CM_1984_G_46.pdf (2.869Mb)

International Council for the Exploration of the Sea

~- 1984/G: 46 Demersal Fish Committ

PRELIMINARY REPORT OF THE NORWEGIAN GROUNDFISH SURVEY AT BEAR ISLAND AND WEST-SPITSBERGEN IN THE AUTUMN 1983

by

Olav R. God~, Kjell Randa and Odd M. Smedstad Institute of Marine Research

Box 1870, N-5011, Bergen, Norway

ABSTRACT

This report describes the results from a stratified bottom trawl survey carried out by R/V "Eldjarn" .and M/Tr "B~traL 4"

in the period 6 September to 1 October 1983. Cod were most abundant in the Bear Island area and most numerous was the

1982~yearclass. The former most abundante 1979-yearclass was redused with 60% compared to the 1982 results. Older haddock were scarce, but some recruitement of the 1982-yearclass was recorded. The most abundant species in the area were Long rough dab and redfish.

INTRODUCTION

The investigations described are partly a supplement to the investigations carried out on cod and haddock in the Barents Sea during the winter and partly a monitoring of the demersal fish stocks in the area. During the first years of the Spitsbergen investigations, acoustic surveys were carried out

2

CDalen, R~rvik and Smedstad 1977 and Dalen and Smedstad 1978). The drastic reduction of the cod stock in the area has, however, made it almost impossible to record the cod with acoustic equipment. Therefore the investigations in 1981,1982 <Randa and Smedstad 1982, 1983) and 1983 were carried out as stratified bottom trawl survey~.

MATERIAL, AND METHODS

The survey was carried out by R/V ¹¹Eldjarn" and M/Tr

"B~tr~L 4" in the period September 6 - October 1 1983. Both vessels were equipped with a Campelen 1800 meshes shrimp trawl with rubber bobbins and codend mesh size of 35 mme

Sweepwir~s were 80 m. During a standard haul, the trawl was towed for three n. miles at a speed of three knots. The trawl stations are shown in Fig.1. Hydrographical observations were obtained with CTD-sondeCFig.2)a

The survey was designed as a stratified random trawl survey. The investigated area was devided into 45 strata based on depth and geographic Location <Figa1). The following depth intervals were used: 0 -100 m, 100 - 200 m, 200 300 m, 300 - 400 m and >400 m. The total area was devided into two subareas. The area north of 76° consists of the stratas 1-22 and the southern area of the stratas 23-45.

The allocation of trawl hauls and the statistical calculations are described by Randa and Smedstad <1982). Mean catch indices are presented in the cieted report, while swept area indices are calculated from the cruise results 1983.

RESULTS

The temperature Fig. 4 and 5. The generally higher

in 100 m and at the bottom are shown in temperature

than in 1982.

in all surveyed area was The temperature around the

3

Bear Island was occasionally 2-5 C above the 1982 results. 0

Cod was recorded in the trawl catches in all areas, but only in small quantities on the western side of Spitsbergen north of 76° N <Fig. 6). The highest catch rates were obtained east and south east of the Bear Island in the strata 31,39 and 40, and with a mean catch higher than 150 specimens per hour trawling. North of the Bear Island the mean catches were 52 and 62 cod in the strata 22 and 26. By weight the catches were highest in stratum 40 with a mean catch of 171 kg per hour trawling.

Age compositions of cod are shown in Fig. 13. In the areas shallower than 300 m, the 1982-yearclass was most numerous.

The 1977-yearclass dominated in the deeper areas. The 1979- yearclass which totally was

during the 1981 ·and 1982

the most numerous yearclass cruises, was most frequent in depths between 100 and 300 m.

Stratified indices of cod in numbers are presented in Table 1 and 2. They show that the·main cod consentrations were south if 76° N. The indices on numbers were highest in the areas shallower than 200 m. The weight indices did not vary as much as the corresponding on numbers a~ the Largest cod we·re found in the deeper areas.

The stratified indices on yearclasses (Table 3) indicate yearclass was most numerous.

<Table 4), it was stronger than

numbers as well

for that

the different the 1982- Compared

both the

to earlier years 1980- and 1981- yearclasses at the 1-group stage. If the indices increase as much during the three-four first years of life as it has done for the previous yearclasses, the 1982-yearclass will be the strongest yearclass recorded during these investigations

<Table 4). It has, however, to be stressed that the confidence limits are almost ±70%.

