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INTRODUCTION

After 1959 the Norwegian spring-spawning herring have been spawning along the western coast of Norway north of

62'

N. During the sixties the stock was reduced to a minimum. In the recent years there has been a slight increase in the spawning stock and in 1983

a

rich year class was produced.

In 1985 the Institute of Marine Research started a project to study the recruitment mechanisms of the herring. Preliminary results from the project's larvae investigations in 1985 and 1986 have been reported (BJgRKE, FOSSUM and SIETRE, 1986, FOSSUM, BJ0RKE and SIETRE, 1987). In addition to the early larvae studies in March-April, the project includes investigations of drift and distribution in May and in July. In August-September the distribution is covered by the international 0-group investigations in the Barents Sea,

The present report gives some preliminary results from the investigation on the herring larvae in March-April 1987.

MATERIALS AND METHODS

The study was carried out during the periods 28 March - ^{8 April and}

¹⁰

-

²⁰

April. The first coverage (Fig,

1)

was the most complete while the second one was hmpered by bad weather. Herring larvae were sampled with a modified eonical net of

0.5 m 2

opening and 395

p

m mesh

size (ELLERTSEN et al.

1984)

from

150

m (or 5

m

above the bottom) to the surface. The vertical distributions of temperature, salinity, nutrients and chlorophyll contents were observed by a CTD sonde with a rosett sampler. Seven Argos satellite-tracked, drifting buoys were depboyd. These were equipped with a 10 m window-blind drogue attached

2

to the buoys via a

60

m tetherline.

The materials for the vertical studies were derived from three

experiments; one made 10-11 A p r i l n e a r Grip, one 12-13 A p r i l n e a r Storholmen and one

18-19

A p r i l n e a r S k l i n n a ( p o s i s i o n s E , B and F i n F i g . 1 ) . The sampling was made over depths of 213,

175

iknd

147

m r e s p e c t i v e l y . A 1 1 experiments were made with a Mocness 1 m 2 sampler

(mesh

3 3 3 ~ )

(WIEBE e t a 1 1 9 7 6 ) , The tows were made a t a speed of 1.5-2 k n o t s from a f i x e d p o i n t i n a f i x e d d i r e c t i o n ,

Between 50 and 100 m 3 was f i l t e r e d with t h e Mocness sampler w i t h i n each depth i n t e r v a l . A t t h e o n s e t of t h e experiments t h e l a r v a e c o n c e n t r a t i o n s were l o c a t e d with a v e r t i c a l plankton h a u l .

The number of l a r v a e p e r mL s u r f a c e was c a l c u l a t e d by t h e formula:

N=

V

where n i s number of l a r v a e i n t h e sample, I i s depth i n t e r v a l a d V i s volume f i l t e r e d .

The development of t h e l a r v a e was c l a s s i f i e d a c c o r d i n g t o DOYLE ( 1 9 7 7 ) , and t h e d u r a t i o n of t h e s t a g e s a r e given i n Table 1 (below).

Table l . The mean d u r a t i o n of t h e d i f f e r e n t s u b s t a g e s , (For r e f e r e n c e s s e e BJBRKE, FOSSUM, NEDREAAS and SETRE

1987)

S t a g e l a S t a g e l b Stage 1 c Stage 2a S t a g e 2b

3

days

4

days

3

days 11 days

5

days

The h e r r i n g l a r v a e were preserved i n 2% f o r m a l i n f o r s t a g i n g ( a c c o r d i n g t o DOYLE 1 9 7 7 ) , f o r d r y weight and g u t c o n t e n t a n a l y s i s . Because of g u t c o n t e n t voidance i n h e r r i n g l a r v a e (HAY 1981, BLAXTER and HOLLIDAY 1963, ROSENTHAL

1969) ,

only a comparative a n a l y s i s with m a t e r i a l sampled t h e two previous y e a r and q u a l i t a t i v e a n a l y s i s were performed. Because of weight l o s s d u r i n g f o r m a l i n f i x a t i o n JmEILAKER and DORSAY 1 9 8 0 ) , samples of l a r v a e were a l s o s t a g e d and l e n g t h

measured i n v i v o , d r i e d t o c o n s t a n t weight and weighed i n t h e l a b o r a t o r y on a Cahn e l e c t r o b a l a n c e t o s e a r e s t yg.

I f food organisms could be recognized through t h e e p i t h e l i u m of t h e g u t of t h e preserved l a r v a e , they were d i s s e c t e d o u t and c l a s s i f i e d i n t o one of t h e following two groups; copepod eggs and copepod n a u p l i i . No o t h e r food items were found. The l a r v a e were r i n s e d i n f r e s h w a t e r , d r i e d t o c o n s t a n t weight and weighed a f t e r t h e p r e s e n t e d procedure.

