fr_02_1982.pdf (704.2Kb)

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Spawning of haddock (Melanogrammus aeglefinus) in captivity

Gyting hos hyse (Melanogramnus aeglefinus) under eksperimentelle betingelser]

ERLEND MOKSNESS

Statens Biologiske Stasjon FlØdevigen N-4800 ARENDAL

JØRGEW RIIS

VESTERGARD

Zoofysiologisk Laboratorium Aug. Krogh Institutt

DK-2100 KOBENHAVN Ø

!

FLØDEVIGEN Rapportserie Nr. 2, 1982 ISSN 0333-2594

i

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FORORD

Dette arbeidet er presentert på Det internasjonale havforskningsråds årsmote i KØbenhavn

i

oktober 1982 (ICES Report C.M. 1982/G:30).

Arbeidet er derfor skrevet

på

engelsk, men er her forsynt med et norsk sammendrag og norske figur- og tabelltekster.

SAiJIMENDRAG

Gytemoden hyse ble fisket i slutten av januar 1982 og overfØrt til et gytebasseng ved Statens Biologiske Stasjon FlØdevigen, Arendal.

Gytingen foregikk fra 26 februar til 27 mai, med hovedgyting i mars og april. Et beregnet middel

på

1300 ml egg ble gytt i flere puljer fra hver hunnfisk i 1Qpet av gyteperioden. Eggdiameteren avtok fra 1,50 mm til 1,30 mm i lØpet av perioden. TØrr-/våt-vekt forholdet på eggene var 7,6%.

ABSTRACT

Maturing haddocks were caught in late January 1982 and transferred to a spawning basin at the State Biological Station FlØdevigen, Arendal. The spawning took place from February 26th to May 27th, with a maximum in March and April. A calculated average of about 1300

ml

eggs were spawned in several batches from each female during the period. The egg diameter decreased from 1.50 mm to 1.30

_m

during the spawning period. The dry/wet weight ratio of the eggs was 7.6%.

INTRODUCTION

As

a

part of a project on larval haddock, mature haddocks were

kept in a

spawning basin to produce fertilized eggs during the

entire spawning period.

This

paper discusses the results obtained.

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MATERIALS AND _METHODS

Haddock were c a u g h t by l o n g l i n e n e a r A r e n d a l , Norway, i n l a t e J a n u a r y 1 9 8 2 . The f i s h were C r a n s f e r r e d t o a 4 5 m3 s p a w n i n g b a s i n

( F i g . 1) a t t h e S t a t e B i o l o g i c a L S t a t i o n F l Ø d e v i g e n , A r e n d a l . T h e t e m p e r a t u r e i n c r e a s e s f r o m 4 . 0 t o 7 . 0 ' ~ d u r i n g t h e e x p e r i - m e n t a l p e r i o d . P h ~ t o p e r i o d was k e p t on 9 h r s l i g h t a n d 1 5 hws d a r k w i t h 30 min, d i w e d l i g h t i n t h e morning a n d t h e e v e n i n g .

~ g g s were rarnoved e v e r y m o r n i n g f r o m a n e g g c o l l a c t i n g d e v i c e ( F i g . 1) a n d t h e e g g d i a m e t e r a n d cpawned volume was m e a s u r e d . A spawned

volume o f 1 m l e g g s were c o u n t e d t o a n a v e r a g e number o f 400 e g g s , No u i s e a s e s were o b s e r v e d o n t h e f i s h w h i l e b e i n g i n t h e b a s i n . They were f e d s h r i m p s e v e r y d a y ,

On A p r i l 1 6 t h o n e m a l e a n d o n e f e m a l e ( s t a n d a r d l e n g t h 4 2 a n d 4 7

c m ,

r e s p e c t i v e l y ) w e r e i s o l a t e d i n a 2 m3 a q u a r i u m a t t e m p e r a - t u r e 6.0°C.Spontaneouslyspawned egcjs were o o l l e c t e d a t t h e s u r - f a c e water o u t l e t , A t e a c h spawning e g g d i a m e t e r a n d spawned volume was m e a s u r e d . Wet w e i g h t was f ~ u n d by s h o r t l y p l a c i n g g r o u p s o f

2 0 e g g s on f i l t e r p a p e r ( t o rernove a d h e r i n g s e a w a t e r ) a n d t h e n k r a n s i e r r i n g Chem t o a p r e w e i g h e d s t r i p of aauminium f o i l . The e g g s were t h e n weighed 4

t i v e s a t

1 5 sec. i n t e r v a l s on a Cahn 2 5 A u t ~ m a t i c F l e c t r o b a l a n c e , a n d t h e i n i t i a l w e i g h t was f o u n d by l i n e a r e x t r a p o l a t i o n . Dry w e i g h t was f o u n d by r e w e i g h i n g t h e e g g s a f t e r b a i n g d r i e d f o r 2 4 h r q a t 95OC.

