This paper not to be eited withoutprior referenee tothe author

International Couneil for

the Exploration ofthe Sea

BundesforschungxmsioltHir Fischerei Hombvrg

Bibliothek

C•M. 197 2/F : 40 '

Demersal Fish(Northern)Cornrnittee

Report on the distribution of eod,haddoek,whiting and

Norway pout from a eruise with R/V "G.O.Sars"in June­

July 1972.

by

" , )Didrik Danielssenx John Lahn-Johannessen and Rikard Lj~enxx)

•INTRODUCTION

The main objeetivesof the eruise were to investigate the

hydrographieal eonditions, the d~stribution of 'plankton,

fish eggs and.larvae, and theresourees of demersal and

pelagie fish in the northern North Sea and Skagerrak. The

region eovered isshown in fig.l.

Thispaper mainly deals with the distribution and abundanee

of eod,haddoek,whiting a~d Norwaypout in relation to the

.. hydrographieal eonditions.

MATERIAL'AND METHODS

Hydrographieal eonditions were investigated by sampling 261

stations. On almost every stationsthe STD-sonde was used

as shown in fig.l.

Aeoustieregistrations were eontinually reeorded during the

eruise by means of an eehosounder (38 kHz) and 3 integrators.

x) Biological Station

Fl~devigen

Arendal,Norway

xx) Institute of Marine

Researeh,Direetorate of

Fisheries,. Beraen. NO'rwav

- 2 -

Assessments were made by estimating the running mean value of

echo abundance pr.naut.mile based on intervals of 5 naut.miles

: each. '

Identification of' registrations were' made by trawling, which. '

usually was carried out on apparently good registrations. A. .

total of 35 trawl hauls were made, out of which 18 pelagic

(Harstad and Engel trawl) and 17 'demersal (fig.l). Adequate

sampIes weret~ken'fro~~veryhaui: . Th~ s~mples were'sorted

~ccording t~'sp~cle~~a~d le~gth m~a~ureme~~~ ~ade ~o th~ nearest

~ cm below for O-groups and to the nearest cm below for bigger

fish. The total numbe~ and weight were estimated. Otholiths

were collected from cod,haddock,whiting,Norway pout and several

other species.

RESULTS AND DISCUSSION

HYDROGRAPHY

In ,th~ figure 2 and 3 are shown the temperature and salinity of"

th~ mixed bottom layer,. the thickness of which varies from min.

20'm on the North Sea-shelf to' appr~ximately 200 m inthe inner, "

part of the Skagerrak.

•

•

•

The investigated region may be divided into 3 areas reflecting

significant different hydrographical conditions. The diffe­

rences seem to hav~ so~~ relation to':th~ fish distribution.. , .The areas are "as follows: A) 'The Norwegian Deeps ' up to 150 m,

B) The shallow Danish coastal area'and C) The northern North ttSea with depths between 100 and 150m•

•

As indicated in'fig.l the whole region covered corresponds mainly

to the'ICES areas IVa and·IIIa.

The water masses of area Aare mostly of North Atlantic origin

and have high salinity and lowest temperature. Only under

exceptional winter conditions' the temperature of the bottom

layer i5 drastically changed'(Lj~en and Svansson 1972)~

In'area B, with'salinity below,3S% o, continental coastal\;. , . : . .waters are dominant~· The temperatuie, the annual variation of

whi~h iSSi9~ifi~ant,~as high compared to the·otherareas.

• • • • ~ M .i

- 3

"-- ..-.._--~'-

.~-::---....

/",-'.""'.....,

"".... ~""'~"

•

•

The water mass ofarca C is also of a-North Atlantic type,however locally coolcd during thc ~lintcrs. Thc typicül_.q.unl j ti GS"....

of the central part of it üre.slow movcments and high stabilityto the upper layers in thc su~~er. Thc area is limited'by I

\1<lrmcr, North At1antic ~later intruding on the western and eüsternside, and divided into two parts by ü tongue of water with

", . , , 0're1ative1y high temperature and sa1inity be10w 35,1/00. Sucha'hydrographic situation'is frequcnt1y observed in this season(Lj~en 1971).

