Witt 1984 Aquacultural-Engineering

7/28/2019 Witt 1984 Aquacultural-Engineering

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4quacuP.ural Engineering 311984~ 177-190

S u r v i v a l a n d G r o w t h o f T u r b o t L a r v a e Scophthalmusmaximus L . R e a r e d o n D i f fe r e n t F o o d O r g a n i s m s w i thS p e c ia l R e g a r d to L o n g - C h a i n P o l y u n s a t u r a t e d F a t tyA c i d s

*U. Wit t , G. Quantz , D. Kuhlmannlnst i tu t f f i r M eeresku nde an der Univers it~ it Kie l , Df i s ternbroo ker W eg 20 ,D - 2 3 0 0 K i e l , W e s t G e r m a n y

andG. Kattner

In s t i tu t f t ir O r g a n i sc h e C h e m i e u n d B i o c h e m i e d e r U n iv e rs it gt H a m b u r g ,M a r t in - L u t h e r- K i n g -P l a tz 6 , D - 2 0 0 0 H a m b u rg 1 3 , W e st G e r m a n y

A B S T R A C TTurbot larvae reared on ro t i fers (Brachionus pl icat i l i s ) a n d Artemia (SanF r a n c i sc o b r a n d ) n a u p l ii [ A ) w e r e c o m p a r e d w i t h t h o s e f e d o p t d i f f e r e n tc o p e p o d (Eurytenlora affinis) s tages (B) . In one tr ia l , growth and survivalo f la r~ 'a e f r o m h a t c h i n g t o d a y 2 1 , t h e i r f a t t y a c M p a t t e r n a n d t h a t o f t h e i rJ b o d o r g a n is m s w e r e e x a m i n e d . A t t h e ag e o f 21 d a y s la rv ae o f g r o u p Am e a s u r e d 1 1 .1 + 1 .6 m m t o t a l l en g t h ( T L ) c o m p a r e d w i t h 1 4 . 8 +- 1 .1 m mTL fo r g roup B . Fro m day 3 to 8 surviva l was 29% (A ) and 38% (B) . Long-c h a in p o l y u n s a t u r a t e d f a t t y a c id c o m p o s i t i o n o f t u r b o ts r e s e m b l e d t h a to f t h e i r c o r r e s p o n d h t g d i e t s . Artemia a n d Artemia f e d larvae were lack ing22 : 6 n -3 fa t t y ac id .

In a J i t r ther s tudy , surv iva l o f larvae f ro m day 11 to 21 f e d on Artemian a u p l ii ( C ) o r c o p e p o d s { D ) w a s f o u n d t o b e g r e a te r w i t h rite l a t t e r d i e t( 73 ver sus 93% ) whereas gro wth dur ing th is exp er im en t w as s im i lar in bo thgroups . BeJOre the s tar t o f th i s t r ia l they had been reared on a m ix tu re o fc o p e p o d n a u p l i i a n d Brachionus. N o i n f l u e n c e o n w e a n i n g s u c c e s s w a sobserv ed. 22 ." 6 n-3 fa t t ) , a c id is seen to be essent ia l fo r turb ot larvae:e longa t ions o fa t O , ac ids by the la rvae were no t fou nd .

* Present address: W i n d eb y e r W e g 40, D-_.~30 Eckernfoerde, West Germany.177

A q u a c u l t u r a l E n g i n e e r i n g 0144-8609/84/$03.00 Elsevier A p p l i e d S c i e n c ePubl ishers Ltd , E nglan d , 1 98 4 . Pr in ted in Great Br i ta in


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178 g ( W i tt , G . Q u a n r z , D . K u h l m a n n , G . K a r r n e r

I N T R O D U C T I O NC o n s i d e ra b l e p r o g re s s h a s b e e n a c h ie v e d i n t h e d e v e l o p m e n t o f h a tc h e r yt e c h n i q u e s f o r t h e m a s s - c u l t u r in g o f t u r b o t ( K i n g w e l l e t a l . , 1 9 7 7 :J o n e s e t a l . , 1 9 8 1 ; P e r s o n - L e R u y e t e t a l . , 1 9 8 1 : B r o m l e y a n d H o w e l l ,1 9 8 3 : O l e s e n a n d M i n c k , 1 9 8 3 ) . N e v e r t h e l e s s , o n e o f t h e p e r s i s t in gp r o b l e m s i s t h e h i g h l a r v a l m o r t a l i t y s u p p o s e d t o b e m a i n l y c a u s e d b yn u t r i t i o n a l d e f ic i e n c ie s .

