Baltic Marine Environment Protection Commission Group on Ecosystem-based Sustainable Fisheries Gothenburg, Sweden, 11-12 May 2016 FISH 4-2016 Document title Seals-fisheries conflict in Sweden Code 4-5 Category INF Agenda Item 4 Interactions between fisheries and marine ecosystems Submission date 29.4.2016 Submitted by Sweden Background This document contains information on a seals-fisheries conflict in Sweden. Action required The Meeting is invited to consider the information and act as appropriate. Page 1 of 6
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 FISH 4-2016, 4-5 The seal-fisheries conflict in Sweden, Programme Seal and Fishery Sweden has a long coastline, with favourable conditions for an extensive small-scale inshore fishing industry. An ever-increasing threat to this industry is the rising seal population, with the damage to gear and catches and the significant catch losses this has brought with it. Seal populations were at a low point in the 1970s as a result of intensive hunting effort combined with serious marine pollution, but since then all seal species in Swedish waters have bounced back strongly. Not only have numbers risen, seals have become much bolder since hunting was stopped during the 1980s and are now much less wary of human activity. To the new generations of seals, traditional fishing gear such as gill nets, long-lines and fish traps of different types began to look like a help-yourself buffet. Thus in the 1990s the Seals and Fisheries Project was set up in order to bring together the authorities, the commercial fishermen and the conservationist organisations to address the problem. The conservationist NGOs left the project when seal hunting was tested as a solution, but the project continued with annual funding to support measures intended to reduce the seals' impact on our fisheries. The Seals and Fisheries Project has focused on four areas: 1. Carrying out scientific research into the conflict 2. Developing new fishing gear to limit the seals' ability to help themselves to fishermen's catches 3. Studying ways of keeping the seals away from fishing gear 4. Giving advice and information to the public and the authorities In the last 20 years, a great deal of information has been collected, describing the conflict both from the fishing industry's and the seals' point of view. A number of studies have also been carried out into the behaviour of seals in the vicinity of fishing gear. This research has shown that damage and losses due to seal activity have brought large economic losses to small-scale fisheries all around the coast of Sweden. The trap fisheries for salmon and trout have been most severely affected, but in recent years damage and losses in the southern Baltic inshore cod fishery have also increased dramatically. (Figure). 120 100 80 60 40 20 0 Number boats that fish in the area Proportion days with seal damage % Figure 1 Gillnet fishing for cod as an example of a conflict between fisheries and seals. Figures from the island of Öland in the central Baltic. Page 2 of 6
Seals impact on fisheries in two clearly visible ways: by damaging the gear (ripping the nets) and by spoiling the catch (taking bites out of fish caught). However, our research suggests that by far the greatest damage they do is hidden, consisting of catches they eat without leaving any remains, fish which escape from ripped nets and fish that are frightened away by seal presence around the gear. To mitigate this, attempts have been made to scare seals away from fishing gear using loud noises in the frequency ranges they are sensitive to. Acoustic Harassment Devices (AHDs) have been shown in trials to have some effect, but they have been unreliable in operation due to technical and physical problems. They are also expensive to maintain, so are not currently considered to be a sustainable practical method. Figure 2 Trials of an AHD in a gillnet fishery. The big box houses a large lead battery; the transducer is suspended below the small box, which contains the controller. Some seals have learnt to specialise in using fishing gear as their foraging grounds. If we are going to cull seals, it is more effective to target these individuals than the general seal population. Modified fish traps have been developed to catch the problem seals in a humane way in order to remove them from the population. However, due to technical problems, these have not caught on with commercial fishermen. Page 3 of 6
Figure 3. A pontoon seal trap raised from its normal position just under the water surface, positioned close to a salmon trap. We are left with far and away the most successful method of mitigating the seals-fisheries conflict, which is the development of new seal-safe fishing gear. This development has continued in close co-operation between fisheries biologists, professional fisherman and gear manufacturers. Fishermen get to try out new gear in the field without having to commit to buy it. The most significant progress has been made with the development of large seal-safe fish traps, which have replaced both the traditional traps that were subject to seal attacks and also some gill-nets in certain areas. The basis of the new trap is that the fish should be live-caught in such a way that the seals cannot get at them. This is achieved firstly by means of a grating over the entrance to the fish chamber (the final part of the fish trap where the catch is held) which prevents the seals going any further. To stop the seals ripping the nets apart with their sharp teeth, a very strong type of nylon also