The indices of the 1979-yearclass, which was the strongest yearclass in 1981 and 1982, showed a reduction of almost 60%

from 1982 to 1983 (Table 4)e The yearclass was probably exposed to intensive fishing as three - four year old fish which as well is indicated by the Arctic Fisheries Working Group <Anon 1983). The decrease may also partly be a result of migration out of the area.

The haddock resources in the area were ·small. The stratified indices in numbers increased, however, from 984 in 1982 to 3720 in 19832 Mainly this was a result of relativly h i g h re c r u i t em en t of t he 1 9 8 2- ye a· r c lass • F i g .. 11 show that the catches are dominated by haddock shorter than 25 cmm Haddock was recorded in about half of the stratae The mean catch was mainly Less than 10 fish per hour trawlinge The higest mean catch was obtained in the strata 6 <north of 76°

N), 32 and 40 and was highest in stratum 39 with 28 haddock per hour trawlingm

~~Q~~t~~--m~n!~1!9 is the dominating redfish species at the Bear Island and West-Spitsbergen. The identification of the redfishes may be very difficult, especially between small

~~m9riDY~ and ~~m~nt~119· In 1983 an unusual high proportion of the redfish north of 76° N was recorded as ~~m~rinY~

compared with earlier years <Tabell 1). ~~-m~rinY~ made up 38% and 37% of the indices based on catch in numbers and weight respectivly, while the corresponding figures from the previous years were about 1%. Fig. 14 show that ~~m~rinY~

caught north of 67° N was mainly smaller than 15 ~m, while

~~m~n!~11~ was mostly larger than 15 cm. The results consequently indicate that species identification problemes of small rediish may have strongly influenced the results.

The probleme may also have influenced the results from the southern area.