S e v er al a t t th o r s h a v e s u g g e s t e d t h a t t h e n u t r i t i o n a l v a l u e o f t h e f o o do r g a n i s m s f e d t o m a r i n e f is h la rv a e d e p e n d s o n t h e i r p o l y u n s a t u r a t e df a t t y a c id s ( P U F A ) , e s p e c ia l ly t h e i r c o n t e n t o f e i c o s a p e n t a e n o i c ( 2 0 : 5n -3 ) a n d d o c o s a h e x a e n o i c ( 2 2 : 6 n -3 ) ac id s ( C o w e y e t a l . , 1 9 7 6 ; F u j i ia n d Y o ne , 1 9 7 6 ; G a t e s o u p e e t a l . , 1 9 7 7 : F u k u s h o e t a l . , 1 9 8 0 : F u j i t ae t a l . , 1 9 8 0 ; W a t a n a b e e t a l . , 1980 ; L e Mi l i na i r e e t a l . , 1 9 8 2 ; W a t a n a b ee t a l . , 1 9 8 3 ) . O w e n e t a l . ( 1 9 7 5 ) e v e n d e sc r i b e d 2 0 - c a r b o n a n d 2 2 - c a r b o nf a t t y a c i d s o f t h e n - 3 s e r i e s a s e s s e n t i a l r e q u i r e m e n t s i n t h e d i e t f o rO - g r o up t u r b o t .

P r e s e n t l y r o t i f e r s B r a c h i o n u s p l i c a t i l i s a n d A r t e m i a na up l i i a r e t hem o s t c o m m o n l i v i n g f e e d s u s e d t o r e a r m a r i n e f i s h l a r v a e . T h e f a t t ya cid c o m p o s i t i o n o f r o t if e rs d e p e n d s v e ry m u c h o n t h e f o o d alg ae( S c o t t an d M i d d l e t o n , 1 9 7 9 ) w h e r ea s t h e c o m p o s i t i o n o f A r t e m i a var iesf r o m p l a c e t o p l a c e a n d f r o m y e a r t o y e a r ( F u j i t a e t a l . , 1 9 8 0 ) . C o n t r a r yt o m a ri n e c o p e p o d s A r t e m i a n a u p li i o f m o s t o f t h e s tr ai n s c o n t a i n n o n eo r o n l y t r a c e s o f 2 2 : 6 n - 3 f a t t y a c id ( S c h a u e r e t a l . , 1 9 8 0 ) .

B a se d o n t h e d e v e l o p m e n t o f m a s s c u l t u r es o f c a la n o i d c o p e p o dE u r y t e m o r a a f f i n i s a s a n a l t e r n a t i v e l i v e f o o d f o r f i s h l a r v a e ( K u h l m a n ne t a l . , 1 9 8 1 ; N e l l e n e t a l . , 1 9 8 1 ) , s e ve r al g e n e r a t i o n s o f B a l ti c t u r b o tl ar va e c o u l d b e s u c c e s sf u l ly f e d o n t h e s e c o p e p o d s .

T h e p r e s e n t s t u d y c o m p a r e s t h e su rv iv al a n d g r o w t h o f t u r b o t l ar va ef e d o n t h e s e t h r e e a l t e r n a t i v e liv e f e ed s , r o t i f e r s B r a c h i o n u s , A r t e m i an a u p l ii a n d c a l a n o i d c o p e p o d s w i t h s pe c ia l e m p h a s i s o n t h e i n f l u e n c e o ft h e d i f f e r e n t f a t t y a c i d p a t t e r n s o f t h e s e d ie ts .

M A T E R I A L S A N D M E T H O D ST w o e x p e r i m e n t s w e r e r u n i n o r d e r t o d e t e r m i n e t h e i n fl u e n c e o f t h ed i f f e r e n t f o o d o r g a n i s m s o n g r o w t h , s u rv iv a l a n d f a t t y a c id c o m p o s i t i o no f t u r b o t la rv a e.


