Hu 1986 Aquacultural-Engineering

7/28/2019 Hu 1986 Aquacultural-Engineering

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Aquacultural Engineering 5 1.986)235-252

I n t r o d u c ti o n t o t h e D e s i g n o f C o a s t a l A q u a c u l tu r eS y s t e m s i n T a iw a nSing-Hwa H u

Taiwa n Fisheries Bureau. 8 , Sect ion l , Chu ng Hsiao E. Road . Taipei , Taiwan. RO C

A B S T R A C TThe t rad i t iona l cu l ture o f she l lf i sh in the coas ta l wa ters o f Ta iwan has along h is tory . The cu l tt tre area was l imi ted to the sandy b eaches o f thesou th an d sou thw es t coast. In the pas t decade , d ue to the shor tage o flan d resources an d water po l lu t ion , coas ta l wa ter aquaczd ture has beenex tended to in ter t ida l rock) ' a reas and the sub l i t tora l zone . Concre tep o n d s h a ve b een co n s t r u c ted o n t h e i n te r t id a l z o n e o f t he r o ck) ' co a s tspec if i ca l ly fo r cu l tur ing such spec ies as sm al l aba lone , Haliot is d iver-s ico lor super tex ta , grass shr imp , P e n a e u s m o n o d o n , g r o u p e r Ep in e -p h e lu s sp . e tc . FMz cul ture in ~7oat ing cages a nd oyster cul ture onJloat ing lon g-l ines an d rafts are a lso pract iced. This" pa pe r presentsdetai ls o f con struct io n designs, wi th ernphasis on ut i l iz ing w ater circu-la t ion, construct ion costs and wave resis tance. Some exarnples areselected to i l lustrate the lavoztts use d an d th e prob lerns faced.

I N T R O D U C T I O NIn Taiwan, t h e d e v e l o p m e n t s i n t h e f ie ld o f a q u a c u l t u r e d u r i n g t h e l as td e c a d e h a v e r e s u l t e d in a n i n c r e a s e o f a b o u t 1 0 0 % in a q u a c u l t u r ep r o d u c t i o n s in c e 1 9 7 5. C o n s i d e r a b l e a t t e n t i o n is n o w b e i n g p a i d t ot h e p o t e n t i a l u s e o f m a r i n e a n d c o a s t a l w a t e r f o r fi sh a n d s h e ll fi s hc u l t u r e ( C h e n , 1 9 7 7) . I n 1 9 8 3 , a q u a c u l t u r e p r o d u c t i o n in c o a s t a lw a t e rs w a s 1 0 0 2 0 8 t o n n e s w h i c h w a s 1 3 3 2 9 t o n n e s m o r e t h a n t h ep r o d u c t i o n i n 1 9 8 2 . T h i s c o n s i s t e d m a i n l y o f m i l k f i s h C h a n o s c h a n o s ,g r a s s s h r i m p P e n a e u s m o n o d o n , o y s t e r s C r a s s o s t r e a g i g a s , h a r d c l a mM e r e t r i x h t s o r i a , s e a - w e e d G r a c i l a r i a c o n f e r o i d e s , e t c . , s o m e g r e y

235Aquaczdtural Engineering 01 44 -86 09 /86 /S0 3.5 0 - Elsevier Applied SciencePublishers Ltd, England, 1986. Printed in Great Britain


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236 S.-H. Hum u l l e t M u g i l c ep h a l u s , s m a l l a b a l o n e Hal io t i s d iver s ico lor super tex ta ,c r a b Scylla serrata, s e a b r e a m S p a r i d a e a n d g r o u p e r E p i n e p h e l u s (L ia n d L i a o , 1 9 7 9 ) .

S e a f a r m i n g c a n b e c o n d u c t e d i n v a r io u s w a y s d e p e n d i n g o n t h et o p o g r a p h y o f t h e c o a s t a l l a n d , t h e c l i m a t e , s u b s o i l , w a t e r e x c h a n g ea n d t h e s p e c i e s t o b e c u l ti v a te d . B u i l d in g p o n d s f o r b r a c k i s h w a t e rs p e c i e s c u l tu r e o n t h e s h o r e s o r i n t e r t id a l z o n e s o f s o u t h w e s t T a i w a nh a s a l o n g h i s t o r y . C o n s t r u c t i o n o f f a c i l i t i e s c a n b e e i t h e r o n s h o r ew i t h p u m p i n g s y s t e m s u s e d t o g e t s e a w a t e r o r i n t h e i n t e r t i d a l z o n ew h e r e t h e t i d a l f l u x i s u s e d t o f i l l a n d d r a i n . T h e i n t e r t i d a l z o n e i st r a d i t io n a l l y u s e d f o r m o l l u s c c u l t u re . S h e l l f is h f a r m i n g i n t h e c o a s t a lw a t e r s o f T a i w a n is c o n f i n e d t o th e s o u t h a n d s o u t h w e s t c o a st s w h e r el a rg e s t r e tc h e s o f s a n d y b o t t o m a r e a v a il a b le ( K u o , 1 9 6 4 ). G e n e r a l l ys h e l l fi s h c u l t i v a t i o n s a r e e x t e n s i v e o r s e m i - e x t e n s i v e . N o f o o d is g i v e nt o c u l t u r e d o r g a n i s m s a n d v e r y l it tl e e q u i p m e n t is re q u i r e d . D u e t ol i m i t e d la n d a n d p o l l u t i o n p r o b l e m s o f c o a st a l w a t e rs i n T a i w a n , m a n ys e a f a r m s a r e n o w t u r n i n g t o o f f s h o r e s i t e s . T h e g e n e r a l c o n c e p t o fc o a s t al c u l t u r e h a s b e e n c h a n g e d . I n t e n s iv e o p e r a t i o n s h a v e b e e n t r i e di n th e i n t e r t i d a l z o n e a n d s u r f a c e w a t e r o f s u b l i t to r a l z o n e , u s in g t h e i ra d v a n t a g e s o f g o o d w a t e r c i rc u la t io n . S o m e o f t h e m h a v e b e e n s u c -c e s sf u l a n d s o m e a r e s ti ll u n d e r e x p e r i m e n t a t i o n .

