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HAFORSMINGSINSTI~ETS EGG- OG LARVEPROGRAM (HEIP)

H. Bjørke, P. Fossum, K. Nedreaas og R. Sætre Fiskeridirektoratets Havforskningsinstitutt

Postboks 1870, 5024 BERGEN

FORORD

Denne rapporten består av f~lgende tre delrapporter:

Side

Herring larvae off western Norway in April 1985 2

O-group saithe off the northern Norwegian coast in May 1985

₂₇

Undersøkelsene over sildelarver på Møre - Trøndelagskysten i mars-

april og over fordelingen av fiskeyngel på norskekysten i mai ble

begge startet opp

i

1985. Disse har fra i986 fortsatt under HELP. For

at rapportserien fra disse undersøkelser skal være komplett er derfor

året 1985 inkludert i HELP-rapportene.

MVFORSrcNINCSINSTI~TS EGG- OG _{WIVEPROGM (BP)}

HERRING LARVAE OFF WESTERN NORWAY IN APRIL

1985

BY

H. B j ~ r k e , P. Fossum and R. Sætre I n s t i t u t e of Marine Research

P.O.Box 1870, 5024 BERGEN

ABSTRACT

The r e c r u i t m e n t t o t h e Morwegian spring-spawning h e r r i n g have d u r i n g t h e l a s t twenty y e a r s been on a very low l e v e l . However, t h e s i z e of t h e spawning s t o c k has i n c r e a s e d i n r e c e n t y e a r s and i n

1983

a r i c h y e a r c l a s s was produced. The i n c r e a s e of t h e s t o c k a s w e l l a s development of new g e a r s and methods was t h e background f o r a new p r o j e c t t o s t u d y t h e r e c r u i t m e n t mechanisms. The p r e s e n t r e p o r t p r e s e n t s some p r e l i m i n a r y r e s u i t s from a p i l o t s t u d y i n A p r i l

1985-

I t d e a l s with t h e h o r i z o n t a l and v e r t i c a l d i s t r i b u t i o n of h e r r i n g l a r v a e i n r e l a t i o n t o p h y s i c a l c o n d i t i o n s a s w e l l a s growth and d i e t .

INTRODUCTION

During the sixties the Norwegian spring-spawning herring was reduced to a minimum. Except for 1983, the recruitment to this stock during the last twenty years has been on a very low leve1 (TORESEN 1985).

Only the year classes 1966, 1973, 1979 and 1984 may be rated slightly above the average if the 1983 year class is deleted. However, the size of the spawning stock of the Norwegian spring-spawning herring has gradually increased and in 1983 the stock produced a rich year class (RØTTINGEN 1984),

After 1959 the Norwegian spring-spawning herring have been spawning 'along the western coast of Norway north of 62'~. The main spawning area is found between 62' and 6 5 ' ~ at depths of 70-150 m. The spawning last for 4-6 weeks with a naximum intensity during the first part of March. The incubation time is 18-24 days depending on the actual temperature (DRAGESUND et al. 1980).

Sampling of herring larvae along the coast of Norway has been carried out for a long period (e.g. WIBORG 1960, DRAGESUND 1970, BJØRKE 1981).

The increase of the stock in more recent years as well as the development of new gears and methods, actualized the formulation of a project to study survival and growth of herring larvae and thereby the recruitment mechanisms. Data on development of hatching, feeding conditions, predation and larval drift in relation to physical conditions will be collected. The following questions will be attempted answered during the project period:

1 . Is the concept of a "critical larvae stage" valid?

2. Is the recruitment to the stock based on the whole larvae population or only on a specific part of it with a high survival rate?

3. Are the larval population split into a northern and

soui:hern component and if so, what is the drivikig mechanism?

4. Are there special retention areas for the larvae and how do these influence the survival rate?

5 .

What is the major factor governing the larval survival

rate; predation, feeding conditions or environmental variability?

Among problems that arises from these general questions are the vertical distribution and migration of the herring larvae.

In

1 9 8 6

the project on the Norwegian spring-spawning herring was

included in a national program to study the consequences on fish eggs and larvae of oil exploration north of 62'~ (FØYN and BJØRKE

1 9 8 6 ) .

The present report gives some preliminary results from the investigation in

1 9 8 5 .

This is regarded mainly a pilot study and a thoroughly discussion of the results is considered to be beyond the scope of this paper.

MATERIALS AND METHODS

The study was carried out during the period

1 0 - 18

April with the main survey during

1 0 - 1 6

April (Fig.

1 ) .

On each station herring larvae were sampled with modified conical nets of

0 . 5

m opening and

2

3 7 5 p111

mesh size (ELLERTSEN et al.

1 9 8 4 ) ,

from

1 5 0 m

(or 5m above the

bottom

)

to the surface, and the vertical hydrografic distributions observed by CTD casts. Two Argos satellite-tracked, drifting buoys were deployed (Fig. 1

)

. These were equipped with a

9

mL window blind drogue attached to the buoys via a 30 m elastic nylon tetherline.

The herring larvae were preserved in 2% formaldehyd in

1 0 % .

sea water for morphometric measurements and gut content analysis. Because of gut content voidance in herring larvae during catching and fixation

(

HAY

1 9 8 i ,

BLAXTER and HOLLIDAY

1 9 6 3 ,

ROSENTHAL

1 9 6 9 )

only

a

qualitative

aiialysis were performed with the gut content.

On board the ship, standard length (SL) measurements of up to 50 herring larvae per station were taken to the nearest mm below. In the laboratory a material of 1077 herring larvae was analysed. Up to

2 0

larvae from each station were staged according to

DOYLE

(1977). Larvae with standard length <lomm were measured to nearest O.lmm below, while larger larvae were staged to the nearest 0.5mm below.

If food organisms could be recognized through the epithelium of the gut, they were dissected out and classified into one of the following groups, copepod egg, copepod nauplii or copepodite. No other prey organisms were found. The larvae were rinsed in fresh water, dried to constant weight and weighed on a Cahn electrobalance to the nearest

vg.

The vertical distribution study was carried out during a 43 hours period near Buagrunnen

16-18

April 1986 (Location B,Fig.l). A drifting drouque was placed at 30 m depth in a larvae concentration.

Sampling was done with a

I

m2 Mocness sampler

(WIEBE &

al.

1 9 7 6 )

with

2 0

m depth intervals starting at

160-140

m. Around 30 m3 was

filtered at each interval. Sampling was made each second hour. After

3 0

hours of sampling the number of larvae caught fell drastically,

indicating a drift of the drouque away from the larvae consentration.

Sampling was then continued at the point where the droque was released. Light measurements were made at the surface before each hau1 .

RESULTS AND DISCUSSION

Hydroqraphy

The typical vertical hydrographic structure of the investigated area

is shown iri Fig.

2 .

Tlie Coastal Water (t0 <7,

S < 3 5 )

form a wedge

above the underlying Atlantic Water. The bottom temperature was

between

7.5'

and 8OC and the bottom salinity about

3 5 . 2

for the whole

area. Surface temperatures and salinities were

_4-6'C

and

_{3 2 . 5} - 3 4 . 0

respectively. There was a pycnocline between

3 0

and 50 m, seen in the distribution of temperature as well as in salinity. The bottom topography of the area is rather complicated and influence strongly the circulation pattern. One of the most conspicuous bathymetric featurec is the shallow bank of Buagrunnen (Fig.