RESULTS

A t o t a l o f 5 1 h a d d o c k s , 2 8 f e m a l e s and 2 3 males ( T a b l e l ) , were k e p t

i n

t h e spawning b a s i n . A s shown i n Fig. 2 t h e s p a w n i n g s t a r t e d F e b r u a r y 2 6 t h and e n d e d May 27th, w i t h a maximum f r o m a b o u t March 1 5 t h ta A p r i l 1 5 t h . A e a l c u l a t e d a v e r a g e o f 1300 m i e q g s p e r f e m a l e .

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w e r e spawned i n s e v e r a l b a t c h e s , c o r r e s p o n d i n g t o a b o u t 520.000 e g g s . The a v e r a g e egg d i a m e t e r d e c r e a s e d from 1 . 5 0 m t o 1.30 .mm d u r i n g t h e spawning p e r i o d ( F i g . 3)

.

The i s o l a t e d f e m a l e , s p a w n e d a t o t a l of 410 m l e g g s i n 3 l a r g e r and 3 smaller b a t c h e s o v e r a p e r i o d o f 1 4 d a y s ( T a b l e 2 ) . Both egg d i a m e t e r ( F i g . 3 ) and w e i g h t d e c r e a s e d t h r o u g h o u t t h e o b s e r - v a t i o n p e r i o d . The d i a m e t e r d e c r e a s e d from 1.40 t o 1.31 mm and t h e wet w e i g h t from 1.49 t o 1 . 2 4 mg. The dry/wet w e i g h t r a t i o of t h e s e e g g s w a s c o n s t a n t l y 7.6

f

0 . 1 % .

DISCUSSION

The spawning p e r i o d of t h e c a p t i v e haddocks a n d t h e maximum spawning d u r i n g March and A p r i l a r e i n a c c o r d a n c e w i t h e a r l i e r r e s u l t s

from f i e l d i n v e s t i g a t i o n s (SAVILLE 1 9 5 9 ) . The r e s u l t s a l s o c o r r e - spond w i t h t h a t of a n o t h e r s t o c k o f haddocks k e p t i n t h e same b a s i n i n 1981.

The c a l c u l a t e d nurnber of e g g s , 520.000 p e r f e m a l e , E s i n a c c o r d - a n c e w i t h t h e mean f e c u n d i t y o f 470.000 e g g s e s t i m a t e d by RAITT

(1933) from haddocks w i t h a l e n g t h o f 45.5 cm.

S e v e r a l r e p o r t s have been c o n c e r n e d w i t h f a c t o r s i n f l u e n c i n g e g g s i z e . I t h a s been found f o r s e v e r a l e u r y h a l i n e s p e c i e s , t h a t e g g s spawned i n a low s a l i n i t y a r e l a r g e r t h a n t h o s e spawned i n a h i g h s a l i n i t y ( e . g . , K#NDLER and TAN 1 9 6 5 ) . SOLEMDAL (1971 and 1973) h a s shown f o r f l o u n d e r t h a t t h i s i s l a r g e l y due t o g e n e t i c a l l y f i x e d d i f f e r e n c e s between p o p u l a t i o n s w i t h i n t h e s p e c i e s . GRAUMANN

(1965) h a s found f o r B a l t i c c o d s , t h a t t h e mean e g g d i a m e t e r de- c r e a s e s d u r i n g t h e spawning s e a s o n . She assumed t h a t t h i s was b e c a u s e t h e s m a l l e r f e m a l e s , known t o produce smaller e g g s , t e n d t o spawn l a t e r t h a n t h e l a r g e r f e m a l e s . The same argument may w e l l a p p l y t o t h e r e s u l t s i n F i g . 3 . According t o HAWKINS

-

e t a l . (1967) t h e spawning p e r i o d f o r a f e m a l e haddock i s a b o u t one month o r l e s s . Thus t h e a c t u a l "spawning p o p u l a t i o n " i n t h e b a s i n must have i n c l u d e d d i f f e r e n t f e m a l e s a t d i f f e r e n t t i m e s , b u t it

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h a s n o t been d i r e c t l y v e r i f i e d , w h e t h e r t h e l a t e r s p a w n e r s w e r e t h e smaller o n e s , o r w h e t h e r e g g d i a m e t e r i s r e l a t e d

t o

t h e s i z e o f t h e f e m a l e i n haddock.