RESULTS AND DISCUSSION

Hydrography

The d i s t r i b u t i o n s of s u r f a c e temperature and s a l i n i t y d u r i n g t h e f i r s t coverage ( F i g s . 2 and

3)

show approximately t h e same p a t t e r n a s i n

1986

w i t h h i g h e r v a l u e s i n t h e n o r t h e r n o f f s h o r e a r e a s . The n o r t h e r n p a r t i s u s u a l l y i n f l u e n c e d by A t l a n t i c Water masses (S>35) while i n t h e s o u t h e r n p a r t t h e C o a s t a l Water dominate d u r i n g t h i s p a r t o f t h e y e a r . The northbound C o a s t a l Water i s flowing a t t h e e a s t e r n s i d e of

t h e shallow bank c e n t e r e d a t about

64' 40'

N ,

09' 00 E.

The A t l a n t i c Water i s u s u a l l y a s s o c i a t e d with high v a l u e s of n i t r a t e a s seen i n F i g .

4.

The r e l a t i v i t y high v a l u e s of n i t r a t e i n t h e Co%stal Water i n d i c a t e t h a t t h e phytoplankton spring-bloom have n o t reach i t s peak,

F i g .

5

shows t h e v e r t i c a l hydrographic s t r u c t u r e i n t h e t h r e e s e c t i o n s A, B and C . The l o c a t i o n of t h e s e c t i o n s appear i n Fig.

l.

I n t h e two southernmost s e c t i o n s ( A and B ) t h e C o a s t a l Water i s occupying t h e upper

l00

m over t h e e n t i r e s h e l f a r e a . I n t h e northernmost s e c t i o n , however, t h e C o a s t a l Water i s confined t o a narrow zone along t h e c o a s t . Under t h e C o a s t a l Water a t

SECTION

C water of A t l a n t i c o r i g i n i s p r e s e n t . This has p e n e t r a t e d i n t o t h e t r e n c h a t t h e e a s t e r n s i d e of t h e bank from t h e s o u t h and i s c l e a r l y s e e n i n 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 s of temperature and s a l i n i t y From t h e deeper l a y e r s -

F i g .

6

shows t h e d r i f t i n g t r a c k s 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 from t h e seven Argos buoys while F i g .

7

shows t h e t o t a l t r a c k s , The c i r c u l a t i o n

p a t t e r n o f t h e a r e a i s t o a l a r g e degree governed by t h e bottom topography. Around t h e shallower banks an a n t i - c y c l o n i c c i r c u l a t i o n is favoured. S i x of t h e buoys a r e confined t o t h e C o a s t a l C u r r e n t while one was brought i n t o t h e A t l a n t i c water flowing a l o n g t h e c o n t i n e n t a l s l o p e ,

The d r i f t t r a c k s a l s o i n d i c a t e r e t e n t i o n a r e a s with prolonged r e s i d e n c e t i m e of t h e water. One i s t h e bank a r e a a t about 63' 05'

N

where t h e buoy r e l e a s e d i n t h a t a r e a described a n t i - c y c l o n i c movement over t h e bank f o r 12 days b e f o r e i t grounded a t t h e c o a s t . Another such a r e a i s t h e bank a t 63' 40' N where t h e d r i f t e r c i r c u l a t e d f o r about

30

days. These f e a t u r e s seem t o r e p e a t themselves each y e a r . The same i s t h e c a s e f o r t h e apparent meandering of t h e t r a c k s between 65 0

N and 65' 30' N which a l s o i s an e f f e c t o f t h e bottom topography. The i r r e g u l a r movements of two of t h e buoys j u s t s o u t h of 66 N , however, 0

i s probably a r e s u l t of more t r a n s i e n t p r o c e s s e s along t h e C o a s t a l Current f r o n t . I n s t a b i l i t i e s of t h e f r o n t a l system i s f r e q u e n t l y seen i n s a t e l l i t e I R images,

The average t r a n s p o r t speed of t h e d r i f t e r s between

64'

N and 66' N was 10

-

12 n a u t i c a l miles/day i n t h e C o a s t a l Current and

3 -

⁶

n a u t i c a l m i l e s l d a y along t h e c o n t i n e n t a l s l o p e ,

H o r i z o n t a l l a r v a e d i s t r i b u t i o n

The h a t c h i n g of h e r r i n g l a r v a e s t a r t e d around 16 March w i t h a peak i n t h e l a s t days of March, The h a t c h i n g continued u n t i l about 25 A p r i l b u t with r a t h e r s m a l l l a r v a e production a f t e r t h e f i r s t week of A p r i l

(BJgRKE,

1988).

The h o r i z o n t 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 of t h r e e d i f f e r e n t l e n g t h groups from t h e f i r s t coverage 28 March

- 8

A p r i l i s shown i n F i g s .

8

^-10. The d i s t r i b u t i o n of t h e s m a l l e s t l a r v a e i n d i c a t e t h e spawning grounds ( F i g . 8 ) . I n t h e s o u t h e r n p a r t two such a r e a s a r e a p p a r e n t . These a r e about t h e same a s observed both i n

1985

and i n 1986 (BJgRKE, FOSSUM and SETRE, 1986, FOSSUM, BJgRKE

and

SETRE, 1987).

A d d i t i o n a l l y , spawning have occurred i n t h e n o r t h e r n n e a r - c o a s t a r e a ,

The d i s t r i b u t i o n of l a r g e r l a r v a e ( F i g s .