6 )

with a minimum depth of about 50 m.

The tempcrature and salinity distribution in

3 0

m (Figs.

3

and

4 )

give some indications of the currents above the pycnocline. Coastal Water of temperature and salinity below

5' C

and

3 3 . 5

respectively, intrudes the area from southwest. This water seems to follow mainly the western edge of Buagrunnen. Northwest of this bank, water of Atlantic origin is penetrating eastward. There is indications of an anticyclonic circulation around Buagrunnen. Also in the salinity distribution in

1 0 0

m (Fig.

_{5 )}

the intruding Atlantic Water north of Buagrunnen is clearly seen. This feature is therefore most likely a result of topographic steering of the current which during the winter/spring situation is reflected in the upper layer circulation.

Close to the shore in the southern part of the area, a southward transport is indicated (Figs. 3 and

4 ) .

Fig. 6 shows the track of the two Argosbuoys with the drogues in

3 0

m dep th . Position is indicated for each five days period. The most near-shore buoy (dotted line) was drifting southward to about

61' ~ o ' N ,

then west and northwest and entered the investigated area again around

2 0

May. It needed about

4 0

days to pass the investigation area.

During 15 of these it was circulating over Buagrunnen. The more off -shore buoy (whole line) used approximately

2 0

days to pass the area. Both tracks indicate the anti-cyclonic movement around Euagrunnen and they leave the area close to the coast in the northern part. They both ended up in the Lofoten area around

6 7 O

N after

90

and

1 1 2

days.

Horizontal larvae distribution

The horizontal distribution of herring larvae of four different leriyth

groups is shown in Figs.

7 - 1 0 .

The distribution of the youngest

larvae

(

< ⁹ mm) clearly indicate two separated spawning areas;

Buagrunnen and Runde (Fig. 7). From the Runde area, most of the larvae are drifting northwards. A mindr part, however, seems to be drifting toward the south. This southward drift is also indicated on the distribution of larger larvae (Figs. 8 and

9)

and is in accordance with the drift of the most near-shore Argos buoy (Fig. 6). The drainage of the youngest larvae from Buagrunnen (Fig.

7 )

is following closely the route of the Argos buoys (Fig. 6).

For the older larvae the horizontal distributions get more complex and the patchiness increase (Figs. 8

-

10). However, it seems possible to deduce the following drift pattern for the herring larvae:

Most of the larvae from the Runde area are drifting northwards around the western edge of Buagrunnen. Here they merge with the drift from this spawning area, flow eastward and northwards along the coast. The more western distribution of the older larva in the northernmost area (Figs. 8-10) is probably due to an offshore movement of the Coastal Water. This is indicated in Fig. 4 as well as by the Argos drifters just north of 63'30'~.

The amount of newly hatched larvae is much higher at Buagrunnen than at the Runde area (Fig. 7). For the older larvae, however, no such feature is evident (Figs. 8-10). This observation invites to several interpretations. It can be a result of differences in spawning time and intensity as well as increased mortality of the larvae from Buagrunnen. The available data offer no preferable explanation.

During the survey, a 38kHz echosounder coupled to an echo integrator

was used. Fig. l

l

shows the distribution of the eclio abundance

classified as plankton. As can be seen, the maximum values are found

in the same areas as where the spawning took place (Fig.

7 ) .

Most

likely, this is not recordings of larvae as these at this stage of

development do not have swim-bladder (BLAXTER

&

al.

1 7 8 1 ) .

More

probably, it is concentrations of zooplankton like krill and Calanus

f ininarchicus . Further study of the plankton samples from the

vertical net hau1 and cumparison of these with the plankton echo

recordings may elucidate this question.

Vertical larvae distribution

DRAGESUND (1970) found that the larvae of Norwegian spring-spawning herring soon after hatching rose into the upper water layers (50-Om) and were scarce in the depth range 50 to 70m. This was pastly in correspondance with earlier findings (DRAGESUND and WIBORG 1963, DRAGESUND 1965, DRAGESUND and HOGNESTAD 1966). Based on these studies the procedure established during previous annua1 herring larvae surveys was continued, during which only the upper 75 m were sampled.

None of these experiments, however, included depths of more than 80m.

In 1976 a Gulf I11 sampler (ZIJLSTRA 1970) was introdused

-

and the sampling took place in the upper 60m.

SELIVERSTOV (1974) found tliat the larvae of the Norwegian spring- spawning herring could reach an amplitude of diurnal vertical migration of 75-100m. He also found newly hatched larvae of depths of 200111.

Fig.12 shows the vertical distribution of different length groups of herring larvae during a 48-hours sampling period. Few larvae <9 mm were caught and this length group is omitted in the figure. The daytime larvae were cauglit between 0900 and 1500 hour and the nighttime larvae between 2100 and 0200 hour. Fig. 12 seems to indicate a downward extention of the vertical distribution of all the three length groups. This is not in correspondance with obser- vations made by DRAGESUND (1970) who found that larvae were most abundant in the upper 20 m by night and between 20 an 40 m by day.

Fig.13 shows the percentage distribution of all herring larvae during a 48-hour period, under varying light conditions. No clear migration pattern is evident. The highest concentrasions of larvae were found between 20 and 80 m, and less than 5

%

were found below 120 m.

Fig.14 shows the mean vertical distribution of all larvae during the

48-hour period, in addition to salinity and temperature.The highest abundance of larvae were found in the middle of the pycnocline. Mure than 65

%

of the herring larvae were caught in the upper

60

m, while

20 %

were caught below 70 m. This means that if herring larvae are to be caught quantitatively the sampling depth must be extended down to at least

150

m.

It should be stressed that these results are preliminary and that further investigations are necessary before any valid conclusions can be made concerning the vertical distribution and migration of herring larvae .

Condition of the larvae

The material consists of

1077

herring larvae of standard length

8-18

mm. A length (SL)/dry weight plot is shown in fig.15.There is a strict relationship between the length (SL) and the dry weight with a exponential correlation coefficient of r

2 =0.81.

There seem to be very few "runts" in the population and most of the larvae are growing at a steady rate from yolk-sac resorption, corresponding to a mean standard length of 10.3 mm.

The larvae material was staged according to

DOYLE ( 1 9 7 7 ) .

The standard length,dry weight and number of larvae in each staye are shown in Table 1 .

I f

all larvae are growing at the same rate, DOYLE's morphometric criteria can be used as an index of age. The following indicationc of constant growth was seen in the present material

-

a strong correlation in the length/weight relationship.

- little standard deviation in dry weight of the larvae resorbing the yolk-sac.

To verify that the growth rate is constant, time consuming daily

increment counting is necessary.

Table 1 . The mean standard length and dry weight of the larvae in the different stages.

M s n length S tage SL(mm1 SD

Mean dry weight

-

DW(clg) SD N

The length frequency distribution of the larvae in the different stages is given in in Fig.16. This figure gives additional information of a larval population in growth.

Laboratory experiments with larvae of Norwegian spring spawning herring were performed in FlØdevigen, to calibrate DOYLE'C results.

(MOKSNESS,pers comm.). A size hierarchy was present in the lab experiments, and there was some overlap between the stagec > ^{Id. The}

mean duration of the larval substages la

-

2b after

DOYLE(l977),MOKSNESS(pers

comm.),ØIESTAD(1983) and MAC LACHLAN et al.

