REPORT OF THE INTERNATIONAL 0-GROUP FISH SURVEY IN THE BARENTS SEA AND ADJACENT WATERS IN AUGUST - SEPTEMBER 2001 I M R / PI NRO T E P O R T

Transcription

1 T E P O R T IE R 2001 E IN JO R 8 S I M R / PI NRO S REPORT OF THE INTERNATIONAL 0GROUP FISH SURVEY IN THE BARENTS SEA AND ADJACENT WATERS IN AUGUST SEPTEMBER 2001 Institute of Marine Research IMR Polar Research Institute of Marine Fisheries and Oceanography PINRO

2 This report should be cited as: Anon Report of the international 0group fish survey in the Barents Sea and adjacent waters in August September IMR/PINRO Joint Report Series. No. 8/2001. ISSN pp.

3 IMR/PINRO Joint Report Series, No. 8/2001 REPORT OF THE INTERNATIONAL 0GROUP FISH SURVEY IN THE BARENTS SEA AND ADJACENT WATERS IN AUGUST SEPTEMBER 2001 The 37th annual international 0group fish survey was conducted during the period 10 August 8 September 2001 in the Barents Sea and adjacent waters. The following research vessels participated in the survey: State Name of vessel Period Research Institute Norway G. O. Sars Institute of Marine Research, Bergen Norway Johan Hjort Institute of Marine Research, Bergen Russia AtlantNIRO The Polar Research Inst. of Marine Russia Fridtjof Nansen Fisheries and Oceanography, Murmansk Names of scientists and technicians who participated are given in the Appendix. Preliminary analyses of the survey data were made on board G. O. Sars and AtlantNIRO and the final report was finished by correspondence. Observations concerning the geographical distribution of 0group fish and their abundance are given in this report together with a brief description of the hydrographical conditions in the survey area. 1

4 MATERIAL AND METHODS The geographical distributions of 0group fish were estimated based on samples from a small mesh midwater trawl. All vessels that participated in the survey in 2001 used a type of midwater trawl recommended in 1980 (Anon. 1983). The standard procedure consisted of tows of 0.5 nautical mile at each of 3 depths with the headline of the trawl located at 0, 20 and 40m, respectively. Additional steps at 60 and 80m per 0.5 nautical mile were made when the 0group fish layer was recorded deeper than 60m or 80m on the echosounder. Trawling procedures were standardized in accordance with the recommendations made in Most of the stations were taken 35 nautical miles apart. Hydrographical observations were made at each trawl station and at several permanent hydrographical sections (Fig.1). Figs 2 5 show the temperature and salinity conditions along the hydrographical sections: Bear Island West, Bear Island North Cape, Cola and Cape Kanin North. The mean temperatures in the main parts of these sections are presented in Table 1. Horizontal distributions of temperature and salinities are shown for 0, 50, 100, 200 m and at the bottom in Figs 615. Trawl stations with and without catch are indicated on the distribution charts (Figs ) as filled and open symbols, respectively. The density grading is based on catch in numbers per 1.0 nautical mile trawling. Double shading indicates dense concentrations. The criteria for discriminating between dense and scattered concentrations are the same as used in earlier reports (Anon. 1980). Abundance indices are given in Table 2. All area based abundance indices were estimated using standard computer programs (Fotland et al. 1995). Logarithmic transformed abundance indices are given for 0group herring, cod and haddock (Table 3), calculated according to Randa (1984). These are based on the number of fish caught during a standard trawl haul of one nautical mile. Mean values of the abundance indices were only calculated for the period 1985 to 2001 (Table 2), since Nakken and Raknes (1996) show that previous surveys might not be comparable for methodological reasons. Estimated length frequency distributions for the main species are given in Table 4. HYDROGRAPHY The following temperature deviations from the long term means were observed in 2001; +0.C in the Norwegian and Coastal Murmansk currents, +0.C in the central branch of the North Cape current, +0.8 C in the Novaja Zemlja current and +1.C in the Kanin current. The temperature in the upper layers of the Murmansk current was close to the long term mean. These temperature measurements are from the 0200 m layer in the Bear Island West, Kola section and in Cape Kanin section (Table 1). However, a negative deviation (0.C) was observed in the 0200 m layer in the North Cape Bear Island section (North Cape current) with extreme values of up to 1.C near the coast (Coastal North Cape current) and 1.C in the near surface layer (2050 m, North Cape current), which penetrated into the Barents Sea from the Norwegian Sea. Negative deviations of up to 1.C were observed in the Spitsbergen current in the 0100 m layer of the Bear Island West section. Reduced temperatures were also observed in the central and eastern parts of the Barents Sea with deviations of 2.C in the 3050 m layer of the Kola section (Central Branch of North Cape current) and up to 2.C in the 2540 m layer in the 2