Thc observcd tcmporature of the cen~ra1 parts (6.5-7.0oC) is

cornparab1e to that ofthe summers 1967 and 1971 (Lj~en 1971) •

ACCUSTIC ASSESSMENTS OF FISH ABUNDANCE

'Fig. 4 shows thc cstirnatcd abundancc of fish in the region covercd.Thc highest va1uc8 were obtained in thc northcrn centra1 partand along thc slop~of the western and southcrn scctions of;theNorwcgian Dccps with naxima.south of Lindesnes, and in the contralnorthorn North SGc. rcspoctivcly. Uorway pout appearcd to bc

thc dominating cont=ibutor to the high va1ucs in the central andsouthwestern p~~~ ~f area C whilc blue whiting was thc most,

I

prcdominatc' SP€l=.:i.~~ in area' A. The concentrations of Norway pout

found in tho ne·:: thc:-:n North Sea corrcsponds with the observationsmade byRaitt and f-!nson (1968) and others. Abundant occurr~mce ,of b1ue \rlhiting has bcen reportcd by Hamrc and Nakken (1970, 1971)

in area A~

RELATIVE COHPOSITION OF FISH

Arca A: - Cod, hüddock and whiting co~tributed very litt1c tothc to~al c~tch. .In general also catches of Norway pout wcresm~11, b~t on t~o ~~~tions the yield was comparativoly high,abcnt. 1/30f thc. total (table 1). Thc most irnportant specics

.'_ in th~ t~~w1'hauls were blue whiting, coalfish, grcater si1vcr.._,.,__... smo.:'.t ~nd other doep water species.

!Area B: About 2/3 of thc guantity caught in this arca consistcd

of cod, haddock and whiting and the by-catch mainly of dab,:sandeal, horse-mackerel arid plciica (tablc 1).

.,._-.......'---- I

- 4 -

Area C: - On an average Nor\,]aypout Irade up nearly 3/4 of the'.

total yield, and cod, haddock and ~hiting together about 1/10

(table 1). The re~aining by-catch consisted of coalfish, herringand several other species. C

I-GROUP AND OLDER GADOIDS

COD: - The species was· found in rather small numbers in the wholeregien (table 1). In area A cod occurred in nearly all thc hauls,but very fcw in numbers. On the Danish coast (area B) station

142 gave a good catch on thc contrary to station 140 with orily.3 individuals per hour of trawling. In'the northern North Sea(erea C) the nunbcr of specirncns were co~paratively small, but

tt cod was found on all stations.

Due to the small numbcrs caught the length frcquency distributionsI

and thc age compositions are made scparately for each area only,and the length material is prescnted in 5-cm groups (fig. 5).

•

.~.'

In area A thc cod was comparatively large with an age of 2 to 7years, bclonging mairily to the lI-IV groups. Thc sampies fromarea B consist of smaller fish from the I-IV group, with thcII-group being prcdominant. In arca C fish from the I toVII-group occurrcd with the I to III-group as dominating.

HADDOCK: - Table 1 indicates that,area Band C gave the best,

catches of haddock, thc species was occasionally'found in area A.

Fig. 6 shows that specimens caught in aren A generally were:

srnall and belongcd mainly to the I-group. 'Trawl stat~on 156.also includes some older individuals. In area B sevcralage-groups wcre rcprcscnted with a predominating II-group asshovr. in fig. 6a. In area C as in area A the I-group ."ms

I

stro:1:Jly represontcd (fig. 6b). In the northern part of thc,

areD, ho~cvcr, thc contribution of thc V-group (1967-ycar-class)

\-Tat1. c~~aptionally high. As reported by Anon (1971) this was nncxtremcly strong ycar-class •

- 5 - , .,

"•

•

WHITING: - !tJhiting was ,,,eIl represented both in areü B emd C,I

but did almost not occur in area A (table 1). Fig. 7 shows;that the younger aga groups were abundant in area B. In area Cthore were more older individuals. On trawl station 155 therewas an exceptionally high catch of the V-group (1967 year-clüss).

. - I

This was ülso reported by Anon (1971) as bcing a very good 'I

ycür-class in the North Sea. Knudsen 1968 mentions that it~seems

to be amigration with increasing aga from southcast to northwcstand that this also was in accordancc with his tagging cxper~mcnts

(Knudsen 1964) for the part of the stock north of Dogger Bank.

NORWAY POUT: - Area C i5 by far the most important one with:catches up to 1700 kgs per hour of trawling. Norway pout is

• I

~lso representcd in area A, occurring in all hau1s, but in :substantial numbers in a fcw hauls only. At thc Danish coast(area B) Norway pout was absent.