(1981) are presented in Table 2.

In Fig. 17, the diet of the herring larvae in the substages la-2b zorrespondiny to a age of 0-28 days post hatcliing (Table 2) is shown.

The dominant prey organism in number in all size groups of larvae wau Table 2. The mean duration of the different substages, (MOKSNESS,pers comm.,DOYLE 1977,ØIESTAD 1983 and MAC LACHLAN et a1.1981).

Stage la 3 days

Stage 1b 4 days

Stage lc 3 days

Ctage Id 2 days

Stage 2a 1 1 days

Stage 2b

5 days

copepod nauplii and this prey organism constituted

90%

of the gut content of the herring larvae investigated. The youngest larvae found with gut content were in the age group

4-7

days old. In the gut of these larvae a few copepod eggs and copepod nauplii were found, and the relative importance of copepod eggs as food items was higher than in older larvae. The highest number of copepod eggs was found in

8- 10

days old larvae. The importance of copepod eggs as a food item decreased in larvae older than

10

days, when the yolk-sac was resorbed.

The highest number of copepod nauplii was found in larvae between

11-23

days old,later on this food item will be replaced by copepodites.

Copepodites are sporadically found in the larval guts from

9

days of age, but they are of minor importance until the larvae are about one month old, and larger than

15

mm

(SL).

BJØRKE (1978)

found a high percentage of copepod eggs in the diet of young larvae. His conclusion was that a large amount of copepod eggs in the gut of the herring larvae could be an expression of mismatch between the first feeding of herring lasvae and of their prey. The present material with its high impact of copepod nauplii can be seen as an expression of successful first feeding.

From the mean length and stage duration data,Table 112, the growth rate can be calculated. A mean growth rate of

0.36

mm

d - '

in the period of

1-25

days post hatching was found. The growth rate in the yolk-sac period is somewhat slower with

0.23

mm d-' , and the growth in the post yolksac period

0.42

mm d-' . This results is in accordance with previous results based on the same stock

(DRAGESUND

and

NAKKEN

19731,

and results with larvae from otlier stocks

(LOUGH

et al.

1 9 5 2 ,

WOOD and BURD

1976). CHRISTENSEN (1985)

reviewed information about

field studies on growth rates of North Sea herring. These ranged from

0.16-0.35

mm d-'.

Dry weight can be fitted to the exponential growth equation to estimate the specific growth rate (SGR),k , of the larvae

(WARREN 1971).

W2= dry weight at time 2 W1

=

dry weight at time 1 tl

=

time 1 / days

t*= time 21 days

The spesific growth rate from day 5 post hatching, when the larvae had the lowest dry weigth, to day 25 was found to be 6.8%. This is an underestimate because of the shrinkage in dry weight due to preservation, but in accordance with the theoretical values calculated by BEYER and LAURENCE(1979) on first feeding herring larvae.

A mixture of larvae from the two spawning components is present at Buagrunnen, while the larval population outside Runde

(

Fig.

1 . )

comes from the southern spawning stock. Length /dry weight plots from the larval population in these two areas are shown in Fig.18. No growth differences can be seen between the mixture of larvae and larvae from the southern stock components.

CONCLUSIONS

The circulation pattern of the investigated area seem to be highly influenced by the bottom topography.

The drift of the larvae is in reasonable accordance with the circulation pattern deduced by hydrography and Argos drifters.

I f

herring larvae are to be caught quantitatively the sampling volume

must a least include the upper 160 m. No clear vertical migration

pattern was evident during changing light conditions. The highest abundance of larvae was found in the middle of the pycnocline.

The vertical distribution of three lenyth groups, 9-10 mm, 11-12 mm and >l3 mm indicated a downward extension during nighttime.

4-7 days old larvae were found with gut content, and the

herring larvae had recovered their hatching weight at yolk resorption.

The larval diet was dominated of copepod nauplii; copepod eggs were found in the smallest larvae and copepodites in the larger ones.

A daily growth rate of 0.36 mm and a spesific growth rate of 6.8

%

were calculated.

No growth differences was observed between the larvae from the southern and northern stock component.

REFERENCES

BEYER, J.E. and LAURENCE, G.C. 1979. Modelling growth and mortality of larval herring (Clupea harensus).Int. Coun. Explor. Sea. ELH S~mp,,(M:6): 1-88.

EJØRRE, H. 1978. Food and feeding of young herring larvae of Norwegian spring spawners. Fisk.Dir. Skr. Ser. HavUnders., 16: 405-421.

BJØRKE, H. 1981. Distribution of fish eggs and larvae from Stad to Lofoten during April 1976-80. In: R. Sætre and M. Mork

(Eds.), The Norwegian Coastal Current. Proc. Norw. Coastal Current Symp., Geilo, 9-12 Sep. 1980,2:583-603.

BLAXTER, J.H.S. and HOLLIDAY, F.G.T. 1963. The behaviour and

physiology of herring and other clupeids. Advances in marine

bioloqv., 1:261-393.

BLAXTER, J.H.S., E.J. DENTON and J.A.B. GRAY. 1981. The auditory bullae-swimbladder system in late stage herring larvae.

J. Mar. biol. Ass. U.K., a: ^315-326.

CHRISTENSEN, V. 1985. Estimation of herring larval production.Coun.

Meet. int. Coun. Explor. Sea, (H:60):1-9.

DRAGESUND, O., 1965. Forekomst av egg og yngel av fisk i vest og nord norske kyst og bankfarvann varen 1964. Fiskets aanq, U:9-15.

DRAGESUND,

0.

1970. Factors' influencing year-class strength of Norwegian spring spawning herring. FiskDir. Skr. Ser.

HavUnders., 15

:

381-450.

DRAGESUND, O., HAMRE, J. and ULLTANG, 0. 1980. Biology and population dynamics of tfie Norwegian spring spawning herring. Rapp.

P.-v. Reun. Cons. perm. int. Explor. Mer, 177: 43-71.

DRAGESUND, 0. and HOGNESTAD, P. T., 1966. Forekomst av egg og yngel i vest- og nordnorske kyst- og bankfarvann varen 1965. Fiskets

52: ^467-472.

DRAGESUND, 0. and NAKKEN,

0.

1973. Relationship of parent stock size and year class strength in Norwegian spring spawning herring.

Rapp. P.-v.Reun. Cons. Perm. int. Explor. Mer, m : 1 5 - 2 9 .

DRAGESUND,

0.

and WIBORG, K. F., 1963. Forekomst av egg og yngel i vest- og nordnorske kyst- og bankfarvann våren 1963. Fiskets

w, 41: ^71-76.

ELLERTSEN, B., FOSSUM, P., SOLEMDAL, P., SUNDBY,

C.

and TILCETH, S.

1984.A case study on the distribution of cod larvae and availabiliotybility of prey organisms in relation to physical processes in Lofoten.1n: E.Dah1, D.S.Danielssen, E.Moksness and P.Solemda1 (Eds.),The Propagation of Cod Gadus morhua L.

FlØdeviqen rapportser.,l:453-477.

FØYN, L. and BJØRKE, H. 1986. Strategies in assessment of potential oil pollution effects on the fish resourses. Coun. Meet. int.

