1975_B_25.pdf (924.0Kb)

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T h i s p a p e r n o t t o be c i t e d w i t b o u t p ~ ~ i o r r e f e l - e n c e t o t;he a u t h o r s

I n t e r n a t i o n a l C o u n c i l f o r t h e

",b?/.

1 9 7 5 / ~ : 25

w = - > " w

E x p l o r a t i o n o f t h e S e a G e a r aiid B e b a v i o u r Cornmit t e o

'L'IIE APPLICZ1SION O F AN ECIIG INTEGRATION S Y C T l 11; IINVESTIGATJONS O N 'I'IIE CTOCK STRENG'I'II OF 'i'1In BAREN'17S

. .

C,js::LI>J (F~IU/LOTUS VILLOSUS, ?.;ULLER) 1971

- ¹⁹⁷⁴

\

by

Odd Naliken and

-Are

Dommasnes I n s t i t u t e o f I l a r i n e H e s e a r c h , 3 e r g e n

I hrrI'RODUC'L'IOTV

D u r i n g t h e l a s t d e c a d e a c o u s t i c methods f o r i i s h abuizdance e s t i m a t i o n have b e e n l a r g e l y impro-ved (BODIIOL'I'

1969,

C R A I G and I.'ORBEL'; 1969,

C U S I I I N G 1 9 6 8 , DP?IGESUND and OLSEN 1965, FOIiBE:' and PJAlilCZX 1 9 7 2 ,

SCl iERDIN0 and TKUSICANOV 1966, TI-IORNE and IJ'OODEY 1970 and TIIOIINE 1973)

.

. A t p r e s e n t s u c h methods a r e w i d e l y used t o o b t a i n i n f o r m a t i o n on s t o c k s i z e on b o t k e x p l o i t e d and u n e x p l o i t e d f i s h p o p u l a t i o n s (13LINDTIEI~' and WIZTCICEN

1971,

J37rZEi'h and

NAICJCTCi\T 1975, Do1;'D e t al-, 1970, DRAGESlJPTD e t a l . 1973, ,JOIIJ\.;\~T\.'ESSOW and LOSSE 1973, J:IDTrTJN and NAlCICi3N 1373, TIIO!INi-: e t a l . 1 9 7 1 ) . The r e l i a b i l i t y o f tlie a c o u s t i c n b i i ~ d a n c e es ti.-:ates o f f i s h d e p e n d s on a number o f f a c t o r s , some o f which have been d i s c u s s e d b y EI:IJI?LCNBEItC and

LYTLX

1973, RODIIOLT 1973 rincl i7C!'rrL'II'\'GJi:?J

1975.

U s t i n a t e s have most o f t e n b e e n itorked o u t u n d e r t h e a s s u m p t i o n t l i a t t h e s c a t t e r i n g c r o s s s e c t i o n o f t h e f i s l z i s p r o p o r t i o n a l t o i t s w e i g h t (UI:IC:; 1 9 6 7 ) . T h i s a s s u m p t i o n i n t r o d u c e s a b i a s \t-hich i s d e p e n d e n t on t h e s i z e

d i s t r i b u t i o n of klle f i s h i n q u e s t i o n (C'TZJ\IG

1973,

~ ' ~ / L I < I ; ; ~ K 1975)

.

The e s t i m a t e s of abundance whicl: a r e p r e s e n t e d h e r e a r e worlted o u t

u s i n g t h e o b s e r v e d l e n g t b d e p e n d e n t s c a t t e r i n g c r o s s s e c t i o n s . ( N A x ~ c ~ : ? ~ and O L S Z N 1 9 7 3 ) .

S i n c e 19'71 t h e I n s t i t u t e o f : l a r i n e R e s e a r c h h a s c a r r i e d o u t a c o u s t i c s u r v e y s e a c h autumn w i t h t h e aim o a s s e s s i n g t h e s t o c k s t r e n g t h of

t h e B a r e n t s Sea c a p e l i n (UP!AG$:SUND e t a l , 1973, bITD?VLIUN and

!\TAIdCEN 1 9 7 3 ) . Some p r e l i m i n a r y r e s u l t s f r o n t h e s e c r u i s e s a r e g i v e n i n e a r l i e r r e p o r t s ( I > ~ ? ~ ? G I C S I J ~ \ T ! ~ og Y,L;J<:(i!: 1972, C + J W S / L T C ! l e t a l , 1972, DOi,T.',%S1TG:i e t a l , 1974, BU:4sj."i'i e t a l . 1 9 7 4 ) .

S i n c e 1973 t h e i n s t i t u t e h a s a l s o c a r r i e d o u t a c o u s t i c s u r v e y s i n ;Lay

-

June f o r ctocI< a s s e s s m e n t of c a p e l i n (IZ,'LUG og :.O:;.';TIJu 1974, DALEK og D0FIIt;ASNZS 19741 AKSLl\L?Tr) e t al. 1375)

.

