International Development Research Centre
SAFIS Extension Manual Series No. 16, 1985
NURSERY MANAGEMENT OF PRAWNS
by
Made L. Nurdjana, B. Martosudarmo and
Anindiastuti
NURSERY MANAGEMENT OF PRAWNS
by
Made L. Nurdjana, B. Martosudarmo and
Anindiastuti
Directorate-General of Fisheries Jakarta, Indonesia
The Secretariat
Southeast Asian Fisheries Development Center January 1985
B. Martosudarmo and Anindiastuti. It was included in Pedoman pembenihan udang penaeid
("Manual on the nursery of penaeid prawns"), published by the Directorate-General of Fisheries (DGF), Jakarta, in 1980. This is an English translation prepared by Mr. A.
Soegiri of the Directorate of Enterprise Development of DGF for the SAFIS project.
This manual has been adapted and edited by the SEAFDEC Secretariat.
Made L. Nurdjana, B. Martosudarmo and
Anindiastuti
INTRODUCTION
In 1942, Dr. Motosaku Fujinaga was the first scientist to successfully hatch prawn eggs and able to rear them to the postlarval stage. By applying the technique evolved by Dr. Fujinaga, a system of nursery management of penaeid prawn was later developed and became known as the
Japanese method. After improvements over a
number of years, this method has been used for the successful production of larvae oh a large
scale. When Western experts who were interested
in the rearing of prawn larvae studied the Japanese method and applied it in their own countries, they came to the conclusion that it
had some weaknesses. The Western experts,
therefore, presented a new technique called the Galveston method, which derives its name from the place called Galveston where the method was first applied by an American scientist.
Both above-mentioned methods were the origin of techniques for rearing penaeid prawn that were developed by several countries, and adapted to the local conditions. At Jepara, Indonesia, for example, the Brackishwater Pond Institute is developing a breeding system for
p e n a e id prawn t h a t d i f f e r s i n s e v e r a l re s p e c ts fro m th e above m ethods. There a re a ls o
d if f e r e n c e s between th e Japanese and th e G a lv e s to n m ethods, e . g . , i n th e ty p e o f ta n k used and th e te c h n iq u e f o r r e a r in g la r v a e .
EXISTING CULTURE METHODS
The Japanese method uses la r g e square ta n k s o f 150 to n s and 200 to n s . Because o f th e la r g e volume o f w a te r w h ic h such ta n k s c o n t a in , i t i s d i f f i c u l t to c o n t r o l th e w a te r te m p e ra tu re .
The G a lv e s to n method on th e o t h e r hand uses a s m a ll- s iz e d cone-shaped ta n k between 2 and 3 t o n s , so t h a t th e te m p e ra tu re i s e a s i ly c o n t r o ll e d . The J e p a ra method uses a 6 - t o 10- to n t a n k . W ith ta n k s o f t h i s s iz e , i t i s n o t n e c e s s a ry to c o n t r o l th e te m p e ra tu re , because th e volume o f w a te r i s such t h a t no v e r y g r e a t change i n te m p e ra tu re o c c u rs .
To p r e v e n t a decrease i n th e w a te r te m p e ra tu re e s p e c ia l ly a t n i g h t - t im e , th e ta n k s h o u ld be c o v e re d w it h a p l a s t i c s h e e t.
The system u s in g la r g e ta n k s as a p p lie d i n In d o n e s ia g iv e s r i s e t o p ro b le m s m a in ly as re g a rd s s t o c k in g . O b ta in in g a la r g e q u a n t i t y o f g r a v id fe m a le s i s alw ays a p ro b le m . A 6 0 - to n ta n k r e q u ir e s a t le a s t te n such fe m a le s . To c a tc h t h a t number i n one s e a -g o in g o p e r a tio n i s v e r y d i f f i c u l t . By u s in g a m e d iu m -s iz e d ta n k , one g r a v id fe m a le i s s u f f i c i e n t f o r a p r o f i t a b l e o p e r a tio n .
C u ltu r e o f la r v a e u n d e r th e Japanese method i s g e n e r a lly c a r r i e d o u t a t a r e l a t i v e l y
lo w d e n s it y o f abo u t 10 t o 40 la r v a e p e r l i t r e , whereas th e G a lv e s to n method s to c k s a h ig h d e n s it y o f a b o u t 250 la r v a e p e r l i t r e . Because o f t h i s h ig h d e n s it y , th e c u l t u r e r e q u ir e s much more c a re i n th e G a lv e s to n method th a n i n th e Japanese m ethod. S to c k in g i n th e J e p a ra method i s a t a d e n s it y o f 50 la r v a e p e r l i t r e .
I n th e Japanese method fe e d i s p r o v id e d i n th e c u l t u r e ta n k by a d d in g f e r t i l i s e r f o r g ro w in g p la n k t o n , m a in ly d ia to m s . The f e r t i l i s e r g e n e r a lly used i s KNO3 (2 ppm c o n c e n tr a t io n ) and K2HPO4 a t 0 .2 ppm (S h ig u e n o , 1 9 6 9 ). In Japan t h i s system i s f e a s ib le and i t g iv e s s a t i s f a c t o r y r e s u l t s because th e f e r t i l i s e r in d u c e s th e
b lo o m in g o f S keletonem a c o s ta tu m . The g ro w th r a t e o f t h i s d ia to m re m a in s c o n s ta n t and c o n t r o l l a b l e .
