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HAVFORSI(NINGSINST1TUTTETS ER- OG W P R O G R A M (HELP)

O-GROUP SAITHE AND HERRING OFF THE NORWEGIAN COAST IN

1986

AND

1987.

K j e l l Nedreaas and Odd M . Smedstad I n s t i t u t e of Marine Research

P.0 .Box 1870 N-5024 Bergen, Norway

Norway

ABSTRACT

I n

1985

i n v e s t i g a t i o n s were s t a r t e d t o t r y t o measure t h e abundance of O-group s a i t h e b e f o r e t h e main c o n c e n t r a t i o n s e n t e r e d t h e i n s h o r e w a t e r s . I n 1986 t h e i n v e s t i g a t i o n a r e a were expanded t o a l s o cover t h e e a s t e r n p a r t of t h e n o r t h e r n North Sea. T h i s r e p o r t g i v e s some r e s u l t s from t h e c r u i s e s i n April-May 1986 and April-May 1987. The r e s u l t s i n d i c a t e t h a t t h e end of A p r i l i s too l a t e t o g e t a good measurement of t h e O-group from t h e North Sea. For t h e n o r t h e r n s t o c k t h e chosen time seem t o be a l l r i g h t .

INTRODUCTION

One of t h e b i g g e s t problems i n a s s e s s i n g t h e s a i t h e s t o c k s i n t h e North A t l a d l i c i s t h e l a c k of good recruitment e s t i m a t e s . The 0- group s a i t h e a r e very e a r l y d i s t r i b u t e d i n t h e i n s h o r e waters and i t i s almost impossible t o measure t h e abundance when t h e f i s h a r e s o c l o s e t o t h e s h o r e . I n

1985

a c r u i s e were undertaken with t h e aim of measuring t h e abundance of p o s t l a r v a e of t h e Northeast A r c t i c s a i t h e b e f o r e t h e main c o n s e n t r a t i o n s reached t h e shore (Nedreaas ,1986)

.

^{I n}

1986 t h e i n v e s t i g a t i o n were expanded t o a l s o cover t h e North Sea. This r e p o r t g i v e s some r e s u l t s from t h e i n v e s t i g a t i o n s i n 1986 and

1987.

MATERIALS AND METHODS

I n

1986

t h e i n v e s t i g a t i o n was c a r r i e d o u t with R/V "Håkon Mosby" i n t h e p e r i o d 28. A p r i l

-

28. May. I n

1987

R / V "Håkon Mosby" covered t h e s o u t h e r n a r e a i n t h e p e r i o d 22. A p r i l

-

6. May, while R / V "Eldjarn"

covered t h e n o r t h e r n a r e a i n t h e period

7.

May

-

30. May.

A mid-water c a p e l i n t r a w l with a 30 meter l o n g codend with

8

mm s t r e t c h e d mesh was used. 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 have given information about t h e t r a w l geometry on t h e d i f f e r e n t c r u i s e s

.

S i x e x t r a 70' ' f l o a t s were t i e d t o t h e headrope. The t r a w l was towed with

3

knots 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 d e p t h . T o t a l d i s t a n c e towed was

1 . 5

n a u t i c a l mile.

The i n v e s t i g a t e d a r e a was covered by a r e c t a n g u l a r survey g r i d . The d i s t a n c e between t h e t r a c k s i s 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 i s

15

n a u t i c a l m i l e s ( F i g s . l

-

3 ) .

Hydrographical s t a t i o n s were taken on each t r a w l s t a t i o n .

Measurements of t h e t r a w l geometry on R / V "Håkon Mosby" showed a v a r i a t i o n around 20 x 20 meter i n a l l depths. On R/V " E l d j a r n " , however, measurements showed t h a t t h e geometry was d i f f e r e n t i n t h e d i f f e r e n t d e p t h s . A t t h e s u r f a c e t h e heighth were measured t o 20.0 m and t h e width t o 10.7 m, a t 20 m depth t h e t r a w l opening was 1 8 . 3 m x 1 4 . 2 m and a t 40 m depth 15.0 m x 17.5 m . The volume of a t r a w l haule

4 3

taken by

R I V

"Eldjarn" i s c a l u l a t e d t o be VI (E) = 1.075 x 10- nu

.