T h e p u r p o s e o f th is p a p e r is t o p r e s e n t t h e d e s i g n o f c o a s ta l w a t e rc u l t u r e i n T a iw a n . F i g u r e s a r e g i v e n f o r s e l e c t e d sa m p l e s o f e a c h f a r m -i ng s ys te m . R e c e n t i n f o r m a t i o n o n t h e d e v e l o p m e n t o f co a st al f a rm i n gi n t h e i n t e r t i d a l z o n e a n d s u r f a c e w a t e r o f t h e s u b l i t t o r a l z o n e o fT a i w a n is d e t a i l e d .

P O N D C U L T U R E IN T H E I N T E R T I D A L Z O N EM a n y f i s h f a r m s h a v e b e e n c o n s t r u c t e d i n t h e i n t e r t i d a l z o n e f o r t h ec u l t u r e o f b r a c k i s h w a t e r f i s h e s . T h e m a j o r i t y o f t h o s e p o n d s w e r ec o n s t r u c t e d f r o m m u d a n d s o m e t i m e s c la y o n t h e in t e rt id a l m u d f la t sn e a r r i v e r m o u t h s . T h e c o s t o f c o n s t r u c t i n g p o n d s o n r o c k y s h o r e s ise x c e ss iv e . T h e s e a r e f e w in t e r t id a l c o n c r e t e p o n d s w h i c h h a v e b e e nb u il t. I t is o n l y r e c e n t l y t h a t p o n d c o n s t r u c t i o n i n t h e r o c k y a r e a s o ft h e i n t e r t i d a l z o n e s p e c i f i e d f o r c e r t a i n s p e c i e s , s u c h a s s m a l l a b a l o n e ,g r o u p e r , e tc ., h as b e e n t r i e d o n t h e n o r t h e a s t c o a s t o f T a i w a n a n d t h eP e s c a d o r e s ( P e n g h u I sl a n d ).


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The design of coastal aquaculture systems in Taiwan 237P o n d s w i t h n e t f e n c eI n th e b e g i n n in g , s i m p l e p o n d s e n c l o s e d b y a 1 - 1" 5 m c o n c r e t e b a s ew i t h a n e t f e n c e w e r e b u i l t o n t h e r o c k y a r e a s b e t w e e n h i g h t i d e a n dn e a p t id e l e ve l. T h e s e a w a t e r i s e x c h a n g e d f r e e ly t h r o u g h t h e n e tf e n c e a c c o r d i n g t o th e t i d a l m o v e m e n t . T h e w a t e r l e v el is m a i n t a i n e dby t he c onc r e t e ba s e a t l ow t i de . A s i m p l e s l u i c e ga t e i s s e t a t t he ba s et o w a r d t h e s e a d i r e c t i o n s o t h a t t h e p o n d c a n b e d r a i n e d f o r h a r v e s t -i n g o r c l e a n i n g a t l o w t id e . A l t h o u g h t h e s e p o n d s a r e o f s i m p l e d esig aaa t a m i n i m u m c o s t, f o r p o n d m a n a g e m e n t a n d p r e d a t o r c o n t r o l i tw o u l d b e b e t t e r t o h a v e s e p a r a t e i n le t a n d o u t l e t c h a n n e l s a n d a w a t e rc o n t r o l s y s t e m . I n 1 9 8 4 , a f i s h f a r m w a s c o n s t r u c t e d o n t h e r o c k ya r e a s o f th e i n t e r ti d a l z o n e i n t h e P e s c a d o r e s . T h e g e n e r a l l a y o u t a n dd e s i g n i s s h o w n i n F i g . 1 .

T h e 3 0 h a f a r m i s a c o m p l e x e s t a b l i s h m e n t i n c l u d i n g (i) p o n d s f o rv a r i o u s p u r p o s e s s u c h a s l i v e b a i t c u l t u r e , h a t c h e r y , n u r s e r y , c u l t u r ea n d h o l d i n g p o n d s ; (ii) a w a t e r c o n t r o l s y s t e m w i t h e m b a n k m e n t s ,

F i g. 1 . E l e v a t i o n a n d g e n e r a l l a y o u t o f a f is h fa r m i n t h e P e s c a d o r e s : A , c u l tu r a lp o n d ; B , fr y r e a r in g p o n d ; C , h a t c h e r y h o u s e .