By comparing catch data (tab1e 1) and integrator valucs (fig. 4)it is indicated tImt the biggest conccntrations of Nor\'1ay pout

I

probübly can be dividcd into a northern, central sub-aren hctween580 and 610 N (trawl station 145 and 155), and a south-wcsternsub-area which southern"boundary is unkncwn (fig. 3). Fig.:9

~ :shows that thc sarnp1es in area A main1y consist of I-group fish;but the II~group was also representcd in- all hauls. On trawlstations 133 and 156 thc III-group even occurred. In area Cthe I-group is strongly dominating. In the northern part of thearca the II-group and even the III-group were represented. I

O-GROUP GADOID FISH

Table 2 gives theThese were most1yby bottom tra\'11.

number of O-group fish per hcur of trawling.,

caught by pelagic trawl, occasionally also

O-group cod occurred both in area Band C, though always in'small nuobers. The best catch was 162 fish per hour of traw1ing.Those takan by pclagic trawl rangcd in length frcm 3.0 to 7~0 crnand by bottom tr~w1 fram 4.5 to 11.0 crn.

Haddock occurrcd frequcntly in the whole region, but appcared

• I

•

•

- 6 -

to be concentrated to a certain extent in the central part of

the northern North Sea, the largest haul bcing 2700 number ~er

hour. The specimens taken by pelagic trawl rneasured from 2.5

to 10.0 crn, and those taken by bottom trawl from 3.5 to 11.0 cm.

Whiting occurred only in area A and B, and were caught both :

pelagic and demersal in vcry small numbers, the largest individual

catch per hour bcing 50. Taken by pelagic.trawl it ranged from, "

5.5 to 10.0 cm in length and from 4.0 to 9.0 cm in bottom hauls.

I

O-group Norway pout was only caught in the central part of area. I

C except on trawl station 128 in area A \-,here a fcw numbcrs '

occurrcd. In this central part Norway pout was found in greatnumbers. The best catch taken ~1as .31510 fish per hour. It

appears that the distribution this year was more to the norththan in 1970 (Hislop 1971) when the highest 6oncentrations werefound in the Fladen Ground area. Norway pout was only caught

by pelagic trawl and ranged from 1.5-5.5 CID. Fig. 9 shows theecho registration of O-group ~orway pout in about 50 m dept~ ontrawl station 152.

Catches of O-group gadoids gave bigger individuals in demersal·than in pclagic trawl. The rncan length in' the pelagic catches

- I

is in aecordance with Hislop (1971) except for haddock whic~

i8 larger in his material. The abundance in the area covcrEd

appear to be smallwith regard to cod and whiting. Thc haddock

was more abundant than the form~r, but the far most abundant ­spccies was Norway pout ,,]hich \-7as also found to be the most·.,abundant spccies in 1969 and 1970 as rncntioncd by Hislop (1970,

1971). From the results of this cruise and also IIislop's d~ta

(Hislop loc. eit.) thc northern North Sea appears to bc animportant O-group area, especiö.lly '-1ith regard with nalso to some extcnt to haddock.

•

- 7 -

CONCLUSION

Thc hydrographical condition in thc invcstigatcd region of theNorth Sea ünd Skügcrrak reveülcd thc cxistcnce of different

water masses wlth typical qualities. Thc distribution ofNorway pout and bluc whiting seerns to be strongly corre1atcd\to such differences.

Of thc four species dealt with in this paper Norway pout seomsto be by far thc most irnportant ona, especia11y in the central

northcrri North Sea. The other species occurrcd in comparnblysInall nurnbers.

Tho conccntrations of O-group fish, particularly of the Norwaypout w~s rnainly rcst=ictcd to the centra1 part of the northernNorth Sca where th<;,m~change of intermediate and bottom water

prob~bly has been r~~ch loss than in areas with intrudingAtlüntic \lrater.