4 3

while a haule taken by R / V "Håkon Mosby" i s V1 ( H ) =

1.75

x 10- nu

.

Because of t h e d i f f e r e n t h e i g h t s of t h e t r a w l s t h e square around each t r a w l s t a t i o n of 15 x 30 nm w i l l a l s o have d i f f e r e n t volumes. The t r a w l on R / V "Eldjarn" has a h e i g h t of about

15

m a t 40 meter d e p t h , which means t h a t t h e trawl f i s h e s down t o

55

m . On R / V "Håkon Mosby"

t h e t r a w l f i s h e s down t o about

58

m depth. The s q u a r e s covered by R / V

"Eld j a r n " w i l l have a volume of V2 ( E ) = 13.36 nm3, while t h e squares covered by R / V "Håkon Mosby" w i l l be V2 ( H ) = 14.09 nu 3

.

The abundance i n d i c i e s ( I ) a r e then c a l c u l a t e d by t h e formula:

were X' i s t h e number of O-group on s t a t i o n i . .R

RESULTS

Hydrography

H o r i z o n t a l d i s t r i b u t i o n of temperature and s a l i n i t y i n 25 m depth a r e shown i n F i g s .

4 -

7 . I n t h e North Sea t h e hydrography seems t o be v e r y s i m i l a r i n 1986 and 1987. North of Stad t h e temperatures a r e a b i t h i g h e r i n 1986 than i n 1987. The temperature d i s t r i b u t i o n i n 1987 i s very s i m i l a r t o t h e d i s t r i b u t i o n found i n

1985.

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

The d i s t r i b u t i o n s of O-group s a i t h e a r e shown on F i g s .

9

and 10. The d i s t r i b u t i o n a r e a seems t o be w e l l covered both y e a r s . However, south of S t a d t h e h i g h e s t c a t c h e s a r e c l o s e t o t h e c o a s t e s p e c i a l l y i n 1987.

I n a d d i t i o n no s a i t h e were caught s o u t h of 60 N o i n o f f s h o r e w a t e r s ,

while O-group s a i t h e a r e observed s o u t h t o about

5 9 ' ~

i n i n s h o r e waters both y e a r s . This i n d i c a t e t h a t some of t h e O-group a l r e a d y had come i n t o i n s h o r e waters i n t h i s a r e a . North of Stad t h e i n v e s t i g a t i o n covers t h e main c o n c e n t r a t i o n s of O-group s a i t h e i n both y e a r s

.

Tables 1 and 2 shows l e n g t h d i s t r i b u t i o n s from d i f f e r e n t survey t r a c k s and a r e a s . South of 62 N no i n c r e a s e o r decrease i n mean o l e n g t h a r e

observed from n o r t h t o s o u t h . The s m a l l e s t specimens were found on t h e western s t a t i o n s ( s t . 53-55 and 75-77 i n 1987). North of 6 3 ' ~ an i n c r e a s e i n t h e mean l e n g t h s were observed northwards i n both 1986 and

1987.

This may i n d i c a t e t h a t most of t h e recorded 0- group o r i g i n a t e s from t h e spawning a r e a s on MØre.

The abundance i n d i c e s f o r t h e d i f f e r e n t a r e a s i n t h e d i f f e r e n t y e a r s a r e given i n t h e t e x t t a b l e below:

North Sea NE A r c t i c

1985 no d a t a 828.2 x

lo6

1986 19.6 x

lo6 ^544.5

^{x 10 6}

1987 60.9 x

lo6

^{284.5 x}

lo6

The 1987 y e a r c l a s s i n t h e North Sea i s measured t o be about t h r e e times t h e 1986 y e a r c l a s s . However, t h e u n c e r t a n t i e s about how much of t h e y e a r c l a s s which have reached i n s h o r e waters b e f o r e t h e time of t h e i n v e s t i g a t i o n i n t h e s e two y e a r s makes i t very d i f f i c u l t t o u s e t h e measured v a l u e s f o r t h e North Sea.