9 -

10) i n d i c a t e t h e l a r v a l d r i f t r o u t e s . Most of t h e l a r v a e are confined t o t h e C o a s t a l Current c l o s e t o t h e c o a s t . A minor p a r t of t h e l a r v a e seems t o follow an o u t e r r o u t e along t h e c o n t i n e n t a l s l o p e a s a l s o i n d i c a t e d by one of t h e Argos d r i f t e r s ( F i g .

6 ) .

A s p r e v i o u s l y mentioned, t h e second coverage,

g -

20 A p r i l was hampered by bad weather and i s t h e r e f o r e incomplete. However, t h e d i s t r i b u t i o n of t h e s m a l l e s t l a r v a e from t h i s coverage i s included ( F i g . 11) because i t i n d i c a t e s minor spawning a l s o n o r t h of t h e a r e a of t h e f i r s t coverage. Fig. 12 shows t h e d i s t r i b u t i o n of l a r v a e s o u t h of

63'

N f o r t h r e e l e n g t h groups d u r i n g t h e second coverage. A s expected, t h e numbers of t h e s m a l l e s t l a r v a e a r e low a s t h e peak h a t c h i n g was over d u r i n g t h a t p e r i o d . The number of l a r v a e between

9

and l l m m i s approximately a s d u r i n g t h e p r e v i o u s coverage while t h e amount of l a r v a e l a r g e r than 12 mm i s c o n s i d e r a b l y h i g h e r . T h i s may i n d i c a t e a r e l a t i v e l y long r e s i d e n c e t i m e of t h e l a r v a e i n t h i s a r e a .

The i n v e s t i g a t i o n s i n

1987

seem t o confirm t h e t e n t a t i v e p a t t e r n of d r i f t r o u t e s and r e t e n t i o n a r e a s p u t up f o r t h e s i m i l a r s t u d i e s i n 1986 (FOSSUM, BJ0RKE and SETRE, 1 9 8 7 ) - The d r i f t speed, however, was a p p a r e n t l y h i g h e r i n

1987

than i n 1986,

V e r t i c a l l a r v a e d i s t r i b u t i o n

Table 2 shows t h e number of l a r v a e p e r m2 s u r f a c e sampled d u r i n g t h e experiments. Larvae without yolk-sac axld without t h e c h a r a c t e r i s t i c s of s t a g e 2a described by DOYLE

(1977)

a r e omitted from t h i s t a b l e .

F i g ,

13

shows t h e v e r t i c a l d i s t r i b u t i o n of l a r v a e of a l l l e n g t h groups when a l l depth i n t e r v a l s were sampled. Hence t h e samples from n e a r Grip 11 A p r i l a t 07 h r s . a r e omitted. Near Grip and Storholmen t h e v e r t i c a l d i s t r i b u t i o n was almost i d e n t i c a l with a maximum of l a r v a e i n t h e 0-19 m i n t e r v a l . A t t h e s e two s t a t i o n s

94

and

99 %

of t h e l a r v a e were sampled i n t h e upper

59

m r e s p e c t i v e l y * Near S k l i n n a t h e v e r t i c a l d i s t r i b u t i o n was d i f f e r e n t with t h e m a j o r i t y of t h e l a r v a e i n t h e

40-59 m i n t e r v a l . A t t h i s s t a t i o n only

5%

,% of t h e Larvae were sampled i n t h e upper

59

m.

Were any d i f f e r e n c e s i n v e r t i c a l d i s t r i b u t i o n observed a t d a y l i g h t and a t n i g h t ? Fig.

14

shows t h e v e r t i c a l d i s t r i b u t i o n of l a r v a e caught by day and by n i g h t d u r i n g t h e experiments. The l a r v a e caught d u r i n g t h e day were sampled between 0900 and 1500 hour and t h e l a r v a e caught d u r i n g t h e n i g h t were sampled between 2100 and 0200 hours GMT, both hours included. Only l a r v a e from Table 1 a r e i n c l u d e d i n t h e s e f i g u r e s . Near Grip t h e l a r v a e seemed t o c o n c e n t r a t e i n t h e 0-19 m i n t e r v a l by n i g h t and i n t h e 20-39 m i n t e r v a l by day. Near Storholmen t h e m a j o r i t y of t h e l a r v a e were found i n t h e 0-19 m i n t e r v a l both by day and by n i g h t . Near S k l i n n a l a r v a e were found throughout t h e i n v e s t i g a t e d water column though mainly below 40 m . There seems t o be no c l e a r changes i n v e r t i c a l d i s t r i b u t i o n d u r i n g a 24-hrs. p e r i o d a t t h e s e s t a t i o n s .

F i g s ,

15-19

shows t h e v e r t i c a l s t a g e d i s t r i b u t i o n of t h e l a r v a e shown i n F i g .

1 4 .