A d d in g f e r t i l i s e r t o th e c u l t u r e ta n k i n J e p a ra has a n e g a tiv e e f f e c t on th e g ro w th o f th e la r v a e . The re a so n i s t h a t e x c e s s iv e p la n k to n bloom s o c c u r . T h e ir g ro w th i s
u n c o n t r o lla b le because o f th e h ig h l i g h t i n t e n s i t y . The w a te r f i r s t becomes d a rk brown and, w i t h i n two t o t h r e e d a y s , i t changes t o m i l k i s h - w h i t e . T h is in d ic a t e s t h a t c i l i a t e d p ro to z o a and
b a c t e r ia have begun t o m u l t i p l y . W it h in a s h o r t tim e th e la r v a e p o p u la t io n d ecrea ses o r may even be w ip e d o u t c o m p le te ly .
In a d d it io n th e f e r t i l i s e r a ls o in d u c e s th e g ro w th o f d ia to m s i n genus L io m o p h o ra . These d ia to m s i n s m a ll numbers a re n o t a d a n g e r to th e la r v a e . B u t th e y may have a h a r m fu l e f f e c t i f th e y o c c u r i n la r g e num bers. These d ia to m s
a t ta c h th e m s e lv e s t o th e la r v a e 's b o d ie s .
The reb y th e y imped th e l a r v a l movements and a ls o r e s t r i c t t h e i r a b i l i t y to fe e d . I n th e end, th e la r v a e d ie o f s t a r v a t i o n .
A t J e p a ra th e f e r t i l i s e r used i s KNO3 1 ppm K2HPO4 0 .1 ppm. I t o f t e n causes th e e x c e s s iv e g ro w th o f C haetocer o s , one o f th e common d ia to m s use as fo o d f o r prawn la r v a e . However, i f th e d ia to m d e n s it y i n th e c u l t u r e ta n k re a ch e s more th a n 30,000 c e l l / c c when th e la r v a e a re a t th e z o e a l s ta g e s , th e e x c e s s iv e a v a i l a b i l i t y o f fo o d m ig h t cause th e fa e c e s o f th e la r v a e t o become so lo n g t h a t th e y enwrap th e l a r v a l b o d ie s . The la r v a e b e in g th u s u n a b le to swim, w o u ld f i n a l l y d ie . As i n th e case o f o t h e r p la n k t o n , th e b lo o m in g o f Chaetoc er os i s f o llo w e d by th e g ro w th o f c i l i a t e d p ro to z o a and b a c t e r ia t h a t have h a rm fu l e f f e c t s on th e la r v a e .
The Japanese method o f p r o v id in g fe e d th ro u g h a d d in g f e r t i l i s e r i n th e w a te r i n th e c u l t u r e ta n k d i f f e r s fro m th e G a lv e s to n m ethod.
In th e l a t t e r method fe e d i s p re p a re d fro m c u lt u r e d s to c k o f S keletonem a and B ra c h io n u s i n a s e p a ra te ta n k . S keletonem a i s h a rv e s te d by u s in g a sand f i l t e r and i s g iv e n t o la r v a e a t th e z o e a l s ta g e s . T h is method i s a ls o used i n In d o n e s ia because o f i t s r e l a t i v e l y low c o s t . The p r i n c i p l e o f th e sand f i l t e r i s t h a t i t f i l t e r s th e d i r t i n th e w a te r w h ile th e p la n k to n a re r e t a in e d . I n t h i s way, th e p la n k to n
S ke letone m a can be c o lle c t e d and s to r e d t o be re a d y as fe e d f o r th e la r v a e . I t i s u s u a lly
s to r e d i n a c o o l p la c e , such as an a ir - c o n d it io n e d room, i n o r d e r to keep th e p la n k to n a l i v e . F resh w a te r i s added t o th e Ske letone m a by l e t t i n g i t f l o a t on th e w a te r o f th e r e a r in g ta n k .
T h is method o f c u l t u r i n g p la n k to n i n a s e p a ra te ta n k p re v e n ts th e c o n ta m in a tio n o f th e w a te r i n th e l a r v a l c u l t u r e ta n k by th e f e r t i l i s e r F e r t i l i s e r , such as KNO3/ K 2HPO4 in a c e r t a in
c o n c e n t r a t io n , i s l i a b l e t o k i l l th e la r v a e . In th e lo n g ru n , th e a c c u m u la tio n o f f e r t i l i s e r i n th e c u l t u r e ta n k may have an i n d i r e c t h a rm fu l e f f e c t on th e la r v a e . F e r t i l i s e r may in d u c e e x c e s s iv e p la n k to n bloom i n th e ta n k .
E f f o r t s have been made b y th e J e p a ra B r a c k is h w a te r Pond I n s t i t u t e t o s i m p l i f y prawn n u r s e r y te c h n iq u e s so t h a t th e y can be e a s i l y a p p lie d . The p la n k to n a re n o t h a rv e s te d i n advance b u t a re pou re d d i r e c t l y i n t o th e r e a r in g t a n k . To t r a n s f e r p la n k to n t o th e r e a r in g t a n k , an o r d in a r y p a i l may be used . The t r a n s f e r s h o u ld be done c a r e f u l l y and g r a d u a lly t o re d u c e th e e f f e c t s o f a sudden change o f w a te r q u a l i t y .
The re a re s e v e r a l ways o f r e d u c in g th e a d ve rse e f f e c t s o f a d d in g f e r t i l i s e r . F i r s t l y , th e maximum g ro w th o f p la n k to n s h o u ld be m o n ito re d T h is can be deduced fro m th e p la n k t o n 's d e n s it y and th e number o f days o f c u l t u r i n g . The b lo o m in g o f S ke letone m a o r T e tr a s e lm is w i l l o c c u r w i t h i n f o u r t o f i v e days i n th e n o rm al h e a lt h y c u l t u r e . The maximum number o f S keletonem a has been known t o re a c h a b o u t 3 m i l l i o n c e l l / c c i n a 400 l i t r e t a n k , w h ile th e number o f T e tr a s e lm is has re a ch e d 0 .5 m i l l i o n c e l l / c c i n a 3 - to n t a n k . The b e s t tim e f o r h a r v e s t in g th e p la n k to n is when
maximum g ro w th has been re a c h e d . T h is w i l l e nsu re t h a t m ost o f th e f e r t i l i s e r has been used by th e p la n k t o n . Thus, th e a c c u m u la tio n
o f th e f e r t i l i s e r i n th e c u l t u r e ta n k i s so l i m i t e d t h a t i t poses no dan ger t o th e la r v a e . M ore over e u t r o p h ic a t io n can be re d u c e d .