REFERENCES

Anon 1971. :;:"::-,sL'.z.,j nary Report of thc North Sea Roundfish,

~~~~~:n7 Group. Int. Coun. Exp1or. Sea, C.~.1971/F:4.

U.~rnrc, J. an:: H~1.:"'~{Gi';.r O. 1970. Akustiskc og bio1ogisko under­u~~01Gcr i Nordsj~en og Skagerak i februar-mars

.. 1970. Fiskcts Gang 26: 477-482.

1971. Unders~ke1ser av fiskeforekcrnster iNordsj~en

0'; m~~gerak i september 1970. Ffskets Ganq 4:

6t;~o? •

Hislop, J.R.G. l?':v. P=c1iminary invcstigations on thc pe1agic0-g~oup phase of some dernersa1 gadoids. Int. Coun.Explor. Sea,C.M.1970/F: 12.

Hislop, J.R.G. and Bai1cy, R.S. 1971. Scottish investigat~ons onthc pc1agic O-group phase of some demersa1gadoids in 1970. Int. Coun. Exp1or. Sea, C.M.1971/F:11.

•

---~- -

- 8 -

Knudsen, H. 1964. Studios on whiting (Mer1angius merlang!u~4~.)

in the North Sea, Skagerrak and Kattegat. I-lI.

Medd. Darum. Fisk Havunders. N.S.4: 95-136.

1968. Studies on whiting (Merlangius mer1angius, L.)

in the North Sea, Skagerrak and Kattegat. 111.Medd. Darum. Fisk Havunders. N.S.6: 7-45.

Lj~en, R. 1971. On the temperature variation in the bottom waterof the northern North Sea. Int. Coun. Exp1or. Seü,

C.M.1971/C:33.

Lj~en, R. and Svansson, A. 1972. Long-term variations of subsurfacetemperatures in the Skagerrak. Deep. Sea Res. 19:

277-288.

Raitt, D.F.S. and Mason, J. 1968. The distribution of Norwaypout in the North Sea and adjacent waters. Mar.

Res. 1968 (4) :1-19 •

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Fig. 1. Survey route and grid of stations. l)STD sonde, 2)Nansen cast, 3)pelagic trawl,

4) demersal trawl_ e

. 61',':

" ...1.•

Fig.2. Temperature of the mixed bottom layer in theNorth Sea and Skagerrak. l)Q-group Norway'pout •

•

;"

.,"'~.

I

.,.

4' 2'

... '

O' 2' 10'

•

Fig.3.. ,; ~. . Salinity of the mixed bottom layer in the.NorthSea and Skagerrak. l)Norway pout, 2)blue whiting,A, Band C indicate the different areas as referredto in the text.

'"61·

[JI

~.~,

Q

60·

4·

\~

,v

57~ /

1·

J.,~"2·I •

o·I i • i i • i i i • i i i i j i I i i

2· 4· 6· 8· 10·

Fig.4. Relative fish abundance. Iso1ines indicate def1ection (in rnm x 10)

of echo abundance in the North Sea and Skagerrak in June-July 1972~

(Relative va1ues) .

18

12

6

A 30

10

• :., :

: \:

42

36

30

70

60

30

20

10

A T 147

N lOS

24..z~ 18a:...~ 12

l'12

6

B

c

30

20

10

30

::1 1lA T IS6 ~J 0

N S9

20~~~, ('..

z...ua:...

~ ::IL_.....-....--~~-Jt~~~.,-,..:...,~BL?~T~140A __-:- _. ,~6s~,

::]I~~~B~T142~~ ~~ <>~:96 llLCL-\'2 14 1& 1'& 20 22 24 2G 28 30 32 34 36 38 40 42 44 46 I 2 3 4 S

LENGTH IN CM AGE IN YEARS.20 30 40 50 60 70 80 90 100

LENGTH I N C~

Fig.5.

1234567

AGE IN YEARS

Cod. Length frequency distri~

bution and age composition.A)Norwegian Deeps,B)Danishcoast,C)northern North Sea.

Fig.6a. Haddock. Length frequencydistribution and age compo­sition. A)Norwegian Deeps,B)Danish coast.

20

16

JO12 T 140

C T132

~'IB

N 50

0 •20N 95 60

410

C T 143 "I 0 20

20

~I JS GO 16

10 20l[b

,6 12 60

BT 142

'''IN143

040

C T 145 ..zN 80 ~ 4 20.., N 41 uu a: ..0:' 20 '"~ 10

Cl.

12TISS

CNI03

40

4

30 C TISS

"I 020 N 71 16.. 50

10 2012 60

T 163C N 49

40

20 C T IG3 60] 0 4 20