5 Kanin section (Novaya Zemlya current). The upper 20 m layer had positive deviations along all sections. The waters of the Bear Island current in the North Cape Bear Island section had a significant positive deviation (up to +3.8 C). Average water temperature differences between 2001 and 2000 were; 0.C (Norwegian current), 0.C (North Cape current), 0.C (Coastal Murmansk current), 0.C (Murmansk current), +0.C (Central Branch of North Cape current), 0.C (Novaja Zemlja current) and 0.C (Kanin current) in the 0200 m layer in the Bear Island West, North Cape Bear Island, Kola and Cape Kanin sections. The waters of the upper 100 m layer were saltier than usual, except for the currents with positive temperature anomalies, such as the Spitsbergen, North Cape, coastal and central Branches of North Cape, Murmask, coastal Murmansk and Novaja Zemlja currents, which had negative salinity deviations. DISTRIBUTION AND ABUNDANCE OF OGROUP FISH AND GONATUS FABRICII Herring (Fig.16) In the central area of the Barents Sea, 0group herring had a smaller spatial distribution than in the previous 5 years, while west of Spitsbergen an increased spatial distribution was observed. No dense concentrations were found. The abundance index, 0.13, which is below the longterm average (Table 3), indicates a continuous decrease in abundance during the period The year class can be characterized as weak. The estimated mean length of 0group herring was 62.3 mm, which is similar to that observed in Capelin (Fig.17) 0group capelin were mainly found in the central part of the sea, from the coast to 76º30'N and from Bear Island extending to the coast of Novaja Zemlja. The area index equaled 221, which is somewhat below the mean for the period (Table 2). The year class can be characterized as medium. The abundance index may be biased due to incomplete coverage of the spatial distribution towards the north. The length distribution and mean length were slightly higher than last year. Cod (Fig. 18) 0group cod were found in a smaller area than last year. Scattered concentrations were observed from 80ºN northwest of Spitsbergen to 43ºE. East of this area only small scattered patches were observed. Both the logarithmic (0.23) and the abundance index (212) are much lower than the longterm mean and close to what was observed in 1999 (Tables 2 and 3). This implies that the 2001 yearclass is much smaller than average, and it can be characterized as weak. The estimated mean length of 0group cod is 72.4 mm, which is about 3 mm less than in

6 Haddock (Fig. 19) Haddock is experiencing a continued period of high and stable recruitment. The spatial distribution of 0group haddock was slightly smaller than in previous years. The abundance index equaled 394, which is the fourth largest observed. Only the indices for 1991, 1998 and 2000 were higher (Table 2). As was the case last year, dense concentrations were found over a large area in the central Barents Sea. The logarithmic index (0.67) is also significantly above the longterm mean (Table 3). The length distribution and mean length of 0group haddock are given in Table 4. The estimated mean length was 99.9 mm, which is almost 20 mm greater than last year. Polar cod (Fig. 20) As in previous years, two separate areas (components) of 0group polar cod were found. To the west of Spitsbergen, dense concentrations were observed in a larger area than last year. The eastern component was smaller than in the last 2 years. The abundance indices for both polar cod components may be biased due to incomplete coverage of the northern part of the distribution. Nevertheless the abundance index of the eastern component seems to be lower than the longterm mean and lower than in 2000 (Table 2). The estimated mean length of polar cod is smaller than last year. Saithe (Fig. 21) 0group saithe were found between Bear Island and 32ºE. No abundance index was calculated, but based on the spatial distribution it seems that the component of the 2001 yearclass in the Barents Sea might be somewhat smaller than in Redfish (Fig. 22) The recruitment of redfish has continued to deteriorate. In 2001 only a small area of 0 group redfish was found, which was to the west of Spitsbergen. The abundance index of the 2001 yearclass is at an all time low (Table 2). The estimated mean length was 32.9 mm, which is somewhat smaller than last year. Greenland halibut (Fig. 23) There was a slight increase in the abundance of 0group Greenland halibut, which were found in two areas one to the south and one to the west of Spitsbergen. The abundance index is significantly higher than average and the highest since 1987 (Table 2). The estimated mean length of 0group Greenland halibut was 63.3 mm, which is close to last year s mean. Long rough dab (Fig. 24) 0group long rough dab were observed in scattered areas. Larger patches were found to the west and south of Spitsbergen and in the central Barents Sea. There was a slight increase from 2000 in areal extend, and the abundance index of 0group long rough dab (Table 2) was slightly higher than last year. The estimated mean length was less than in