I t i s c l e a r t h a t while s t a g e 2a was i n m a j o r i t y n e a r Grip and Storholmen, s t a g e 1b was i n m a j o r i t y n e a r S k l i n n a , Hence t h e v e r t i c a l d i s t r i b u t i o n of t h e s e s t a g e s w i l l be r e f l e c t e d i n t h e v e r t i c a l d i s t r i b u t i o n s shown i n f i g u r e

1 4 ,

Near Grip s t a g e 2a was most common i n t h e 20-39 m i n t e r v a l by n i g h t a i d i n t h e 0-19 m i n t e r v a l by day. Near Storholmen, however, t h i s s t a g e was found mainly i n t h e 0-19 m i n t e r v a l both by day and by n i g h t . Near S k l i n n a l a r v a e i n t h i s s t a g e were found i n r a t h e r low numbers, b u t they tended t o c o n s e n t r a t e i n t h e 0-19 m l a y e r a t n i g h t ,

Near S k l i n n a l a r v a e i n s t a g e 1b was i n m a j o r i t y , Here, t h i s s t a g e was found throughout t h e i n v e s t i g a t e d water column though mainly below 40 m . There seems t o be no c l e a r changes i n v e r t i c a l d i s t r i b u t i o n d u r i n g the 24-hrs, p e r i o d , Near Grip

and

Storholmen l a r v a e i n t h i s s t a g e was found i n h i g h e r numbers i n t h e 20-39 m i n t e r v a l by n i g h t and i n t h e 0-19 m i n t e r v a l by day. However, t h e number of l a r v a e i n t h i s s t a g e ( I b ) a t t h e s e s t a t i o n s i s too low t o draw any f i r m c o n c l u t i o n s . By t h e same reason no firm conclusions can be made concerning t h e s t a g e s Ea, 1 c og 2b.

Both a t t h e s t a t i o n s n e a r Grip and Storholmen s t a g e 2a was most abundant. The l a r v a e i n t h i s s t a g e were, however, d i f f e r e n t l y d i s t r i b u t e d by day a t t h e s e s t a t i o n s . While they were most abundmt i n t h e upper 19 m a t t h e s t a t i o n n e a r G r i p , they were most abundant i n t h e 20-39 m i n t e r v a l n e a r Storholmen. The hydrographical c o n d i t i o n s were almost i d e n t i c a l with no pronounced pycnocline ( F i g . 1 4 ) ~ Food c o n d i t i o n s could have been d i f f e r e n t a t t h e s e s t a t i o n s . Samples a r e t a k e n , b u t have n o t been worked up y e t . Light c o n d i t i o n s could a l s o have been d i f f e r e n t , but t h e s e were u n f o r t u n a t e l y n o t measured. This i s h i g h l y recommended d u r i n g f u r t h e r t r i a l s . Hence, t h i s f a r , no e x p l a n a t i o n can be given f o r t h e observed d i f f e r e n c e s i n 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 t a g e 2a n e a r Grip and Storholmen.

Conclusion: Herring l a r v a e 12-32 days o l d a r e mainly found i n t h e upper

59

m and they seems t o c o n c e n t r a t e i n t h e upper

19

m by n i g h t . Larvae

3-7

days o l d a r e found throughout t h e i n v e s t i g a t e d water column though mainly below 40 m . There seems t o be no c l e a r changes i n v e r t i c a l d i s t r i b u t i o n d u r i n g a 24 h r s . p e r i o d of l a r v a e i n t h i s s t a g e . These o b s e r v a t i o n s does n o t d e v i a t e from o b s e r v a t i o n s made during s i m i l a r s t u d i e s i n

1985

(BJgRKE e t a l . 1987) and

1986

(FOSSUM, BJgRKE and SRTRE

1987).

Condition of h e r r i n g l a r v a e

The m a t e r i a l c o n s i s t e d of 1770 h e r r i n g l a r v a e of standard l e n g t h

8-18

mm and d r y weight 50-1265 pg. 1692 l a r v a e were preserved i n f o r m a l i n , while

78

were s t a g e d and measured i n v i v o . The mean s t a n d a r d l e n g t h and d r y weight of t h e l a r v a e i n d i f f e r e n t developmental s t a g e s a r e given i n Table

3

and

4.

The l a r v a l m a t e r i a l sampled an t h i s survey was composed of both y o l k s a c - l a r v a e and p o s t - l a r v a e , The development of t h e Larval population was somewhat delayed compared t o what was found i n

1985

when t h e p o p u l a t i o n was composed of p o s t - l a r v a e i n s t a g e 2a.

Compared t o 1986, however, when t h e l a r v a e were i n t h e yolksac s t a g e , t h e l a r v a e had reached a more advanced s t a g e i n t h e p r e s e n t m a t e r i a l

(FOSSUM, BJORKE and SETRE

1.987)~

I t can be seen from t h i s t a b l e s t h a t t h e l a r v a e s h r i n k d u r i n g

f i x a t i o n , and tests of t h e means of l e n g t h and weights b e f o r e and a f t e r f i x a t i o n a l l show a h i g h l y s i g n i f i c a n t l e n g t h and weight l o s s

(47<

t < 1 1 . 6 )

.

The p e r c e n t shrinkage i s given i n Table

5,

The l a r v a l samples a r e from t h e second coverage. The m a t e r i a l sampled t h e p r e v i o u s y e a r had only h a l f t h e length-shrinkage compared t o t h e p r e s e n t (3.3-6.5%)

.

while t h e weight l o s s was s l i g h t l y h i g h e r (38.6-

45.5%)

, (FOSSUM, BJ0RKE & SETRE

1987) .