A n o th e r means i s t o c o v e r th e s u r fa c e o f th e ta n k w i t h bamboo m a tt in g . The o b je c t iv e i s t o re d u c e th e l i g h t i n t e n s i t y e n t e r in g th e r e a r in g t a n k . Thus, a lth o u g h th e p ro c e s s o f e u t r o p h ic a t io n s t i l l ta k e s p la c e , th e b lo o m in g o f p la n k to n i s c o n t r o ll a b l e due t o th e lo w l i g h t i n t e n s i t y .
I n th e Japanese m ethod, th e la r v a e are h a tc h e d and c u lt u r e d i n th e same t a n k . A f t e r th e spawners have been removed fro m th e t a n k , th e ta n k i s f u r t h e r used as th e c u l t u r e t a n k . In th e G a lv e s to n m ethod, on th e o t h e r hand,
s e p a ra te ta n k s a re used f o r h a tc h in g and c u l t u r i n g th e la r v a e . The cone-shaped ta n k i s used f o r
l a r v a l c u l t u r e . A n o th e r ta n k f o r spaw ning and h a tc h in g i s needed. A t J e p a ra b o th methods a re a p p lie d . I n f a c t th e method by w h ich n a u p l i i a re t r a n s f e r r e d fro m th e spaw ning ta n k t o th e c u l t u r i n g ta n k g iv e s a b e t t e r r e s u l t .
TANK PREPARATION
A lth o u g h ta n k p r e p a r a t io n seems s im p le , i t i s o f p rim e im p o rta n c e f o r th e s u c c e s s fu l r e a r in g o f la r v a e . B e fo re u se , th e ta n k s h o u ld be c le a n e d t o remove th e d i r t t h a t m ig h t have a d ve rse e f f e c t s on th e la r v a e . The c le a n lin e s s re q u ire m e n ts o f ta n k s may v a r y a c c o r d in g t o th e p u rp o s e f o r w h ic h th e y w i l l be u se d . F or prawn r e a r in g , th e ta n k s h o u ld be f r e e fro m l i v i n g
o rg a n ism s a d h e rin g t o th e ta n k w a ll s . C o n ta m in a t i o n o f in o r g a n ic m a t e r ia l i n s m a ll amounts i s a llo w a b le . However i t i s n e c e s s a ry t o remove a l l o r g a n ic m a tte r e s p e c ia l ly ammonia o r ammonium compounds. The prawn la r v a e a re v e r y s e n s i t i v e t o p o is o n o u s gase s. Ammonia no h ig h e r th a n 1 .3 ppm i s l i a b l e t o k i l l prawn la r v a e .
A f t e r c le a n in g th e ta n k w a lls i t i s b e s t t o keep them d r y f o r two t o t h r e e days t o make s u re t h a t a l l a q u a tic o rgan ism s have d ie d . Thorough d r y in g i s a ls o in te n d e d t o p r e v e n t d is e a s e s . I f t h e r e i s n o t s u f f i c i e n t
tim e t o l e t th e ta n k d r y o u t p r o p e r l y , a c h lo r in e s o l u t i o n can be used t o c le a n th e s id e s o f th e ta n k i n o r d e r t o remove any a d h e rin g o rg a n is m s . T h is s o l u t i o n i n th e fo rm o f h y p o c h lo r in e can be b o u g h t fro m a c h e m is t a t a r e l a t i v e l y low c o s t . The s id e s o f th e ta n k a re washed w it h a c lo t h soaked i n a s o l u t i o n o f c h lo r in e a t 100 ppm
(100 ml c h lo r in e s o l u t i o n o f 10% t o 1 m3 o f w a t e r ) . P r io r t o f i l l i n g th e ta n k w it h w a te r , i t must
be l e f t t o d r y f o r one t o two h o u rs . T h is i s t o e n s u re t h a t a l l c h lo r in e i s removed t o a v o id th e p o is o n o u s e f f e c t t h a t c h lo r in e w o u ld have on th e la r v a e o r on th e p la n k t o n .
The ta n k i s f i l l e d up w it h f i l t e r e d sea w a te r a f t e r i t has been p r o p e r ly c le a n e d . The w a te r used i n th e h a tc h in g and r e a r in g ta n k s h o u ld be f r e e fro m p o l l u t a n t s such as heavy m e ta ls and o r g a n ic m a t e r i a ls . The sea w a te r used s h o u ld be c le a n , w it h a s a l i n i t y o f 30 p p t .
D u rin g th e d r y season th e s a l i n i t y i s 34 p p t . I t i s t h e r e f o r e n e c e s s a ry t o re duce th e s a l i n i t y by a d d in g f r e s h w a te r . I t has been o b s e rv e d t h a t th e a p p r o p r ia te s a l i n i t y i s between 28 and 32 p p t .
D u rin g th e r a in y seaso n, th e s a l i n i t y i n th e sea w a te r i s lo w . T h e r e fo r e , i t i s n e c e s s a ry t o in c r e a s e th e s a l i n i t y i n o r d e r t o ensu re
s u c c e s s fu l la r v a e r e a r in g . T h is can be done by a d d in g s a l t i n s o l u t i o n . I t i s b e s t t o use n a t u r a l s a l t t h a t c o n ta in s none o f th e
p r o c e s s in g c h e m ic a ls w h ic h a re d e t r im e n t a l to th e prawn la r v a e .