Tlze p r e s e n t p a p e r d e s c r i b e s t h e t e c h n i q u e u s e d d u r i i l g t h e s e s u r v e y s and t h e r e s u l t s a c h i e v e d d u r i n g t h e autumn s u r v e y s i n t h e p e r i o d 1971

-

^1974.

Fig.1 shows t h e s u r v e y s o u t e s and i i s h i n g s t a t i o n s i n 1973 and comparison of Fig.1 and T a b l e 1 i n d i c a t e s t h e approxi1;zate coverage t h e o t h e r y e a r s . I n t h e f o l l o w i n g we s h a l l f i r s t e s t a b l i s h a s e t of forniulas f o r l a t e r u s e , ' r i ~ e r e a f t e r tve s h a l l consider. t h e

t echni-qties

p r a c t i c a l a s p e c t s of b o t h t h e o b s e r v a t i o q 4 a n d t h e computations.

blien f o u r c a t e g o r i e s M ( a g e g r o u p s , s i z e groups or s p e c i e s ) of f i s h a r e mixed and t h u s s i m u l t a n e o u s l y c o n t r i b u t e t o t h e echo, t h e n t h e i n t e g r a t e d echo i n t e n s i t y , l ; , can be w r i t t e n (FCZBXS and NA;,7?2?? 1972) :

, c 7 c - .

J i l 9

'

3

^{a n r i ' -}

4

a r e the c o n t r i b i l b i crrs t o t h e i n t e g r a t e r !

e c h o iiite::sit y f r o n eacl-i cakegory

,

'!'Ile i'el-a Lioi1s::ip beti..reen t h e f i s h d e n s i t y and i n t e g r a t e d e c h o i n t e n s i t y i s Jineai-:

wliere

p,

^{i s} t h e nuzber of f i s h p e r u n i t area, V i s t h e d c n s i t y

t ,

c o e f f i c i e n t , d i s a t h r e s h o l d d e n s i t y and i d e n o t e s tlie c n t e g o r y .

\/hen d i s n e g l e c t e d e q u a t i o n T I r e d u c e s t o :

Assurne now t h a t f r e q u e n t s a m p l i n g shovs t h e t r u e d e n s i t y r a t i o s between t;Eie d i f f e r e n t c a k e g o r i e s of i i s h . T:hen k e x p r e s s e d t h e

i i - t h c a t e g o r y l s p r o p o r t i o n of t h e t o t a l c a t c h , t h e n :

Combination of i and V will now g i v e T ' a s a f u n c t i o - I of :r, C and i

I:, and by u s i i i g e q u a t i o n

%'Il

t h e d e n s i c y o f eacll categor-y o f fis11 c a n be e x p r e s s e d by observed q u a n t i t i e s only. The r e s u l t i s :

B y t h e s e f o r m u l a s t k o a b s o l u t e .ris21 density

9,

^{* L} (11ui.bcr p e r u n i t a r e a ) cali: Se ~ o i : i p u t e d , p r o v i d e d tt-iat c o r r e s p o ~ ? d i i ~ g v a l u e s o f ^{'I, Ic and} C a r e Icno~m. L'he computations above c a n e a s i l y b e

c a r r i e c l o u t f o r b o t h a l e s s and a l a r g e r ilu:.iber o i i i s i i c z t e g o r ' i e s .

I n t e g r a % e c l echo i n t e n s i t y . .

,

'i'he v e s s e l s used i n t h e s u r v e y s were all equipped w i t l l .<i:nrad scientific s o u n d e r s and Cimrad echo i n t e g r a t o r s (BODI!OI,L 1 9 6 9 ,

cliannels were added and t h e " s p e c i e s " colui;in ii? F i g . 2 were

0

f i l l e d i n .

VESTNES I 969, GEI3iAItDSEN e t a l , 1968, Ni1I;ICEN og VESTNES 1970, 1 D R A G E S W D e t a l . 1 9 6 8 ) . The main a d v a n t a g e of t h e s c i e n t i f i c s o u n d e r i s t h e c a l i b r a t e d tirne v a r i e d g a i n f u n c t i o n , T h i s f u n c t i o n was used i n t h e mode 20 logli f o r a l l t h e o b s e r v a t i o n s , Tlie s i x echo i n t e -

!

g r a t o r c h a n n e l s onboard ^"G,O. S a r s " and t h e

4

c h a n n e l s onboard

The t l i r e e y e a r s wl~en trfo sl2ips were used ^{i r i} t h e i n v e s t i g a t i o n s , i n t e r c a l i b r a t i o n r u n s were c a r r i e d o u t i11 orclei t o liave coi;l- p a r a b l e val-ues of l:. 'Pj!e two s l ~ i p s s a j - l e d one b e l l i ~ ~ c l al?d s l i g h t l y t o t h e s i d e or^ t h e o t h e r f o r 2 0 - 3 5 n a u t - i c a ? n i i l e s ,

