3.14 Stocks in the Baltic

3.14.1 Overview (Including overview of Salmon and Sea trout)

The main for in the Baltic use demersal mortality rate of 0.6, and for the Western trawls, high opening trawls (operating both pelagically stock 1.0, both for appropriate age groups as and demersally), and gillnets. There has been an defined by ICES. increase in gillnet fisheries in the 1990s and the share of the total catch of cod taken by gillnets has in recent 3. Should the SSB fall below a reference point of years been about 35-50%. The Baltic herring is 240 000 tonnes for the Eastern stock and 23 000 exploited mainly by pelagic trawls and demersal trawls tonnes for the Western stock, the fishing mortality and, during the spawning season, by trapnets/pound- rates referred to under paragraph 2 will be nets in coastal areas. The herring trawl is largely adapted in the light of scientific estimates of the a mixed herring and sprat fishery where the share of conditions then prevailing, to ensure safe and rapid herring varies significantly by Subdivisions and recovery of spawning stock biomasses to levels in seasons. The main part of the sprat catch is taken by excess of 240 000 tonnes and 23 000 tonnes, pelagic pair and are used for industrial respectively, for the Eastern and Western stocks. purposes. There has been an increase in catches of sprat in the most recent years, and 1997 catches were at a 4. For allocation purposes, a combined TAC will be record high of 529 000 t for the whole Baltic. The sprat established. The Contracting Parties agree to catches have since decreased continuously to 342 000 t further collaborate, inter alia, through bilateral in 2001. Baltic salmon is exploited by drift net, trapnet, agreements to ensure an efficient management of and longline fisheries. the cod stocks.

An overview of catches of fish in the Baltic until 2000 5. The exploitation pattern in the fisheries for cod and as officially reported to ICES, is given in Section in particular, the selectivity shall be improved in 3.14.2. the light of new scientific advice from ICES with the objective to enhance the spawning biomass of For Baltic cod there is one management unit covering cod and reduce discards. all Subdivisions 22–32. ICES considers the stocks in Subdivisions 22–24 and Subdivisions 25–32 as separate 6. Additional technical measures including, inter alia, stocks, however, and advice is provided on them further limitation on effort, restrictions on fishing separately. days, closing of areas and/or seasons, obligation to change fishing ground in case of high abundance of juveniles, special reporting requirements, and ICES reiterates its advice that the cod stocks should be other appropriate control measures should be managed separately in order to better adapt the considered. exploitation to the present development in the two stocks. 7. The IBSFC shall, as appropriate, adjust management measures and elements of the plan on IBSFC has in September 1999 adopted a Long-Term the basis of any new advice provided by ICES. Management Strategy for the Cod Stocks in the Baltic Sea: A review of this arrangement shall take place no later than year 2003. The IBSFC agreed to implement a long-term management plan for the two cod stocks, Eastern and IBSFC has in September 2001 adopted a Recovery Western stocks, as defined by ICES, which is consistent Plan for the Baltic Cod: with a precautionary approach and designed to ensure a rational exploitation pattern and provide for stable In conformity with the Long Term Management Strategy and high yield. The plan shall consist of the following for Baltic Cod the Contracting Parties agree to elements: establish a recovery plan for the Baltic cod. They also took note that the spawning biomass of the Western 1. Every effort shall be made to maintain a minimum stock is above the agreed Bpa. The plan shall include the level of Spawning Stock Biomass (SSB) greater following elements. than 160 000 tonnes for the Eastern stock and 9 000 tonnes for the Western stock.

2. A long-term management plan shall be implemented, by which annual quotas shall be set for the fishery on the Eastern stock, reflecting a