I f s a l t i s added d i r e c t l y t o th e w a te r , t u r b i d i t y w i l l r e s u l t fro m th e im p u r i t i e s i n th e s a l t . To keep th e w a te r c le a r , th e s a l t s h o u ld f i r s t be d is s o lv e d i n a s e p a ra te v e s s e l and th e s o l u t i o n l e f t u n d is tu r b e d t o a llo w th e i m p u r i t i e s to s e t t l e . G e n e r a lly w i t h i n one o r two days c le a r w a te r w it h a h ig h s a l i n i t y can be o b ta in e d . T h is h ig h s a l i n i t y s o l u t i o n i s th e n p o u re d i n t o th e w a te r , i n o r d e r t o in c re a s e th e s a l i n i t y .
The spaw ning ta n k s h o u ld be f i l l e d w it h sea w a te r t o a d e p th o f 40 cm. Some a ir s t o n e s s h o u ld be s c a t t e r e d on th e b o tto m o f th e ta n k
i n o r d e r t o p r o v id e weak a e r a t io n . The a i r speed s h o u ld be 2 -4 l i t r e s / m i n u t e / 3 m2 . T h is i s meant t o keep th e movement o f th e w a te r c o n s ta n t.
S tro n g a e r a t io n may d i s t u r b e i t h e r th e spawners o r th e eggs t h a t have a lr e a d y been l a i d . On th e o t h e r han d , weak a e r a t io n has an ad ve rse e f f e c t on th e spaw ning c a p a c it y o f th e spaw ner, as w e l l as on th e number o f eggs t h a t w i l l h a tc h .
The i n t e n s i t y o f th e l i g h t e n t e r in g th e ta n k s h o u ld be l i m i t e d . S in c e spaw ning ta k e s p la c e b e t t e r i n d a rk n e s s , lamps aro u n d th e ta n k s h o u ld be s w itc h e d o f f . I f spaw ning s h o u ld o c c u r d u r in g m o o n lig h t, i t i s v e r y im p o r t a n t t o c o v e r th e ta n k w it h bamboo m a tt in g o r a c l o t h . B r ig h t l i g h t may cause p a r t i a l s p a w n in g , t h a t i s , o n ly a p o r t io n o f th e eggs i s l a i d . In such a c a se , th e eggs r e m a in in g i n th e body o f th e
spawner may be a b s o rb e d .
The ta n k s h o u ld be checked t o a s c e r t a in t h a t e v e r y t h in g i s i n o r d e r a f t e r th e p r e p a r a t io n s . The m ain p o in t s t o be checked a re i n t e n s i t y o f a e r a t io n , w a te r d e p th , and s a l i n i t y . The m a tu re fe m a le s can th e n be p la c e d i n th e ta n k .
REARING OF LARVAE
Spawners a t th e s ta g e o f f u l l gonad m a t u r i t y ( t h i r d s ta g e ) may r e le a s e th e eggs d u r in g th e f i r s t n i g h t a f t e r h a v in g been t r a n s f e r r e d t o th e spaw ning t a n k . I f th e spawners do n o t r e le a s e th e eggs d u r in g th e f i r s t n i g h t , th e y s h o u ld n o t be fe d th e n e x t e v e n in g i n o r d e r t o a v o id th e eggs b e in g
a b s o rb e d . D u rin g th e f o l l o w i n g n i g h t , th e eggs s h o u ld be r e le a s e d . The spawners s h o u ld be r e tu r n e d t o th e c o p u la t io n ta n k i f th e eggs a re n o t r e le a s e d . G e n e r a lly when a spawner i s r e tu r n e d t o th e
c o p u la t io n t a n k , th e u n la id eggs a re a b s o rb e d .
PenaeusmonodonFabricus English common name:Gianttigerprawn
Penaeusmerguiensisde Man Englishcommonname: Whiteprawn; Bananaprawn
T ig e r prawn (Penaeus monodon) spawn d u r in g th e n i g h t , whereas Banana prawn (Penaeus mer g u ie n s is ) sometimes spawn i n th e a fte r n o o n . The egg h a tc h e s t o become a n a u p liu s w i t h i n
2 t o 16 h o u rs . The n a u p liu s undergoes m etam orphosis s i x tim e s w i t h i n 46 to 50 h o u rs u n t i l i t becomes a zoea. The r a t e o f deve lop m en t o f n a u p l i i is in flu e n c e d by th e c h e m ic a l and p h y s ic a l c o n d it io n s o f th e w a te r , m a in ly te m p e ra tu re and s a l i n i t y . G e n e r a lly an in c re a s e i n te m p e ra tu re as w e ll as s a l i n i t y up to a c e r t a in l i m i t w i l l a c c e le r a te th e g ro w th o f th e n a u p l i i .
Soon a f t e r th e eggs have h a tc h e d and become n a u p l i i , a e r a t io n i n th e ta n k s h o u ld be
in c re a s e d . The i n t e n s i t y o f a e r a t io n s h o u ld be aroun d 10 l i t r e s / m i n u t e f o r a d e p th o f 50 cm, th e t o t a l a e r a t io n b e in g c a lc u la t e d on th e b a s is o f one a e r a t o r p e r one m2 . Thus f o r a ta n k o f 4 x 4 m2 i n s iz e a t le a s t 16 a e r a to r s a re needed, p la c e d a t r e g u la r i n t e r v a l s a t th e b o tto m o f th e ta n k . To a t t a i n th e h ig h e s t e f f i c i e n c y o f a e r a t io n , a ir s t o n e s t h a t pro d u ce s m a ll b u b b le s s h o u ld a ls o be used . The a ir s t o n e s s h o u ld be p la c e d 50 cm fro m th e s id e s o f th e t a n k . T h is i s t o a v o id c r u s h in g some n a u p l i i t o d e a th a g a in s t th e s id e s o f th e ta n k i f a ir s t o n e s a re p la c e d to o c lo s e t o th e s id e s .