"Iiavdrerntt and "Johan H j o r t f f were s e t t o c o v e r t h e d e p t h column from 10 m d e p t h t o 300 m o r bottom. The o u t p u t s of t h e i n t e g r a k o r s were s t o r e d f o r e a c h n a u t i c a . 1 m i l e and t h e a v e r a g e o u t p u t s p e r n a u t i c a l m i l e were logged f o r e v e r y f i v e n a u t i c a l x i l e s s a i l e d

(li'ig, ^3,) C o n t i n u o u c ~ ~ a t c f - i e s were l t s p t o n t h e a c o u s t i c i n s t r u c ~ e n t s th~-oughout t h e e n t i r e c r u i s e a n d wllenever t h e r e c o r d i n g

-

^{a s i t}

a p p e a r e d on tEie eclio sounder r e c o r d e r

-

^{changed, a} sai:?ple was t a k e n w i t h t h e a p p r o p r i a t e g e a r . The echograns and i n t e g r a t e d echo i n t e n s i t i e s were s c r u t i n i z e d e a c h d a y , and c o n t r i b u t i o n s f r

" f a l s e f f e c h o e s (wakes and f a l s e b o t t o m s ) were removed, The c o n t r i b u t i n g s p e c i e s were i d e n t i f i e d and t h e i r contri.bu!;Lors t o t h e i n t e g r a t o r readinrgswere d e t e r m i n e d on t h e b a s i s o f t h e c o m p o s i t i o n of tlie t r a r i l c a t c h e s and t h e p a t t e r n s of t h e

echograms, ( F i g ,

3 ) .

Tl-ie c o n t r i b u t i o n s frorn t h e d i f f e r e n t dept11

tlius observj.ng t h e sar,ie r i s 3 c o n c e n t r a t i o i l s

,

Care was ta?:eil s o tile secolid s h i p d i d n o t come i n t o t h e w d r e o f t h e f i r s t .

s t r a i g h t l i n e ( 1 3 ~ u a t i o n VI']

)

^was f i k t e d t o tlie observed i n t e g r a t o r o u l p u t s by a l e a s t mean s q u a r e a - i i a l ~ ~ s i s l

l l

i . ; , = st;. -!- b ( V I L )

1 i

n l

I? and

Mg

a r e i n t e g r a t o r r e a d i n e s i n mm d e v i a t i o n per n a u t i c a l

A

m i l e f o r t h e two s l i i p s A ar.d

D.

a aixl 1.) a r e cons t n 7 - t t s r " ( ; , O , S a r s f ' w a s always talren a s sl;ip i , Values i o r a , b a n d t h e c o r r e l a t i o n a r e g i v e n i n Table 1 *

Catch c o m p o s i t i o n p r o p o r t i ~ n ~ 1c.

The t o t a l . n u n b e r s of f i s h i n g s t a t i o n s i n t h e d i f f e r e n t y e a r s a r e g i v e n i n T a b l e 1 . was c a r r i e d o u t whenever t h e p a t t e r n of t h e ecbo r e c o r d i n g changed o r when t h e need f o r b i o l o g i c a l d a t a made i t n e c e s s a r y . The t r a w l s u s e d were a l 1 of com~xercial s i z e s w i t h an i n n e r n e t of meshsize

7

mm b a r i n t h e codend. The p e l n g i c t r a w l s had s q u a r e o p e n i n g s w i t h a c i r c u n f e r e n c e of l 1 0 0 t o 1600 :neshes 200 mr1 ixesh s i z e ; t h e bottoiii t r a w l s were of t h e Granton t y p e . A l l slrips wcre equipped w i t h n e t sondes t h u s

a l l o w i n g v e r y p r e c i s e dep bh p o s i t i o n i n g of t h e p e l x g i c t r a v ~ l s . S t a n d a r d towing time w a s 20 m i n u t e s , but when t h e n e t sonde i i i d i c a t e d t h a t a sar;.,pl.e of r e a s o n a b l e s i z e ( s e v e r a l b a s k e t s ) was caught tlic t r a w l was h a u l e d e a r l i e r . The c a t c h e s were

s o r t e d irnmediately a c c o r d i i i ~ t o s p e c i e s , and l e n g t h measinre:-~ents a s w e l l a s a:. exarnination of s e x , m a t u r i t y s t a g e and stomach

c o n t e n t s were c a r r i e d o u t f o r a l l samples, 111 s e l e c t e d sarnples, o b s e r v a t i o n s on l e n g t h / w e i g h t r e l a t i o n s of i n d i v i d u a l f i s h

were c o l l e c t e d and o t o l i t h s were p r e s e r v e d f o r l a t e r age d e t e r t n i i l a t i o n . h g e / l e n g t h keys were t h e n made and used to transforrii t h e observed l . e a g t h d i s t r i b u t i o n on each s t a t i 0 1 1 t o d i s t r i b u t i o n s of a g e , From t h e s e d i s t r i b u k i o n s t h e p r o p o r t i o n s which e a c h y e a r c l a s s c o n t r i b u t e d t o t h e t o t a l c a t c h , !L, were f ound