Coun. Explor. Sea,(E:34):

HAY,D.E. 1981. Effects of capture and fixation on gut contents and body size of Pacific herring larvae. Rapp. P.-v. Reun. Cons.

perm. int. Explor. Mer, 178: 395-400.

MAC LACHLAN, P., SEATON, D.D and GAMBLE, J.C. 1981. Developmental patterns of experimentally enclosed populations of autumn and spring- spawning Atlantic herring 1arvae.loun. Meet. int Coun. Explor. Sea,(L:21):1-7.

LOUGH, X.G., M. PENNINGTON, G.R BOL2 and A.A. ROSENBERG. 1982. Age and growth of larval atlantic herring Clupea harenqus L.based on otolith growth increments. Fish. Bull., m:187-199.

ROSENTHAL, H. 1969. Verdauungsgeschvindigkeit, Nahrungswahl und Nahrungsbedarf bei den Larven des Herings,Clu~ea harensus L.

Ber.

D t s c h .

Komm. Meeresforsch., a: 60-69.

RØTTINGEN, R. 1984. Investigations on the 1983 year class of Norwegian Spring-spawning herring.

1384 (H:39):1-6.

SELIVERSTOV, A.S. 1974. Vertical migratians ov larvae of the Atlanto-Scandian Herring (Clupea harensus L.) 1n:J.H.S.

BLAXTER (Ed.). The early life history of fish.

Springer-Verlag. Berlin: 253-262.

TORESEN, R., 1985. Recruitment indeces of Moewegian spring spawning herring for the period

1965-1984

baced on the international O-group fish surveys. Coun. Meet. int. Coun.Ex~lor. Sea,

( H : 5 4 ) : 1 - 1 0 .

WARREN, C.E.

1 9 7 1 .

Biology and water pollution control. W.B.

Saunders, Philadelphia:

1 - 4 3 4 .

WIBORG, K.F.

1 9 6 0 .

Forekomst av egg og yngel av fisk i vestnorske kyst- og bankfarvann og ved Skrova i Lofoten varen

1 9 6 2 .

Fiskets sanq, 48

: 6 8 9 - 6 9 0 .

WIEBE,

P . H . ,

BURT, K.H., BOYD,

S . H .

and MORTON, A.W.,

1 9 7 6 .

A multiple opening/closing net and environmental sensing system for sampling zooplankton. J. Mar. Res., 34:

313-326.

WOOD,J. and BURD, A.C.

1 9 7 6 .

Growth and mortality of herring larvae in the central North Sea. Coun. Meet. int. Coun. Explor.

a,

( H : 8 ) : l - 7 .

ZIJLSTRA, J.J.

1 9 7 0 .

Herring larvae in the central North Sea. Ber.

dtsch. wiss. Komm. Meresforsch., a:

9 2 - 1 5 5 .

ØIESTAD, V. 1983. Growth and survival of herring larvae and fry (Clu~ea harenaus L.) exposed to different feeding regimes in experimental ecosystems; outdoor basin and plastic bag5.Ph.d.

thesis:l-299.University of Bergen.

Fig.

1.

Investigated area and grid of stations.

Fig. 2. Vertical distribution of temperature and

salinity in the central part of the area.

Fig. 3. Distribution of temperature in 30 m depth.

Fig. 4. Distribuiton of salinity in 30 m depth.

Fig. 5. Distribution of salinity in 100 m depth.

Fig. 6. Track of the drifting Argos buoys drogued

at 30 m depth.

Fig. 7. Distribution of herring larvae

<

9 mm

( ~ . m - ~ ) .

Fig.

8

Distribution of herring larvae

between 9 and 11 mm ( ~ . m - ~ ) .

Fig. 9. Distribution of herring larvae

- 2

between 11 andl3 mm (N.m

) .

Fig. 10. Distribution of herring larvae

- 2

>l3 mm (N.m

) .

Fig. 11. Plankton echo abundance from the 38 khz echosounder.

140 - 160 f

I * ~ - ~ r

100 O 1W O 100 O 100 100 O 100 O 100 O 100 P E R C E N T 9 -10 11-12 Z- 13 9-10 11-12 > 13 L E N G T H nn

Fig. 12. Vertical distribution of different length groups during day and night.

n

=

numbers of larvae.

l o

; ; ;

^{; .}

^. :

^{, ,}

^. : : ^; : : ^; : 1

140

0. O

. .

160

05 07 09 11 13 15 17 19 21 23 O1 03 O5 07 09 11 13 15 17 19 21 23 (11 0 3 05 G M T

Fig. 13, Top: Light intensity at surface.

Below: Percentage vertical distri-

bution all length groups during 48 hours.

5 10 1 5 20 25 30 P E R C E N T

Fig. 14 Mean vertical distribution of larvae and hydrographic parameters.

. Percentage of larvae x...x Salinity

O ---

o Temperature

2 5

BRY WEIGHT

'pG' 400

300 200

1

O0

0

STANDARD LENGTH (MM)

Fig. 15. A length/dry weight plot of the present herring larvae material.

THE PER CEN1 DISTRIBUTION

20 - 10 -

O - . , . . . . . . . . . . . " .

c8 8- 85- 9- 9.5-10-105-11-11.5- 12-12513- 13514-145-15- 155-16- 16517 >l15 LENCTHGROUPS

Fig. 16. The percentage length distribution of the larvae

in the different substages (Doyle 1977).

FEEDING RATIO ARBITRARY UNITS

S TAGE

%,mm

w

e

- * COPEPOP NAUPLII

.-

^{- - -* n EGGS}

...

- - - ^.._

e... ... ...-. ':C .--. -. - - - - - - - -*

1 3 5 7 9 11 13 15 17 19 21 23 25 27' 29 31 33

I I I

AGE (01YS POST HATCHINGI

Fig. 17. The diet of the herring larvae in the "age" group 4-29 days post hatching.

DRY WEIGHT (JJG

I

400

o I

^{I I I l}

8 10 12 14 16

STANDARD LENGTH (MM)

r

m-

o

^{I I I I}

8 10 12 14 16

STANDARD LENGTH (MM)

Fig. 18. A length dry weight plot of the larvze off Runde ( A )

and on the Buagrund (B).

O-GROUP SAZTHE O F F THE NORTHERN NORWGIAN COAST I N MAY

1985

K j e l l Nedreaas

I n s t i t u t e of Marine Research P.O.Box 1870

N-5024 Bergen-Nordnes Norway

ABSTRACT

From 11 May t o

31

May 1985 a p e l a g i c t r a w l survey was c a r r i e d o u t o u t s i d e t h e Norwegian c o a s t n o r t h of

62

o N. The purpose o f t h i s p i l o t survey w a s t o examine t h e p o s s i b i l i t y of g e t t i n g u s e f u l information about t h e y e a r c l a s s s t r e n g t h of t h e North-East A r c t i c s a i t h e b e f o r e t o o many of t h e p o s t l a r v a e had d r i f t e d o r migrated i n s h o r e . Attempts a t t h i s have s o f a r n o t been s u c c e s s f u l f o r any s a i t h e s t o c k , and r e c r u i t m e n t e s t i m a t e s a r e badly needed f o r t h e c a t c h p r o j e c t i o n s . The sampling was c a r r i e d o u t with a mid-water t r a w l and t h e r e s u l t s a r e promising. There a r e a l s o i n t e r e s t i n g b i o l o g i c a l a s p e c t s . Some s y s t e m a t i c s i z e d i f f e r e n c e s of t h e s a i t h e p o s t l a r v a e seemed t o appear w i t h i n t h e i n v e s t i g a t e d a r e a . D i s t r i b u t i o n c h a r t s and t a b l e s of p o s t l a r v a e of d i f f e r e n t s p e c i e s have been p r e s e n t e d . An index of t h e y e a r c l a s s s t r e n g t h of s a i t h e has been c a l c u l a t e d .