N a u p lii need n o t be fe d because th e y have enough re s e rv e fo o d i n t h e i r y o lk - s a c s . The d ia to m c u l t u r e o f S keletonem a and T e t r a s e lm is s h o u ld s t a r t two days p r i o r t o th e spawners b e in g moved to th e spaw ning ta n k i n o r d e r t o be re a d y as fe e d f o r th e z o e a l la r v a e .
A t th e n a u p liu s s ta g e , th e ta n k s h o u ld be co v e re d w i t h bamboo m a tt in g t o re d u ce th e l i g h t i n t e n s i t y . T h is can a ls o re d u ce m o r t a l i t y as w e ll as p r e v e n t t h e e x c e s s iv e p la n k to n b lo o m . T e m p e ra tu re f l u c t u a t i o n s a re c o n t r o ll e d by c o v e r in g th e ta n k i n o r d e r t o p r o v id e s u i t a b le c o n d it io n s e n h a n cin g th e l a r v a l g ro w th r a t e .
A f t e r th e n a u p l i i have d e v e lo p e d i n t o zoea, th e la r v a e need t o be fe d . S ke letone m a o r T e tr a s e lm is can be pou re d d i r e c t l y i n t o th e
l a r v a l ta n k a few h o u rs b e fo r e th e n a u p l i i change i n t o zoea. The t im in g t o add d ia to m c u l t u r e i n t o th e ta n k s h o u ld be c a r e f u l l y m o n ito r e d .
D ir e c t fe e d in g o f Ske letone m a o r T e tr a s e lm is i n t o th e l a r v a l ta n k has an a dva nta ge o f r e d u c in g th e d e n s it y o f la r v a e i n th e t a n k . As th e la r v a e d e v e lo p and grow l a r g e r , th e d e n s it y s h o u ld be re d u ce d t o a v o id th e c ro w d in g e f f e c t . A t th e n a u p liu s s ta g e , th e a p p r o p r ia t e d e n s it y s h o u ld be 50 i n d i v i d u a l s p e r l i t r e . T h is can be d e cre a se d t o 35 - 40 i n d i v i d u a l s p e r l i t r e by a d d in g w a te r .
The r a t i o s o f S ke letone m a o r T e tr a s e lm is added t o th e w a te r o f th e n u r s e r y ta n k a t zoea s ta g e I i s 5 ,0 0 0 - 10,000 c e l l / c c ; a t zoea s ta g e I I 10,000 - 15,000 c e l l / c c ; and a t zoea s ta g e I I I 15,000 - 20,000 c e l l / c c . A t th e m ysis s ta g e s (M I , M I I , M I I I ) , S ke letone m a and T e tr a s e lm is can be g iv e n a t a d e n s it y o f 20,000 c e l l / c c .
R o t i f e r can a ls o be g iv e n b e s id e s
S ke letone m a and T e t r a s e lm is . I t can be g iv e n a t zoea s ta g e I I I . The optimum d a i l y amounts a re shown i n T a b le 1.
T a b le 1. Optimum amount o f R o t i f e r a d ju s te d t o th e deve lop m en t s ta g e s o f la r v a e
Stage T o t a l amount o f R o t i f e r / m l o f W a te r/d a y
Zoea I -
I I -
I I I 3 .0
M ysis I 4 .0
I I 5 .0
I I I 6 .0
B e sid e s th e fo o d m e n tio n e d above, f r e s h " t a h u " (a C hinese cake made o f soybean f l o u r ) has g iv e n s a t i s f a c t o r y r e s u l t s . I t s h o u ld be s h re d d e d and added w it h fr e s h w a te r b e fo r e fe e d in g
i t t o th e la r v a e . To o b t a in s m a ll p a r t i c l e s ,
" t a h u " i s c ru sh e d by a b le n d e r o r passed th ro u g h a f i l t e r . I t i s g iv e n as soon as th e n a u p l i i have d e v e lo p e d i n t o zoea. The d is a d v a n ta g e o f
" t a h u " as a fe e d f o r la r v a e i s t h a t th e p a r t i c l e s s in k r a p i d l y and s e t t l e a t th e b o tto m o f th e ta n k .
T a b le 2 shows th e s iz e o f th e p a r t i c l e s and th e t o t a l w e ig h t o f " t a h u " r e q u ir e d a t th e v a r io u s s ta g e s o f la r v a e re a re d i n a ta n k o f 5 to n s w it h a d e n s it y o f 40 z o e a / l i t r e , and g iv e n f i v e tim e s a day, n a m e ly, a t 7 .0 0 , 1 2 .0 0 , 16.00 1 9 .0 0 , 22.00 h r s .
From m ysis I s ta g e onwards la r v a e o f p e n a e id prawn a re no lo n g e r f i l t e r fe e d e r s . T h e re fo re th e s iz e o f a p a r t i c l e i s n o t as c r i t i c a l as a t th e zoea s ta g e . T a k in g i n t o a c c o u n t t h a t " t a h u " s in k s e a s i l y , th e s iz e o f th e p a r t i c l e f o r th e m ysis s ta g e s h o u ld be a ro u n d 75-105 m ic ro n to re duce th e speed a t w h ic h th e p a r t i c l e s s e t t l e . F o r p o s t la r v a e th e p a r t i c l e s can be l a r g e r because p o s t la r v a e a re b o tto m fe e d e rs and w i l l e a t th e fe e d t h a t s in k s t o th e b o tto m o f th e ta n k .