,

D e n s i t y c o e f i i c i e n t , C ,

: J u t i ~ e r i c a l v a l u e s of t h e d e l y s i t y c o e f f i c i e i l t , C , were d c ter!-:inal by t h e rilethod d e s c r i b e d by hlIDTrI'UX ancl 'TA1;:T8??:

(

1971 ancl 1973)

,

Corresponcling v a l u e c of ^Ji,% and ;,I ( e q u a t i o n 1

I )

irere o b t a i i i e d by c o u n t i n g of t r a c e s on the p a p e r r e c o r d w3en f i s l i were r e c o r d e d a s i n d i v i d u a l s , The r e l a t i o n between t h e ~ l u i i ? b c ~ of fisk t r a c e s on t h e p a p e r r e c o r d , N , and t h e number of f i s h p e r u n i t a r e a , f J 4 , when no o v e r l a p p i n g between s u c c e s s i v e t r a n s m i s s i o n s

o c c u r s , i s ( F G R B ~ C S and NAIGiEW 1972) :

-

wliere ' i s tlie mean deptil of t h e counted specii??eils,

Q

i s t h e

s a m p l i n g aiigle of t h e beam and n t h e number of t r a n s ; ? i s s i o i l s o v e r 1 n a u t i c a l i n i l e , Tlie sampling a n g l e ,

6 ,

was d e t e r c i i n e d in t h e d i r e c t i v i t y diagram a s t h e a n g l e c o r r e s p o n d i n g t o t h e d i f f e r e n t between t h e g a i n s e t t i n g d u r i n g t h e c o u n t i n g r u n and t h e g a i n s e t t i n g a t whicli t h e coiinted c a p e l i n gave a j u s t v i s i b l e mark on t h e p a p e r s e c o r d . F i n a l l y a s t r a i g h t l i n e was f i t t e d t o t h e o b s e r v e d v a l u e s of :i and

Q,

by ineans o f a l e a s t nean s q u a r e

a n a l y s i s whereby t h e n u m e r i c a l v a l u e s of t h e d e n s i t y c o e f f i c i e n t C and t h e -Elxrec!iold d e n s i t y d were detemilined ( ~ ~ u a t i o n 11)

,

Such c o u n t i n g r u n s were al-ways f o l l o w e d by a f i s h i n g s t a t i o n t o g e t t h e l e n g t h d i s t r i b u t i o n of t h e counted f i s h . The

dependency of C on f i s h l e n g t h f o r c a p e l i n was assumed t o be s i r n i l a r t o t l i a t f o r s p r a t , D a t a f o r s p r a t a r e a v a i l a b l e (NAE;IC:CN and OLSEN

1973,

NAKICEN

1975)

and g i v e :

The n u m e r i c a l v a l u e o f CIC was determined from

S

'Phe d e n s i t y c o e f f i c i e n t , C , VJaS found fro;vi t h e l e a s t inean s q u a r e a n a l y s i s of t h e c o u n t i n g observa-l;ions, and t h e inean

-

l e n g t h

l

of t h e f i s h from t h e c o r r e s p o n d i n g t r a w l s t a t i o n .

Values of C f o r d i f f e r e n t l e n g t h groups were t h e r e a f t e r d e t e r - , mined b y e q u a t i o n I X .

Computations.

The s u r v e y e d a r e a was d i v i d e d i n t o s u i t a b l e s u b a r e a s c o r r e s p o n d i n g t o t h o s e used f o r s t a t i s t i c a l purposes by t h e Norwegian D i r e c t o r a t e of F i s h e r i e s ( F ' i g .

4 ) .