INTRODUCTION

The North-East A r c t i c s a i t h e spawn a t 150-200 meter d e p t h s o u t s i d e t h e Norwegian c o a s t . North of 62 N t h e main spawning grounds a r e on t h e o banks o f f Møre, Haltenbanken, and i n t h e Lofoten a r e a .

I t i s w e l l known t h a t a l e v i n s and p o s t l a r v a e d r i f t , o r a s they grow l a r g e r , probably migrate i n s h o r e . However, w e have s o f a r n o t been a b l e t o a r r i v e a t t h e understanding of what p h y s i c a l o r b i o l o g i c a l mechanisms t h a t a r e involved. From a s i z e of 2-4 cm u n t i l becomrning 3-6 y e a r s o l d , o l d e s t i n t h e n o r t h e r n p a r t of Norway, t h e s a i t h e s t a y i n s h o r e . Above a minimum s i z e t h e s a i t h e a r e d u r i n g t h i s p e r i o d exposed t o a c o n s i d e r a b l e p u r s e s e i n e f i s h e r y .

While t h e s a i t h e s t a y i n s h o r e i t i s almost impossible t o measure t h e s t r e n g t h of t h e y e a r c l a s s , and b e f o r e i t i s p o s s i b l e t o g e t any i n f o r m a t i o n about t h e r e c r u i t m e n t , t h e s t o c k i s exposed t o f i s h i n g . T h e r e f o r e t h e aim of t h i s p i l o t survey was t o bound t h e a r e a of d i s t r i b u t i o n and t o t r y t o g e t a measure of t h e y e a r c l a s s s t r e n g t h b e f o r e t h e a l e v i n s o r p o s t l a r v a e reached t h e c o a s t .

H i t h e r t o very l i t t l e has been done on t h i s s u b j e c t . DAMAS (1909) d e s c r i b e d t h e d i s t r i b u t i o n of f r y and a l e v i n s of s a i t h e o f f Møre.

WIBORG (1954,1956,1957,1960a, 1960b, 1961,1962) and DRAGESUND AND

HOGNESTAD (1966) have d e s c r i b e d t h e occurrence of f i s h eggs and l a r v a e i n Norwegian c o a s t a l and o f f s h o r e waters. BJØRKE (1983) has done come r e s e a r c h on t h e d i s t r i b u t i o n of eggs and l a r v a e of gadoid f i s h e s from S t a d t o Lofoten d u r i n g A p r i l 1976-1983, and on p o s t l a r v a e of gadoid f i s h e s n o r t h of Lofoten i n June and J u l y ( i n t e r n a l survey r e p o r t s ) . However, most of t h e s e r e p o r t s p r e s e n t t h e r e s u l t s from surveys c a r r i e d o u t e i t h e r t o o e a r l y o r t o o l a t e t o g i v e a r e l i a b l e measure of t h e abundance of O-group s a i t h e .

MATERIALS AND METHODS

A mid-water c a p e l i n t r a w l with a 10 meter f i n e meshed

(8

mm s t r e t c h e d mesh) n e t i n s i d e t h e cod-end, was used a s t h e main g e a r i n t h i s survey. Height and depth s e n s o r s from SCANMAR A/S t o g e t h e r with s e n s o r s measuring t h e d i s t a n c e between t h e wings of t h e t r a w l , gave i n f o r m a t i o n about t h e t r a w l geometry.

The t r a w l was towed with J k n o t s f o r 10 minutes with t h e headrope a t t h e s u r f a c e , then 10 minutes i n 20 meter, and 10 minutes i n 40 meter.

S i x 70' ' b l a d d e r s were f a s t e n e d t o t h e headrope. It took some time t o s t a b i l i z e t h e t r a w l i n t h e s e depths. The t o t a l s a i l e d d i s t a n c e t h e r e f o r e became

1.8

n a u t i c a l miles a s a mean, with a t o t a l towing t i m e of about 36 minutes. The t r a w l survey was c a r r i e d o u t both day and n i g h t .

The known spawning grounds of t h e s a i t h e and a c a l c u l a t e d d r i f t o f t h e l a r v a e up t o t h e beginning of t h e s u r v e y , were used a s t h e b a s i s f o r how f a r s o u t h i t was necessary t o go. However, t h e southernmost t r a c k gave no s a t i s f a c t o r y s o u t h e r n l i m i t of t h e abundance o f s a i t h e , and i t was t h e r e f o r e decided t o do some t r a w l i n g f u r t h e r s o u t h on t h e r e t u r n t o Bergen. These t r a w l - and hydrographical s t a t i o n s were consequently taken l a t e r i n t i m e .

The a c t u a l a r e a was covered by a r e c t a n g u l a r survey g r i d ( F i g u r e 1).

The d i s t a n c e between t h e main t r a c k s , which have been numbered by Roman numerals I - X I I , was 30 n a u t i c a l m i l e s , and t h e d i s t a n c e between two s t a t i o n s on t h e same t r a c k was

15

n a u t i c a l miles.

The c a t c h was shaked down i n a t u b with water and f i l t e r e d o u t . Afterwards t h e whole cod-end was thoroughly shaked and t h e remainder swept up from t h e deck. The e n t i r e c a t c h was s o r t e d , and t h e l e n g t h of each f i s h s p e c i e s o r c a t e g o r y measured.

Because of t h e u n c e r t a i n t y concerning t h e c h o i c e of t h e b e s t sampling d e v i c e , a n o t h e r two sampling g e a r s were t e s t e d . The c a t c h e f f i c i e n c y of I s a a c s Kidd

( g

m * ) and MOCNESS (1 m 2 ) midwater t r a w l s were on r e s p e c t i v e l y f i v e and two s t a t i o n s compared with t h e b i g g e r c a p e l i n t r a w l . The I s a a c s Kidd t r a w l was lowered down t o 60 meter, and t h e MOCNESS was hauled through 1000 m3 seawater i n each of t h e f o u r d e p t h s L O , 20, 30, and 40 meter.

I n o r d e r t o t r y t o e s t i m a t e a c o u s t i c l y t h e abundance of a l e v i n s and p o s t l a r v a e an EK-400 (Simrad), connected t o a Nord 10 e k k o i n t e g r a t o r w i t h a Simrad QX p r e p r o c e s s o r , was used. However, i t was impossible t o s e p a r a t e t h e p o s t l a r v a e from k r i l l and zooplankton, and t h e a c o u s t i c e s t i m a t e was t h e r e f o r e judged t o be u n r e l i a b l e a s a measure o f t h e p o s t l a r v a e abundance.