Compared with the results from 1982, the stratified indices

5

for redfish based on numbers increased wh i le the corresponding weight indices decreased.

~~~~0!~11~ was most numerous in depths between 200 m and 300 m north of 76° N and in depths between 200 m and 400 m south of 76° N <Table 1). The influence of larger fish increased with depth as observed during the previous cruises.

Greenland halibut was caught in most strata deeper than 200 m. Some small halibut we re caught in the depths betwe·en 100 m and 200 m. The biggest catches were obtained in the area between the Storfjord Channel and the Kings Bay (Fig. 8).

As in 1982 the influence of older fish in the catches increased in the deeper areas <depth >400), and the Greenland hallibut north of 76° was distinctly smaller than that further south (Fig.16). The stratified indices did not change cansiderably compared to the 1982"results.

Together with the redfishes long rough dab was the most numerous species in the area. Its distribution covered all the area investigated, but it was most abundant around the Bear Island and in the Storfjord Channel where the catchrates exceeded 1000 individuals per hour trawling <Fig.9). The stratified indices were roughly unchanged compared to the 1982 results.

Blue whiting was mainly caught in the southern area. The catches were largest in 200-300 m depth <Table 1 and 2). The catches were mainly made up of fish between 30 and 40 cm

<Fig. 12). The stratified indices showed a small increase compared to the 1982 results.

6

All catches in the strata deeper than 200 m contained shrimps. The Largest catches were obtained in the Isfjord Channel, in the Storfjord channel and east-southeast of the Bear Island <Fig. 10). The stratified total indices were reduced with 20% compared to the 1982 results (Table 6). This was mainly caused by the considerable reduction <48%) of the catches north of 76° N, but also in the southern area the results indicate a decrease in the stock.

In all area small quantities of catfishes were caught. The indices of both jelly cat and smaller catfish increased, while a decrease in the catfish indices were observedm

REFERENCES

Dalen,J., R~rvik,C.J. and Smedstad, O.M. 1977. Bunnfisk-

unders~kelser ved Bj~rn~ya og Vest-Spitsbergen

h~sten 1976. Investigations on demersal fish at Bear Island and West-Spitsbergen in.autumn 1976.

£i§~~o~9~~~-12ZZ<3): 29-51.

Dalen,J. and Smedstad, O.M. 1977. Bunnfiskunders~kelser ved

Bj~rn~ya og Vest-Spitsbergen h~sten 1977.

Investigations on demersal fish at Bear Island and West-Spitsbergen in autumn 1977. fi~~~Otl~~~L

12£§(3): 1-14.

Randa,K. and Smedstad,O.M. 1982. The Norwegian groundfish survey at Bear Island and West-Spitsbergen in the autumn 1981. ~Q~o~M~~!~io!~-~Q~D~-s~Q!Qr~-~~9~

12§~<G:42): 1-17. [MimeoJ

Randa,K. and Smedstad,O.M. 1983. Preliminary report of the Norwegian groundfish survey at Bear Island and West-Spitsbergen in the autumn 1982. ~Q~O~ M~~!~

io!~-~Q~o~-s~Q!Qr~-~~9~_12§3<G:34>: 1-17. [MimeoJ

'\.

Table 1. Strat1fied indices on numbers for different deoths and areas in ^1983.

~

Species 0-100 100-200 200-300 300-400 >400 Total 0-100 100-200 200-300 300-400 >400 Total Total

Cod 917 1 893 154 191 96 3 251 15 350 13 870 8 89-1 2 400 2 160 42 670 45 920

Haddock 77 218 10 0 0 362 235 1 1'ao 1 073 164 14 3 358 3 720

s.tiar;inys 35 3 718 31 650 285 648 36 330 0 1 712 3 134 1 224 0 6 070 42 400 S.tien:telli ^{44 4 462 46 070 4 514 3 278 58 360 87 7 616} 94 720 103 500 42 170 248 100 306 5oo ^I Greenland halibut 21 1 905 6 479 2 246 3 711 14 360 0 50 2 280 2 255 7 742 12 330 26 690 Long rough dab 1 084 12 950 11 490 5 825 1 221 32 560 10 110 224 200 82 290 10 210 13 010 339 800 372 400

Blue whiting 0 0 0 44 83 128 0 157 19 630 9 423 1 270 30 480 30 610

Jelly cat 0 0 38 14 6 56 29 562 229 280 355 1 456 1 511

Catfish 24 244 212 191 19 690 59 339 411 40 111 960 1 650

Smaller catfish 14 457 187 192 124 ^~75 117 1 497 318 172 52 2 155 3 130

- - - - L _ - - - - -

...:1

Table 2. Stratified indices on weight for different depths and areas in ^1983.

North of 76 0 N South of 76 ⁰ N

Species 0-100 100-200 200-300 300-400 >400 Total 0-100 100-200 200-300 300-400 >400 Total Total