10

. ..= ,6 20 24 28 32 36 40 44 48 52 I 2 3 4 5 5 7 99 lENGTH IN CM AGE IN YEARS

Fig.6b. Haddock. Length frequency Fig.7. Whiting. Length frequency distri-distribution and age compo- bution and age cornposition.

sition. C)northern North Sea. B)Danish coast,C)norhtern NorthSea.

60

100

80

60

40

20

80T139 60

40

20

80

T 136 60

N 100 40

20

T 133

N 163

~'7 60111.N160 40

20i r==;====

c

c

c

201 c

~ c . T 156 60 ~ n---l20 j .1~2 ~~Ulb

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2O~ C Nl11

i

20

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20.....zwU

0:

~

1 2 3AGE

80

6040

20

100

80

60

40

20

100

80

60

40

20

2220

T 163

T 155

100

T 11,3 80

60

N 123 40

20

N 126

T 11,5

N 100

N 70

100

T 132 80

60N 76 1,0

20

1812 14 16lENGTH IN CM

108

A

A

A

40

1,0

20

20

20

1,0 A

20

1,0 A

..... 1,0zwU

0: 20wa.

Fig.8. Norway pout. Length frequency distribution and age composition.

A) Norwegian'Deeps, C)northern North Sea •

, ,

'.

•

Fig.9.

•

:,:: :::

Echo record of O-group'of Nor~ay poUt at approx. 50 m depth

on trawl :station 152.

:

l

.iL:=r,:""J

Tab1e 1. Catch and number per hour of cod,haddock,whiting and Norway pout from dernersa1 trawl

hau1s in the northern North Sea and Skagerrak during June and Ju1y 1972.

•

. Area A: The Norwegian Deeps

Trawl Date Depth Total catch Cod Haddock ~vhiting Sum Norway poutstation metres kgs/hour kgs No. kgs No. kgs No. kgs No. kgs No.

125 22.6 284 552 1 36133 25.6 191 476 3 4 - . 3 4 8 326135 26.6 232 213 9 3 9 3 4 182136 27.6 216 647 49 19 49 ' 19 227 9080138 28.6 218 374 35 12 35 12 1 38139 30.6 150 415 42 17 1 1 43 18 27 664147 04.7 201 677 1 2 38 664 1 8 40 674 254 10160156 08.7 222 653 29 207 29 207 95 1996164 17.7 319 305 3 1 1 1 4 2 2 43

r1ean 226 479 16 6 8 97 + 1 24 104 69 2503

Area B: The Danish coast

140 30.6 29 80 + 3 18 46 29 231 47 280142 01.7 34 467 119 240 171 558 29 143 319 941

i1ean 32 274 60 122 95 302 29 187 183 611

Area C: The northern North Sea

132 25.6 142 670 12 4 46 363 58 367 377 31593143 02.7 100 2188 117 126 36 107 14 82 167 315 1718 76860145 03.7 135 1639 20 8 13 290 35 170 68 468 1437 72944155 07.7 135 2454 86 46 53 422 109 206 248 674 1689 84440163 17.7 137 275 25 6 37 160 30 98 92 264 99 4456

Hean 130 1445 52 38 37 268 38 111 127 418 1064 54058

Tab1e 2 O-group gadoid fish. Number per hour of traw1ing from pe1agic and demersa1 trawl hau1s

in the northern North Sea and Skagerrak during June and Ju1y 1972.

."

Area A: The Norwegian Deeps

Trawl Date Oepth Trawl 1) Type of . Cod Haddock Whiting Norwaystation metres depth m. trawl pout

128 23.6 130 85 Pe1agic 2 20 28131 25.6 158 110-145 11 2 2135 26.6 232 Demersa1 14 10137 27.6 183 85-125 Pe1agic 2 18138 28.6 218 Demersa1 5 5139 30.6 150 11 75 29146 04.7 283 165-206 Pe1agic 1 6147 04.7 201 Demersa1 10 2

Area B: The Danish coast", ..140 30.6 29 Demersa1 50 9 50

Area C: The northern North ·Sea

148 05.7 109 40 Pe1agic 58 296 24800149 05.7 158 100 22 116 13600150 06.7 137 20 12 2151 06.7 131 100 36 2152 06.7 136 45 26 18 28320153 07.7 160 50-100 33 569 4190154 07.7 164 115 162 2700 31510

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