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Com parison of" tur bo t larvae die ts w ith special regard to PU FA s 179E g g s w e r e s t r i p p e d f r o m a c a p t iv e b r o o d s t o c k o f B a l ti c S e a t u r b o t s ,

g r o w n o u t a t t h e A q u a c u l t u r e E x p e r i m e n t a l S t a t io n a t K i el- B ~lk . T h ee g g s w e r e i n c u b a t e d a t 1 5C a n d 1 7 /o o s a l i n it y in J u n e a n d J u l y 1 9 8 2f o ll o w in g th e m e t h o d s d e s c r ib e d b y K u h l m a n n e t a l . ( 1 9 8 1 ) .T h e r o t i f e r s w e r e r a i s e d o n ? v ' a n n o c h lo r i s sp . (Wi t t e t a l . , 1981 ) andt h e c a l a n o i d c o p e p o d s E u ~ t e m o r a a f f i n i s w e r e c u l t u r e d in 2 8 m 3o u t d o o r t a n k s as d e s c r ib e d b y N e l le n e t a l . ( 1 9 8 1 ) . T h e A r t e m i a ( S a nF r a n c i s c o s t r a in ) w e r e i n c u b a t e d a t 2 5 C a n d 1 7 - 1 8 % o a n d f e d w i t h i n1 2 h o f h a t c h i n g .

T r i a l IT h e f e e d i n g s c h e d u l e i s s h o w n in T a b l e 1. T w o b l a c k 8 0 -1 itre t a n k s w e r ee a c h s t o c k e d w i th 1 20 n e w l y h a t c h e d l a rv ae . T h e m e a n t e m p e r a t u r ean d sa l i n i t y w er e 17 .3 --- 1 .5C an d 14 .0 + 0 -5% 0 , r e s pe c t i v e ly . L en g thm e a s u r e m e n t s w e r e c o n d u c t e d 3 , 4 , 8 , 1 1, 17 a n d 21 d a y s a f t e r h a t c h -in g . M o r t a l i t y b e t w e e n d a y s 3 a n d 8 w a s e s t i m a t e d in a p a r a ll e l t ri al ,w i t h t h e s a m e c o n d i t io n s , b y d i r e c t c o u n t i n g o f th e l ar va e at days 3 a n d 8 .

F o r t h e f a t t y a c id a n a l y s e s 3 - d a y - o l d e g gs , n e w l y h a t c h e d l ar v ae a n dl a rv a e o f 5, 1 I , 1 7 a n d 2 1 d a y s w e r e s a m p l e d . A t t h e s a m e t i m e s a m p l e so f t h e c o r r e s p o n d i n g f o o d o r g a n i sm s w e r e t a k e n a n d s t o r e d in a m i x -t u r e o f c h l o r o f o r m a n d m e t h a n o l ( 2 : 1, v / v ) in g la ss t u b e s ( S o v i r el ) a t- - 2 0 C u n t i l f a t t y a c id a n a l y s e s w e r e c a r r ie d o u t fo l l o w i n g t h e m e t h o dd e s c r i b e d b y K a t t n e r e t a l . ( 1981 ) .T r i a l I IS u rv iv a l a n d g r o w t h o f t u r b o t s f e d o n A r t e m i a n a u p l i i o r c o p e p o d s ,r e s p e c ti v e ly , w e r e c o m p a r e d b e t w e e n d a y s 11 a n d 2 5 p o s t h a t c h i n g

T A B L E 1Feeding S chedules of Trials I and II

Da y s 3 -1 0 Da y s 1 1 -2 1ATrial I BCTria l II D

Brachionus p l icat i lis Ar tem & naupliiCopepod nauplii, copepodites, adult copepodsM ixture of cop epo ds nauplii A r t e m i a naupliiand Brachionus Copepods


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1 8 0 ( . ' : Witt, G. Quantz, D. Kuhlmann, G. Kattner(Table 1). Until the beginning of the experiment at day 11, all larvae werefed on a mixed diet of copepod nauplii, copepodites and Brachionus.

Two conical 500-1itre tanks were each stocked with 700 larvae. Meanwater temperature was 20.2 + 0.6C at a salinity of 14.0 + 0.5/oo .Water was continuously exchanged at a rate of 700 litres day- ( Mortalityrates were estimated from the number of dead larvae syphoned dailyfrom the tank bottoms.

To compensate for the difference in body mass of the copepods(mean dw weight = 7 #g per individual) and Artemia nauplii (1.6/agper individual), the latter were offered in approximately 4-5 timeshigher concentrations . Tile mean numbers of food organisms addeddaily were 3.5 + 1.5 X l0 s copepods and 1.8 + 0.6 x 106Artemia nauplii.

Weaning on to a moist compound diet started at day 19. Availabilityof living food organisms ended at day 21.

