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International Council for the Exploration of the Sea

.C. M. 1975/K: 52

Shellfish and Benthos Committee

By·-cat.ches in fisheries for Pandalus bor_ealis from the northern part of the Norwegian Deeps in 1965 - 1972

by

THORE THOMASSEN

Institute of Biology and Geology University of Troms~

N-9000 TROMS0 Norway

1. Introduction

This contribution gives some information on the com- position and ma~nitude of the by-catches in the fish- eries for the deep sea prawn (Pandalus borealis) in the northern part of the Norwegian Deeps (ICES area 4 A). The data used were brought forward both by investing catch-statistics covering the period 1965 - 1972, and subsampling commercial by-catches landed throughout a year.

Only catch-data from prawn-trawling west of Sotra, Hordaland, were regarded. Statistical data were used to calculate catch per unit off effort (kg/10 hours) both for fish used for human consumption, and for the part of the by-catches used for industrial reduction. A total of 1051 fishingdays throughout 8 years were examined.

To learn the composition of the "industrial " part of the by-catches, subsampling from commercial prawn-trawlers fishing in the actual area were accomplished. From May 1971 to July 1972, 42 catches spred on 27 days were sampled •

. '2' ... Results

The calculated figures for the total by-catch per 10 hours a year, show that none of the years (l965 - 1972) are deviating from the mean (1 256.5 kg) by more than 16 per cent. Regarding the two groups

- 3 -

"consumption" and "reduction" separately, the diviations from the means reach 25 - 26 per cent

(Table 1, a).

The monthly means for 10 hours fishing (Table I, b) show that fish for consumtion amounts well over

500 kg in the winter months, while only about 200 kg in the summer. Fish for reduction purposses, however, show two peaks, one in the winter and one in April- May, both reaching 1 200 - 1 300 kg.

Fish for consumption broken down to species show that in the 1960's Squalus acanthias by far was the dominating species in the annual 10 h. catches, but was passed over by Molva ^dyper~ in the seventies.

While 10 h. fishing gave about 190 kg in 1965, only 96 kg was gained in 1972. ~. dYEter~~ia increased from 56 kg to 103 kg respectively (Table 2) .

Of the other consumption species both Raja sp., g,adl.lsmorhua, ,!3rosme _pros~ and Lophius pisca tor ius give about 20 kg per 10 hours fishing annually, while r.1erluccius merluccius and Molva molva each

----~~:....

.. ----

^'

reaches about 30 kg. Sebast,es marinus gave in 1966 41 kg per 19 h., but only 2 kg in 1969.

~~c:hiUs .J?ol1.~,chiu~, ~~s and !!.i12pogl-ossus

hil?1?oglg~s~~ are all' of minor importance in these catches. One should note, however, the increased catches of Po_Ylrens in 1970 and onward (Table 2).

The weight-composition of the by-catches of fish for consumption throughout a year, is shown in

Table 3. In the three first months of the year this part of the by-catches is dominated by the S.

acarl"thia~s.' which also contributes with at least one fourth until June. In April and May, the

- 4 -

share of M. merlucciu~ reaches about 42 and 28 per cent respectively. From July until Oktober M.

~erygia by far is the most dominant species with more than forty per cent. Then for the two last months

s.

acanthias again tops the list with twq thirds of the' "consumption" by-catches (Table 3).

Table 4 gives the composition in nuniller per species of the samples taken from the commercial by-catches for reduction purposses. The monthly distributiori by weight in these samples is shown in Table 5. In May,

these by-catches are by far dominated by Micromesistius poutassou (85%). Already in June the situation have changed. Now Argentina sp. make up for 50 per cent, while M. poutassou is redused to nearly 40 per cent.

These two species together with Sebaste::> viviparus, which in August comes up to fairly twenty per cent, are the dominating species up to and including October.

As there were no fishing in the area examined in November and Desember in 1971, there are no samples

from these months. The first four months i.n 1972 are characterized by great changes in the composition of these by-catches from month to month. Only

s.