T a b le 2 . P a r t i c l e s iz e and t o t a l w e ig h t o f
" t a h u " r e q u ir e d a t d i f f e r e n t s ta g e s o f l a r v a l developm ent
Stage P a r t i c l e s iz e (m ic ro n )
T o t a l w e ig h t o f
" t a h u " (gramme)
Zoea I 35 - 48 10
I I 48 - 75 15
I I I 48 - 75 20
M ysis I 75 - 105 25
I I 75 - 105 30
I I I 75 - 105 30
P o s tla r v a 1 105 35
2 105 40
3 105 45
4 105 45.
5 105 45
6 105 45
7 105 45
8 105 45
9 105 45
The b e s t fe e d f o r p o s t la r v a e i s n a u p l i i o f A r te m ia s a l in a . However, th e eggs o f A r te m ia m ust be im p o rte d fro m abroad a t a r e l a t i v e l y h ig h c o s t . A r te m ia eggs s h o u ld f i r s t be h a tc h e d i n a s e p a ra te ta n k b e fo r e th e y a re g iv e n as fe e d . H a tc h in g la s t s a b o u t 24 h o u rs , a f t e r w h ic h th e n a u p l i i a re washed i n sea w a te r . H a tc h in g can a ls o ta k e p la c e i n a p a i l , a t a d e n s it y o f 2 g o f A r te m ia eggs p e r l i t r e o f sea w a te r .
Owing t o A rte m ia spawn b e in g d i f f i c u l t and c o s t ly t o o b t a in , p e l l e t fe e d c o n t a in in g a b o u t 60 p e r c e n t o f p r o t e in can a ls o be g iv e n f i v e tim e s a day a t th e p o s t l a r v a l s ta g e s . The p e l l e t c o n s is ts o f p a r t i c l e s o f a b o u t 200 m ic ro n s .
A f t e r th e p o s t la r v a e have re a ch e d s ta g e 9 , th e y a re t r a n s f e r r e d t o th e f r y t a n k . To a v o id m o r t a l i t y among th e p o s t l a r v a e / f r y as a r e s u l t o f t h i s t r a n s f e r , i t i s n e c e s s a ry t o s lo w ly a c c lim a t iz e them t o th e new c o n d it io n s .
ACCLIMATIZATION OF FRY
A c c l im a t iz a t io n , th e p ro c e s s whereby an a n im a l t h a t i s b e in g r e a re d i s g r a d u a lly
accustom ed t o th e c o n d it io n s o f i t s new
s u r ro u n d in g s , in c lu d e s a d a p ta tio n t o a l l a s p e c ts o f th e new e n v iro n m e n t. A new e n v iro n m e n t may b r in g a b o u t p h y s i o l o g ic a l and b e h a v io r a l changes i n th e o rg a n is m .
H ig h m o r t a l i t y o f t e n o c c u rs a f t e r th e f r y a re r e le a s e d i n t o th e f r y t a n k . T h is i s a s e r io u s p ro b le m . I t i s due t o la c k o f a t t e n t i o n t o th e d i f f e r e n c e between th e s u rro u n d in g s t o w h ic h th e p o s t la r v a e were accustom ed and th e c o n d it io n s o f th e f r y ta n k a t th e tim e o f t r a n s f e r r i n g th e f r y . Death may be caused by p h y s i o l o g ic a l s t r e s s ow ing t o a sudden change o f e n v iro n m e n t.
T e m p e ra tu re and s a l i n i t y a re th e two most im p o r ta n t f a c t o r s i n a c c l i m a t i z a t io n . T e m p e ra tu re has a d i r e c t in f lu e n c e on th e p h y s io lo g y o f th e a n im a l, m a in ly on i t s
m e ta b o lis m . S a l i n i t y i s one o f th e f a c t o r s t h a t a f f e c t s th e o s m o re g u la tio n p ro c e s s . S e v e ra l m a rin e a n im a ls a re u n a b le t o a d ju s t t o th e new s a l i n i t y because t h e i r o s m o re g u la to ry a b i l i t i e s a re l i m i t e d . Thus th e s a l t c o n c e n tr a t io n i n t h e i r body f l u i d s may change beyond t h e i r t o le r a n c e . The t i g e r prawn however i s one o f th e m a rin e a n im a ls t h a t i s a b le t o l i v e i n sea w a te r as w e ll as i n b r a c k is h w a te r . The s a l t c o n c e n tr a t i o n i n th e body f l u i d r e g u la t e i n re sp o n se t o new s a l i n i t y .
In v ie w o f th e above, p h y s i o l o g ic a l a d a p ta tio n i s v e r y im p o r ta n t when r e le a s in g f r y i n t o a ta n k . Prawn r e a r in g r e q u ir e s h ig h
s a l i n i t y , b u t th e degree o f th e s a l i n i t y o f th e w a te r i n t o w h ic h th e f r y a re r e le a s e d may v a r y . The s a l i n i t y o f th e w a te r i n th e f r y r e a r in g ta n k must be d e te rm in e d b e fo r e th e f r y a re t r a n s f e r r e d .
I f th e r e i s a d i f f e r e n c e i n th e s a l i n i t y i n th e r e a r in g ta n k and th e f r y t a n k , a l t e r a t i o n o f s a l i n i t y s h o u ld be c a r r ie d o u t i n th e f r y r e a r in g t a n k . The method o f lo w e r in g s a l i n i t y i s t o d e cre a se th e w a te r i n th e f r y t a n k , and to r e p la c e i t g r a d u a lly w it h f r e s h w a te r as f o llo w s th e w a te r le v e l o f th e ta n k i s lo w e re d by 5 to 10 cm, th e n b ro u g h t up to i t s p r e v io u s le v e l by a d d in g f r e s h w a te r . The same can be done th e n e x t day and re p e a te d s e v e r a l tim e s u n t i l th e r e q u ir e d s a l i n i t y i s re a c h e d . H ig h s a l i n i t y u s u a lly h in d e r s th e g ro w th r a t e o f praw n s.