RESULTSTrial IThe growth of turbot larvae fed as shown in Table I is illustrated inFig. 1. Until metamorphosis, growth is significantly (t-test, P< 0.01)higher for copepods. At day 21, the total length was 11.1 + 1-6 mm ingroup A and 14.8 + !:2 mm in group B. Overall survival from days 3 to8 was 29% for Brachionus fed larvae (A) and 38% for copepod naupliifed larvae (B).

The fatty acid analysis of tile differen t food organisms and turbotlarvae is given in Tables 2(a) and (b). A graphic description of the mostimportant polyunsaturated fat ty acids (> 20 : 3 n-3) is given in Fig. 2.

Comparing the fatty acid patterns of Brachionus and Eurytemoranauplii, some differences in the PUFA can be dete rmined. Both, copepodnauplii (16%) and rotifers (21%), are provided with sufficient amountsof eicosapentaenoic (20' 5 n-3) acid compared to only 7% in Artemianauplii. The differences are more pronounced when docosahexaenoic(22:6 n-3) acid is taken into account. Copepod nauplii contain 10.8%and adult copepods 4.9% of this PUFA in contrast to only 1.3% inBrachionus. In Artemia nauplii of the San Francisco strain the fattyacid 22 : 6 n-3 is lacking.The fatty acid composition of the larvae widely depends on that oftheir food organisms.


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15

C o m p a r i s o n o$" t u r b o t l a rv a e d i e t s w i t h s p e c i a l r e g a r d r.o P U F A s 1 8 1

A r t - n o u p l l ir o t i f e r s Ac o p e p o d s t o g e s

I/B

B

....jE

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....j

A

5

F i g . 1 . Tr ia l

5 1 0 1 5 2 0A g e ( d a y s )

I . G r o v , t h o f t u r b o t l a r v a e t e d o n r o t i f e r s a n d A r t e m i a n a u p l i i ( A )a n d c o p e p o d s ( B ) .


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182 b: Witt, G. Quantz, D. Kuhlmann, G. KattnerT A B L E 2 ( a )

F a t t y A c i d P a t te r n ( a s P e r c e n t a g e o f T o t a l F a t t y A c i d s l o f F o o d O r g a n is m s

Fat O" acM N a n n o - B r a c hi o - A r t e m i a Copepod Copepod- Adultch lo r i s nus nauplii nauplii ires copepods14 "0 8.6 4.6 1.1 4.1 6.1 6.716 "0 24-5 15.9 11-5 22.2 16"6 19-51 6 '1 n- 7 "~'~ 1 "~ ~ 16.8_ . 9 18.1 1"~-6 13.316" 2 n - 6 0 . 4 1 . 4 1 -8 0 . 9 0 - 9 I . 81 8 : 0 0 . 8 3 . 6 4 . 5 5 . 9 4 .4 4 .91 8 1 n-9 7 .0 8 .6 29 .7 8 .6 13.1 8 .218 :2 m 6 3-7 4 .0 7 .1 3 .1 3 .8 3 .118 :3 a n-3 0.2 2.0 14.8 2.3 3.5 3.718 :4 n-3 0-3 1-3 3 .0 2 .2 2 .9 2 .52 0 : 1 1.3 . . . .2 0 : 2 n - 6 + + 0.1 0.2 0.520 : 2 n-3 2.7 0.2 0-4 0-4 1-I20 : 3 n-9 5.5 4.0 2.6 2-7 2.1 3.32 0 :5 m 3 24.9 21 .4 6-8 16-4 15 .5 15 .922 : l 2.0 0-5 1.3 2 .3 1-3")" "~/ '~~4 0.9 0.5 4. + 0.4 0.42 2 :5 m 3 - 3 .8 0 .2 0 .6 1 .5 0 .72 2 :6 m 3 - 1 .3 - - 10 .8 8 .6 4 .9a 20 : 0 includ ed.

T r i a l I I

T h e a im o f t h i s e x p e r i m e n t w a s t o d i s c o v e r p o s s ib l e e f f e c t s o n g r o w t ha n d s u rv i v a l o f o l d e r t u r b o t l a rv a e f r o m d a y I 1 o n , c a u s e d b y t h e d i f f e r -e n t d i e t a r y v a l u e s o f Artemia n a u p l i i a n d c o p e p o d s . A l l l a rv a e h a v eb e e n t e d o n c o p e p o d s t a g e s b e f o r e e n t e r i n g th e e x p e r i m e n t a l f e e d i n gs t a g e .