North of S t a d t h e measurements should cover most of t h e y e a r c l a s s . A s seen from t h e t e x t t a b l e t h e 1985 y e a r c l a s s i s t h e b e s t one while t h e 1987 y e a r c l a s s i s t h e p o o r e s t . A t t h e moment i t i s n o t p o s s i b l e t o e v a l u a t e t h e measured v a l u e s a s r i c h , average o r poor, b u t i n a few y e a r s when t h e s e y e a r c l a s s e s have r e c r u i t e d t o t h e f i s h e r y i t should be p o s s i b l e t o e v a l u a t e t h e y e a r c l a s s e s .

Herring. Clupea harengus.

The d i s t r i b u t i o n s of h e r r i n g l a r v a e a r e shown i n F i g s . 11 and 12.

There a r e two d i f f e r e n t d i s t r i b u t i z n a r e a s , one s o u t h of Stad and one n o r t h of Smøla. Table

3

and

4

show t h a t t h e l e n g t h d i s t r i b u t i o n s a r e d i f f e r e n t f o r t h o s e two a r e a s .

We caught more h e r r i n g l a r v a e i n 1987 than i n 1986. For t h e North Sea component t h e t o t a l c a t c h of h e r r i n g l a r v a e were 1261 specimens i n

1987

a g a i n s t 215 i n 1986. For t h e Atlanto-Skandian component t h e c a t c h e s i n 1985,

1986

and

1987

were 12 872,

447

and 1127 r e s p e c t i v e l y .

C a t f i s h . Anarhichas lupus.

F i g s .

13

and

14

show t h e d i s t r i b u t i o n of O-group c a t f i s h . This s p e c i e s i s found i n small numbers s c a t t e r e d over t h e whole i n v e s t i g a t i o n a r e a . North of 6 2 ' ~ t h e t o t a l c a t c h e s i n 1985,1986 and

1987

were 256, 297 and 253, i n d i c a t i n g a very s t a b l e s i t u a t i o n . South of 6 2 ' ~ t h e c a t c h e s i n

1986

and

1987

were

44

and 106. The l e n g t h d i s t r i b u t i o n s a r e given i n Tables

5

and

6.

Squid. Gonatus f a b r i c i i .

F i g s .

15

and 16 show t h e d i s t r i b u t i o n of t h i s s m a l l s q u i d . The d i s t r i b u t i o n a r e a i s very s i m i l a r f o r t h e two y e a r s , b u t t h e abundance seems t o be s m a l l e r i n

1987

than i n 1986. The s q u i d was a l s o s m a l l e r i n

1987.

REFERENCES

NEDREAAS, K . 1986. Abundance and d i s t r i b u t i o n of p o s t l a r v a e i n t h e O-group s a i t h e survey i n t h e n o r t h - e a s t A r c t i c i n

1985.

ICES Doc. C.M. 1986/G:87 32 pp.

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'I'able 3 . L r i t g t l i d i s t r i b u t i o n ( % l o f I t e r r i n g l a r v a e i n 1986.

.. .- - - .. .- -. .- - -. - - - .- - -. - . - - - - - - .- - - - .- - - -. - -. - - - - - - - - - - -. - - - - - - - - -

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I I.ei>gti.t-- S o f G2 N N o f 62 N West o f L o f o t e n TOTAL I

I grotip s t . n u . s t . n o . s t . n o . s t . n o . I

l rnin 1-68 69..223 194--223 1-223 1

I Mean I

I l e n g t l i 39.71 27.74 26.90 31.49 l

I S t . d e v . 4 . 5 6 4.23 2.37 7.04 1

T a b l e 4 . L e n g t h d i s t r l b u t i o n s ( X ) o f h e r r i n y l a r v a e i n 1987.

.. - - - - - ^.- - -. - - - - - - -- -- - - - - - - -

-

- ^." - - -. - - ^-. - - - - ^.-w - -. - - - -

- -

- - - - -- -

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- - -- - -

-

- --

-

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I L e n g t h - S 8f 5FJ030 ^O ' 0 0

61030' S ef 1 62020' N 8f N gf I

I group 59 3 0 ' -60 311' -61 30' -62 20' 6 2 2 0 ' 1 - 6 6 0 0 ' 6 6 0 0 ' 6 2 2 0 ' I

I mm I I

l Mean I I

l l e n g t h 3G.0'7 35.66 36.90 39.22 36.35 1 2 7 . 6 4 27.43 27.48 1

l S t . d e v . 3.52 3.19 3.92 3.00 3.64 1 4.84 2.00 2.35 1

I Measured 577 271 345 58 1259 1 125 962 1087 1

I ( C a t c h ) (12611 1 ( 1 1 2 7 ) 1

O o

T.iblc- 6 . I . e n g t l i d i s t r i b u t i o n : ; ( 1 ) o f otllt-I- s p e ~ : i l - : ; / ~ ~ . ~ ~ p s i n 1987. N- N o r t h o f 6% kl, S- South o f 62 N.