I n f i g . 20 l e n g t h l w e i g h t p l o t of t h e l a r v a e n o t exposed t o formalin i s shown. There i s a s t r o n g lengthlweight-relationskip i n d i c a t e d by a c o r r e l a t i o n c o e f f i s i e n t r=0.97. The s l o p e i s h i g h e r than was seen with t h e unpreserved m a t e r i a l f o r 1986. 0.095 compared t o 0.082, i n d i c a t i n g a f a s t e r growth i n

1987

than i n

1986.

The p l o t s of t h e preserved m a t e r i a l i s shown i n f i g s . 21-23. There i s a s l i g h t l y h i g h e r growth parameter ( t h e s l o p e of t h e c u r v e ) d u r i n g t h e second coverage, and a t e s t of t h e c o n d i t i o n shows t h a t t h i s i s s i g n i f i c a n t l y h i g h e r on t h e second than on t h e f i r s t coverage

( t = 4 . 1 4 ) .

The reasons f o r t h i s a r e n o t f u l l y understood, There can be problems with t h e sampling procedure, t h e prey c o n d i t i o n s can have improved ( n o t an i t e m f o r t h e i n v e s t i g a t i o n t h i s y e a r ) o r i t can be a g e n e r a l condition-improvement of growing l a r v a e .

A

p l o t of t h e c o n d i t i o n f a c t o r (k=l(mm)3/lOw(pg) v e r s u s s t a n d a r d l e n g t h f o r t h e two coverages i s shown i n f i g s . 24

aid 25,

The m a t e r i a l i s somewhat s c a t t e r e d b u t t h e r e i s a tendency of? d e c r e a s i n g c o n d i t i o n t o ~ ~ a r d s y o l k r e s o y t i o n , and then t h e c o n d i t i o n i s i n c r e a s i n g when t h e l a r v a e s t a r t s t o grow, So t h e reason f o r t h e d i f f e r e n c e i n c o n d i t i o n between t h e two coverages may be t h a t tile samples c o n t a i n l a r v a e of d i f f e r e n t a g e , Lengtb/weight p l o t s of preserved m a t e r i a l have weaker Length/

weight r e l a t i o n s h i p s , because of v a r i s b l e weight l o s s d u r i n g f i x a t i o n , r=0.85 f o r t h e f i r s t coverage m d r=O,gJ f o r t h e second, The growth p a r a m e t e r ( t h e sLope = 0,08) i s h i g h e r than i n

1986

_(0.04) and equal t o t h e parameter found i n

1985

( t h e s l o p e = 0 + 0 8 ) , i n d i c a t i n g reduced growth i n

1986.

The d i e t of t h e l a r v a e d u r i n g s t a g e s l a - 2 b , a time span e s t i m a t e d t o be 28 days (BJfdRKE, FOSSUM & SWTRE 1986)' i s shown i n f i g . 26. There were found

345

cop, n a u p l i i and 156 cop. eggs i n t h e l a r v a l g u t s . No

o t h e r food i t e m s were found, The low f e e d i n g r a t i o i n t h e l a r g e r l a r v a e i s most probably due t o t h e emptying of t h e gut d u r i n g c a t c h i n g and p r e s e r v a t i o n , The p e r s i s t a l t i c movements of t h e gut must be much s t r o n g e r i n t h e more advanced l a r v a e . There i s a s t r o n g e r impact of cop, eggs t h i s y e a r than t h e p r e v i o u s two. The number of cop. n a u p l i i i s on t h e same l e v e l a s i n

1985

and h i g h e r than i n 1986, a n o t h e r i n d i c a t i o n of good l a r v a e c o n d i t i o n s i n

1987.

F i r s t f e e d i n g was seen i n s t a g e l b l a r v a e

(3-6

days o l d ) . Cop. eggs seems t o be

an

important f i r s t f e e d i n g i t e m . L a t e r on, t h e importance of t h i s food item i s reduced.

From t h e mean l e n g t h and s t a g e d u r a t i o n d a t a t h e growth r a t e can be c a l c u l a t e d . A mean growth r a t e of 0.36 mm/day i n t h e p e r i o d 2-26 days p o s t h a t c h i n g were found. I n t h e yolksac-period t h e growth was slower, 0.28 mm/day, but i n t h e p o s t - l a r v a l p e r i o d 0.41 mm/day. The s p e c i f i c growth r a t e can be c a l c u l a t e d t o be 6 . 8 % , by t h e method shown i n

BJmRKE;

FOSSUM & SETRE (19861, Both t h e growth r a t e i n l e n g t h

and

t h e s p e c i f i c growth r a t e a r e almost i d e n t i c a l t o t h e s a t e s found i n 1985, and a r e i n accordance with previous r e s u l t s on t h e same h e r r i n g s t o c k (DRAGESUND & NAKKEN

1973)*

and w i t h r e s u l t s with l a r v a e from o t h e r s t o c k s (LOUGH e t a l . 1982, WOOD & BURD

1976).

BJgRKE, H.

1988.