V i t h i n each s u b a r e a , iiiean v a l u e s of FI

and Ic k k and k a s w e l l a s rilean v a l u e s o f C

1 ' 2'

3

^LI

,

^{2 C}

³

^and

C were c a l c u l a t e d and t h e computations ( i n V I ) were c a r r i e d o u t . Lc

ItESUL'PS ilND D I S C U S S I O N

F i g s

5-8

show t h e d i s t r i b u t i o n of t h e i n t e g r n t e d echo i n t e n -

s i t i e s f o r c a p e l i ~ z i n the f o u r y e a r s , ^'J'1.i~ e s t i i - 7 a t e s o f C C t o be l s

used i n e q u a t i o n I X a r e g i v e n i n T a b l e 2 . F i g s 9-1 2 show t h e d e n s i t y d i s t r i b u t i o n of t h e f o u r y e a r c l a s s e s of e a p e l i n i r i

autumn

1974

a s cornputed from e q u a t i o n s V I , d s t i n a t e s of t h e number of specir~ieizs i n each y e a r c l a s s t h e d i f f e r e n t y e a r s a r e g i v e n i n 'rable 3,wliere a l s o t h e t o t a l s tock ancl tlie . v a t u r i n g p a r t of t h e stoclc a r e g i v e n . T h e i ~ a t u r i i i g stoc!: i n T a b l e

3

^{i s}

t h e p o r t i o n of t h e c a p e l i n s t o c k which on t h e b a s i s o i o b s e r - v a t i o n s of' m a t u r i t y s t a g e w a s expected t o spaiirn d u r i n g t h e f o l l o w i n g w i n t e r . The e s t i m a t e s a r e of c o u r s e s u b j e c t t o v a r i o u s e r r o r s and we w i l l now d i s c u s s t h e most important s o u r c e s of e r r o r and t h e i r i n f l u e n c e on t h e r e s u l t s .

I n t e g r a t e d ecbo i n t e n s i t y ,

:!.

Tlze v a r i a n c e e r r o r i n v o l v e d i n t h e e s t i r i a t e of ? I i s c o n s i d e r e d t h e o r e t i c a l l y by BOXIOLT (1973) and EIIRETJBERG and LYrI'LE ( 1 9 7 3 ) and on t h e b a s i s of t h o s e i n v e s t i g a t i o n s i t seems f a i r t o con- c l u d e t h a t e r r o r s of t h i s t y p e a r e n e g l i g i b l e . T h i s c o n c l u s i o n i s s u p p o r t e d by t h e h i g h c o r r e l a t i o n between t h e o b s e r v a t i o n s of D! from t h e two d Y f f e r e n t s h i p s d u r i n g t h e i n t e r c a l i b r a t i o n r u n s ( ~ a b l e 1 ) .

If

t h e i n t e g r a t o r o u t p u t was s u b j e c t t o l a r g e v a r i a n c e e r r o r s , one s h o u l d e x p e e t t h e c o r r e l a t i o n c o e f f i c i e n t

to be l o w e r ,

Vithin t h e a r e a s u r v e y e d , c a p e l i n was t h e main con tri bu to^ t o t h e echo r e c o r d i n g s , I n t h e e a s t e r n p a r t o f t h e a r e a s c a t t e r e d c o n c e n t r a t i o n s of p o L i z r cod a t t i m e s r)ccurrecl i i l : i i x t u r e ?!rit!z c a p e l i n , e s p e c i a l - l y in 1 9 7 2 9 but accordiri,r t o LI-~c t r a v ~ l c a t c l i e s t h e t o t a l c o : ~ t s i b u t i o n c of o t h e r s p e c i e s no y e a r exceeded

5

p e r c e n t o r tlie c o n k r i b u t i o n r r o r i c a p e l i n , and Llie e r r o r - due t o mixod r e c o r t l i n g s i s t l ~ e ~ e f o r e c o n s i d e r e d t o be n e g l i g i b l e f o r t h e a r e a a s a whole, I n s i n a l i e r p a r t s of t h e a r e a , however, t h i s type of e r r o r w i l l be of s i g n i f i c a n e e soine y e a r s .

1 : i s k i c o n c e n t r a t i o n s wlzich a r e s h a l l o w e r t h a n 10 n depkli o r l e s s t l i a r l

2-3

^12: fror:i t h e bottoli: a t 200 ^rri dept11 w i l l n o t c o n t r - i b u t e t o : I , I t h a s been shown (RELTECTAL), NAIZCXN and S31EDSri?!iD

1975)

t h a t O-group c a p e l i n w i l l s t a y c l o s e t o t h e s u r f a c e d u r i n g t h e d a y , above t h e d e p t h o r t h e echo s o u n d e r t r a n s d u c e r . T11is rqas a l s o e x p e r j e n c e d during t h e p r e s e n t i n v e s t i g a t i o n s from

o b s e r n a t i o n s w i t h s o n a r and s i d e - i o o l ~ i n g echo sounder ( V C ~ T E C

1

_l

og NAICIiEN,

1 9 7 1 ) .

Consequently t h e c o n t r i b u t i o ~ i s t o t h e i n t e g r a t e d 1 echo i n t e n s i t y from O-group c a p e l i n were s y s t e r n a t i c a l l y t o o s i n a l l .