7 Sandeel (Fig. 25) A small area of 0group sandeel was found in the southeastern part of the Barents Sea, but there was only one large catch. In the central Barents Sea there were only small catches. The total abundance and the spatial distribution seem to be much smaller than last year. No abundance index was calculated for this species. Catfish (Fig. 26) The 0group catfish were distributed in the northwestern Barents Sea, as was the case last year, and in patches to the west and south of Spitsbergen. In the central Barents Sea there were only a few insignificant catches. No abundance index was calculated for this species. Gonatus (Fig. 27) The spatial distribution of 0group Gonatus fabricii was similar to its distribution in previous years; that is in the western part of the survey area from the Norwegian coast to Spitsbergen. No abundance index was calculated for this species. REFERENCES Anon., Preliminary report of the International 0group fish survey in the Barents Sea and adjacent waters in August/September Annls biol., Copenh., 35: Anon., Preliminary report of the International 0group fish survey in the Barents Sea and adjacent waters in August/September Annls biol., Copenh., 37: Fotland, Å., Mehl, S. ans Sunnanå, K Methods of index calculation and presentation of fish abundance data using standard computer programs. Pp in Hylen, A.(ed.): Precision and relevance of prerecruit studies for fishery management related to fish stocks in the Barents Sea and adjacent waters. Proceedings of the sixth IMR PINRO symposium. Bergen, 1417 June Institute of Marine Research, Bergen; Norway. Nakken, O. and A.Raknes Corrections of indices of abundance of 0group fish in the Barents Sea for varying capture efficiency. ICES CM 1996/G:12, Ref.M. Randa, K Abundance and distribution of 0grouo ArctoNorwegian cod and haddock Pp in Godø, O.R. and Tilseth, H. (eds): reproduction and recruitment of Arctic cod. Proceedings of the first SovietNorwegian symposium; Leningrad, 2630 September Institute of Marine Research, Bergen; Norway. Tereshchenko, V.V Some results from longterm oceanographic observations during 0group surveys in the Barents Sea. ICES CM 1992/C:18. Toresen, R Recruitment indices of Norwegian springspawning herring for the period based on the international 0group fish surveys. ICES CM 1985/H:54. Ushakov, N.G. and Shamray E.A The effect of different factors upon the Barents Sea capelin yearclasses. Pp in Hylen, A. (ed): Precision and relevance of prerecruit studies for fishery management related to fish stocks in the Barents Sea and adjacent waters. Proceedings of the sixth IMRPINRO symposium. Bergen, 1417 June Institute of Marine Research, Bergen, Norway. 5

8 Table 1. Mean water temperature 1 in selected subsections of standard sections in the Barents Sea and adjacent waters in AugustSeptember Year Section 2 and layer (depth in meters) bot. 0bot ) ) Earlier presented temperatures have been slightly adjusted (Tereshchenko, 1992). 2) 13: Murmansk Current; Kola section (70º30'N72º30'N, 33º30'E) 4: Cape Kanin section (68º45'N70º05'N, 43º15'E) 5: Cape Kanin section (71º00'N72º00'N, 43º15'E) 6: North Cape Current; North CapeBear Island section (71º33'N, 25º02'E 73º35'N, 20º46'E) 7: West Spitsbergen Current; Bear Island West section (74º30'N 06º34'E 15º55'E). 3) In 1998 only the central branch and the eastern branch of the West Spitsbergen Current were covered, and the temperatures were 5.4 and 4.5ºC respectively. 6

9 Table 2. Abundance indices of 0group fish in the Barents Sea and adjacent waters in *)Assessment for in Anon (1980) and for in Ushakov and Shamray (1995). **) Indices for adjusted according to Nakken and Raknes (1996). Year Capelin* Cod** Haddock** Polar Polar Redfish Greenland Long rough cod W cod E halibut dab

10 8 Table 3. Estimated logarithmic indices with 90% confidence limits of yearclass abundance for 0group herring, cod and haddock in the Barents Sea and adjacent waters Herring Cod Haddock Year Index Confidence limits Index Confidence limits Index Confidence limits Mean

11 Table 4. Length distribution of 0group fish in percent in the Barents Sea and adjacent waters in August September Length (mm) Herring Capelin Cod Haddock Polar cod Redfish Sandeel Greenland halibut Long rough dab No. measured Total catch Mean length, mm

12 8N 78 N 7N 7N 7N 7N 68 N E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig.1. Ctdstations taken by the four vessels in the Barents Sea during the period

13 'N 330'E St 'N 330'E St A 'N 330'E St 'N 330'E St B Fig. 2. Temperature (A) and salinity (B) in the Kola Section 11

14 'N 19 20'E St 'N 229'E St A 'N 19 20'E St 'N 229'E St B 500 Fig. 3. Temperature (A) and salinity (B) in the North Cape Bear Island Section 12

15 'N 034'E St 'N 18 30'E St A 'N 034'E St 'N 18 30'E St B Fig. 4. Temperature (A) and salinity (B) in the Bear Island West Section 13