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2 3 8 S.-H. H,~c a n a l s a n d s l u i c e s ; a n d < i ii ) o t h e r f a c i li t ie s . T h e t o ta l a r e a o f t h e f i s hc u l t u r e p o n d i s 8 h a a n d w a s b u i lt b e t w e e n - 0 . 5 m a n d + 0 . 5 m o f E L( e q u a l t o m e a n h i g h w a t e r l e ve l /. T h e p o n d s a r e e n c l o s e d b y c o n c r e t eb a s e s 5 0 c m h i g h a n d 4 0 c m w i d e i n t o w h i c h t h e n e t f e n c e s a r e f ir m l yd r iv e n . T h e f e n c e s a r e c o m p o s e d o f tw o l a y e rs o f p la s ti c m e s ha t t a c h e d to w o o d e n p o s t s. T h e d i s t a n c e b e t w e e n p o s t s is 3 m . B e a m sa b o u t 2 0 c m w i d e a r e f i x e d a t t h e t o p , m i d d l e a n d b o t t o m o f th ec o l u m n s t o s tr e n g t h e n t h e n e t f e n c e . T h e n e t f e n c e is 1"2 m h i g h a b o v et h e c o n c r e t e b a s e s o t ha t t h e t o ta l h e ig h t o f th e e m b a n k m e n t w i th t h en e t f e n c e i s 3-5 m a b o v e g r o u n d l e v e l. T h a t is e q u a l t o t h e h e i g h t o f t h em a x i m u m s p r i n g t i d e in th i s a re a (F i g . 2 ). T h e h e i g h t o f t h e p e r i m e t e rd i k e a n d t h e n e t f e n c e i s d e c i d e d b y t h e t i d a l d a t a a t t h e f a r m s i t e i no r d e r t o r e g u la t e w a t e r e x c h a n g e a t a m i n i m u m c o n s t r u c t i o n c o s t .W i t h i n th e p e r i m e t e r d i k e t h e r e a re 1 6 p o n d s , f r o m 0 "3 5 t o 0 . 7 0h e c t a r e s , a n d a 1 5 m w i d e w a t e r c a n a l d i v i d e s t h e p o n d s i n t o t w o

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The destgn o f coastal aq uacu lture systems in Taiwan 2 3 9p a r ts . T h e w a t e r g a t e s a r e i n s t a ll e d a t b o t h s i d e s o f t h e c a n a l f o r i n t a k eo f a n a d e q u a t e q u a n t i t y o f t i d a l f l o w a n d a l s o f o r t h e d i s c h a r g e o fw a t e r f r o m t h e p o n d s . T h e w a ll s b e t w e e n p o n d s a l s o c o n s i st o f ac o n c r e t e b a s e a n d n e t f e n c e . E a c h p o n d h a s t w o s l u ic e g a te s at th ec a n a l a n d s e a s i d e s f o r s e p a r a t e d r a i n a g e . T h e b o t t o m o f t h e p o n d i sa b o u t 0 . 2 - 0 . 6 m b e l o w g r o u n d le v el. T h e r e i s a ls o a d i t c h a b o u t - 1 mo f E L a l on g t h e p e r i m e t e r o f th e e m b a n k m e n t f o r d r a in a g e . In g en e r al .p o n d w a t e r is k e p t 0 " 8 - 1 ' 2 m a t l o w t id e a n d e x c h a n g e s f r e el y w h e nf l o o d w a t e r g o e s u p t o 0 .6 m o f E L .S e v e n 3 0 0 m 2 n u r s e r y p o n d s a r e b u i lt a t t h e sit e b e ~ v e e n 0 m a n d+ 0 -5 m , a ls o c o n s i s t in g o f c o n c r e t e w a ll s a n d n e t f e n c e s . T h e h a t c h -e r y p o n d s o f 8 m x 4 m x 2 m a r e se t in a h a t c h e r y h o u s e f o r f is hb r e e d i n g a n d l a r v a r e ar i n g . T h e l iv e b a i t p o n d c o n s i s ts o f a n a lg a ep o n d a n d a z o o p l a n k t o n p o n d in a l a d d e r c o n s t r u c ti o n . S e a w a t e r isp u m p e d u p t o t h e al g a e p o n d f o r a l g ae b l o o m t h e n a lg a e w a t e r is s e n tto th e z o o p l a n k t o n p o n d a t t h e s e c o n d l e v e l t h r o u g h t h e p i p e s b yg r a v it y a n d z o o p l a n k t o n is c o l l e c t e d a t b o t t o m o f th e p o n d ( Fig . 3).

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240 S.-H. HuC u l t u r e o f s m a l l a b a l o n e

