while fishing in the northern area is mainly carried out by Finnish vessels (Figure 6). In general, the Finnish fleet used more or less the whole Bothnian Sea as fishing ground, while the Swedish fleet mainly operated in the southern parts, with a substantial proportion closer to its own baseline. Figure 4. Important areas for commercial herring fishery produced by combining VMS- and logbook data from Finland and Sweden during Important areas are visualized by showing the 50 % proportion of the area that had the highest catches of herring. 6

8 Figure 5. Seasonal pattern of the commercial herring fishery in the Bothnian Sea by quarter of a year. Combined data from Swedish and Finnish VMS records and logbook during Important areas are visualized by showing the 50 % proportion of the area that had the highest catches of herring. 7

9 Figure 6. Fishing from Swedish vessels (left) and Finnish vessels (right). Points show VMS signals identified as fishing activity. Fish and fisheries in relation to other activities During the marine planning process it is important to adopt an ecosystem based approach to make sure that sea use is sustainable in the long term. This point is illustrated by herring in the Bothnian Sea. A majority of the important spawning and nursery grounds for herring are located in shallow coastal areas outside the planning area. In order to maintain a viable stock of herring it is thus critical ensure proper functioning of these areas. Also, a substantial part of the important areas for large herring, which are particularly important for the stock, are located near the coastline. Thus, it is important to remember that processes outside the planning area are likely to effect the situation inside the target area. The environmental impacts of the commercial fishery and the nature of potential conflicts with other interests of sea use obviously differ depending on the type of fishery. In this study we focus on the bottom trawl fishery because of its potential impact on sea floor integrity and possible conflicts with other interests, such as offshore wind farms. Figure 7 shows areas with the largest catches of herring in the bottom trawl fishery. The bottom trawl fishery is mainly conducted on soft bottoms that in general are species-poor habitats in the Bothnian Sea. The area is lacking larger sessile species that would be vulnerable to trawling. However, bottom trawl activity causes resuspension of sediment, which may lead to release of nutrients and toxins (Thrush et al. 2002). Although generally considered more environmentally sound, also pelagic trawling may have some negative environmental effects. Preliminary results from recent studies indicate that by-catches of post-smolt salmon (Salmo salar) during pelagic trawling could be significant and have an effect on the overall post-smolt survival in the Bothnian Sea (ICES 2011). The magnitude of this potential 8

10 problem is not yet known. Pelagic trawling has a similar distribution in the area as bottom trawling, except for an intensely fished area in the northern part of the area (Fig 4 and 7). The trawl fishery of the Bothnian Sea may potentially have conflicting interests with shipping, wind farms, electrical cables and marine protected areas. As both existing protected areas and wind farms are mainly located in shallow waters (less then 30 meters), where trawling vessels generally do not operate. However, the technical development of wind power towards construction at deeper areas and even floating platforms is ongoing and could result in a future conflict with the fishery. The trawl fishery may potentially interfere with shipping and plans for cables or pipelines. By performing a spatial overlay analysis of the maps in this section with maps of other activities these relationships can be explored in detail. Figure 7. Bottom trawl fishing intensity, measured as the catch of herring. High pressure areas, where disturbance of benthic habitats is likely, are visualized by showing the 50 and 75% proportions of the area with the highest catches of herring. 9

11 References Bastardie, F., Nielsen, J.R., Ulrich, C., Egekvist, J., Degel, H Detailed mapping of fishing effort and landings by coupling fishing logbooks with satellite-recorded vessel geo-location. Fisheries Research. 106 (2010) Fiskeriverket Fiskbestånd och miljö i hav och sötvatten Resurs- och miljööversikt ICES Report of the Baltic International Fish Survey Working Group (WGBIFS). 31 March4 April 2008, Gdynia, Poland. ICES CM 2008/LRC: pp. ICES Report of the Working Group on Baltic International Fish Survey (WGBIFS), 30 March 3 April 2009, Lysekil, Sweden. ICES CM 2009/LRC: pp. ICES Report of the Baltic International Fish Survey Working Group (WGBIFS), March 2010, Klaipeda, Lithuania. ICES CM 2010/SSGESST: pp. ICES [International Council for the Exploration of the Sea] Report of the Baltic fisheries assessmentj working group (WGBFAS), April ICES Headquarters, Copenhagen, Denmark. ICES Report of the Baltic Fisheries Assessment Working Group (WGBFAS), April, ICES Headquarters, Copenhagen. ICES CM 2011/ACOM: pp. Lindgren, M., Östman, Ö., Gårdmark, A Interacting trophic forcing and the population dynamics of herrring. Ecology, 92(7), 2011, pp Thrush, S.F., Dayton, P.K Disturbance to marine benthic habitats by trawling and dredging: Implications for marine biodiversity. Annual Review of Ecology and Systematics, Vol. 33, (2002), pp