I I-engtti-- A . l u ~ ~ k -- C.asr-an1 -- ⁱ -- I.unipenus s p . Ammodytidae Cod Redf i s h A r n e n t i n a c p . l

I g r n c i ~ S N N N S N S M S N I

I ni111 I

... l

I Mean I

I l e n g t h 29.90 31.13 28.67 39.75 34.94 46.50 17.20 17.84 74.44 52.25 1

I S t . d e v . 7 . 2 0 7.IJO O. 58 1.89 5 . 9 5 9.04 1.64 6.81 7.26 5.56 1

I Meaoured 106 251 3 4 3 1 4 5 5 7 9 4 1

l ( C a t c k i l (106) 1253) ( 3 ) i 5 ) ( 3 4 ) ( 0 ) ( 5 ) ( 6 0 ) (9) ( 4 ) 1

Fig. 2 .

Fig. 3 . Survey t r a c k s and trawl stations taken by R I V "Eldjarn" in 1987.

Fig.4. Temperature in 25 m in 1986.

Fig. 5 . Temperature in 25 m in 1987.

F i g . 6 . S a l i n i t y i n 25 m i n 1986.

i ' S i 8 2 D O i 8 X '

+ Li<

i 'i.

4.

8 , b 0 d

Fig.7. Salinity in 25 m in 1987.

Fig. 9. SAITHE 1986. Distribution of postlarvae. Numbers per 1 . 5 nautical miles.

Stations without catch are marked with dots.

Fig. 10. S A I T H E 1987. Distribution of postlarvae. Numbers per 1 . 5 nautical miles.

Fig. 11. H E R R I N G 1986. Distribution of larvae. Numbers per 1 . 5 nautical miles.

7 1 9 , -

T o # * -

6 S . I .

( I . . -

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( I * * -

1 6 i 1 -

I L ( 1 -

es..-

- ^IYI)

89.. -

. m m

e o * ,

k

""b

Fig. 1 2 . H E R R I N G 1987. Distribution of larvae. Numbers p e r 1. 5 nautical miles.

tical miles.

Fig. 1 4 . CATFISH 1987. Distribution of postlarvae

.

Numbers per 1 . 5 nautical miles.

Fig. 15. Distribution of the squid Gonatus fabricii in 1986. Numbers per 1.5. nautical miles.

Fig. 16. Distribution of t h e squid Gonatus fabricii in 1987. Numbers per 1 . 5 nautical miles.

Denne rapportserien har begrenset distribusjon, Opplysninger om programmet og rapportene kan rettes til

Programledelsen for NELP

Fiskeridirektoratets Havforskningsinstituet Postboks 187'0

5024 Bergen

Oversikt over ti-dligere utkomne ras-orter,

1987 N r 1. P.Colemdal og P,Bratland: KlekkeforlØp for lodde i Varangerfjorden 1986,

Nr. 2, T.Baug og S,Sundby: Kveltelarver og miljØ, Unders~kelser på gytefeltene ved SØrØya,

Nr, 3, H,BjØrke, ReHansen og CaSundby: Postlarveunder- ssbkelser i 1986,

Nr,

4,

H.BjØrke, R,Hansen og W,Melle: Sildeklekking og seigyting på M@re 1986.

Nr. 5 , N,BjØrke and S,Sundbyo Abundance indicec for the Arcrio-Nonqegian cod in 1979-1986 based on larvae investigations.

Nr, 6. P.Fossumr Sult under larvestadiet - en viktig rekrurteringsmekanicme ?

Nr, 7, P.Fossum og S,Tuene: Loddelarveunders@ke9.~ene 1987,

Nr, 8, P,Foccurn, B,Bj@rke and R,Sætre: Ctudiec on berring larvae off western Norway in 1986,