S m a l l a b a l o n e Haliotis diversicolor supertexta i s one o f t he s he l l f i s hs p e c i e s w h i c h h a v e b e e n e x p l o i t e d i n s h a l l o w r o c k y a r e a s . T h e s i t es e l e c t i o n s o f a s m a l l a b a l o n e f a r m a r e ( i) c l e a r s e a w a t e r w i t h o u t p o l l u -t i o n a n d f r e s h w a t e r d i l u t i o n ; (ii) r o c k y s u b s t r a t e w i t h o u t d r if t in g s a n da n d m u d ; a n d ( i i i ) g o o d w a t e r c i r c u l a t i o n t o s u p p l y e n o u g h o x y g e n( T z en g , 1 9 7 7 ; L i a o , 1 9 7 9 ) . A r t if ic i a l b r e e d i n g a n d s e e d c u l t u r e o fs m a l l a b a l o n e s h a s b e e n c a r r i e d o u t i n m a n y p l a c e s in T a i w a n. T h en e w t ec h n i q u e s a n d e q u i p m e n t h av e p r o d u c e d a b a l o n e s e ed c o m m e r -c ia U y ( C h e n a n d Y a n g , 1 9 7 9 ) . D u e t o t h e h i g h p r i c e o f s m a ll a b a lo n e s ,c o n c r e t e p o n d s a re e m p l o y e d f o r ea sy m a n a g e m e n t a n d l on g d u ra t i on .T h e p o n d s a r e b u i l t i n t h e i n t e r t i d a l z o n e w i t h l i t t l e t i d a l r a n g e . T h el a y o u t o f s m a l l a b a l o n e f a r m s v a r i e s f r o m p l a c e t o p l a c e , t a k i n ga d v a n t a g e o f t h e t o p o g r a p h i c a l f e a t u r e s o f t h e s i t e , b u t t h e g e n e r a ls c h e m e i s t h e s a m e . T h e g e n e r a l l a y o u t o f a s m a l l a b a l o n e p o n d i nT a i w a n i s s h o w n i n F i g . 4 . I d e a l l y , t h e p o n d i s r e c t a n g u l a r i n s h a p e ,1 5 0 - 2 5 0 m 2 i n ar ea , a n d is d i v id e d i n to s ix o r m o r e p o n d s . T h e p o n dis d i v i d e d b y 3 0 c m h i g h b r i c k s w i t h 1 0 c m d i a m e t e r P V C p i p e s a t t h eb o t t o m f o r w a t e r e x c h a n g e . W a t e r is a d m i t t e d b y m e a n s o f a s e ri e s o fP V C p i p e s t h r o u g h t h e p o n d w a ll s c o n n e c t i n g th e m t o th e w a t e r i n le tc a na l. T h e w a t e r i nl et c a n a l a r o u n d t h re e s id e s o f t h e p o n d i s a b o u t1 . 2 -1 . 5 m w i d e a n d 3 0 c m d e e p e r t h a n t h e r e a r i n g p o n d t o f a ci li ta t ed r a i n a g e . E x c h a n g e o f p o n d w a t e r i s e f f e c t e d b y t h e r i se a n d f all o f t h et i d e s t h r o u g h t h e s l u i c e g a t e a t e i t h e r s i d e o f t h e o p e n m o u t h o f t h ec a n a l . T h e s l u i c e g a t e i s s u r r o u n d e d b y a s c r e e n o n t h e i n s i d e t op r e v e n t t h e i n t r u s i o n o f p r e d a t o r y a n i m a l s . T h e c o n c r e t e w a l l o f t h ep o n d is 3 m h i g h a n d is p e n e t r a t e d b y 8 c m d i a m e t e r P V C p i p e s a t1 m a n d 1.7 m a b o v e t h e b o t t o m . T h e d i s t a n c e b e t w e e n t h e p i p e s is1"5 m . F r o m t h o s e p i p e s, s e a w a t e r is e x c h a n g e d b e t w e e n t h e w a t e ri n le t c a n a l a n d t h e r e a r in g p o n d s . U s u a ll y , t h e p o n d w a t e r d e p t h m a i n -t a i n e d i s a t l e a s t 1 m t o a v o i d h i g h t e m p e r a t u r e s i n s u m m e r . A s m a l lt a n k , 2 0 - 3 0 c m d e e p e r t h a n t h e c a n a l , i s b u i l t a t t h e c o r n e r o f t h ec a n a l f o r p u m p i n g w a t e r o u t . I n th e r e a r i n g p o n d , s to n e s a b o u t 1 0 c m 3o r m o r e a r e l a i d o n t h e b o t t o m f o r a b a l o n e s t o a d h e r e t o . R e i n f o r c e di r o n i s p u t i n t o t h e p o n d t o f i x t h e s t o n e s o n t h e b o t t o m s o t h a t t h es t o n e s w il l n o t b e d i s t u r b e d d u r i n g t h e t y p h o o n s e a s o n .I n s m a l l a b a l o n e c u l t u r e , t h e s t o c k i n g d e n s i t y o f 1-5 c m s e e d s i sa b o u t 2 0 - 3 0 s e e d s p e r sq u a r e m e t er . Gracilaria i s u s e d t o f e e d t h e


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8/18

. 4 = S.-H. Hua b a l o n e , w i t h a c o n v e r s i o n r a t e o f 1 5" 1. A f t e r sLx m o n t h s o f c u l ti v a -t io n , t h e a b a l o n e s r e a c h m a r k e t a b l e s i z e a n d a r e r e a d y f o r h a rv e s t.Intertidal underground pondsU n d e r g r o u n d p o n d s i n t h e i n te r ti d a l z o n e a r e a s p ec i al m e t h o d u s e df o r f is h c u l t u re i n t h e P e s c a d o r e s o f T a i w a n. T h e u n d e r g r o u n d p o n d ise x c a v a t e d i n t h e i n t e r t i d a l z o n e , a l l o w i n g t h e f l o o d t i d e t o c h a n g e t h es e a w a t e r a n d u s i n g th e e b b t id e t o fe e d t h e fis h. T h e p o n d s it e s h o u l di d e al ly b e s u c h t h a t t h e p o n d c a n b e f e d e v e r y d a y a n d b e c o v e r e d b yf l o o d w a t e r a s e a r l y a s p o s s i b l e . T h e s t r u c t u r a l c h a r a c t e r i s t i c s a n dt e x tu r a l g r a d e o f t h e s o il d e t e r m i n e t h e b e a r i n g c a p a c i ty o f th e f o u n d a -t i o n a n d t h e s ta b i l it y o f t h e w a l ls a n d a l so a f f e c t t h e c o s t o f p o n d c o n -s tr u c ti o n . S o ft p o r o u s m a t e r i a ls a r e t o b e a v o i d e d , b e c a u s e t h e w a v ea c t i o n a n d w i n d f o r c e w i l l e r o d e a n d c o l l a p s e t h e w a l l s o f t h e p o n d .R o c k s h o u l d e x t e n d f r o m t h e t o p o f th e p o n d w a ll t o th e b o t t o m f o rp r o t e c t i o n if t h e s u b s t r a t e is n o t s u i t a b le .