698 ICES Cooperative Research Report No. 255 I which a maximum of 5 per cent may be of undersized cod, 1. For 2002 the fishing mortality for the Eastern stock shall be reduced to below F and shall pa 10. Delete Fishing Rule 8.2, thereby prohibiting not be greater than 0.55 within a global TAC the landing of undersized cod; of 76 000 tonnes; 11. Request ICES to review all relevant data 2. Manage the fishery for Eastern cod stock in related to the selectivity of cod in the Baltic sea year 2003 and subsequent years with the and to revisit the mesh size of the diamond 130 objective of reducing the fishing mortality for mm mesh size with a view to establishing a Eastern cod stock to below Fpa in order to mesh size ensuring a similar selectivity as the ensure safe and rapid recovery of the spawning 120 mm BACOMA window; stock to levels in excess of 240 000 tonnes; 12. Request the Working Group on Fisheries Rules 3. Request ICES to evaluate the findings of the to consider additional technical measures and IBSFC Scientific Meeting on Technical provide proposals for amendments relating to Measures for the Fisheries on Baltic Cod fisheries rules that have an impact on cod with (Brussels 20 - 24 August 2001) and to provide the view to improving the recovery plan; advice and catch options for 2003 and subsequent years taking into account improved III selectivity and additional technical measures; 1. Establish a comprehensive and efficient II Control and Enforcement scheme (Action Plan) to support the cod recovery plan 1. Extend the summer ban to the period from 1 consisting of the following main elements: June to 31 August; a. Inspection Strategy. 2. Establish spawning area closures in the Bornholm Deep; b. Co-operation which will include, where practical, an exchange of 3. Establish additional spawning area closures in fisheries inspectors on a bilateral the Gdansk Deep and the Gotland Deep in the basis in 2002 and in subsequent case of new scientific information; years. 4. Fix the minimum mesh size for gill nets to 110 c. Evaluation of the efficiency of the mm to be implemented from 1 September 2002; measures taken. 5. Establish the maximum length of gill nets per 2. In order to enforce the implementation of the vessel fishing for cod : cod recovery plan the Parties will notify the Secretariat of IBSFC of the results of the A. For vessels with an overall length of up to Action Plan. The IBSFC Secretariat will and including 12 m limit the use of nets to present a Report of the Action Plan at the 28th a maximum length of 12 km; Session of IBSFC. B. For vessels with an overall length of more For cod, unusually strong year classes in 1976, 1979, than 12 m limit the use of nets to a and 1980 formed the basis for an increase in the stock in maximum length of 24 km; the eastern Baltic and an expansion in the fisheries. Catch levels more than doubled and the fishery attracted 6. Establish a soak time when fishing with gillnets vessels from other Baltic fisheries and from fleets of a maximum of 48 hours, the start and normally operating outside the Baltic Sea. , In almost all recovery time to be recorded in the fishing years landings have been far above the levels logbook; recommended by ICES. The decline in stock size and landings started around 1985 and continued up to 1992. 7. Improve the marking system and introduce a Fleet capacity and fishing effort have now been reduced tagging system for gillnets; to some extent, but fishing mortality increased as the stocks declined. Improved recruitment in the early 8. Review the minimum landing size for Cod in 1990s has resulted in spawning stock biomasses the Baltic in the light of experience with the increasing above the 1992 minimum, and this increase use of fishing gears with improved selectivity has been seen especially in the western Baltic cod stock. After a slight increase in 1994–1995, the SSB of the 9. Set the by-catch of cod (in weight) in the eastern Baltic cod stock has decreased again in 1999- herring and sprat fisheries at 3 per cent of 2001 to a historically low level.