S i l d e k l e k k i n g p& More i

1986-87. HELP

(Havforskningsinstituttets Egg-- og L a r v e p r o g r m )

,

l988 ( 1 5 ) : 1 - 2 5 *

BJaRKE; H . , FOSSUM, P , , MEDREAAS, K , and SmRE, R . 1987.

Yngelundersskelser

- 1985,

HELP ( H a v f o r s k n i n g ~ i n s t i ~ t u t t e t s (12):1-q4.

BJgRKE, H , , FOSSUM, P , and SETRE, S , 1986, D i s t r i b u t i o n , d r i f t and c o n d i t i o n of h e r r i n g l a r v a e o f f western Norway i n

1985.

Coun.

Meet. i n t , Coun. Explor. Sea,l987(H:39):1-15,

BLAXTER,J.H.S. and HOLLIDAY, F.G,T. 1963, The behaviour and physiology of herring and other clupeids, P. 262-394 in

RUSSEL, F.S. ed. Adv. mar, Biol, Academic Press, London and New York: 410 p.

DOYLE, M.J. 1977. A morphological staging system for the larval devel- opment of the herring, (Clupea harengus L.).

J.

mar. biol.

B. , E : 859-867.

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: ^15-29,

ELLERTSEN, B., P. FOSSUM, P. SOLEMDAL, S. SUNDBY and S. TILSETH. 1984.

A case study on the distribution of cod larvae and availability of prey organisms in relation to physical processes in Lofoten. The Propagation of Cod Gadus morhua L.

Flgdevigen rapportser,, 1:453-477.

FOSSUM,P,, BJGRKE, K, and SETRE, R, 1987, Distribution, drift and condition of herring larvae

off

western Norway in 1986. Coun.

Meet. int. Coun, Explor, Sea91987(E:13):1-10.

FOSSUM,P., BJgRME, H. a d SIETRE, R,, 1 9 8 ~ ~ Studies on herring larvae off western Norway in 1986. HELP

(Havforskningsinstituttets

Egg- o (8):l-16,

+

appendix 23

p,

HAU,D.E, 3.981. Effects of capture and fixation on gut contents and body size of Pacific herring larvae. Rapp. P,-v, Reun. C o n k perm. int. Explore Mer, G: ^395-400,

LOUGH, R.G., M. PENNIMGTON, G.R BOLZ

and

A.W, ROSENBERG. 1982.

Age

and growth of larval atlantic herring Clupea harenos L,based on otolith growth increments. Fish. Bull., 803187-199,

ROSENTHAL, H. 1969.

Verdauungsgeschwindigheit,

Nahrungswahl und

Nahrungsbedarf bei den Larven des Herings, Clupea harengus L.

Ber. dt, wiss, Mommn, Meeresforsch,, 20: 60-69,

THEILACKER, G. and DORSEY, K, 1980. Larval fish diversity, a summer of laboratory and field research. IOC Workshop Report no. 28:

105-142.

WIEBE, P.H., BURT, K.H., BOYD,

S . H .

and MORTON, A.W., 1976. A multiple opening/closing net and environmental sensing system for sampling zooplankton. J. Mar. Res. , 34: 313-326.

WOOD, J. and BURD, A, C. 1979. Growth and mortality of herring larvae in the central North Sea. Coun, Meet int, Coun. Explor.

Sea,(H:8) :l-7.

WJEBE, P.H., BURT, K.H., BOYD, S.H. and MORTON, A.W., 1976, A multiple

opening/closing net and environmental sensing system for

sampling zooplankton. J, Mar. Res . , 34: 313-326.

T a b l e 2 , Number o f l a r v a e p e r m 2 s u r f a c e sampled d u r i n g t h e e x p e r i m e n t s .

S t .

444,

n e a r G r i p .

Date 1 0 A p r i l 1 9 8 7 1 1 A p r i l

Hour

17

20 22 24 02 04 05 07 09 12

13 15 17

Depth

S t . 478, n e a r Storholmen.

Date 12 A p r i l 13 A p r i l

1987 1987

Hour 20 23 01

03 05 07

09 11 13 15

17 19

Depth

St,

519, n e a r S k l i n n a ,

Date

18

A p r i l 19 A p r i l

Hour

19 21 23 01

03 05

07

09

11 13

15

17

Depth

Table 3 . Standard length and dry weight in the different developmental stages (preserved material).

Stage Mean standard Mean dry Nos. of

length (mm) weight (pg) larvae

Table 4 . Standard length and dry weight of larvae staged and measured in vivo.

--_-_---___-_-_-_-_---

Stage Mean standard Mean dry Nos of

length (mm) weight (M) larvae

Table 5 . Shrinkage due "i fixation

Stage Length ("h) Weight (%)

Fig. l. Grid of stations during the first coverage, 28 March

-

8 April 1987, Bathymetric contours for each 100 m are

included, Inserted map shows the location of the studied

area,

Fig. 2. Surface temperature, 28 March

- 8

April 1987.

Fig. 3. Surface salinity, 28 March

- 8

April 1987.

Fig, 4 , Surface values of nitrate, 28 March

- 8

April 1987,

Fig. 5. Hydrographic sections A , B and C. The location of

these is indicated in Fig, l.