G r o w t h in b o t h g r o u p s o f l a r v a e (C a n d D ) w a s n e a r l y id e n t i c a l( F ig . 3) . O n t h e o t h e r h a n d m a r k e d d i f f e r e n c e s w e r e f o u n d in s u rv i va lr a t e s w h i c h w e r e 2 0 % h i g h e r in c o p e p o d f e d l a rv a e ( 9 3 v e r s u s 7 3 % ) a td a y 2 1 , th e e n d o f liv e f o o d a d d i t i o n .

A s i m i l a r s t u d y w i t h t h e s a m e f o o d s c h e d u l e s w a s c o n d u c t e d in 1 9 81w i t h 1 5 0 0 1 2 - d a y - o ld l a r v a e in e a c h t a n k ( 1 4 0 0 1 i t r e s ) . T h e m e a n


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C o m p a r i s o n o1" t u r b o t l ar va e d i e t s w i t h s p e c i a l r e g a r d t o P U F A s 183T A B L E 2 (b )

F a t t y A c i ds ( as P e r c e n t a g e o f T o t a l F a t t y A c i d s) o f T u r b o t E gg s. N e w l y H a t c h e dLarvae and Larvae Fed on [A) B r a c h i o m , s [day s 5 an d 11 ) and A r t e m i a Naupl i i(days 17 and 21) and (B) Cop epo d Naup l i i (day 5 ). Cop epo d i tes (days 11 and 17}a n d A d u l t C o p e p o d s ( d a y s 17 a n d 2 1 )Far 0 , ac id Eggs ', e w ly L ar v ae

h a t c h e dlan 'ae da y 5 da y 11 da y 1 7 da ,v 21

.4 B A B A B A B14 :0 2 .4 3 -816 :0 14 .0 16-81 6 1 n-7 8-5 5 . 61 6 : 2 n - 6 1 . 4 0 .818 :0 6 -0 4 .318 '1 n -9 16.4 _ , . 018 :2 n -6 3 .2 6 -01 8 3 a Jr-3 1.3 1-21 8 : 4 n - 3 - - -2 0 1 0 .9 3-52 0 ' 2 n -6 0 - 2 0 -72 0 2 n -3 0 -4 0 .92 0" 3 ~z-9 2-8 1-520 "5 n-3 5-6 4 .72 2 1 1.5 1 .92 2 3 / 2 2 : 4 0-3 +22 "5 n-3 2 .4 1 .62 2 6 n -3 16.2 14.3

3-5 3-1 3.0 2.9 1-1 2.8 1,0 3.320-7 21-3 17.9 20-6 12-8 18.5 12,3 18.2

5-2 5.5 6.5 7.8 9.2 7.8 8,2 12.70.8 0-6 1.2 1.0 1.9 1.0 1.6 0.98-0 6.8 9.3 8.9 7-4 7-6 7-6 7.2

20 -2 15-1 13.0 12.2 28-5 11.6 29 .7 10.93.6 3.1 4. 4 1-3 5.8 1-3 6.3 1.8I-1 1-4 1.9 1-1 9- 9 1.0 10.1 1.4- - - 2.8 1-6 - - - 2-0 1-2

5.0 3-7 -- - 2-4 1-3 0.4 -- - - - - 0.2 0-4 0 .3 0-6 0 .4

0-9 0 .7 0 .6 0-2 0-3 0 .3 0 .3 0 .41.9 2.3 2.7 2.0 3.9 2-0 4.6 2.74-6 8-2 1 4 . 1 17 .6 9-2 17-7 8 .8 14-9

- - - - 2 - 6 1 . 0 2 - 4 1 . 0 1.1 0.9- - + 0.6 0-6 + 0 .7 0 .4 0-7

0-8 1.2 8.5 4.8 1.9 6.0 1.8 4-814.4 19.5 7-3 13.4 1.1 14-9 0.6 12.6a 20 : 0 include d.

t e m p e r a t u r e b e t w e e n d a y s 12 a n d 3 3 w a s 1 7 ,5 C . R e s u l t s a re s h o w n inT a b l e 3 .

I n c o n t r a s t t o tr ia l II , t h e 1 98 1 e x p e r i m e n t s h o w e d t h a t n o t o n l ys u r v i v a l b u t a l so g r o w t h w a s s i g n i f i c a n t l y h i g h e r ( t - t e s t , P < 0 - 01 ) i n t h ec o p e p o d f ed b a t c h o f l a r v a e . T h e m o r e d i s t i n c t d i f f e r e n c e s m a y b ee x p l a i n e d b y t h e l o n g e r d u r a t i o n o f t h e e x p e r i m e n t .