U s u a l ly a n u n d e r g r o u n d p o n d is 1 0 m l on g , 5 m w i d e a n d 2 md e e p . A s m a l l c o n c r e t e s u r f a c e w h i c h is 30 c m w i d e a n d 2 0 c m a b o v et h e g r o u n d is b u i l t a l o n g t h e t o p o f th e p o n d w a ll . T i m b e r b a t t e n s a r ef i x e d o n t h e c o n c r e t e s u r f a c e s o t h a t n y l o n n e t c a n b e f a s t e n e d a n dc o v e r t h e s u r f a c e o f t h e p o n d t o p r e v e n t f i s h f r o m e s c a p i n g ( F i g . 5 ) .T h e r e is n o w a t e r g a te o r d r a i n a g e p i p e i n t h e p o n d . T h e w a t e r s u p p l yis e n t i r e l y f r o m t h e p o n d s u r f a c e . P o n d s i z e is li m i t e d , b e c a u s e h a r v e s t -in g is c a r r i e d o u t b y p u m p i n g w a t e r o u t o f t h e p o n d a t l ow t id e .

Fig . 5 . P rof il e o f i n t e r ti da l und ergro und pond .


9/18

T h e d e s i g n o f c o a s t a l a q u a c u l t u r e s v s ; e m s i n T a i w a n ~ ;

T h e c o s t o f u n d e r g r o u n d p o n d c o n s t r u c t i o n a n d m a i n t e n a n c e isv e r y lo w . I t h a s l it tle w a t e r t e m p e r a t u r e f l u c t u a ti o n c o m p a r e d t o p o n d sa b o v e g r o u n d . B e c a u s e t h e p o n d i s u n d e r g r o u n d t h e d a m a g e s f r o mw i n d f o r c e a n d w a v e a c ti o n c a n b e a v o i d e d .

M a r i n e f o u l i n g s o f v a r i o u s t y p e s a r e u s u a l ly a s e r i o u s p r o b l e m i nn e t t in g o f t h e m a r i n e c a g e s a n d e n c l o s u r e s . B u t t h e c o s t o f m a i n -t e n a n c e w a s r e d u c e d to a m i n i m u m b e c a u s e le ss m a r i n e f o u li n g w a sf o u n d o n n e t s a n d it w a s v e r y c o n v e n i e n t t o c le a n t h em

B e c a u s e t h e w a t e r i n th e p o n d is u n c h a n g e d a t lo w t id e , t h e o x y g e nc o n t e n t o f t h e p o n d w a t e r i s c o n s u m e d r a p i d l y . F r o m T s a i a n d H u( 1 9 8 2 ), i n a n u n d e r g r o u n d p o n d l 0 m l o n g . 5 m w i d e a n d 2 m d e e ps t o c k e d w i th 8 0 0 g r o u p e r s , t h e o x y g e n c o n t e n t w ill d e c r e a s e f r o m7 5 p p m t o 2 -5 p p m i n 6 h . B u t w h e n t h e f lo o d w a t e r c o m e s , t h eo x y g e n o f p o n d w a t e r w i ll g o u p t o th e n o r m a l c o n t e n t (F i g . 6 ).

T h e c u l t u r e d s p e c i e s a n d d e n s i ty r a t es a r e h i g h ly i m p o r t a n t inu n d e r g r o u n d c u ltu r e. G r o u p e r salrnonoides i s a su i t ab l e spec i e s fo r i t sh i g h e c o n o m i c v a l u e a n d i n a c t i v e h a b i t s . S t o c k d e n s i t y i s l i m i t e d t o

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g r o u n d p o n d , i n w i n t e r (a ) a n d s u m m e r (b ).


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244 S.-H. Hu

5-15 individuals m- 3 depending on the site of the pond. In addition tooxygen deficiency, there are also some problems in the culture such assediment introduced into the pond by wave action, and limited timefor harvesting. Not all of the intertidal underground ponds weresuccessful, some having failed due to the poor site of muddy, sandysubstrate or because of limited water exchange.

FLOATING FARMING IN THE SUBLITTORAL A REAFloating farming in sublittoral zones include fish culture in floatingcages and oyster culture in floating long lines and rafts. The floatingtechniques permit optimal culture environment with minimal capitalcosts. Although floating techniques for sea farming have been deve-loped in many countries for years, design and construction mightdiffer because of environmental condi tions and lifestyle of the people.In the coastal waters of Taiwan there is no well sheltered placeprotected from both typhoons in the summer and strong monsoons inthe winter. The floating system should be designed with attention toresisting wind and wave action.Oyster cultureThe general culture season for oyster farming is from February toSeptember. It is not only because the spat collecting period is mainly inthe winter, but also because the strong monsoon which comes fromOctober will wipe out the oysters if they are not harvested in time.Oysters cultured for the Taiwan market will reach a favorable size(about 5 g of meat weight) in 4-5 months (Lin and Tang, 1980; Huand Sheu, 1982a).Long-line cultureThe long-line system consists of horizontal lines near the watersurface from which strings of seed oysters are suspended. The hori-zontal lines are attached to a series of floats and the end of each line isanchored by a 60 kg anchor. Usually each set is 50-60 m long with 10floats arranged in rows. Four main parallel polyester ropes, 3 cm indiameter, are fastened on the floats at a distance of about 20 cm apart.About 500 strings of oysters, each string about 4-5 m long with 20


