CM_1972_H_12.pdf (772.3Kb)

International Council for the Explor ation of the Se a

C. M. 1972/H: 12

~elagic Fish (Northern) Committee

INTRODUC TION

O:3SERVATIONS ON CAPELIN (MALLOTUS VILLOSUS) IN NEWFOUNDLAND WATERS

By

Olav Dragesund and Terje Monstad

)nstitute of Marine Research, Bergen, Norway

Annually capelin rn.ig'rate towards the shores of Newfoundland and Labrador to spawn. Mas s beach spawning of capelin occur s Inainly in June off the east coast of Newfoundland and progressively later northwards along the coast.

The Labrador coast spawning comlnences in mid-July. Off the west and south coast beach spawning begins at the end of May. The beach spawning lasts from four to six weeks at temperatures ranging froln 5.5 to 8. 5⁰ C. When beach spaw-

'I,

ning is completed, spawning may continue in deeper water s near shore (TEMPLEMAN 1948, 1968). Capelin also spawn at the Southeast Shoal on the Grand Ban..'4:.s in

June-July (PITT 1958). At this time mature capelin have also been trawled on the eastern slope of the Grand Bank and on the St. Pierre Bank.

Little information is available on the distribution and Inigratbn of capelin

previous to the time they approach the different spawning grounds. The presence of the capelin on the Grand Banks, at the same time as along the coast, suggests that the inshore capelin may be discrete from those spawning offshore on the banks •.

Several authors (e. g. TEMPLEMAN 1948, 19?8, WINTERS 1970, DEVOLD, DEVOLD and WESTERGAARD 1972) suggest that the capelin resource off

Newfoundland and Labrador must be large. However, the utilization of the cape1in has been very limited, and no exact information exists on the size of this resourc e.,

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, The aim of the present paper is to :report some preliminary results of Norwegian capelin investigations carried out in Newfoundland waters in early summer of 1972, with emphasis on:

1)

2) 3)

distribution and migration~

, ,

structure and size of the capelin resource~

catchability of capelin, especially the mature stock just prior to, and during, the spawning season.

MATERIAL AND METHODS

The material is obtained from a survey carried out with RV IIJohan Hjort"

from 17 May to 19 June 1972. The distribution and abundance of the capelin were studied from combined acoustic surveys and fish sampling with trawl.

RV "Johan Hjortll was equipped with vertical echo sounders and horizontal

. , 3D

ranging sonar. A Simrad echo integrator was linked to a Simrad EK )~ kHz echo sounder. The setting of the EK sounder was: Output power 1 kW, time varied gain (TVG) 20 Log R and receiver gain 0 dB. The source level was

o 0

121. 8 dB, receiving voltage response 5.2 dB! the beamwidth 7 and 13 along and athwartship between the 3 dB points. The threshold on the integrator was

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set at 1, and the gain at 30 dB. In order toavoid)i1:aturation of the echo integrator the gain was adjusted when necessary.

Two integrator channels covered the depth intervals from 5 to 50 rn, and from 50 m to the bottom. Echo integrator readings were made each nautical mile and average values for each five nautical miles were plotted on maps. When other fish species were recorded within the same depth interval, the echo

abundance was divided between capelin and the other species. Both experimental fishing and analysis of the echo traces were used for dividing the total echo

abundance (BLINDHEIM et al. 1971).

The m.ethod used to estim.ate the stock size is described by MIDTTUN and

NAKKEN (1971), BLINDHEIM and NAKKEN(l971) and later applied by NAKKEN (person~l communication), JAKUBSSTOVU and MIDTTUN (1972), DRAGESUND, GJ0SA.:TER and MONSTAD (l972). The constant C was calculated from the relation of MIDTTUN and NAKKEN (1971).

fl ⁼

^{CM ( 1 )}

where

fl

is given in number of fish or fish weight per unit area and M the integrator echo intensity.

\( Capelin were caught with a Norwegian capelin trawl with an opening of 12 x 12 fathoms, mesh size (str~ched) .ranging from 200 mm (wings and squares) graded down to 22 mm (cod end). An ordinary Granton bottom trawl with coyer net equipped with bobbins was also available.

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The capelin w.ere examined fresh. Total length was measured to the nearest mm arid grouped in half cm class il).tervals. Otoliths, taken stratified, were used for age determination and age length keys were established. The maturity

stages were classified according to a scale modified from NIKOLSKY (1963).