Cod 76 1 722 197 978 253 3 226 7 904 19 150 7 963 10 190 9 143 54 350 57 580

Haddock 3 16 16 0 0 35 7 381 70 12 2 474 509

S.Mar;inus 1 51 3 648 60 224 3 984 0 160 1 024 68 0 1 252 5 236'

S.M~n:telli 1 311 4 544 1 158 883 6 896 1 1 012 11 120 12 400 10 920 35 450 42 350¹ Greenland halibut 8 642 677 1 286 2 355 4 967 0 134 1 820 3 291 12 920 18 170 23 130 Long rough dab 44 895 762 390 230 2 322 1 987 32 850 9 068 1 156 1 548 46 610 48 930

Blue whiting 0 0 0 14 24 38 o. 50 5 928 2 908 463 9 349 9 387

Jelly cat 0 0 105 78 33 217 439 4 797 2 128 2 832 3 938 14 130 14 350

Catfish 36 182 169 62 16 462 47 337 1 089 108 755 2 335 2 797

Smaller catfish 30 678 166 179 50 1 104 387 5 499 236 166 21 6 309 1 412 Shrimps 0 2 548 2 807 4 277 3 606 13 240 0 10 780 18 460 11 700 20 160 61 090 74 330

Table 3. Stratified trawl indices on numbers for different ages of cod in 1983.

Age

Depth 1 2 3 4 5 6 1 8 9 10+ Total

0-100 0.8.:!:,0.7 0.2.:!:,0.2 + 0 0 0 0 0 0 0 0.9.:!:, 0.8

North 100-200 0.9.:!:,1.6 0.2.:!:,0.3 0.1.±_0.2 0. 6.±.1. 1 0.1.±_0.1 + + + + + 1. 8.:!:. 3. 0

1~~N

300-400 0 0 + + + 0. 1.±.0. 1 ⁺ + + + 0.2.±, 0.2

>400 + + + + + + + + + + 0. 1..±. 0. 1

Total 1. 7.±.1. 7 0.4.:!:,0.3 0.1.:!:,0.1 0.6.:!:,0.9 0. 1.±.0. 1 0.1.:!:,0.1 0.1.:!:,0.1 0. 1.±.0. 1 + + 3.3.:!:. 3.3

0-100 3.9.:!:_4.6 2.9.:!:,4.7 4.2.:!:,5.9 2.7.:!:,2.0 0.2.:!:,0.2 ⁺ + 0 0 0 15.4..±.16.6

South 100-200 5. 1.±.4. 6 1 • 3.±.1 . 1 1.4.±.1.3 3.7.;!:.2.6 0.9.;!:.0.6 0.4.:!:,0.3 0.2.:!:,0.1 0.5.;t0.3 0. 1.:t0. 1 0. 1.±.0. 1 13.8.:!:. 7.7

1~~

>400 0 ^{+ +} 0.2.:t0.1 0.4.±,0.2 0.8.:!:,0.2 0.4.:!:,0.2 0.3.±.0.1 0.1.:t0.1 ⁺ 2. 1.±. 0. 6

I

Total 12.9.±_9.5 4.8.:!:,4.9 6. 1.±.6. 2 8.9.:t4.0 2 ⁰ 8.±..1 ⁰ 1 2.4.:!:_0.9 1o2.:t0.4 1.6.±.0.7 0.4.±,0.2 0.2.:!:_0.1 42.7.±.22.5 ⁰⁰

I

Total all areas 14.6.±.9.6 5. 1.±.4. 8 6.2.;!:..6.2 9.5.±,4.0 J. 0.±.1. 1 2.5.±,.0.8 1.3.±,.0.5 1.6.±,.0.5 0.4,!.0.3 Oo2.±,.0.1 45.9.±.22.5

- - - - - -

Table 4. Stratified trawl indices on numbers for different year-classes of cod in 1981 - 1983.

Year of Year-class

investigation 1982 1981 1980 1979 1978 1977 1976 1975 1974 1973 1972 1971 Total

1981 0. 1 22. 2' 9. 0. 5.5 1. 3 6. 1 ^I• 3 ⁰ 8 0.7 0.4 0.4 49.8

1982 1.5 4.0 22.2 9.3 2.8 1. 9 2.9 0.4 0. 1 0. 1 45.6

1983 14. 6 5. 1 6.2 9.5 3.0 2.5 1 ⁰ 3 1 • 6 0.4 0.2 44.4

Table 5. Stratifie1 trawl indices on numbers in 1981 - 1983.

Year Number Greenland Long rough Blue Jelly Smaller

of hauls Cod Haddock _S.miriDY~ s.mentelJ.a halibut dab whiting cat Catfish Catfish

North 1981 66 1 467 327 3 415 45 680 13 600 48 720 1 821 35 621 1 209

7~JN

7~JN

I

1981 185 49 770 808 61 670 179 500 20 100 336 300 28 470 1 270 1 411 2 450 ^!

Total 1982 192 45 600 984 11 990 277 600 26 000 370 300 27 760 1 391 2 609 1 730 ^I 1983 187 45 920 3 720 42 400 306 500 26 690' 372 400 30 610 1 511 1 '650 3 130

Table 6. Stratified trawl indices on weight in 1981 - 1983. _\..0

Year Greenland Long rough Blue ~elly Smaller

Cod Haddock s.mirinys s.mentella halibut dab whiting cat Catfish Catfish Shrimps

North 1981 3 156 942 453 11 030 3 645 4 125 400 30 1 032 343 17 060

7~JN

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36

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Fig. 2. Survey tracks and hydrographical stations taken by F/F "Eldjarn" in the period 7 September - 9 October 1982.

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Fig. 4. Temperature distribution in 100 m depth.

TEMPERATUR VED BUNNEN SVALBARC SEPTEMBER t9BS

Figo 50 Temperature distribution at the Jbbttom~

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Fig. 6. Distribution of cod in the trawl ' catches (numbers per hour).

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Fig. 13. Age distribution of cod: A: .o m-100 _.n depth, B: 100 m- 200 m depth, D: 300 m-400 m depth, E: Deeper than 400m, F: North- ern area, G: Sothern area, H: Total area.

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0 40 20 ~ -46 60 0 t6l 20 m ^iQ so c 20 "tO eo eo ^'0 20 "ff 60 80

LENGTH IN CH lENGTH IN Q1 LENSTHUNICH LEN6THINQ11

Fig. 16. Length distribution of lonor rdugh dab .. ^f'igo 11 ⁰ Length distribution of Greenland halibut$

(Legends as in F.ig. 13) ^{0 ~Legends} as i:r 'Fig., 13) ⁰