S a l i n i t y a l t e r a t i o n can a ls o be c a r r ie d o u t in th e r e a r in g ta n k .
NOTES
R o u tin e A c t i v i t i e s o f a Prawn N u rs e ry O p e ra tio n The l a r v a l s ta g e i s th e c r i t i c a l s ta g e i n th e l i f e c y c le o f th e praw n. Hence th e ca re ta k e n i n r e a r in g th e la r v a e d e te rm in e s th e
success o r f a i l u r e o f prawn c u l t u r e . The la r v a e s h o u ld be g iv e n s p e c ia l a t t e n t i o n th ro u g h o u t 24 h o u rs o f th e d a y, i f n e c e s s a ry . There a re many r o u t in e a c t i v i t i e s i n th e r e a r in g o f prawn
la r v a e w h ic h may appear s im p le , y e t i f th e y a re n o t c a r r i e d o u t p r o p e r ly , th e e f f o r t s p u t in t o r e a r in g th e prawn w i l l have been i n v a in and m a t e r ia l in p u t s w i l l have been w a s te d .
I n th e p r e p a r a t io n o f th e t a n k , i t s s id e s must be p r o p e r ly c le a n e d . F i l t e r e d sea w a te r i s s t r o n g ly recommended.
A f t e r a spawner has r e le a s e d a l l o f i t s e g g s, th e p e rc e n ta g e o f eggs h a tc h e d s h o u ld be a s c e r ta in e d by th e use o f a m ic ro s c o p e .
E x p e rie n c e has shown t h a t i f 60 p e r c e n t o f th e eggs h a tc h , th e la r v a e a re h e a lt h y . I f th e p e rc e n ta g e i s b e lo w 30 p e r c e n t, th e n th e la r v a e a re u s u a lly weak. T h e r e fo r e , i t i s n e c e s s a ry t o m o n ito r th e p e rc e n ta g e o f eggs h a tc h e d .
When th e eggs h a tc h , th e la r v a e
p o p u la tio n s h o u ld be a sse sse d . The p r a c t i c a l method i n d e te r m in in g th e l a r v a l d e n s it y i s t o
ta k e a sample i n a 1- l i t r e b a s in . T h is b a s in i s u s u a ll y t r a n s p a r e n t . T h is p ro c e s s s h o u ld be re p e a te d many tim e s . By know in g th e volume o f w a te r i n th e ta n k and th e averag e d e n s it y p e r l i t r e o f w a te r , p o p u la tio n d e n s it y can be d e te rm in e d ( i n d i v i d u a l / l i t r e ) .
In o r d e r to re a c h a more a c c u ra te
asse ssm e n t, th e f o ll o w i n g s te p s s h o u ld be ta k e n : (a) P o p u la tio n assessm ent s h o u ld be
c a r r i e d o u t i n th e m o rn in g , when th e r e i s le s s s u n l i g h t , and th e la r v a e a re n o t fo rm in g s c h o o ls i n one s p o t . L a rvae g a th e r i n clumps i n re s p o n s e t o p o s i t i v e p h o t o t a x is .
(b) Random s a m p lin g i s n e c e s s a ry . The h a b it o f la r v a e t o c o n g re g a te where th e r e i s an a e r a t o r s h o u ld be ta k e n i n t o a c c o u n t. Thus some samples s h o u ld be ta k e n fro m a p a r t o f th e ta n k where th e r e i s an a e r a t o r and fro m o t h e r p a r t s w it h o u t a e r a t o r s .
(c ) P o p u la tio n assessm ent o f n a u p l i i and zoea can be done by u s in g a lo n g p i p e t t e f o r c o u n tin g th e la r v a e t h a t have been c o lle c t e d i n th e b a s in . A t th e m ysis and p o s t l a r v a l s ta g e s i t i s b e s t n o t t o use a p i p e t t e , due t o i t s la r g e s iz e .
(d ) P o p u la tio n assessm ent u s in g a b a s in o f a known c a p a c it y can be c a r r ie d o u t o n ly up t o m ysis I I I o r p o s t la r v a 1. A f t e r p o s t la r v a 2 th e b e h a v io u r o f la r v a e has
changed to t h a t o f b o tto m o rg a n is m s . P o p u la tio n assessm ent u s in g a b a s in has a d d it io n a l a d v a n ta g e s , such a s:
( i ) The c o n d it io n o f th e la r v a e can be a s c e r ta in e d by o b s e rv in g t h e i r swimm ing, c o lo u r , and b e h a v io u r i n respon se t o l i g h t .
( i i ) The s ta g e o f deve lop m en t o f th e la r v a e can be e s tim a te d . T h is i s v e r y im p o r ta n t f o r d e te r m in in g th e k in d and optimum amount o f fe e d r e q u ir e d .
( i i i ) A ro u g h e s t im a t io n can be made o f th e c o n d it io n o f th e l i v i n g fo o d and th e amount o f p a r t i c l e s suspended i n th e l a r v a l r e a r in g w a te r .
C iv) I t r e v e a ls w h e th e r th e la r v a e have been g iv e n s u f f i c i e n t fe e d o r n o t . A t th e zoea s ta g e t h i s can be d e te rm in e d fro m th e le n g t h o f th e f a e c e s .
(v ) I f th e r e a re some dead la r v a e i n th e b a s in , a p p r o p r ia te measures s h o u ld be ta k e n q u i c k ly .