RESULTS Hydrography

Hydrographical o b s e r v a t i o n s w e r e normally made on each t r a w l s t a t i o n along a l l t h e survey t r a c k s ( F i g u r e 2 ) . Horizontal temperature d i s t r i b u t i o n i s shown f o r 0 , 25, 50, and 100 meter ( F i g u r e s 3 - 6 ) . Figure

7

shows some temperature s e c t i o n s with t h e number of s a i t h e p o s t l a r v a e caught on each s t a t i o n recorded i n t h e r i g h t r e l a t i v e p o s i t i o n i n t h e s e c t i o n . The h o r i z o n t a l d i s t r i b u t i o n o f t h e s a l i n i t y i n 25 meter i s shown i n Figure

8.

D i s t r i b u t i o n and abundance of O-group f i s h

Trawl s t a t i o n s with and without c a t c h a r e f o r t h r e e s p e c i e s given on t h e d i s t r i b u t i o n c h a r t s i n Figures

9 ,

11 and

13.

I s o l i n e s have been d r a m t o b e t t e r v i s u a l i z e t h e d i s t r i b u t i o n .

An abundance index has only been c a l c u l a t e d f o r O-group s a i t h e , t h e t a r g e t s p e c i e s of t h e survey. With t h e a i d of hydroacoustic equipments from SCANMAR A/S t h e h e i g h t and width of t h e t r a w l e n t r a n c e was found, and t h e volume, V I , of a hau1 was c a l c u l a t e d .

V l = 0.0108 nm ( h e i g h t of t h e entrance=20 meter) 0.0108 nm (width of t h e entrance.20 meter)

1.8

nm ( d i s t a n c e towed) = 2.0995 lo-' nm ³

Around each t r a w l s t a t i o n a square of

15

x 30 n a u t i c a l miles has been drawn with t h e s t a t i o n i t s e l f i n c e n t e r . Knowing t h e maximum depth of t r a w i i n g ,

58

meter when t h e headrope i s i n 40 meter, t h e volume, VI

,

of such a c o n s t r u c t e d block can be found.

V 2 =

15

nm 30 nm 0.0313 nm (maximum depth.58 meter) = 14.09 nm3

C a l c u l a t i o n of t h e index, I:

I= V /V x ⁼ V2/V1 X

,

where x is t h e nurnber of O-group s a i t h e

2 1

caught d u r i n g a hau1 of

1.8

nm on s t a t i o n i.

S a i t h e , P o l l a e h i u s v i r e n s ,

The geographical d i s t r i b u t i o n of O-group s a i t h e i s shown i n Figure

9.

It shows many s i m i l a r i t i e s with t h e h o r i z o n t a l d i s t r i b u t i o n of t h e temperature, e s p e c i a l l y i n 25 and 50 meter. Areas w i t h temperature e q u a l o r above

7

o C turned o u t t o c o n t a i n t h e g r e a t e s t numbers of O-group s a i t h e ( F i g u r e 7 ) . Far n o r t h i n t h e i n v e s t i g a t e d a r e a where t h e temperature d i d n o t become t h a t h i g h , t h e g r e a t e s t c a t c h e s of O-group s a i t h e were done i n t h e warmest water.

Very l i t t l e can be s a i d about t h e v e r t i c a l d i s t r i b u t i o n o f t h e p o s t l a r v a e . I n a d d i t i o n t o t h e two experiments u s i n g t h e MOCNESS t r a w l ( s e e t h a t p a r a g r a p h ) , t h e c a p e l i n t r a w l was on t r a w l s t a t i o n 238 only towed a t t h e s u r f a c e f o r t e n minutes, on s t a t i o n 239 o n l y i n 20 meter, and on s t a t i o n 240 only i n 40 meter. The t r a w l was u n f o r t u n a t e l y a l s o towed through t h e water column t o and from t h e s e d e p t h s . This o n l y experiment showed l e a s t p o s t l a r v a e i n 20 meter (Table 3 ) . The h o r i z o n t a l d i s t r i b u t i o n s of t h e temperature o r t h e s a l i n i t y i n s e v e r a l d e p t h s may a l s o t e l l something about t h e v e r t i c a l d i s t r i b u t i o n of s a i t h e p o s t l a r v a e s i n c e they seem t o s t a y i n water masses of a c e r t a i n temperature o r s a l i n i t y .

The l e n g t h d i s t r i b u t i o n s of O-group s a i t h e caught on each survey t r a c k have been shown i n Table 1. On t h e f i r s t e i g h t t r a c k s ( I - V I I I ) t h e mean l e n g t h s v a r i e d between 27.7 mm and 29.5 mm. On t r a c k s IX, X , and X 1 t h e mean l e n g t h s a r e somewhat l e s s , 2 5 . 1

- 26.6

mm. The s i x p o s t l a r v a e caught on t h e northernmost t r a c k , t r a c k X I I , were l a r g e r . The mean l e n g t h was

31.3

mm. Trawl s t a t i o n s 236

-

^{247 were taken on}

t h e r e t u r n t o Bergen a t t h e end of May, and i t i s t h e r e f o r e n a t u r a l t h a t t h e s e p o s t l a r v a e were l a r g e r . The mean l e n g t h was

35,O

mm.

Between i n n e r and o u t e r c t a t i o n s on t h e same t r a c k t h e r e were more pronounced l e n g t h d i f f e r e n e e s of t h e O-group s a i t h e . I n o r d e r t o i l l u s t r a t e t h i s t h e f i v e southernmost t r a c k s ( I - V ) were d i v i d e d i n t o an i n n e r , a c e n t r a l , and an o u t e r p a r t w i t h l / 3 of t h e t r a w l s t a t i o n s i n each p a r t . F i g u r e 10 shows t h e l e n g t h d i s t r i b u t i o n of O-group s a i t h e from each of t h e s e t h r e e p a r t s . The p o s t l a r v a e on t h e i n n e r s t a t i o n s were l a r g e r than on t h e o u t e r s t a t i o n s i n d i c a t i n g a d r i f t o r m i g r a t i o n inwards t o t h e c o a s t .

An index of t h e abundance of O-group s a i t h e has been c a l c u l a t e d : Number of O-group s a i t h e within t h e a r e a covered by t h e r e g u l a r survey t r a c k s , :

I1

Il = V2/Vl x = 14.09/2.0995

lo-'

8462 s a i t h e = 567.9

lo6

s a i t h e The t r i a n g u l a r a r e a south of t h e southernmost t r a c k with trawl catches of 100 O-group s a i t h e o r more covered an a r e a of 5,610

nm

2

.

^{With a}

depth of 58 meter o r 0.0313 nm t h e volume is V ⁼ 175.6 nm 3

.

3

Number of O-group s a i t h e within t h i s " t r i a n g l e t ' , IZ :

Iz = V3/Vl ^{X =} 175.6/2.0995

lo-'

³²² s a i t h e (mean p e r s t a t i o n )

= 269.3 10 s a i t h e 6

The volume of t h e a r e a with catches l e s s than 100 s a i t h e p e r s t a t i o n south of t h e southernmost t r a c k , V, =

96.6

^nm3.

Number of s a i t h e within t h i s a r e a , I :

I = V,/Vl x = 96.6/2.0995 10-' 'li s a i t h e (mean p e r s t a t i o n )

3 6

=

5.1

l 0 s a i t h e

The number of O-group s a i t h e , I , within t h e t o t a l i n v e s t i g a t e d a r e a i s used a s t h e index of abundance of t h e

1985

year c l a s s of North-East A r c t i c s a i t h e n o r t h of 6 2 ' ~ :

I= I +12+1 = 842.3

lo6

1 3

Herring, Clupea harengus.