1

O l d e r c a p e l i n were u s u a l l y n o t d i s t r i b u t e d s o c l o s e t o t h e

s u r f a c e t b a t t h e y avoided t h e e c h o s o u n d e r s , b u t on some o c c a s i o n s c o n c e n t r a t i o n s o f a d u l t c a p e l i n were fonnd c l o s e t o , and p a r t l y on,

1

t h e b o t tom. ffotvever, t h e e v e n t u a l u n d e r e s t i m a t e caused by t h i s b e h a v i o u r was b e l i e v e d t o be n e g l i g i b l e ,

Catch c o m p o s i t i o n p r o p o r t i o n , k .

l

The a s s u m p t i o n t h a t t h e sampling showed t h e t r u e d e n s i t y r a t i o s between t h e d i f f e r e n t y e a r c l a s s e s of c a p e l i n does n o t h o l d good.

The b e h a v i o u r of t h e O-group h a s t o some e x t e n t p r e v e n t e d i t from b e i n g f i s l l e d by t h e t r a w l s (BELTESTAD, ?.JAI'ICEN and S?li2DS'i'AD,

1 9 7 5 ) .

I n a d d i t i o n t h e t r a w l i t s e l f w i l l be s e l e c t i v e and under- sample t h e s m a l l e r fish due t o mesh s e l e c t i o n , ¹¹ c o n s i d e r a b l e

amoiint of c a p e l i n g e t s g i l l e d a l o n g t h e e n t i r e t r a w l En e a c h t r a w l hau1 and 50 p e r c e n t o r more of a t h r e e b a s k e t s catcl-i r-iight be

e n t a n g l e d i n t h e rmshes, \ ? a r j - a t i o n s i n iiiesli s e l e c t i o n w i t h f i s l i s i z e and f i s k b e h a v i o u r a r e t h e r e f o r e irriportant s o u r c e s of e r r o r and t h e y w i l l l e a d t o an u n d e r e s t i m a t e of t h e O-group f i s h which i s c l - e a r l y d e m o n s t r a t e d i i ~'rable

3 ,

D e n s i t y c o e f f i c i e n t , C ,

The r e s u l t of' t h e d e t e r m i n a t i o n s of t h e d e n s i t y c o e f f i c i e n t , C , a r e shown i n T a b l e 2 . The v a r i a t i o n f r o n y e a r t o y e a r i n C C

1 s i s p a r t l y due t o changes i n t h e performance and p a r t l y t o changes

in t h e gai-*etti.ngs of t h e i n t e g r a t i o n system onboard t h e t i ~ , ~ . S a r s "

Numerical v a l u e s of C were worked out o n l y f o r t h e c o u n t i n g r u n s where t h e c o r r e s p o n d i n g t r a w l c a t c h e s showed t l i a t t h e c a p e l i n were uniform i n s l a e and t l m t no o t h e r s p e c i e s of s i : n i l a r s i z e ,

j e l l y f i s h , p e l a g i c s h r i m p s , e t c . were nixed w i t h i t .

Tlie a s s u r : p t i o n t h a t t h e s c a b t e r i n g c r o s s s e c t i o n of c a p e l i n shows a s i m i l a r l e n g t h dependency a s t h a t of s p r a t i s p r o b a b l y n o t c o m p l e t e l y met w i t h , ifowever, f r o n t h e e x t e n s i v e t a r g s t s t r e n g t h a e a s u r e m e n t s which were c a r r i e d o u t by ?IllhI.C_77: and

OL.;ZI;

( 1973)

i t cm be suggcsterl t h a t t h e power i n ecluation

IX

cannot be f a r froni 2 . 0 , A s t h e l e n g t h range of t h e c a p e l i n w i 1 1 be r e l a t i v e l y s m a l l , 6-78 cm, a s m a l l e r r o r i n t h e power

i n e q u a t i o n I X w i l l n o t ha.ve much i n f l u e n c e on t h e d e n s i t y c o e f f i - c i e n t C i f t h e v a l u e of C h a s been c o r r e c t l y d e t e r m i n e d from f 3 s h i n t h e n i d d l e of t h e l e n g t h r a n g e . I f , however, C h a s been

d e t e r m i n e d f o r one end of t h e l e n g t h r a n g e , t h e n t h e b i a s a t t h e o t h e r end of t h e l e n g t h r a n g e might be c o n s i d e r a b l e when a wrong power i s used i n ecluation Izi. I2xperiment.s 011 t h e t a r g e t s t r e n g t h / l e n g t h r e l a t i o n s h i p f o r c a p e l i n w i l l c l a r i f y t h i s p o i n t .