^viviparu~ are among the dominating species through- out this period. Argentina sp., which in January

amounts to 30 per cent, will for the next three months not exceed 9 per cent. In February and April Etmopterus 'spin'ax, and M. poutas'sou together with S. viviparus

to'gether make up for about 60 per cent, while in March S.' viviparus and M. dyperygia both reach about 35 per

cent, while E. spinax and M. poutassou are not present at all. In may and July 1972r the composition of these by-catches look very much the same as in 1971, however, M. poutas'sou not so dominent now as in 1971. A mean of all the sampled months shO\'1s that ~outassou

contributes with 29 per cent of these by-catches, while .Argertina sp. and S. vi v..:iparus stand for about

25 and 17 per cent respectively (Table 5).

- 5 -

3. Comments

CJmper~ble data to those here reported, are given by SMIDT (1970, Table 6), in his co-ordination of data conserning Panda1us fisheries in the ICES area. In July 1969, M. JLoutassou and Argentina sp. are the dominating species also in the Coral- and Viking-bank area.together with ~. es~arkii. The abundence here of this last species is obvious a result of the different depths examined, 218 - 254 m in the

Cora1- and Viking~banks compared to 280 - 310 m in the area taken into consideration in this paper.

In February and March, 1956, "Anton Dohrn" made a survey in the northern part of the North-Sea.

RAHARDJO(1961) reports from that survey that the catches of M. mo1va were three times the catChes of M., ^dyper~, and that B. brosme did not occure in the 64 hauls executed. The different proportions between the two Lings, seems again to beexplaineg:

by the different de.pths examined. M. mo1va was caught between 150 - 270 m while M. dyperygia between 200 -

310 m (RAHARDJO, op.cit.). The report on B. brosme, however, stands in contrast to what was found in the present paper (Table 3).

4'. References

RAHARDJO-JOENOES, G. 1961. Ober die Bio1ogie und fischerei1iche Bedeutung der Lenfische

~lva mo1va L., M. byrkelan~ Wa1b.) und des Lumb (Brosmius brosme Asc.). Ber. dt.

wiss.Rommn. Meeresforsch. (N. Fe) 16 (2):

129 - 160.

SMIDT, E. (ed.) 1970. The Pandalus fisheries of the ICES

~._. __ Coul2._:. Mee!:. into Coun. Exp1or. Sea, 1970

(:r<: 2 0) .. :Lo'l: , L 1. ~.lllt;0 ^.

. ~--..

--

Table 1. By-catches .in kg per

io

hours fishing.

a) annually, b) monthly mean for the years 1965 -1972 a) Year: 1965 1966 1967 1968 1969 1970 1971 1972 Mean

For consumption: 411 323 343 321 438 282 309 369 349.5 For reduction: 893 872 893 875 788 892 1 149 894 907.0

Total: 1 304 1 195 1 236 1 196 1 226 1 174 1 458 .1 263

!

1

256.5

b) Month: I 11 III IV V VI VII VIII IX X XI XII Mean

For consumption: 523 311 475 302 268 219 186 246 287 253 564 560 349.5

For reduction: 1 215 704 631 515 1 271 1 366 757 853 802 997 1 058 718 907.3

Total: 1 738 1 015 1 106 817 1 539 1 585 943 1 099 1 089 1 250 1 622 1 278 i 1 256.8

Table 2. Annual by-catch of fisli for consumption broken down to species (kg/l0 h) •

Year:

Species: 1965 1966 1967 1968 1969 1970 1971 1972

Squalus acanthias 189 76 138 111 178 -60 76 96

Raja sp. 22 23 13 16 23 30 8 30

Pollachius pollachius 2 3

"

virens 1 1 1 1 1 7 6 4

Gadus morhua 6 10 20 16 14 10 35 20

Brosme brosme 20 38 17 14 18 18 17 33

Merluccius merluccius 18 28 26 36 61 . 25 39 19

Molva molva 32 36 28 29 31 ·19 22 26

"

dypterygia 56 43 61 75 86 83 84 ID3 Sebastes marinus 22 41 20 5 2 8 6 18 Hippoglossus hippoglossus 2 2 2 1 2 1 1 1

Lophius piscatorius 43 25 17 17 20 21 12 19

Table 3. Monthly by-catch of fish for consumption broken down to species in per cent of weight.