The geographical d i s t r i b u t i o n of h e r r i n g l a r v a e before metamorphosis i s shown i n Figure 11. The a r e a of d i s t r i b u t i o n was n e i t h e r i n t h e south nor i n t h e n o r t h s a t i s f a c t o r y l i m i t e d , and no abundance index has t h e r e f o r e been c a l c u l a t e d .

The two experiments considering t h e v e r t i c a l d i s t r i b u t i o n of h e r r i n g l a r v a e gave two d i f f e r e n t d i s t r i b u t i o n s (number l a r v a e ) a s shown below

.

MOCNESS Capelin t r a w l Depth i n meter St.no.135 S t , no. 238-240

There were r a t h e r s m a l l l e n g t h d i f f e r e n c e s between h e r r i n g l a r v a e caught on d i f f e r e n t s t a t i o n s . For t h r e e a r e a s (A,B,and C ) w i t h a c a t c h of 10 l a r v a e o r more p e r s t a t i o n , s e p a r a t e l e n g t h d i s t r i b u t i o n s have been p r e s e n t e d t o show t h e most pronounced d i f f e r e n c e s ( F i g u r e 1 2 ) . Area A i n c l u d e s i x s t a t i o n s a s shown i n F i g u r e 11. Area C i n c l u d e t h e s t a t i o n s s o u t h of t h e southernmost t r a c k , and a r e a B t h e rest of t h e s t a t i o n s with 10 o r more l a r v a e p e r s t a t i o n . The h e r r i n g l a r v a e i n a r e a A were somewhat s m a l l e r t h a n i n t h e o t h e r a r e a s .

C a t f i s h , Anarhichas l u p u s

S c a t t e r e d c a t c h e s of c a t f i s h p o s t l a r v a e were done a l l over t h e surveyed a r e a ( F i g u r e

1 3 ) .

The c o n c e n t r a t i o n s were small, o n l y on s i x s t a t i o n s i t was caught 10 p o s t l a r v a e o r more. The l e n g t h d i s t r i b u t i o n of a l l t h e c a t f i s h p o s t l a r v a e i s given i n Table 2.

Gonatus f a b r i c i i ( L i c h t e n s t e i n ) :

F i g u r e

14

shows t h e geographical d i s t r i b u t i o n of t h e t e n armed p e l a g i c s q u i d Gonatus f a b r i c i i . The l e n g t h d i s t r i b u t i o n s from t r a w l s t a t i o n s no.

l 5 1

and 218 have been sumrnarized and p r e s e n t e d i n Table 2. The a r e a of d i s t r i b u t i o n and t h e s i z e composition i n t h e c a t c h e s chowed many s i m i l a r i t i e s with o b s e r v a t i o n s done by WIBORG (1979,1982) and WIBORG,GJØSIETER AND BECK ( 1 9 8 4 ) .

Other s p e c i e s

An overview of a l l s p e c i e s o r fauna c a t e g o r i e s caught on each t r a w l s t a t i o n i s given i n Table

3.

P e a r l s i d e s , Maurolicus m u e l l e r i , were o n l y caught around midnight. A t

t h i s t i m e t h e p e a r l s i d e s gathered above 'O meter, and were c l e a r l y v i s i b h e on t h e echo sounder.

Redfish p o s t l a r v a e were r e g u l a r y caught from o u t s i d e Lofoten and northwards. Two s i z e groups of t h e s e p o s t l a r v a e appeared. Up t o s t a t i o n no. 226 t h e l e n g t h of t h e r e d f i s h p o s t l a r v a e was between

8

and

13

mm, while from s t a t i o n no. 229 t h e p o s t l a r v a e were

15

mm o r more.

Table 2 shows t h e t o t a l l e n g t h d i s t r i b u t i o n . Many of t h e r e d f i s h p o s t l a r v a e were probably t o o small f o r t h e trawl t o c a t c h them q u a n t i t a t i v e l y w e l l .

I n t h e e n t i r e surveyed a r e a only f o u r p o s t l a r v a e of haddock were caught, a l l of them west of Haltenbanken. P o s t l a r v a e of cod were n o t recorded a t a l l .

Comparison and judging of g e a r s

On f i v e s t a t i o n s i n t h e beginning of t h e survey t h e c a t c h e f f i c i e n c y of an I s a a c s Kidd mid-water trawl and t h e c a p e l i n t r a w l was compared.

The overview below shows t h e c a t c h taken by t h e s e g e a r s . S t . n o . Capelin t r a w l I s a a c s Kidd

100 C a t f i s h : 10 C a t f i s h : 1

Sculpin : 1

103 C a t f i s h :

4

No c a t c h

108 Herring: 11 No c a t c h

110 S a i th e :

4

No c a t c h

C a t f i s h : 2

Herring:

3

i 1 4

S a i t h e :

331

(22-43 mm) S a i t h e :

3

(32,36,38,mm) C a t f i s h : 2

Gonatus s p . :

19

Norway pout: l

The r e s u l t s show t h a t t h e c a p e l i n t r a w l was t h e b e s t g e a r f o r t h e purpose of t h e survey, and t h i s g e a r was t h e r e f o r e used i n t h e c o n t i n u a t i b n .

On s t a t i o n no.

135

t h e MOCNESS mid-water t r a w l caught 1 s a i t h e p o s t l a r v a e while t h e c a p e l i n t r a w l caught 76. On s t a t i o n no.

147

t h e MOCNESS caught nothing while t h e c a p e l i n t r a w l caught

748

specimens.

The MQCNESS was considered n o t s u i t a b i e f o r catehing s a i t h e postlarvae of t h i s s i z e , but i t seemed t o be a b e t t e r g e a r f o r catching smalles and weaker h e r r i n g l a r v a e .

CONSIDERATIONS

The c a p e l i n trawl seemed t o be a s u i t a b l e gear f o r catching

2-3

mm p o s t l a r v a e of s a i t h e and o t h e r f i s h e s . However, considering t h e permeability of t h e cod-end, i t may be b e t t e r t o use a 2 s i n g l e f i n e meshed n e t i n s t e a d of a standard cod-end n e t with a f i n e meshed n e t i n s i d e .

To what e x t e n t i t i s p o s s i b l e t o t e l l whether t h e index of abundance w i l 1 show t h e r i g h t p i c t u r e of t h e year c l a s s s t r e n g t h , a time s e r i e s of such i n d i c e s i s needed. Then i t w i l l be p o s s i b l e t o compare t h e index with t h e number of s a i t h e of t h a t year c l a s s e n t e r i n g t h e f i s h e r y . Nevertheless, t h i s p i l o t survey was promising.

There were a l s o i n t e r e s t i n g b i o l o g i c a l a s p e c t s . S i z e d i f f e r e n c e s of t h e s a i t h e p o s t l a r v a e may t e l l something about t h e spawning and t h e mechanisms f o r t h e inshore d r i f t o r migration. The bulk of t h e s a i t h e p o s t l a r v a e stayed i n t h e warmest water.

REFERENCES

BJØRKE, H.

1983.

D i s t r i b u t i o n of eggs and l a r v a e of gadoid f i s h e s from S t a d t o Lofoten d u r i n g A p r i l 1976-1983. I n : E. Dahl, D.S.