The weight was estimated by measuring the volume of individual fish using the 'displacement method.

Hydrographit stations with Nansen bottles were taken at six sections in different regions on the Grand Banks. Hydrographic statioh~ with bathythermograph were

. ,

taken at average intervals of 25 nautical miles along the survey route. The sea thermograph recorded the temperature at a depth of about 4 m during the whole survey. A map showing the general bathymetric features on the Grand Banks and names used.in the text ar e given in Fig. 1. The survey routes and grid of stati{)ns are shown in Fig. 2.

DISTRIBUTION AND MIGRATION

Three surveys were carried out during the period of investigation. During the first survey, which was meant to give a brief information of the distribution, only scattered concentrations of capelin were recorded (Fig.

3).

The survey did not cover the whole area, and the survey legs were too far apart to give a representative picture of the distribution. The second and third surveys

(Figs. 4 and 5) showed that capelin were distributed through out the Grand Banks area from the ice border to the tail of the bank. C apelin were most concentr ated in the northern part of the area surveyed, and at the Southeast Shoal. The capelin on the northern Grand Banks had moved slightly towards the south and west

between the second and the third survey.

During the day capelin were recorded in the midwaterlayer or just above the bottom, i. e. in depths ranging from 30 to 150 m. On the northern and central Grand Banks, they appeared in small and scattered shoals during the day, whereas at the Southeast Shoal they wer e recorded in denser shoals in daytime (Fig. 6).

With diminished light in the evening, capelin came close to the surface and dis- per sed. At dawn the fish again clustered in shoals which soon migrated to deeper water.

The capelin in the northern area were mainly found in waters with temperatures below DOe (Figs. 7 and

8).

At the southern Grand Banks capelin were recorded in waters of temperatures above LOCo At the Southeast Shoal the temperatures

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varied between 2.5 and 3. 2o C •

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4

STRUCTURE AND SIZE OF THE STOCK

In the saITlples collected south of 46⁰ 30¹ N; 97,5

%

(weight percentage) of the capelin were ITlature fish. North of this latitude only 34. 7

%

of the capelin were ITlature. Fig. 9 shows the age and length cOITlposition of ITlature capelin in different areas on the Grand Banks The 1969 year-class dOITlinated in all areas, followed by the 1968 year-clas s. The age cOITlposition was very siITlilar in

the northern and western areas, whereas on the southern Grand Banks sOITlewhat larger and older fish occurred. AITlong the ITlature fish, feITlales were by far the ITlost frequently observed in the saITlples froITl the western and southern

Gr and Banks.

The age and length COInposition of iITlITlature fish is illustrated in Fig. 10.

In the s'outhern area the 1969 year-class strongly dOITlinated, while farther north the 1969 and 1968 year-classes were equally represented. The 1971 year-class appeared in the catches Inostly on the southern Grand Banks i. e.

south of 46 30o ¹N. The length cOITlposition of this year-class in different saITlpling areas is illustrated· on Fig. 11.

During the first and the second survey the bulk of the fish were in ITlaturity stages 1 and 2, whereas during the third survey capelin were nearer to spaw- ning on the southern Grand Banks (ITlaturity stages 3 and 4). SOIne of the

c apelin caught 18 June at the Southeast Shoal were already spent (ITlaturity stage 5).

In the northern area the ITlaturing fish were still in stages 1 and 2 on 10 - 12 June.

The echo abundance of capelin in the area was estiITlated on the basis of the second and the third surveys (Figs. 4 and 5). The total abundance of capelin in the area covered was estiITlated to be about 0.8 ITliUion tons (Table 1): using a C of 1. 9 tons/mm x (n. m.) . 2 However, the calculation of C is somewhat

inaccurate, and the results should be interpreted with some caution. The constant C was estimated to be 2. 17 tons/mm x (n. m.)2 for maturing capelin in the

Barents Sea. It is suggested that this figure was somewhat high and a value of about 2.0 tons/mITl x (n. m.)2 seems reasonable.