11/18

-4_he des ign o f coas ta l aqu acu l ture s~ 's tems in Taiwan ~c u l t c h e s o n i t , a r e h u n g f r o m t h e p a r a l l e l r o p e s . S t r i n g s a r e h u n g2 0 c m a p a r t . I n it ia l ly , o i l d r u m s c o a t e d b y p i t c h w e r e u s e d f o r fl o a ta -t i on . T h e o il d r u m s n e e d e d c o n t i n u o u s m a i n t e n a n c e a n d r e p l a c e m e n t ,h a v i n g a li fe o f a b o u t 1 - 2 y e a r s. S t y r o f o a m b o x e s a n d b a l ls a n d f ib e r -g l a s s d r u m s u s e d f o r f l o a t a t i o n a r e s t r o n g e r a n d l a s t l o n g e r . F r o m a ne c o n o m i c s ta n d p o i n t f lo a ts m a d e b y s t y ro f o a m b l o ck s c o v e r e d w i thc a n v a s o r u s e d - t ir e r u b b e r a r e 5 0 % c h e a p e r t h a n o t h e r t y pe s.

I n t h e b e g i n n i n g , fo u r p a r a l l e l m a i n r o p e s f o r h a n g i n g st ri n g s w e r ef a s t e n e d o n t h e f lo a ts . It w a s f o u n d t h a t i n c r e a s i n g t h e d i s t a n c eb e t w e e n t w o f lo a ts a n d u s in g t w o p a r a l le l r o p e s i n s te a d o f f o u r w o u l dr e d u c e l o s s i n r o u g h s e a s , w i t h o u t h a v i n g t o i n c r e a s e f l o a t a t io n e q u i p -m e n t . S t r i n g s n e a r t h e f l o a t s w e r e b r o k e n e a s i l y b y c o n t i n u o u s s t r a i nf r o m w a v e a n d w i n d . T h e s m a l l m o d i f i c a t i o n o f s tr in g s h u n g o n n e wr o p e i n s te a d o f d i r e c t ly o n p a r a ll e l r o p e s c a n a v o i d d i r e c t f o r c e o n t h es t r in g (Fig. 7).

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(b)F i g . 7 . L o n g - l i n e o y s t e r c u l t u r e (a ) a n d m o d i f i c a t i o n ( b ).


12/18

246 S.-H. Hu

Hu and Sheu (1982b) found that by rotating culture of oysters, acombination of long-line (or raft) and harden seeds process, theycould use the space and floating equipment efficiently. Oysters arecultured by floating farming from February to July whereas the hard-erring seeds in shallow water can grow to 4 cm of shell height at sametime. The hardened seeds are transplanted to the floating equipmentfor when the oysters are marketed and can be harvested in 40 days.The third rotation, from September to October, after the oysters aremoved from shallow water to the floating equipment, allows them togrow to 4.6 cm of shell height before the monsoon comes. The growthof rotating culture of oysters is shown in Fig. 8.Oyster drill P urp ura clavigers caused heavy losses in bamboo stickand horizontal hanging oyster farming methods on the west coast ofTaiwan (Kuo, 1964). In the long-line method, predation of oysterleeches caused as high as 25% mortality in some places (Lin and Tang,1980). Changing the culture period from January to July to avoid theabundant season of leeches was operated. Bio-fouling is a seriousproblem in oyster culture. The shells are attractive areas for manyspecies of algae, barnacles, mussels and other organisms. Some

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M o n t hF i g . 8 . G r o s s t h o f o y s t e rs b y r o t a t in g c u l t u r e ; o ; lo n g - l i n c c u l t u r e , e : s ee d h a r d e n i n gi n t h e i n t e r t id a l z o n e .