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1 8 4 U . W i t t, G . Qu an [ z, D . K uh l r n a nn , G . K a tm e rt ~ d t n g s c h e d u l e

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P U F Ac ffoodO'~qn~ s r n s

PUFAa ttclrbo! -/ ~ r v a e

F ig . 2 . Tr i a l I . Lo n g - c h a i n P U F A ( > 2 0 : 3 n - 3 ) as p e r c e n t a g e o f t o t a l f a t t y a c i d sf r o m t u r b o t la r va e fe d a f te r f e e d i n g sc h e d u l e s A a n d B ( l o w e r g r a p h ) a n d t h e ir f o o d

o r g a n i sms ( t o p g r a p h ) .

T A B L E 3C o m p a r i s o n o f t h e G r o w t h a n d S u r v i v a l o f P o s t H a t c h e d T u r b o t B e t w e e n D a y s 1 2

a n d 3 3 , R e a re d o n A r t e m i a N a u p l i i o r C o p e p o d s ( 1 9 8 1 )L i v e eed s A verage length (ram) ~-st a nd a r d de vi a t i o n Su r v i v a l (%),

days 12-33day 12 day 33

A r t e m i a naup l i i 5 .1 z 0 .3 17 .2 -+ 1 .7 (n = 3 0 ) 8C op ep od s 5 .1 +- 0 .3 18 .2 +- 1 .7 (n = 3 0 ) 42

T o b e c o m e a w a r e o f p o s s i b l e a f t e r - e f fe c t s c a u s e d b y t h e d i f f e r e n tf e e d i n g s c h e d u l e s , m o r t a l i t i e s w e r e o b s e r v e d u n t i l d a y 3 5 . B u t th ew e a n i n g s u c c e s s in t r i a l I [ w a s s i m i l a r in b o t h g r o u p s . F r o m d a y 1 9 t od a y 3 5 m o r t a l i t y r a te s w e r e 1 4 % f o r g r o u p C a n d t 3 % f o r g r o u p D .D u r i n g a n d a f t e r w e a n i n g a s e l f - m a d e m o i s t p e l l e t e d d i e t ( 3 3 % w a t e rc o n t e n t ) w a s fe d . T u r b o t s g r e w w i t h o u t l o s s e s a n d r e a c h e d a n a v e r a g ew e i g h t o f 9 . 7 -- 3 - 3 g at a n a ge o f 9 0 d a y s .


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C o m p a r i s o n o f t u r b o t l ar va e d i e t s w i t h s p e ci a l r e ga r d t o P U F A s 185

~ e ' , ' e . ' s i I. ; ~ - - L

F z / . " i : )

7 0 0 " ~ " ~ ~ '~ \- ~ " o , . i ~ l / i "~\ . . . . . . . _ ~ < / j\ . ~ g\ ] / / .

< / ' ! t // / '

I 7 o5 0

II i5 9 t; 9 t 5 2 0 2 5

A g e t ' d c / s )Fig. 3 . T r ia l [ I . Len gth , 'rod surv iva l ra tes o f tur bo t la rva e fed w i th copepods(open circles) o r A r t e m i a nauplii (filled circles) from d ay I 1 to da y 21 and w ith

compound moist pelleted feed from day 19.

D I S C U S S I O NT r m l IF r o m t h e g r o w t h c u r v e s o f tr ia l I it is o b v i o u s t h a t t u r b o t l a rv a e o nt h e ir f ir st f e e d h a v e a b e t t e r s t a r t w h e n f e d w i t h c o p e p o d n a u p l ii c o m -p a r e d t o t h e B r a c h i o n u s d i e t . S e v e r a l t i m e s i n e a r l i e r e x p e r i m e n t s ,t u r b o t l a r v a e f e d o n B r a c h i o n u s s t a r t e d g r o w i n g o n e d a y l a t e r t h a nl ar v ae f e d o n c o p e p o d s . A p a r t f r o m t h e ir h i g h er c o n t e n t o f 2 2 : 6 n -3f a t t y a c id , t h e s iz e o f t h e c o p e p o d n a u p l i i is p r o b a b l y t h e m o s t i m p o r t -a n t r e as o n f o r t h ei r a c c e p t a n c e . R e p e a t e d s t o m a c h c o n t e n t a n a ly s e si n d i c a t e d t h a t t u r b o t l a r v a e b e g i n t o t a k e u p n a u p l i i e a r l i e r t h a n r o t i f e r s( K u h l m a n n e t a l . , 1 9 8 l ) . D u r i n g t ri al I, 1 0 l a rv a e f r o m e a c h t a n k w e r e