The concentrations of mature capelin observed south of Cape Race, i. e. south of about 46 °30¹ N and west of 52°20 ^I W, during the second survey (Fig. 4) were not recorded there during the third survey (Fig. 5). Assuming that these capelin had moved farther west to spawn outside the area covered during the surveys,

0 '

°

the stock size at the Southeast Shoal (south of 46 30¹ N and east of 52 20' W) was estimated to be

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- 170 thousand tons (Table 1). The stock size north of

46°30¹ N was estimated to be 32f - 36{'thou,s'1.nd tons, of which 34.7

%

were mature.

,; ,

CATCI-TAF'.IJ.,j'I'Y OF' CAI:)ELIN

DEVOrl1 ." ^{i I} ( I ! Ii' )"1"') Lt 1 _0- 11 " ,Cl [n e opinion that off Newfoundland-Labrador a capelln:;i(i '.~ (;1 f,() IU.n dll.lin~~ Sllrnnler and early autumn is a relatively lal'b',e ~~lf",:! IIUI ill,!!, tJll pe.lj.uc'\ uf the yeilr therefore, the catchability of capelin with pursE' seine ^it: not the beGl. He concluded that pelagic trawl probably "vas the most suitable gear for catching capelinoff NewfGundland and Labrador.

~xperiences from other fisheries are that catchability is improving during the spawning rnigration, At this time the fish come together from different areas

~~ are grouped in larger and denser shoals than during the feeding period.

The present survey covered the period just prior to spawning. The conditions for fishing at this tinl.e should therefore be the best. Three Norwegian purse

seiners accornpanied RV ^I1 J ohan Hjort ¹¹ during the survey.lIn the northern ar ea the concentr ations wer e not found to be dense enough for pur se seining between 18 and 30 May. The conditions for purse seining were also poor at the Southeast Shoal from 18 Ivlay to 3 June, However, from the fir st week of June onwards, as cone entrations became denser, pur se seining might be a pos sibility

j

The conditions for trawling irnproved gradually during the first week of June at the Southeast Shoal, and throughout this rnonth capelin are available for trawling with midwater trawL The season, howeve'r, seemed to be relatively short since spawning already started 18 - 19 June, and probably would have been completed by the fir st half of July (DEVOLD et a!. 1972).

CONCLUDING REMARKS

The behaviour of capelin off Newfoundland during the spawning migration is apparently sOD}ewhat different from that observed for the Barents Sea capelin.

No dense shoals were observed during the spawning migration on the Grand Banks towards the Southeast ShoaL The mature capelin were segregated from the imrna- ture part of the stock at the tirne the investigations were carried out, and gradu- ally approached the sp3vI'ning grounds in rather small shoals, showing up as a dense, but patchy sc attering layer at the Southeast Shoal. In this shallow part of the bank, capelin find suitable spawning temperatures in about 50 m depth by

mid·~ June, when spawning c omrnence s.

, 0

It is tentatively concluded that not all the capelin recorded south of 46 30^lN during the f3econd survey rnigrated to the Southeast Shoal for spawning. The concentrations recorded in the area south of Cape Race might have migrated westward to spawn either along the south coast of Newfoundland, or at the

St. Pier T e Bank wher e spawning has been recorded in earlier year s (PITT 1958, TEMPLEMAN 1968). No spawning concentrations could be observed in the

Virgin Rock region, although the environmental conditions for spawning in tl,~."

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7

REFERENCES

BLINDHEIM,'J., DRAGESUND, 0., HOGNESTAD, P. T., MIDTTUN, L. og NAKKEN, O. 1971. Lodde- og po1artorskunder sf/5ke1ser i Barentshavet august-september 1970. Fiskets Gang,

22.:

381-384.

BLINDHEIM, J. and NAKKEN, O. 1971. Abundance estimation of the spawning Lofoten cod 1971. Coun. Meet. into Coun. Explor. Sea, 1971 (B:15): 1-5, 3 tabs., 2 figs. llvHmeb"J

DEVOLD, F., DEVOLD, N. og WESTERGAARD, T. 1972. Loddeundersf/5ke1ser f/5 st av Labrador og Newfoundland i juli- august 1971. Fiskets, _Gang,2§: 49-55.

DRAGESUND, 0., GJ(Z}S.!ETER, J. and MONSTAD, T. 1972. Distribution, size

~nd reproduction of the Barents Sea capelin resource.

Lln preparation] .

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JAKUPSSTOVU, S. H. and MIDTTUN, L. 1972. Ko1mu1eundersf/5ke1ser nordve~t for De Britiske (Z}yer i februar-mars 1972. Fiskets Gang, 5.8:

428 -433.