A f t e r th e l a r v a l p o p u la tio n assessm ent, e f f o r t s t o p r e v e n t th e la r v a e fro m b e in g
a f f e c t e d by any a d ve rse e f f e c t s s h o u ld be made w it h o u t d e la y . F or exam ple, i f th e p o p u la tio n i s v e r y dense, a p r o p o r t io n o f th e la r v a e s h o u ld be removed t o a n o th e r t a n k . D u rin g p o p u la t io n assessm ent c a re m ust be ta k e n n o t t o cause any s t r e s s t o th e la r v a e .
A n o th e r r o u t in e a c t i v i t y o f prawn n u r s e r y o p e r a tio n s i s t o o b se rve th e w a te r q u a l i t y . In th e J e p a ra method th e ta n k w a te r i s n e v e r changed, so th e q u a l i t y o f th e w a te r must be k e p t i n a c o n d it io n fa v o u r a b le t o th e g ro w th o f th e la r v a e . T h is can be done b y c o v e r in g th e ta n k w i t h bamboo m a t t in g t o p r e v e n t th e p la n k to n fro m b lo o m in g . The b o tto m o f th e ta n k must a ls o be c le a n s e d th o r o u g h ly t o remove l e f t - o v e r fo o d and o t h e r i m p u r i t i e s .
A l l a c tio n s t h a t have been ta k e n i n re g a rd t o each ta n k i n w h ic h la r v a e a re b e in g re a r e d s h o u ld be r e c o rd e d . T h is r e c o r d can l a t e r on be e v a lu a te d f o r f u r t h e r im p ro ve m e n t.
The r e c o r d s h o u ld a ls o c o v e r w e a th e r c o n d it io n s , te m p e ra tu re , s a l i n i t y o f th e w a te r i n r e a r in g ta n k s , t o t a l p o p u la t io n , fe e d , and o th e r r e le v a n t in f o r m a t io n .
LIST OF SAFIS EXTENSION MANUALS
SEC/SM/1 Khumua li a n g p l a namcheut (F re s h w a te r F is h F a rm in g : How t o B e g in ) - - i n T h a i SEC/SM/2 O y s te r C u ltu r e
SEC/SM/3 M ussel C u ltu r e
SEC/SM/4 Ang pagpuna ug p a g ta p a k sa p u k o t (N et Mending and P a t c h in g ) - - i n C e buan o-B isaya
SEC/SM/5 M ussel Farm ing
SEC/SM/6 M entern ak Ik a n A ir t a w a r (F re s h w a te r F is h F a rm in g : How t o B e g in ) - - i n Bahasa M a la y s ia
SEC/SM/7 Makanan dan Pemakanan Udang H a rim a u , Penaeus monodon ( N u t r i t i o n and
F e e d in g o f Sugpo, Penaeus monodon) - - i n Bahasa M a la y s ia
SEC/SM/8 M acro bra chiu m C u ltu r e
SEC/SM/9 S e le c t io n o f M a rin e Shrim p f o r C u ltu r e
SEC/SM/10 C u ltu r e o f Sea Bass SEC/SM/11 S m oke-C uring o f F is h
SEC/SM/13 C o ckle C u ltu r e
SEC/SM/14 Net Mending and P a tc h in g
SEC/SM/15 K a n lia n g hoy m alangphu (M ussel F a r m in g ) - - i n T h a i
SEC/SM/16 N u rs e ry Management o f Prawns
SAFIS
o What i s SAFIS?
SAFIS i s th e S o u th e a s t A s ia n F is h e r ie s I n fo r m a t io n S e r v ic e . I t i s a p r o je c t o f th e SEAFDEC S e c r e t a r ia t s e t up t o p r o v id e e x te n s io n m a t e r ia ls f o r
s m a ll- s c a le fis h e rm e n and f i s h fa rm e rs i n th e r e g io n .
o What a re i t s o b j e c t iv e s ? The im m e d ia te o b je c t iv e s a re t o c o l l e c t and c o m p ile f i s h e r i e s e x te n s io n m a n u a ls, b ro c h u re s , p a m p h le ts and r e la t e d a id s f o r s m a ll- s c a le f i s h e r i e s d e v e lo p m e n t, and t o t r a n s l a t e s e le c te d l i t e r a t u r e i n t o lo c a l languages f o r d i s t r i b u t i o n t o f i s h e r i e s e x te n s io n w o rk e rs i n S o u th e a s t A s ia .
o What s e r v ic e s w i l l SAFIS p r o v id e ? SAFIS w i l l a tte m p t t o p r o v id e in f o r m a t io n and p u b lic a t io n s such a s :
l i s t s o f a v a ila b le t e x t s i n f i s h e r i e s e x te n s io n s e r v ic e s , - t r a n s l a t i o n o f s u i t a b le m anua ls, - manuals o f a p p r o p r ia t e te c h n o lo g ie s ,
p h o to c o p ie s o f a p p r o p r ia te f i s h e r i e s e x te n s io n l i t e r a t u r e , a c u r r e n t awareness s e r v ic e o f r e g io n a l f i s h e r i e s .
o How much w i l l th e s e s e r v ic e s c o s t?
A n o m in a l c o s t o f US $0 .1 5 p e r page w i l l be ch a rg e d f o r p h o to c o p y in g , h a n d lin g , and s u r fa c e m a il. A ir m a il c o s ts w i l l be e x t r a . The p u b l i c a t i o n c o s t p e r manual w i l l v a r y a c c o rd in g t o th e boo k.
provide extension materials for small - scale fishermen and fish farmers in the region. For additional informa
tion, contact the Project Leader of SAFIS SEAFDEC Liaison Office
956 Rama IV Road
Olympia Building, 4th floor Bangkok 10500, Thailand