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The design o f coasta l aquacu l ture sys tems in Ta iwan 247f a r m e r s p u t o y s t e r s o n a r a f t f o r d i r e c t e x p o s u r e t o s u n l i g h t f o r 8 h i nt h e s e c o n d o r t h i r d m o n t h o f c u l tu r e t o g et r id o f f o ul in g s a n d l e ec h e s .Ra ft cul tureT h e f l o a t i n g r a f t s u s e d f o r o y s t e r c u l t u r e i n T a i w a n a r e u s u a l l y1 0 m x 1 2 m ( 1 0 m l o n g . 6 0 b a m b o o p o l e s : 1 2 m l o n g , 1 5 b a m b o op o l e s ) w i t h f l o a ts u n d e r t h e ra f t, w i t h 8 0 0 - 1 0 0 0 s tr i n g s o f o y s t e r sh u n g o n e a c h r a f t . B a m b o o p o l e s o f 1 0 - 1 5 c m i n d i a m e t e r a r e u s e d ,t h e d i s ta n c e s b e t w e e n t w o p o l e s b e i n g a b o u t 1 5 c m a n d 6 0 c m . S o m e -t im e s p l a s ti c t u b e s w i t h s t y r o f o a m i n s id e a r e u s e d i n s te a d o f b a m b o op o l e s . B u o y a n c y o f t h e r a f t i s f r o m b a m b o o p o l e s a n d f l o a t s b u t e x t r af lo a t s a r e a d d e d a t t h e e n d o f t h e c u l t u r a l s e a s o n w h e n t h e o y s t e r s a r eg e t ti n g b ig g e r. T h e r a ft s a r e g e n e r a l l y b r o u g h t i n s h o r e i n t h e w i n t e r f o rm a i n t e n a n c e . T h e lif e o f a b a m b o o p o l e i s a b o u t t w o y ea r s. A 6 0 k ga nc ho r a t e i t he r s i de o f t he r a f t i s u s e d t o f i x t he r a f t i n pos i t i on .C u l t u r e a n d g r o w t h o f o y s te r s b y th e r a ft m e t h o d a r e t h e s a m e a s inl o n g - l in e o y s t e r c u l t u r e .Subm ers ib le cu#ureS u b m e r s i b l e c u l t u r e o f o y s t e r s b y r a f t a n d l o n g - l i n e m e t h o d s is u s e d i nm a n y p l a ce s i n T a i w a n c o a s t al w a te r s. O y s t e r f a r m i n g b y s u b m e r s i b l ec u l t u r e r e q u i r es a r e a s w h e r e w a t e r d e p t h is m o r e t h a n 10 m in o r d e rt o m a i n t a i n a sa f e d i s t a n c e o f f th e s e a b o t t o m .

I n t h e l o n g - l i n e s u b m e r s i b l e o y s t e r c u l tu r e , t h e o y s t e rs a r e h u n g 2 mu n d e r t h e w a t e r s u r f ac e . T h e m a i n p a r a ll e l r o p e s s in k d o w n t o 2 m b yf a s te n i n g r o p e s t o t h e s u r f a c e f l o a ts . T h e f lo a t s a r e m a d e o f p l a st icb a ll s fi ll ed w i t h s ty r o f o a m . E a c h f l o a ti n g b a ll h a s a b u o y a n c y o f 4 5 k g .T h e o y s t e r s t r i n g s a r e s u s p e n d e d i n s e a w a t e r d u r i n g t h e c u l t u r a lp e r i o d , b u t a r e l if te d t o t h e s u r f a c e f o r h a n g i n g s e e d s a n d h a r v e s t i n g( F ig . 9). T h e a v e r a g e w e i g h t o f a s t ri n g o f o y s t e r s a t h a r v e s t i n g is a b o u t2 0 k g . E a c h f l o a t b a l l c a n m a i n t a i n e i g h t s t r i n g s o f o y s t e r s s u s p e n d e di n s e a w a t er . S u b m e r s i b l e o y s t e r c u l t u r e b y t h e r af t m e t h o d is t h e s a m ea s i n s ubm e r s i b l e l ong - l i ne . A r a f t ne e ds 20 f l oa t ba l l s t o ke e p t he r a f th u n g f r o m t h e w a t e r s u r f a c e w i t h o u t s in k i ng . T h e r e is n o d i f f e r e n c e ino y s t e r g r o w t h r a t e b e t w e e n t h e f l o a t i n g a n d t h e s u b m e r s i b l e s y s t e m s ,b u t i t i s o b v i o u s t h a t s u b m e r s i b l e o y s t e r c u l t u r e h a s l e s s l o s s a f t e rt y p h o o n o r s t r o n g w a v e ac t io n . I n s u b m e r s i b l e o y s t e r c u l tu r e , c o n s t a n te x a m i n a t i o n o f f lo a ts a n d r o p e s is n e c e s s a r y t o e n s u r e t h a t b u o y a n c y iss u f f ic i e n t t o k e e p t h e o y s t e r s s u s p e n d e d i n t h e d e s i r a b l e p l a c e . I f f lo a t


14/18

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F ig . 9 . S u b m e rs ib l e l o n g - l i n e o y s t e r c u l tu r e : t o p v i e w ( a) , p ro f i l e ( b) a n d a t h a rv e s t -i n g ( c ) .

balls are found sinking into the water, extra floats should be added toincrease buoyancy (Tsao, 1984).The submersible cultural systems have permitted the extension ofoyster culture seaward where traditionally no farming was triedbefore.C a g e c u l tu r eThe technique of farming marine fishes in floating cages in Taiwan hasbeen practiced for eight years. Fishes cultured are mainly Sparidae ofthe species Chrysopho's major, Acanthopagrus schlegeli and Lutjanusrusselli, and groupers of~the species Epinepheh~s salmono ides, andPlectropornus m aculatum (Yen and Yen, 1984). The number of fishstocked in each cage depends on the species cultured, the size of thecage, and the practice of the owner. Usually the fry are reared and


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The design of coastal aquaculture systems in Tai~an 249t r a i n e d i n p o n d s b e f o r e t h e y a r e t r a n s f e r r e d t o ca g e s. D i c e d t ra s h fis ha n d a r t if ic i al d i et s a r e u s e d t o f e e d fi sh e s . T h e f e e d i n g r a te d e p e n d s o nc l i m a t e , w a t e r t e m p e r a t u r e a n d c o s t o f t r a s h fis h.