has to be used, namely Dynema. Finally the use of a rigid double-wall net around the fish chamber reduces the seals' ability to get at the fish or stress them from the outside. But seals are resourceful and adaptable. Once excluded from the trap itself, they started exploiting the gear in a different way, by chasing the seals into the net walls and catching them there. Further refinements have been introduced to cope with this, by changing the mesh size in the leading nets so that they still guide fish to the chamber but also allow them to slip through and escape when chased by seals. To facilitate retrieval of the catch, the new fish chamber is mounted on inflatable pontoons which can be filled with compressed air to raise it entirely out of the water. As the chamber is raised, the fish end up in a plastic tray at the front end from where they are easily transferred to fish boxes in the boat. The design of the new traps, known as pontoon traps, has not only kept seals away from the catches and prevented damage to gear, it also makes life easier for the fishermen. As a result it has been widely adopted and has transformed the salmon and whitefish trap fisheries in the Swedish and Finnish Baltic, where the vast majority of all salmon traps in use today are now pontoon traps. Figure 4 and 5 A pontoon fish chamber belonging to a trap net for salmon and whitefish, floating at the surface for emptying. The box contains a video camera for making observations of the behaviour of both fish Page 4 of 6
and seals. Figure 5. A prototype of a smaller pontoon fish chamber with the trap net on a raft for easy transport to the fishing grounds. This fish chamber is positioned on the sea bed down to 15m depth and is raised with inflatable pontoons. The main catch is perch. Similar traps have also been tested for protecting catches of other species such as herring, perch, pike-perch and cod, currently fished with gill nets which are vulnerable to seal predation. More development work is needed to bring these traps to a state of commercial viability as a replacement for gill nets. The big challenge at the moment is to save the inshore cod fishery by finding an alternative to gill nets and long lines. One possibility is to use baited pots similar to lobster pots to entice the fish in and trap them there safe from seal attacks. These have been piloted for several seasons now, but with mixed results. We have shown that it is possible to achieve catch levels comparable with the traditional fishery in some areas, but in others catches have been unacceptably low. However, in the course of the trials we have learnt how to develop fish pots which minimise the bycatch of undersized fish, marine mammals and seabirds. We have also collected data on both cod and seal behaviour around fish pots and have tested different types of entrances, as well as the use of sensory stimuli to attract fish into the pots and increase their catching efficiency. Apart from their seal-safe characteristics, cod pots have many potential advantages, such as the low risk of bycatch of unwanted species, and the higher quality of live-caught fish. A significant amount of development is still required in order to develop a type of pot which will be practical to handle and will offer sufficient economic returns for commercial application. However there are many reasons to invest in this exciting new area, which has the potential to rescue our valuable inshore fisheries from their present precarious state. Many different types of cod pots have been developed. This is one type of pot developed by the Seals and Fisheries Project. The pot is a stable construction, floating just above the bottom with one entrance in the direction of the current. Page 5 of 6
The pots resistance towards seal attacks has been tested. Trials showed that the pots need to be a stable construction made in a small meshed strong material to protect the catch inside the pot. Reference Fjälling, A. 2005. The estimation of hidden seal-inflicted losses in the Baltic Sea set-trap salmon fisheries. Ices Journal of Marine Science 62:1630-1635. Königson, S., A. Fjalling, M. Berglind, and S. G. Lunneryd. 2013. Male gray seals specialize in raiding salmon traps. Fisheries Research 148:117-123. Königson, S., S. Lunneryd, F. Sundqvist, and H. Stridh. 2009. Grey Seal Predation in Cod Gillnet Fisheries in the Central Baltic Sea. Journal of Northwest Atlantic Fishery Science 42:41-47. Königson, S. J., Fredriksson, R. E., Lunneryd, S-G., Strömberg, P., and Bergström, U. M. 2015 Cod pots in a Baltic fishery: are they efficient and what affects their efficiency? ICES Journal of Marine Science, doi: 10.1093/icesjms/fsu230. Lunneryd, S. G., A. Fjälling, and H. Westerberg. 2003. A large-mesh salmon trap: a way to mitigate seal impact on a coastal fishery. ICES Journal of Marine Science 60:1194-1199. Ovegård, M., Königson, S., Persson, A., Lunneryd, S.G., 2011. Size selective capture of Atlantic cod (Gadus morhua) in floating pots. Fisheries Research 107(1-3):239-244. Westerberg, H, Lunneryd, S,G, Fjälling A, and Wahlberg, M (2008). Reconciling Fisheries Activities with the Conservation of Seals through the Development of New Fishing Gear: A Case Study from the Baltic Fishery Grey Seal Conflict. American Fisheries Society Symposium. 2006: 587-597 Contact persons Seals and Fisheries Program: David.jonsson@lansstyrelsen.se Swedish Agency for Marine and Water Management: Susanne.viker@havochvatten.se Swedish University of Agricultural Sciences: sven-gunnar.lunneryd@slu.se, sara.konigson@slu.se Page 6 of 6