Danielssen, E. Moksness and P. Solemdal ( E d i t o r s ) ,

m

propagation of Cod, Gadus morhua L., F l ~ d e v i g e n r a p p o r t s e r . , l ,

1984:

365-394.

DAMAS, D . 1909. C o n t r i b u t i o n a l a b i o l o g i e d e s gadides. Rapp. P.-v.

Reun.Cons.perm.int.Explor.Mer,lO(3): 277 pp.

DRAGESUND, O. AND HOGNESTAD, P.T. 1966. Forekomst av egg og yngel av f i s k i v e s t - og nordnorske k y s t - og bankfarvann våren 1965.

F i s k e t s Gang, 52: 467-472.

WIBORG, K.F.

1954.

Forekomst av f i s k e e g g og -yngel i nordnorske farvann våren 1952 og

1953.

F i s k e t s Gang, 40:

5-9.

WIBORG, K.F. 1956. Forekomst av f i s k e e g g og f i s k e y n g e l i nordnorske farvann våren 1954 og 1955. F i s k e t s G a n g , 42:

133-138.

WIBORG, K.F. 1957. Forekomst av f i s k e y n g e l og f i s k e e g g i nordnorske farvann våren 1956 samt på s t a s j o n M i Norskehavet i 1954-56.

F i s k e t s Gang,

43:

^188-190.

WIBORG, K.F. 1960a. I n v e s t i g a t i o n s on eggs and l a r v a e of commercial f i s h e s i n Norwegian c o a s t a l and o f f s h o r e w a t e r s i n 1957-58.

FiskDir.Skr.Ser.Havunders.,12(7): 1-27,

WIBORG, K.F. 1960b. Forekomst av egg og yngel av f i s k i v e s t - og nordnorske k y s t - og bankfarvann våren

1959.

F i s k e t s Gang, 46:

522-528.

WIBORG, K.F. 1961. Forekomst av egg og yngel av f i s k i v e s t - og nordnorske k y s t - og bankfarvann våren 1960. F i s k e t s Gang, 47:

190-195.

WIBORG, K.F. 1962. Forekomst av egg og yngel a v f i s k i v e s t - og nordnorske k y s t - og bankfarvann våren 1961. F i s k e t s Gang,

48:

161-164.

WIBORG, K.F.

1979.

Gonatus f a b r i c i i ( L i c h t e n s t e i n ) , a p o s s i b l e f i s h e r y resource i n t h e Norwegian Sea. Fisken Hav.

, 1979

^{(1) : 33-46.}

WIBORG, K.F. 1982. Gonatus f a b r i c i i ( L i c h t e n s t e i n ) . I n v e c t i g a t i o n s i n t h e Norwegian Sea and t h e western B a r e n t s Sea, February-September 1980 and July-September

1981.

Fisken Nav.,

1 9 8 2 ( 2 )

: 13-25.

WIBORG, K.F., GJØSKiTER, J . AND BECK, I . M .

1984.

Gonatus f a b r i c i i ( L i c h t e n s t e i n ) . I n v e s t i g a t i o n s i n t h e Norwegian and western B a r e n t s S e a s , June-September 1982 and

1983.

Fisken Hav.,

1984(2)

: 1-11.

Table 1 . Length distributions ( X ) of saithe postlarvae.

. . .

I

Length- Track I Track I1 Track 111 Track IV Track V Track VI Track VI1 Track VI11 Track IX Track X Track X1 Track X11

st.no. st.no. st.no. st.no. st.no. st.no. st.no. st.no. st.no. st.n0. st.no. st.no. l

I

group St.no. j

I ^mm 110-124 125-139 140-154 155-168 169-180 181-190 191-197 198-203 205-210 211-216 217-222 223-230 236-247 1

I_---_---_---l / 10-14

1 15-19 i . 6 2 . 8 0 . 3 O. 2 0 . 7 4 . 8 2 . 0 0 . 2 7 . 1 11.1

i

0.1 1

1 20-24 1 7 . 6 1 6 . 6 1 7 . 7 1 0 . 2 1 6 . 3 7 . 2 2 0 . 8 1 1 . 1 2 8 . 6 7 1 . 4 48. l

4 2 . 2 3 . 2 1

1 25-29 3 0 . 5 30.0 5 2 . 8 5 1 . 6 4 5 . 6 2 9 . 7 5 5 . 3 23.2 1 1 . 1 1 6 . 7 1 5 . 1 l

1 30-34 3 4 . 3 3 2 . 3 2 3 . 1 31.6 2 9 . 4 3 8 . 6 35.6 31.7 3 9 . 3 1 4 . 3 18.5 8 3 . 3 32.4 1

1 35-39 1 5 . 0 1 5 . 3 5 . 4 6 . 0 6 . 9 3 . 6 l i . g i . 4 1 . 8 11.1 27.1

I

1 40-44 1 . 0 2 . 5 O. 6 0 . 4 1 . 2 3 . 6 O. 2 1 4 . 3 1 2 . 8 /

1 45-49 0 . 4 O. 1 6 . 2 j

1

50-59 3 . 1 1

( _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - - -

I

Number 1939 1127 1843 2239 607 8 3 1 0 1 425 5 6 7 6 I

I ^Mean 27 ¹⁹⁶⁴ l

( length 29.28 29.47 27.74 28.63 28.29 29.12 28.31 28.26 26.61 25.14 25.48 31.33 35.04 1 l I St.dev. 4 . 9 0 5 . 4 8 3.78 3 . 7 2 4.19 4.79 5 . 0 1 2 . 9 8 4 . 9 5 8 . 0 3 5 . 9 6 1 . 6 3 6.lt3 j . . .

Table 2 . Length distribution ( % ) of C.fabricii, catfish. and redfish.

. . .

Length gr.

nun G.fabricii Catfish Redfish

. . .

Mean length 3 1 . 8 8 32.80

St.dev. 6 . 5 8 1 6 . 3 3

7.61 5 . 4 5 . . .

I l

0 0 0 0 0 0 1 0 0 0 L n 0 m 0 0 m m 1 m 0 0 0 Q 0 0 O O N 1 m 4 m m m i w el i m o o m

* ' m d d l l d N m

03 I I i d

I I

t l

t

I l

I

I I

l I

l l

C 1 m I .iI 4, l

a I

m I G l M l

6 l .iI

L I L I al l

m I

1 I

a i l C m l m r n i

rn l ffl l C U I1 .iI

id l (B l I C l

1 m i

a x ^l E o i 5 5 1

r l m i I I m l

9 1 C i

m I

a I

E l 7 1

4 l I l 4 l al l

a I .il m l 3 1

C I

m I Q i

a I I

Y l U l

o l

a i

a I id i

z ^l

I

m I

h l

i C I

m C 1

& m l C 3 l

'da I 1 I I C l

m I .d I

l U I

m I U l

I l l

. II

a I

m I I m l

11

^C o ^I

^:

1

a 1 I I I I l I m 1 al l C> t

o l

% I

-

I ^I

w l

z l

V

I

al l

E l .d I E- l

o I i d l I U l

rn l I

t 1 m I I r - P7 ' m m r u i

I r - d 4 r-

I d

I l

'mm* i wlna m* m m m d m ' m Q c - d

* P 7 d m d N

N m 4 Lna c-03 'mo

0 0 0 0 0 0 0 0 i

t i + i d d d i d d