Fig, 6. Tracks of the drifting Argos buoys within the investigation

area drogued at 60 m depth.

Fig, 7. The total tracks of the drifting Argos buoys.

Fig.

8.

Distribution of herring larvae

C

9mm

( ~ / m ' ) .

28 arch

_- 8

April 1987.

Fig. 9. Distribution of herring larvae between 9 and l lmm

( ~ / m ~ r

28 March

-

8 April 1987.

Fig. 10. Distribution of herring larvae Zllmm ( ~ / m 2

) ,

28 arch

-

8 April 1987,

Fig. 11. Distribution of herring larvae

< 9

mm

( ~ / r n ~ ) , 9 - 2 0

April

1987.

6 2 0 0 6

0 4 0 0 0 6 0 0

G . 0 . S A R S 9 - 2 0 / 4 1 9 8 7 . ^{0 6 0 0}

S I L D E L A R V E R 0 - 8 M M P R . M M Z .

0 4 0 0 0 6 0 0 0 8 0 0

G . 0 . S A R S 9 - 2 0 / 4 1 9 8 7 .

S I L D E L A R V E R 9 - 1 9 M M P R . M M Z .

0 4 0 8 0 6 0 0

C . 0 S A R S 9 - 2 0 / 4 1 9 8 7 .

S I L D E L A R V E R 1 2 - 2 I M M P R M M 2

Fig. 12. Distribution of herring 1 rvae in three length groups south of 63ON (N/m 9

) r

9-20 ~pri.1 19C7.

G R I P

-

temperature

... d e n s i t y

- - - -

s a l i n i t y

0

200 400 600 8 0 0 1 0 0 0 1 2 0 0 nos/m2 s u r f a c e

S T O R H O L M E N

-

temperature

...

d e n s i t y

- - - -

s a l i n i t y

S K L I N N A

--- temperature ... d e n s i t y

- - - - s a l i n i t y

8 0 - 9 9 1 0 0 - 1 1 9

1 2 0 - 139 t o C

0 1 0 0 2 0 0 300

400

5 0 0 600 7 0 0 n o s / d surface

FIG. 13. Vertical distribution of herring larvae, temperature, salinity

and

density at the stations near Grip, Storholmen and Sklinna.

G R I P

A

Daylight

G R I P

B

N i g h t

0 - 1 9

1 - 4 [I

AII stages 0 - 1 9

1 - 4 0

AII stages

NOS/MZ SURFACE NOS/MZ SURFACE

S T O R H O L M E N

C

D a y l i g h t

S T O R H O L M E N

D

N i g h t

NOS/M2 SURFACE NOS/M2 SURFACE

S K L I N N A

E

D a y l i g h t

NOS/M2 SURFACE 0 - 1 9 -

2 0 - 3 9 -

4 0 - 5 9 -

6 0 - 7 9 -

8 0 - 9 9 -

1 0 0 - 1 1 9 -

F S K L I N N A

N i g h t

C]i

AII stoges 0 - 1 9

13

AII stages

2 0 - 3 9 4 0 - 5 9 6 0 - 7 9 8 0 - 9 9 1 0 0 - 1 1 9 1 2 0 - 1 3 9

l l l I I

o 2 0 40 60 80 sa

NOS/M2 SURFACE

FIG.

14.

V e r t i c a l d i s t r i b u t i o n of l a r v a e i n a l l s t a g e s a t t h e t h r e e s t a t i o n s d u r i n g t h e day and t h e n i g h t .

S T O R H O L M E N

Daylight

L a r v o e < 3 d a y s o l d

I I l

0 . 0 0 . 5 1 .O

N O S / M 2 SURFACE

S K L I N N A

Daylight

L o r v a e < 3 d o y s o l d

N O S / M Z S U R F A C E

0

S t a g e l a

s t a g e l o 15

S K L l N N A

Night

L a r v o e < 3 d o y s o l d

l I l

0 1 2

N O S / M Z SURFACE

0

S t a g e 1 0

FIG.

15,

V e r t i c a l d i s t r i b u t i o n of l a r v a e i n s t a g e l a a t t h e t h r e e s t a t i o n s d u r i n g t h e day and t h e n i g h t .

G R I P

D a y l i g h t

Larvae < 3 d a y s o l d

G R I P

N i g h t

L a r v a e 5-7 d a y s a i d

II 0-19 S i e g e l b zz 0-19

Z Z

20-39 - _20-39

2 ^_1

2

^{40-59 40-59}

E 12i

60-79

E

60-79

z ^Z

- -

80-99 80-99

I I

k 1 0 0 - \ l 9 100-119

W W

120-139 120-139

0 1 2 9 4 5

NOS/MZ SURFACE NOS/MZ SURFACE

S T O R H O L M E N

D a y l i g h t

L o r v a e 3 - 7 d o y s o l d

NOS/M2 SURFACE

S K L I N N A

Onylight

L a r v a e 3 - 7 d a y s o l d

0 10 20 30 4'0 5'0 6'0 NOS/M2 SURFACE

S t a g e ~b

S T O R H O L M E N

Night

L a r v a e 3 - 7 d o y s o l d

z 0-19 S t a g e l b

Z - _20-39

W

120-139

I l I 1

0 I 2 3 4

NOS/MZ SURFACE

S K L I N N A

N i g h t

L a r v a e 3 - 7 d a y s o l d

S t a g e ~b

0 10 20 30 40 50 60 7 0 80 NOS/M2 SURFACE

FIG.