The r e s u l t s from t h e i s o l a t e d f e m a l e ( T a b l e 2 ) reveal a n o t h e r t i m e r e l a t e d f a c t o r i n f l u e n c i n g t h e s i z e of haddock e g g s , namely t h e spawning t i m e r e l a t i v e t o t h e spawning p e r i o d f o r e a c h i n d i - v i d u a l f e m a l e , T h i s f e m a l e spawned 410 m l e g g s a f t e r i s o l a t i o n , which i s much less t h a n t h e mean volume o f 1300 m l p e r f e m a l e . Presumably s h e had p a s s e d t h r o u g h most o f h e r spawnings b e f o r e b e i n g i s o l a t e d . For t h i s r e a s o n w e c a n n o t know, i f t h e e g g d i a - m e t e r i s d e c r e a s i n g d u r i n g t h e whole cpawning p e r i o d o f a f e m a l e o r i n t h e l a s t few spawnings o n l y .

The r e l a t i v e d r y w e i g h t o f t h e e g g s i s i n d e p e n d e n t o f egg s i z e i n T a b l e 2. The a b s o l u t e d r y w e i g h t i s r e d u c e d by 1 7 % . I t i s t o be e x p e c t e d , t h e r e f o r e , t h a t t h e l a s t spawned e g g s w i l l y i e l d s m a l l e r l a r v a e w i t h s m a l l e r p r o b a b i l i t y o f s u r v i v a l .

ACKNOWLEDGMENTS

We would l i k e t o t h a n k I n g e r H e n r i k s e n who a s s i s t e d i n most o f t h e work. T h i s e x p e r i m e n t was c a r r i e d o u t w i t h f i n a n s i a l s u p p o r t from The Norwegian F i s h e r y R e s e a r c h C o u n c i l , I 703,02, and from The Nordic C o u n c i l f o r Marine B i o l o g y .

GRAUMAN, G.B. 1965. Changes i n t h e egg s i z e o f cod ( 6 a d u s morhua c a l l a r i a s L . ) w i t h i n t h e spawning p e r i o d . ICES C.M. B a l t i c - B e l t S e a s C o m i t t e e , Mo. 4 7 .

HAWKINS, A.D., K.J. CHAPMAM and D.J. SYMONDS 1967. Spawning o f haddock i n c a p t i v i t y . N a t u r e 215, 923-925.

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KANDLER, R. and E.O. TAN 1965. Investigations on the osmoregulation in pelagic eggs of gadoid and flatfishes in the Baltic.

_*

Part

I.

Changes in volume and spec. gravity at different

salinities. ICES C.M. Baltic-Belt Seas Committee, No. 43.

RAITT, D.C.

1933. The fecundity of the haddock. Scient. Invest.

Fishery Bd. Scotl. 1932, 1.

SAVILLE, A. 1959. The Planktonic Stages of the Haddock in Scottish Waters. Mar. Res. No. 3,

23

pp.

SOLEMDAL,

P.

1971. Prespawning flounders transferred to different

salinities and the effects on their eggs. Vie Milieu Suppl. 22,

SOLEMDAL,

P.

1973. Transfer of Baltic flatfish to a marine environ-

ment and the long term effects on reproduction. Oikos

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Table 1. Number (n)

,

mean standard length

(E) ,

standard deviation (SD) and range of the matured haddocks. [~ntall (n)

,

middel standard lengde ( S l ; ) , 'standard avvik (SD) og lengde-spredning (cm) til de gytemodne hyseneJ

Table 2. Changes in size and weight of eggs during successive spawnings by a f e n l e haddock. Diameter is a mean value of 2 0 eggs,

f standard deviation. Weight is the mean value f standard deviation of duplicate determinations of 2 0 eggs each. r~orand- ringer i eggenes stØrrelse og vekt i lØpet

av

fortlØpende

gytinger hos en hunfisk. Eggdiameteren er et middel av 2 0 egg f standard avvik. Vekten er middelverdi standard avvik etter flere veiinger av hver av de 2 0 eggene.]

)

^Eggs^! ^Diameter Wet weight

Date Dry weight

I (ml)

1

^(mm)

^I

^(mg

¹

^%

^of

wet weight

29.

"

17

l

1. May ,

¹⁵

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l " l l T 1 ' ~ ' l l l I 1 " l " ' m l ~

5 i0 15 20 25 30 5

to is

²⁰ ²⁵ ³⁰ 5 10 15 20 25 30

MARCH APRI L M A Y

Figure 3. The daily mean egg-diameter during the spawning period

(.-. ) , SD 0.05. The egg-diameter from tne isolated

female plotted ( x ) . C ~ a ~ l i ~ middel egg-diameter i lØpet av gyteperioden ( 0 - 0 ) , SD = 0,05. Egg-dia- meteren til den isolerte hunnfisken er merket x J