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186 bi W itr, G. Qu antz, D. Kuhlmann, G. Karrnerexamined at day 3. The larvae of batch A had empty stomachs where~sthose of batch B contained up to five copepod nauplii. One day laterstomach analyses showed 0-2 B r a c h i o n u s (A) and 4-15 nauplii (B).The smaller size of copepod nauplii (>50~m length against 180-280/~m of B r a c h i o n u s ) seems to be more suitable to larvae at the first2 or 3 days of feeding. That applies also to other marine fish larvae ofcomparable hatching sizes (Detwyler and Houde, 1970; Kuo e t a l . ,1973; Hussain and Higuchi, 1980; Kraul, 1983).

Although the rotifers exhibit high amounts of 20 : 5 n-3 fat ty acid,they decrease slightly in B r a c h i o n u s fed larvae until day 5. This alsopoints to a later start to feeding on B r a c h i o n u s because larvae feedingon the copepod nauplii diet are already showing increasing PUFA(Fig. 2).

Since, like other marine algae, with the exception of D u n a l i e l l a(Scott and Middleton, 1979), N a n n o c h l o r i s has a high percentage of20 : 5 n-3 fat ty acid in the total lipids, it is generally used as food forrotifers and copepods at the Aquaculture Experimental Station in Kiel.The different 22:5 and 22:6 n-3 contents in N a n n o c h l o r i s andB r a c h i o n u s can also be explained by the ingestion of other micro-organisms and algae species included in the rotifer culture tanks.Enhancement of PUFA content in B r a c h i o n u s can be achieved byfeeding them on yeast cultured with the addition of fish liver oil or bydirectly adding an emulsion of fish oil to the rotifer culture medium(Watanabe e t a l . , 1983). With these methods the 22 : 6 n-3 fatty aciddeficiency can be eliminated. Attempts to alter the dietary value ofB r a c h i o n u s fed to the turbot larvae with inert food (Le Milinaire e t a l . ,1982) seem to have no positive effect on larval growth compared to ourresults with N a n n o c h l o r i s fed B r a c h i o n u s .

The fatty acid patterns of turbot eggs and yolk-sac larvae are nearlyidentical with a slightly lower level of PUFA in the larvae and are com-parable with results from North Sea turbot eggs and larvae (Scott andMiddleton, 1979).

In general the fatty acid compositions of the larvae in this trialgenerally reflect those of thei r corresponding food organisms (Table 2).This becomes evident not only in the PUFA pattern but also in otherfatty acids, as can be seen when the food is changed from B r a c h i o n u sto A r t e m i a nauplii (A). Here, a clear decrease in palmitic acid (16 : 0)and an increase in both oleic acid (18 : 1 n-9) and linolenic acid (18 : 3n-3) can be observed. Looking at the PUFA, there is a drastic decrease


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Com par i son o f tu rb o t la rvae d ie t s w i th spec ia l r egard ro PU FA s 187in 22 :6 n-3 in larvae fed on B r a c h i o n u s and A r t e m i a nauplii (A)whereas the proportion of this fatty acid remains relatively constant inlarvae fed on copepods (B) (Fig. 2). These results confirm the observa-tions of Scott and Middleton (1979) showing that turbot larvae are notable to convert 20 : 5 n-3 to 22 : 6 n-3 fa tty acids. Similar findings aredescribed by Owen e t a l . (1975) for O-group turbot.T r i a l I I

Regarding their PUFA pattern, copepods are evidently superior to SanFrancisco brand A r t e m i a (Fig. 2, Table 2(a)). This is in accordance withthe studies of Watanabe e t a l . (1980, 1983) and Fujita er a l . (1980)who compared A c a r t i a c l a u s i i with different strains of A r t e m i a naupliias food for red sea bream larvae.Nevertheless, it remains difficult to explain why larval survival ismore affected than growth in the different feeding regimes. Furtherexperiments have to be carried out using identical feeds which are onlydistinguished by the lack of presence of single PUFAs. In studies con-cerning the dietary requirements of marine fish for long-chain poly-unsaturated fatty acids, 20- and 22-carbon fatty acids of the n-3 seriesare always taken together as essential fatty acids. No information isavailable on the particular influence of each of these types on growthand survival. The results of trial II (Fig. 3) may lead to the question asto whether a sufficient amount of 20:5 n-3 supplied by the A r t e m i anauplii enabled acceptable growth rates whereas the lack of 22 : 6 n-3caused the higher mortalities until weaning.