16.

V e r t i c a l d i s t r i b u t i o n of l a r v a e i n s t a g e 1b a t t h e t h r e e s t a t i o n s d u r i n g t h e day and t h e n i g h t ,

GRIP

D a y l i g h t

L a r v a e 3 - 7 days old

GRIP

N i g h t

L a r v a e 7 - 1 0 days o l d

NOS/MZ SURFACE NOS/MZ SURFACE

S T O R H O L M E N

D a y l i g h t

L a r v a e 7 - 1 0 doys o l d

NOS/M2 SURFACE

S K L I N N A

D a y l i g h t

L a r v o e 7 - 1 0 days o l d

&

1 0 0 - 1 1 9

W

1 2 0 - 1 3 9

0 1 2 3 4 5 6 7 8

N O S / M 2 SURFACE

S T O R H O L M E N

N i g h t

L a r v a e 7 - 1 0 doys o l d

0 1 2

NOS/MZ SURFACE

S K L I N N A

N i g h t

L a r v a e 7 - 1 0 doys o l d

0 1 2 3 4 5 i . 7

N O S / M 2 SURFACE

Stage I C

FIG.

17.

V e r t i c a l d i s t r i b u t i o n of l a r v a e i n s t a g e l c a t t h e t h r e e s t a t i o n s d u r i n g t h e day and t h e n i g h t .

GRIP

D a y l i g h t

L a r v a e 1 2 - 2 9 d a y s old

GRIP

N i g h t

Larvae 1 2 - 2 3 days o l d

0 2 0 40 60 8 0

NOS/M2 SURFACE

0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 4 5 0 NOS/M2 SURFACE

S T O R H O L M E N

D a y l i g h t

L a r v a e 1 2 - 2 3 doys o l d

S T O R H O L M E N

N i g h t

Larvae 1 2 - 2 3 doys o l d

1

... :...:.. . . :

0

s t a g e 2a ... :.:

. . . _....

....

2 0 - 3 9 .<:;::;;:!;;;!;., . . . _.::::..

1 2 0 - 139

I I I I I I I I

0 2 0 40 6 0 8 0 1 0 0 1 2 0 1 4 0 160 NOS/M2 SURFACE

1 2 0 - ' 3 9

i

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 140 160 1 8 0

NOS/M2 SURFACE

S K L I N N A

D a y l i g h t

L a r v a e 1 2 - 2 3 d o y s o l d

S K L I N N A

N i g h t

L a r v a e 1 2 - 2 3 doys o l d Stage 2a

NOS/M2 SURFACE NOS/M2 SURFACE

FIG. 18. Vertical distribution of larvae in stage 2a at the three

stations during the day and the night.

G R f P

N i g h t

L a r v a e 23-28 days old

GRIP

D a y l i g h t

Larvae 2 3 - 2 8 d a y s old

B

^{Stoge 2 6}

NOS/MZ SURFACE

W

120-139

I l I I I I

0 2 4 6 8 1 0 1 2

NOS/M2 SURFACE

Stage 2b

S T O R H O L M E N S T O R H O L M E N

D a y l i g h t Night

L a r v o e 23-28 d a y s o l d L a r v o e 23-28 days old

Stage 2b I 0-19 Stoge 2b

25 0-19

z - _20-39 ^{Z 28-39}

2 .A

g

^{40-59 40-59}

IL U:

60-79 E 60-79

S Z

80-99 80-99

r ^I

E 100-119

E

^100-119

W W

120-139 ^Q 120-139

0 2 4 6 8 1 0 1 2

NOS/MZ SURFACE NOS/M2 SURFACE

S K L I N N A

D a y l i g h t

L a r v o e 23-28 d a y s o l d

Stoge 2b

&

- 80-99

-i-

t;:

100-119

W

120-139

l 1

0 1 2

NOS/MZ SURFACE

S K L I N N A

N i g h t

L a r v a e 23-28 d a y s o l d

I

100-119

l.Ll

120-139

0 1 2 5 4 5 6

NOS/MZ SURFACE

FIG. 19.

Vertical distribution of larvae in stage 2b at the three stations during the day and the night.

Fig.20. The standard length/ dry weight plot of the larvae not exposed to formalin fixation.

Fig.21. Lengthidry weight plot of the total formalin preserved

material sampled in 1987.

Fig.22.Lengthldry weight plot of the larvae sampled on the first coverage.

Fig.23.Length dry weight p l o h f the larvae sampled on "re second

coverage.

0

8

ST LENGTH (MM)

Fig.24 Length versus condition of the larvae sampled on the first coverage.

0

0

ST LENGTH (MM)

Fig.25. Length versus condition of the larvae sampled

on the second coverage.

Fig.26 The diet of the herring larvae in the period 0-28 days post

hatching.