ICES Cooperative Research Report No. 255 699 The success of cod reproduction is, among other things, been observed since 1993. A continuous decreasing dependent on certain minimum levels of salinity and trend in mean weight at age has been observed in most oxygen concentration for the fertilisation and survival herring stocks in the Baltic since the mid-1980s. This of the eggs and larvae. The unusually long period with decline in mean weight at age partly explains the low influx of North Sea water from the late 1970s to the declining trend in biomass of the herring stock in early 1990s was in general a period of low recruitment. Central Baltic herring in Subdivisions 25–29, 32. At the The influx in 1993 resulted in improved environmental present the mean weight of herring remains at a low conditions, which allowed the possibility of improved level. Still, there have been some indications in the last recruitment but did not secure it. Since 1993 there have few years that the decreasing trend of the mean weight not been major influxes. The effect of an intrusion of is slowing down. Due to the decreasing SSB and North Sea water into the Baltic Sea is usually sufficient increasing trend in fishing mortality the Central Baltic to support better environmental conditions for two herring is assumed to be outside of biological limits. spawning seasons (about 1.5 years) at the most, because Different trends of stock development have been after that period the salinity and oxygen levels in the observed for herring in the Gulf of Riga and for herring deep water layers decrease below the level at which cod in the Bothian Sea (Subdivision 30). Based on eggs can survive. prevalence of abundant year classes during the 1990s SSB of the Gulf of Riga herring has increased The recent improvement in recruitment and the reversal significantly and presently is historically high (120-130 of the downward trend in spawning stock biomass has thousand t). Herring in Bothnian Sea after increase of been seen in both the Western (Subdivisions 22 and 24) recruitment abundance during the 1990s also remains at in 1994–1997 and Eastern (Subdivisions 25–32) cod a relatively high level of 240 000 t. It has, for several stocks in 1994–1995. However, fishing mortalities are reasons, been difficult to estimate the absolute stock still estimated to be high in the Western stock and have size for the pelagic stocks, although the development of increased in the Eastern stock from a lower level. In the stock size in relative terms is better described. Western stock the increase in spawning stock biomass Inconsistencies between years in the results from in recent years was caused mainly by the 1994 year acoustic surveys and low precision in the estimates of class, and it is expected that the spawning stock biomass species composition in the mixed fisheries have will increase with the present exploitation pattern, due contributed to the variation in stock estimates given to the 1997 year class, which is estimated to be above during the latest years. However, a fourfold increase in average. The Eastern stock has been below the long- sprat catches between 1991 and 1997 has been observed term average since 1986, and thus a recovery of the and the development of this fishery, and consequently stock can hardly be expected with the present the rate of fishing mortality, should be closely exploitation pattern and tendency for fishing mortality monitored. to increase. It is therefore considered that reductions in fishing effort is needed if these stocks are to recover on The multispecies interactions may periodically have a a more permanent basis. strong influence on the state of fish stocks in the Baltic, depending on the abundance of cod as the main predator The landings of sprat for industrial purposes have in the Baltic Sea ecosystem. To take into account the increased markedly during the last decade. Herring and multispecies effects, the data from multispecies sprat are used mainly for human consumption when assessment methods are used in the assessment of landed in the countries on the eastern Baltic coasts, but pelagic stocks. However, interactions with other for production of fishmeal and oil in the countries on potential top predators, such as salmon and seal that are the west coast. potentially important in the northern Baltic Sea, are not yet quantified and are therefore not directly included in the present ICES advice. Herring in the Baltic is assessed as five stocks. This is to be regarded as a compromise between using the larger number of stocks/populations that have been The spring-spawning herring stock in Subdivisions 22– identified for biological reasons and the practical 24 and Division IIIa migrates after the spawning season constraints, e.g. in what units are catch figures into the Kattegat, the Skagerrak, and the eastern parts of available, and what are the possibilities for correctly the North Sea, where it mixes with the North Sea allocating individual fish to particular stocks. autumn-spawning herring stock during the feeding period. Difficulties in allocating catches to the Baltic spring-spawning stock and to the considerably larger Sprat is assessed as one unit for the entire Baltic. North Sea stock, uncertain catch statistics, and conflicting trends in survey indices have resulted in The exploitation rate of pelagic stocks in the Baltic has unreliable assessments for the spring-spawning stock of increased since the mid-1990s. Due to the low herring in Subdivisions 22–24 and Division IIIa. abundance of cod the natural mortality of Baltic herring Improvements in methods of stock separation applied and sprat is low at present. The Baltic sprat is for 1991-2001 have, however, resulted in an acceptable considered to be harvested inside safe biological limits. assessment in 2002. A sharp decrease in mean weight at age of sprat has