CONCLUSIONEnhancement of larval survival is important if turbot rearing on acommercial scale is to be accomplished. Until metamorphosis, twoperiods of high mortality are observed: the first is caused by starvationof larvae that do not manage to take up food after hatching. Thepresent study revealed that the survival during this period can beimproved by feeding copepod nauplii instead of, or additional to,B r a c h i o n u s . Apart from their proper size, copepod nauplii are charac-terised by a high percentage of PUFA in their total lipid content.


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188 U [t 'i tr , G. Qu anrz. D. K uh lm an n. G. Kar~nerThe second period for high mortality occurs at the change in the

offered food organisms, B r a c h i o n , t s to A r t e r n i a nauplii. Here, defici-encies in dieta ry value, in particular insuffic ient amount s of PUFA. arethe main reason for bad performance. During this period the copepoddiet appeared to decrease the mort ali ty of turbo t larvae in compar isonto A r t e m i a nauplii. The add ition of suitable copepod stages to the con-ventional diet ( B r a c h i o n u s and A r t e m i a ) may help to improve theyields in producing metamorphosed turbot.

ACKNOWLEDGEMENTSThis study was financed by the Federal Ministry of Research andTechn ology, West Germany.

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compound feeds.A q u a c u l t u r e , 31, 31-40.Cowey, C. B., Owen, J. M., Adron, J. W. & Middleton. C. {1976). Studies on thenutrition of marine flatfish. The effect of different dietary fatty acids oll thegrowth and fatty acid composition of tt, rbot (Scoph tha l rnus max imus) . Br . J .N u t r . , 36,479-86.

Detwyler, P. & Hot,de, E. D. (1970). Food selection by laboratory-reared larvaeof ttle scaled sardine Hareng~t la pemacolae (Pisces, Clupeidae) and the bayanchovy A n c h o a m i t ch i ll i (Pisces. Engraulidae). Mar. B io l . . 7,214-22.Fujii, M. & Yone. Y. (1976). Studies on nutrition of red sea bream - XIII. Effectof dietary linolenic acid and w3 polyunsaturated fatty acids on growth and feedefficiency. Bull. Jap. Soc. Sci. Fish.. 42,583-8.Fujita, S.. Watanabe, T. & Kitajima, C. (1980). Nutritional quality o f A r t e m i a fromdifferent localities as a living feed for marine fish from the viewpoint of essentialfatty acids. In: The Br i n e S h r i m p Artemia, Vol. 3: Ecology Culturing, Use inAquaculture, eels G. Persoone, P. Sorgeloos, O. Roels and E. Jaspers. UniversaPress. Wetteren, Belgium.Fukusho, K.. Arakawa. T. & Watanabe, T. (1980). Food value of a copepod, Tigrio-pus /apon icus , cultured with w-yeast for larvae and juveniles of mud dab,Lb nan da yok och am ae . Bu ll. ,lap . Soc . ScL Fi sh . . 46,499-503.


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Com parison or" tur bo t larvae diets w ith special regard ro PU FA s 189G ates ou pe , F . J . , L eger , C .. Meta i l l e r. R . and L uque t . P. (1977 ) . A l ime n ta t ion

l i p i d i q u e d u t u r b o t (Scoph tha lmus ma .v imus L.) . I - Inf luen ce de la long ueu rde [a ch ain e des ac ides gras de la ser ie 603. Ann . Hvdrob io l . . 8 . 8 9 - 9 7 .

Hussa in , N . A . & H iguch i , M. (1980 ) . Larval r ea r ing and de ve lo pm en t o f the b row ns p o t t e d g r o u p e r, Epinephelus tauvina ( F o r s k a l ) . A q u a c u l tu re , 19 , aa9 -_O.Jones , A . , P r icke t , R . A . & Doug las , M. T . ( I981~ . Rece n t dev e lop m en ts in t ech -

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190 (_1". W itt, G. Q ua nrz , D. K uh lm an n, G. K ar tne rSchauer , P . S . , Johns . D . M. , O lney , L . E . & S impson . K . L . (1980) . In t e rna t iona l

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Witt 1984 Aquacultural-Engineering

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