Mean of the period 1965 -1972.

Species I II III IV V VI VII VIII IX X XI XII

Squalus acanthias 49.2 21.6 65.0 25.0 31.5 3.5 0.4 1.0 24.5 66.0 67.4

Raja sp. 6.6 14.1 3.2 5.1 6.6 9.2 7.9 7.2 5.5 4.3 1.9 2.1

Gadus morhua 3.8 14.1 1.5 1.6 1.8 2.6 3.7 5.6 3.5 3.5 3.4 0.9

Brosme'brosme 2.8 7.8 5.1 7.9 7.7 12.2 9.9 12.0 9.3 5.1 1.7 2.1

Merluccius mer1uccius 6.8 12.5 12.7 42.4 27.8 11.4 1.0 0.4 0.3 0.2 0.5

Molva mo1va 4.8 6.6 1.9 3.2 5.1 11.4 16.8 17.7 18.0 9.7 8.3 7.6

M. dypterygia 13.0 5.6 6.5 3.8 10.3 30.6 45.0 42.6 48.8 42.4 12.9 13.2

Seb.astes· marinus 3.8 6.3 0.6 1.3 1.5 3.9 4.7 6.4 5.9 3.5 1.9 0.9 Lophius piscatorius 8.2 7.5 3.2 7.6 6.6 12.7 9.9 7.6 6.2 5.8 2.7 3.5 Others 1.0 3.9 0.4 2.2 1.1 2.6 1.1 . 1.4 1.2 1.0 1.9 Total 100.0 100.0 100.1 100.1 100.0 100.1 100.0 99.9 99.9 100.0 100.0 100.1

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418 ---...

Table 5. Monthly by-catch of fish for reduction broken down to species in per cent of weight.

1971 1972

~1ay

Jun J u 1 Aug Sep Okt Jan Feb r·1a r Apr May Jul

~1ean

Squalus acanthias

0.1 7.1 1.0 1.3 3.7 1.1

Etmopterus spinax

1.6 2.8 3.2 3.2 3.9 8.8 5.6 14.8 18.1 4.5 0.4 5.6

Raja sp.

0.4 0.2 1.3 0.5 0.6 5.8 0.7

Chimaera'monstrosa

0.5 1.9 O. 2 0.1 3.5 0.3 7.8 4.8 5.8 2.0 2.2

Argentina sp.

'10.5 50.8 45.7 28.5 23.1 24.1 30.9 5.9 8.6 7.1 19 .. 8 4 O. 9 24.7

r~

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0

m e s i s

t

ius poutassou

85.2 38.8 36.8 26.2 24.0 15.9 2.9 15.6 11. 7 53.8 40.0 29.2

Trisopterus esmarkii

0.1 3.4 1.9 2.3 3.1 12.9 9.4 4.6 0.7 0.3 3.2

Gadiculus argentus

1.8 1.4 0.3 1.3 3.8 0.8 4.6 1.2

Pol1achius virens

0.3 0.2 1.7 0.5 0.2

Melanogrammus aeglefinus

0.2 0.1 0.6 0.1

Merluccius merluccius

1.7 0.7 0 .• ~

Mo1va dyperygia

0.2 0.3 4.4 5.1 5.6 38.2 4.2 1.1 2.6 5.1

Rhinonemus cimbrius

0.3 0.1 0.1 2.0 1.3 1.9 0.5 0.3 0.4 0.6

Sebastes viviparus

0.7 3.0 9.4 22.5 26.9 15.6 12.2 2&. 2 34. 6 28.5 8.4 11. 3 16.J::L,

G1yptocepha1us cynoglossus

0.7 0.9 0.9 1.5 2.5 1.9 5.8 5.7 5.4 14.2 2.4 3.5

Hippog1ossoides p1atessoides

0.1 0.6 0.2 11.2,10.0 13.8 6.8 3.9 4.8 3.2 1.5 4.7

Other

0.3 0.5 0.1 0.5 0.3 8.6 O. 2 0.1 0.1 0.2 0.9

100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.1 -100.0

Total