R e l i a b i l i t y of' t h e r e s u l - t s ,

S e v e r a l p o s s i b l e s o u r c e s of e r r o r s have been mentioned, b u t i t h a s n o t y e t beei-t p o s s i b l e t o worlc o u t s t a t i s t i c a l e s t i m a t e s of t h e p r e c i s i o n of t h e r e s u l t s , I n o r d e r t o have same Icnowleclge of t h e c o n f i d e n c e which can be g i v e n t o t h e numbers i n T a b l e

3 ,

^{t h e y}

should be compared t o e s t i m a t e s of stocl: s i z e obtainecl by o t h c r methods, Proin T a b l e

3

i t i s seer, t h a t on t h e b a s i s of t h e a c o u s t i c s u r v e y c a r r i e d o u t i n September 1973 t h e spawning s t o c k of c a p e l i n i n t h e w i n t e r of 1972~ was e x p e c t e d t o be 1.0-1.5 m i l l i o n r n e t r i c t o n s , These v a l u e s c o r r e s p o n d t o one of t h e e s t i r a t e s which were o b t a i n e d from t a g g i n g e x p e r i m e n t s d u r i n g t h e s p a ~ m i n g s e a s o n i n

1974

(DO~I?;ASNI=S 1 9 7 5 ) .

2~ comparison of y e a r l y e s t i m a t e s of t h e number of f i s k i n eacl?

y e a r c l a s s ( ' r a b l e

3 )

i n d i c a t e s a r e a s o n a b l e r e d ~ z c t i o n betyleen t h e second ant1 t h e t h i r d y e a r , The ari~ount of O-group fisly : t r i l l

a s a ule be uxiderestimated, e s p e c i n l l y i ; a

1971

wbex o n l y a smal3 p a r t of t h e O-group d i s t r i b u t i o n a r e a :~ias surveyed.

AKSLAND ,bl.

,

B U L ~ h , I I . , I M i Z E , J , og IlliJTZ'INGEN, I , 1975 : Lodde- u n d e r s ø k e l s e r i. B a r e n t s h a v e t i j u n i 1975.

Relsort t o t h e I n s t i t u t e of K a r i n e i l e s e a r c h .

b n p u b l i s h e d , I

nELTZ3T24D

,A. ,

NAI;ITa:'-, c,. ailc: i l E 3 . i T ; ? 3 , @ ,

1975.

I n v e s t i g a t j 0x3 011 d i e 1 v e r t i c a l n i g r a t i o n of O-grpup f i s k i n t h e T32 r e n t s i e a . ? ' i s ? c 3 i r . ,<!<r. .;er. ;rav<Unders. p

16:

[ ~ n

F r e s s ] ,

-

BLINII)I;UIi.', J . and ?:I?IXI~:, C . 1 37 1

.

^{Lbundance e s t} i i m t i o n ol' t h e l

spa~vxiing L o f o t e n cod 1971,

--

Sea. Coun. i I e e t .

1971

( ~ 1 5 )

BOnHOLT

,

^{H 1}

⁹ 6

^9, Q u a n t i t a t i v e measurements of s c i z t t e r i n g l a y e r s . Simrad Bu11..,(3): 1 - 1 1 ,

DCIDIIOLT ,I-I, 1 9

7 3.

V a r i a n c e e r r o r i n echo i n t e g r a t o r o u t p u t . A c o u s t i c ?,lethods i n F i s h e r i e s jiesearch.

: 1 - 2 3 , RUZETir

,R, ,

DALEN, J .

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september

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o k t o b e r 1974, b'islcets Gang,

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101-104.

0

i3UZ3CTA,:I, and NAI9ZN9O. 1975. Abundance e s t i m a t e s of tile spawning

~ ~ ; i c r o m e s i s t i u s s tocli of blue w l ~ i t i n g

("

o u t a s s o u R i s s o , 1810) i n t h e a r e a v e s t of

?he B r i t i s h I s l o s i n 1972

- ^1974.

r

.

IlavUnders.,

G :

^{[ ~ n} p r e s s ] ^O

~

l

C ? L I I G , R , B . 1973. The q u a n t i t a t i v e u s e of echo s o u n d e r s ,

i n t r o d u c t o r y not.es, FAO F i s h e r i e s U i r c u l a r ,

October 1973: 1 - 1 5 i % e r

C I ~ , L J G , K

,E.

and FOItDES ^,$;,

1369.

i s o n a r for f i s j 1 c o i l l l t i n ~ .

lj'iskllir, Skr.

';_-r.

tlavUnders.,

u:

^210-213. _l

I ,J a 0 '

. ^1974.

~1 , o d d e i ~ n d e r s ~ l r e l s e r i P,arelltshavet l i ntai

-

j u n i 1974. ;?isI;ets : 669-673.