MIDTTUN, L. and NAKKEN, O. 1971. On acoustic identification, sizing and

abundance estimation of fish. FiskDir. Skr. Ser. HavUnders., 16:

36-48.

NIKOLSKY, G. V. 1963. The ecology of fishes. Academic Press, London. 352 pp.

\1ranslated from russia0 . '

PITT, T. K. 1958. Distribution, spawning and racial studies of the capelin, Mallotus villosus (MUller), in the offshore Newfoundland area.

J. Fish. Res. Bd. Can.,~: 275-293.

TEMPLEMAN, W. 1948. The life history of the capelin (Mallotus villosus O. F. M{{ller) in Newfoundland Waters. Bull. New£. Govt.

Lab.,.!2.: 1-151.

TEMPLEMAN, W. 1968. Review of some aspects of capelin biology in the Canadian area of the north-west Atlantic. Rapp.

P.

-v. Reun.

Cons:.J2errn. into Exp1or. Mer, 158: 41-53.

WINTERS, G. H. 1970. Biological Changes in Coastal Capelin from the Over- Wintering to Spawning Condition. J. Fish. Resi.{13d. '~iCan. , 27:

2215 - 2224, 2 figs.

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Date

27.5-

9.6

7.6-

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Table 1. Echo-abundance (in tons) of capelin on the Grand Banks in different areas in May - June 1972.

Area

South of 46 30' ° West of 52 20' °

and east of and south of

North of 46°30'N 52°20' W 46°30' N Total

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Fig .. 2~ Survey routes of RV "Johan Hjort" and grid of statio.p:s 18 May to 19 June 1972, (1) hydrographic station with Nansen:bottles,

(2) hydrographic station with bathytermograph, (3).pelagic trawl station and (4) bottom trawl station.

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27 MAY - 9 JUNE 1972

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Survey route and distribution of capelin 27 May - 9 June 1972.

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Fig. ,4.

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7 -iSJUN E

1972

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(D).

(A) is from the northern (B) southern and (C) central Grand Banks.

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. JUNE 1972

17MAY-18 ,

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1972

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June

1972

Temperature in two sections on the Grand Banks in June 1972.

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Fig. 9. Age and length composition of mature capelin (separated on male and females) on the Grand Banks in Ma,y-June 1972. The border between

south and north is set at 46°30'N and for the western area at 52⁰ W.

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11 12 13 14 15 16 17

LENGTH IN CM

Fig. 10. Age and length composition of immature capelin on the Grand Banks in Mill-June 1972. The border between south and north is set

at 46 30' N.

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10

I:: :t~ ~~

O-~- ^{._. --}

^{1- ,-}

r'l-1 -

I -

Z W U

~ w

20·_·

CL

z

^{I I} I

-,

·-z

I

o

^I

;:::: 10"';

(j)

o I

~ 01-"

... ~ ., J

, !

'/ N:.: 878

! (~If (,

I

; _ . '.'1

i"'T"l

WEST

10-.;

: .;-'" --"1

~ .. -.----rl ': ~

r :... .. ..:

r~;r rL _~ ~

I' J ^{'-<.' -~}

~~,,::.L' .:..:::

F.2jL~

,

f')

=

161

1, ^17;

^b

- I :

I i

0--1--Fr:fI-I---,--1 -

^{1 j}

^{--ji- p=l---}

^r-r-

13 14 15 1617 18 19 20 LENGTH

I

r . , " ' 1

r" .,

, ,

, .~

YEAR-CLASS

D

¹⁹⁷⁰

[J

¹⁹⁶⁹

r~] 1968

;V:::

;;u (

'~~'

• ":~ .-~ =1 ,4"'j

;"=1

N= 581

J!;

^I

'i,

1 Q""

1--"1

Fig. 9. Age and length composition of mature capelin (separated on male and females) on the Grand Banks in May-June 1972. The border between

south and north is set at 46°30'N and for the western area at 52⁰ W.

Fig. 11.

30 191

20 10

20 10

....

z w 30 48 u

~ 20

(l..

z 10 z o

~ 20

(l..

~ ¹⁰

u

30 20 10

106

45

46

51

--"'-

\ _---~-

⁵⁶

64

Length distribution of.the 1971 year-class of capelin on the Grand Banks in May-June 1972.

,

~.' .