700 ICES Cooperative Research Report No. 255

Figure 3.14.1.1

ICES Cooperative Research Report No. 255 701 Salmon and Sea Trout

Salmon

There are 40–50 rivers in the Baltic Sea with wild IBSFC to increase the production of wild Baltic salmon salmon smolt production (Figure 3.14.1.2). Many rivers is to attain at least 50% of the natural production have been dammed and spawning and nursery areas capacity of each river with current or potential have been completely or partially destroyed. To production of salmon by 2010, while maintaining the compensate, hatcheries have been built on these rivers catch level as high as possible. where fish are reared to the smolt stage before release. These fish feed in the sea mainly in the Baltic Main Sea trout Basin and migrate back to rivers as spawners, where they are used as to a varying extent. In some There are wild sea trout populations in approximately rivers with compensatory releases, some homing salmon 400 rivers and streams in the Baltic Sea. Similar to the succeed to reproduce so that there is small amount of situation for salmon rivers, sea trout rivers have been natural reproduction. A major part of wild and reared dammed and natural reproductive capacity has ceased. smolt production takes place in the Gulf of Bothnia. Reared smolts are released to compensate for these losses. Sea trout are also in many cases released to While feeding in the sea, salmon are caught by driftnets provide recreational fishery on returning spawners. and longlines and, during the spawning run, they are Most of the stocks remain in the coastal area within caught along the coast, mainly in trap nets and fixed about 150 km of the point of release, but a high gillnets and, to a minor extent, in a fishery. proportion of those from Poland and some from Where fisheries are allowed in the river mouths, set southern Sweden migrate further into offshore areas. gillnets and trapnets are used. In Sweden and Finland, Coastal populations are mainly taken as by-catch in there is also a traditional recreational and gillnet gillnets or trapnets. The stocks entering the offshore fishery in some of the rivers. In Sweden, there is a area are exploited by salmon drift netting and longlines. considerable broodstock fishery in rivers having reared Sea trout are important for the recreational fishery in populations. The offshore fishery and most of the coastal areas and rivers. coastal fisheries exploit both wild and reared salmon. Wild salmon can normally not be distinguished from The populations in the Gulf of Bothnia, particularly reared fish in the fisheries. those in Subdivision 31, are in a poor state. Several of these populations are overexploited in the sea to the There are two IBSFC management areas for salmon in extent that they now exist mainly as non-migratory the Baltic Sea: (1) Main Basin and Gulf of Bothnia brown trout populations. The state of the populations in (Subdivisions 22-29 and 30–31, respectively) and (2) the remainder of the Baltic Sea is variable, but in Gulf of Finland (Subdivision 32). The offshore and general better than in the Gulf of Bothnia. IBSFC has coastal fisheries have been managed by a single TAC not established any management objectives for sea since 1991. The overall management objective of trout.

702 ICES Cooperative Research Report No. 255 Finland 1. Tornionjoki- Torneälven 82. Kemijoki 81. Simojoki 80. Kuivajoki 79. Iijoki 78. Kiiminkijoki 77. Oulujoki 76. Siikajoki 75. Pyhäjoki 82 81 74. Kalajoki 73. Perhonjoki Sweden 2 1 4 3 80 72. Kyrönjoki 5 1. Torneälven- 8 71. Merikarvianjoki Tornionjoki 7 6 79 70. Kokemäenjoki 2. Sangisälven 78 69. Aurajoki 9 3. Kalixälven 13 77 68. Paimionjoki 4. Råneälven 10 76 67. Karjaanjoki 5. Luleälven 66. Vantaanjoki 15 6. Piteälven 75 65. Kymijoki 7. Åbyälven 11 74 8. Byskeälven 12 73 9. Kågeälven 14 10. Skellefteälven 16 1817 72 11. Rickleån Russia 12. Sävarån 19 64. Neva 13. Umeälven/ 20 FINLAND Vindelälven 21 71 63. Luga 14. Hörnån 62. Narva 15. Öreälven 38. Pregola 37. Prochladnaja 16. Lögdeälven 70 17. Gideälven 22 18. Moälven 19. Ångermanälven 23 65 69 66 RUSSIA 20. Indalsälven 68 24 64 21. Ljungan 67 22. Ljusnan 23. Testeboån 58 24. Dalälven SWEDEN 57 60 62 63 25. Emån 59 26. Alsterån 55 56 54 61 27. Mörrumsån Estonia 28. Helgeån 62. Narva 53 ESTONIA 61. Kunda 60. Selja 59. Loobu 46 52 58. Valgejogi 25 51 57. Jägala 45 50 44 49 56. Pirita LATVIA 26 43 47 48 55. Keila 54. Vasalemma 42 53. Pärnu 27 28 41 Latvia 40 LITHUANIA 52. Salaca 39 51. Vitrupe 50. Peterupe 3435 33 38 RUSSIA 49. Gauja Poland 32 37 30 31 36 48. Daugava 29. Odra/Drawa 47. Lielupe 30. Rega Lithuania 46. Irbe 31. Parseta POLAND 45. Venta 32. Wieprza 45. Venta 29 42. Bartuva-Barta 33. Slupia 41. Sventoji 44. Uzava 34. Lupawa 43. Saka 35. Leba 40. Minija 36. Wisla/Drweca 39. Nemunas 42. Barta-Bartuva River names with a slash (/) show main river/tributary. River names with hyphen (-) show names in different countries. Figure 3.14.1.2 Baltic salmon rivers divided into three categories (see above figure). Only lower parts of rivers with current salmon production or potential for production of wild salmon are shown. The presence of dams, which prevents access to areas, is indicated by lines across rivers. Notation: river name in bold = river with wild smolt production; river name underlined = river with potential for establishment of wild salmon; normal font = river with releases, no natural reproduction.

ICES Cooperative Research Report No. 255 703