~

J ] @ r y r ~ c . ~ T - - ~ *

l 7 ,

1975,

urv viv al o f taggod c a p e l i i l ( i l a l l o t u s v i l l o s u s ,

1

? : u l l e r ) and e s t i m a t e s of t h e 1374 spabming

1

u o n u l a t i o n i n l;he 3 a r e r . t ~ Sea froin t a g

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I)O?!T:ASNES

,A.,

NAICICEN,O., S E T P ? ,l!, og PRBILIINII)

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bTO!IRES , C , i'.' and NAt<iCi3N,O, 1972 ( i ~ d i t o r s )

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';:mua1 of i:ief;hods f o r f i s h e r i e s r e s o u r c e s u r v e y a n d a p p r a i s a l . P a r t 2. The ul;< of acous t i c i n s t;ruriien-ts f o r F i s h d e t e c t , i o n ; i . i ~ ( i abundailce e s t i i : ~ u t j oil.

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'I'ecklnical Corifereilce C r a f t . S e a t t l e 1958

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.;oxe r e s u l t s o f o b s e r v e d ahundance e s titiia t i o i i s i n s e v e r a l IJ?TUP/!+',;O r e s o u r c e s u r v e y p r o j e c t

,

t2coustj-c :;etEiods

i n F i s l i s r i e s R e s e a r c h . :yn~p

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011 a c o x i c t i c i d e n t i - f i c a t i o n , s i z i i i g a n d abuildajice c s tirriat i o n o f I-i sll.

Fisl~l)ir.k~lcr,~~er,iTavTJ~lders.

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T J , and NAII;iu:Ti ,C', 1973, .<on?c resill. t s of c z b i ~ ~ d a n c e e s i;i.::i L ion s t ~ i ( i i e s w i t h ccho i n t e g r a kol-c. .icous t i c

:

i e t h o d s I'j.sl-iery ::e s e a r c l ; , J C 2 C J / i > i A O / l ~ ' . A ~ i ' y . Rergeri

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: t e l a s , j o n e r r:eil O K iiitc:;rei'te ol:::oi ^;i : , c I ~ - s i t e t e r o g fislze L c , l t ~ ~ c k e i - . T l l e s i s _(calid.

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^{1971 12-29 Sept.} G . O . S a r s

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1 9 7 3 . 1)

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2 )

Bottom t r a w l

s i i i r > : G P - X II A I. E: / - 77 I C H E E T ^{S O .} Y 9

is I ' k . < i l ~ r \ T U I I s Y P t: C: I l!: S - l < i c sc>n:i:'-

i ii,>l,ii 1s ^;!l

- _{XOTES U}

:\ I i ( . l ' :\ I I I I nDVl' T O T A : .

' ( d l ILt3 lil_h.Ce.2& 4. 7 6 6

./B6 1 8 5 . ,

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

--p.- -p -. -

w--.

. .

, u -

l - I

I I ^{I I l I l I I}

!&>".,r 5 c l l 1 r 1 y 1.i I i i > - < , i 8 n t i e r 5 r t t t n ~ Su l l n l * ~ r ~ l ~ ~ r iio 11 I t ~ l - c r ; , t o r X < & 111 I v b t e ~ r , ~ l u r

l < ; t n c c . l i . i i i c c - ,\LLL,~D 8-jrlL loJ-~-rn' & ! ~ : > ! W I C - _ ! ! ) : 1" + L > w!. A - I C < > I ~ ~ ~ C !n. !i, ?SL? !E, Frec,*kc"%

. .

ri11 I\d,,<!.\ . .,,,<l ,,ulbe

- _--,,....

....

F f g . 2 . L o g c h e e t f o r a c o u s t i c data.

ITÆ. ST. 3 0 2

I

^{- - - -- -}

I J = r ? L 3 * B O

'

I

Fig.3. Echogram showing s c a t t e r i n g l a y e r s of c a p e l i n . The i n t e g r a t i o n i n t e r v a l s o f t h e d i f f e r e n t c h a n n e l s ,

50m

i n d e p t h and

1

n a u t i c a l

m i l e

i n d i s t a n c e , a r e i n d i c a t e d .

F i 4 . 4 . A r e a s and s u b a r e a s i n t h e B a r e n t s S e a , u s e d by t h e

B i r e c t o r a t e o f F i s h e r i e s f o r s t a t i s t i c a l p u r p o s e s .

Fig.5. The distribution of integrated echo intensities capelin 12-29 September 1971.

for

Fig.6. The distribution of integrated echo intensities capelin 5-20 August 1972.

for

Fig.7. The distribution of integrated echo intensities for capelin 16 September-$ October 1973.

Fig.8. The distribution of integrated echo intensities capelin 15 September-12 October 1974.

for

Fig.9. Density distribution (hectolitres/(nautical of O-grsup capelin.

Fig.10. Density distrihution (hectolitres/(nautical milelL

)

of

%

year old capelin.

Fig. 11. Density distribution (hectolitres/ (nautical miles)

₎

of 2 years old capelin.

Fig. 12. Density distribution (hectolitses/ (nautical mile)

)

of 3 years old capelin.