16 50 730'N 415'E St 'N 415'E St A 'N 415'E St 'N 415'E St B Fig.5. Temperature (A) and salinity (B) in the Kanin Section 14

17 8N 78 N 7N 7N N N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 6. Distribution of surface temperature ( C) 8N 78 N 7N N N N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 7. Distribution of surface salinity 15

18 8N 78 N 7N 7N 7N 8 7N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 8. Distribution of temperature ( C) at the 50 m depth 8N 78 N 7N 7N N 7N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 9. Distribution of salinity at the 50 m depth 16

19 8N 78 N 7N 7N 7N 7N 68 N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 10. Distribution of temperature ( C) at the 100 m depth 8N 78 N N 7N N 7N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 11. Distribution of salinity at the 100 m depth 17

20 8N 78 N 7N 7N 7N 7N 68 N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 12. Distribution of temperature ( C) at the 200 m depth 8N 78 N N N N 7N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 13. Distribution of salinity at the 200 m depth 18

21 8N 78 N 7N 7N 7N 7N 68 N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 14. Distribution of bottom temperature ( C) 8N 78 N 7N 7N 7N 7N N E E 1E 1E 2E 2E 3E 3E 4E 4E 5E 5E 6E Fig. 15. Distribution of bottom salinity 19

22 Fig. 16. Distribution of 0group herring Fig. 17. Distribution of 0group capelin. 20

23 Fig. 18. Distribution of 0group cod. Fig. 19. Distribution of 0group haddock. 21

24 Fig. 20. Distribution of 0group polar cod. Fig. 21. Distribution of 0group saithe. 22

25 Fig. 22. Distribution of 0group redfish. Fig. 23. Distribution of 0group Greenland halibut. 23

26 Fig. 24. Distribution of 0group long rough dab. Fig. 25. Distribution of 0group sandeel. 24

27 Fig. 26. Distribution of 0group catfish. Fig. 27. Distribution of Gonatus fabricii. 25

28 APPENDIX Research vessel Participants AtlantNIRO A. Bendik, O. Dolgaja, T. Gavrilik, S. Ivanov, V. Kapralov, V. Mamylov, T. Prokhorova, D. Prozorkevich (cruise leader), S. Ratushny, M. Rybakov, T. Sergeeva F. Nansen A. Astakhov, I. Dolgolenko (cruise leader), J. Garbut, V. Guzenko, V. Kapralov, S. Kharlin, S. Rusyaev, V. Sergeev, I. Shevelev, O. Vavilova G. O. Sars P. Fossum (cruise leader), H. Gill, A. Hassel, T. Haugland, K. Helle, J. Horne, Ø. Leikvin, A. Sæther, J. Træland, N.Ushakov J. Hjort J.R. Andersen, M. Dahl, K. Gjertsen, H. Græsdal (cruise leader), R. Ingvaldsen, E. Sælen Meland, M. Mjanger, H. Sagen, H.J. Skaug 26

29 IMR/PINRO Joint Report Series 2001 No. 1 Anon Survey report from the joint Norwegian/Russian acoustic survey of pelagic fish in the Barents Sea, September October IMR/PINRO Joint Report Series. No. 1/2001. ISSN pp. No. 2 Anon Report of the international 0group fish survey in the Barents Sea and adjacent waters in August September IMR/PINRO Joint Report Series. No. 2/2001. ISSN pp. No. 3 Anon Report of the international 0group fish survey in the Barents Sea and adjacent waters in August September IMR/PINRO Joint Report Series. No. 3/2001. ISSN pp. No. 4 Anon Report of the international 0group fish survey in the Barents Sea and adjacent waters in August September IMR/PINRO Joint Report Series. No. 4/2001. ISSN pp. No. 5 Aglen, A., Drevetnyak, K., Jakobsen, T., Korsbrekke, K., Lepesevich, Y., Mehl, S., Nakken, O., and Nedreaas,K. H Investigations on demersal fish in the Barents Sea winter Detailed report. Botnfiskundersøkingar i Barentshavet vinteren Detaljert rapport. IMR/PINRO Joint Report Series. No. 5/2001. ISSN pp. No. 6 Shevelev, M., and Lisovsky, S Technical regulations and bycatch criteria in the Barents Sea fisheries. Proceedings of the 9 th PINROIMR Symposium, Murmansk, 1415 August IMR/PINRO Joint Report Series. No. 6/2001. ISSN , ISBN No. 7 Anon Survey report from the joint Norwegian/Russian acoustic survey of pelagic fish in the Barents Sea, September October IMR/PINRO Joint Report Series. No. 7/2001. ISSN pp.

30 Institute of Marine Research Nordnesgaten 50, 5817 Bergen Norway Polar Research Institute of Marine Fisheries and Oceanography (PINRO) 6 Knipovich Street, Murmansk Russia