A l t h o u g h c a g e s v a r y i n s iz e , t h o s e m e a s u r i n g 5 m x 5 m x 4 m a r eo f t e n u s e d a n d 2 - 4 c a g es a r e li n k e d t o g e t h e r to f o r m a u n it . E a c h u n i th a s t w o a n c h o r s w e i g h i n g 6 0 k g a t e a c h s i d e t o k e e p t h e c a g e i n p o s i -t io n . O r i g in a ll y n y l o n b a g n e ts w e r e s u s p e n d e d f r o m b a m b o o f r am e -w o r k s w h i c h w e r e c o n s t r u c t e d b y 4 - 5 b a m b o o p o le s o f 1 5 c m ind i a m e t e r f a s te n e d i n r o w s a n d r e i n f o r c e d w i t h b e a m s . T h i s b a m b o op o n t o o n w a s a c o m b i n a t i o n o f f r a m e w o r k a n d f lo a t un it . T h e n e c es -s i t y f o r c o n t i n u o u s r e p l a c e m e n t o f t h e b a m b o o p o l e s d u e t o t h e i rd e t e r i o r a t i o n i n s e a w a t e r h as c a u s e d c o n c e r n . T h e r e a r e n o e x te r n a ls y m p t o m s o f a s p o i l e d b a m b o o p o l e , a n d it is t o o l a te to r e p l a c e t h e mw h e n t h e c a g e i s b r o k e n . S o m e f a r m e r s h a v e b e g u n t o u s e P V C p i p e sf i l l e d w i t h s t y r o f o a m f o r t h e i r f l o a t i n g c a g e s . T h i s f r a m e w o r k c a n l a s t_ - ~ y e a r s w h i le b a m b o o p o l e s c o u l d o n l y s u rv i v e 1 -'~ y e a rs . T h e P V Cp i p e f i l l e d w i t h s t y r o f o a m n o t o n l y h a s l o n g e r l i f e b u t h a s b e t t e rb u o y a n c y a n d i s e a s i e r t o m a i n t a i n . T h e s u s p e n d e d c a g e n e t i s c o m -p o s e d o f fiv e p i e c e s o f n y l o n n e t. T h e b o t t o m n e ts a r e r e i n f o r c e d a n dw e i g h t e d b y a 2 c m d i a m e t e r r o p e s t r u n g w i t h l e a d w e i g h t s , 2 0 g e a c h ,a t t h e s e a m e d g e o f t h e n e t . U s u a l l y a s i n g l e b a g i s s u s p e n d e d u n d e rt h e f r a m e w o r k . A c o v e r n e t w h i c h is 30 c m a b o v e s e a s u r f a ce is u s e do n t h e f l o a ti n g c a g e t o p r e v e n t f is h e s c a p e a n d i n v a s i o n o f b i rd s . I n1 9 7 9 , f l o a t i n g c a g e s i n t h e f o r m o f c i r c u l a r g a l v a n i z e d s t e e l c o l l a r sw i t h m e t a l b a g n e t s s u p p o r t e d b y p o l y d r u m s w e r e i n t r o d u c e d f r o mJ a p a n . T h e g a l v a n i z e d s t e e l c o l l a r i s i n i t i a l l y m o r e e x p e n s i v e b u t i ss t r o n g e r a n d h a s a l o n g e r life t h a n t h e b a m b o o a n d P V C p ip e s. T h em e t a l n e t s a r e c o n s i d e r a b l y m o r e s t a b l e i n s e a w a t e r a n d r e q u i r e l e s sc l e a n i n g . T h e m e t a l n e t is a fl e x ib l e c h a i n l i n k w i r e w h i c h c a n b e f o l d e df o r t r a n s po r t a t i on , bu t i t i s ve r y d i f f i c u l t t o r a i s e a t ha r ve s t i ng . T hen y l o n n .e t w a s t h e r e f o r e p r e f e r r e d b y f a r m e r s a s i t c a n b e h a u l e d b yh a n d a n d h a r v e s t e d e a si ly . P l a s t ic m e s h h a s its a d v a n t a g e s , b e i n g in t e r -m e d i a t e b e t w e e n t h a t o f n e t t i n g a n d m e t a l m e s h . A f i b e rg l a ss f lo a t in gs u r f a c e s t r u c t u r e w i th a w o o d e n f r a m e w o r k w i th s ty r o f o a m i n si d e a n dc o v e r e d b y l a y e r s o f fi b e rg l a ss w a s t r i e d . W o o d p l a t e a n d f ib e r g la s sl a y e r s r e i n f o r c e t h e s t r u c t u r e a n d p r e v e n t w a t e r s e e p i n g i n t o t h e f l o a t -i n g fr a m e . T h e f i b er g l a ss f l o a t in g s u r f a c e a l s o a c ts a s a c a t w a l k d u r i n go p e r a t i o n s . T h e f ib e r gl as s f r a m e w o r k h a s t h e a d v a n t a g e o f lo n g e r lifea n d is e a s y to m a i n t a i n ( H u , 1 9 8 0 ) .


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250 S.-H. Hu

A n c h o r r o p e s t h a t w e r e l a s h e d d i r e c t l y t o t h e c a g e s h a v e c a u s e dh e a v y d a m a g e t o t h e f r a m e w o r k b y w a v e a c t i o n a n d w i n d f o r c e . Am o o r i n g b u o y is th e r e f o r e se t b e t w e e n a n c h o r a n d c ag e . T h e r o p ef r o m t h e c a g e is f a s t e n e d t o m o o r i n g b u o y s r a t h e r t h a n d i r e c tl y to t h ea n c h o r . T h e s tr a in f r o m w a v e a c t i o n w i ll b e c u s h i o n e d b y t h e m o o r i n gb u o y s i n s t e a d o f b e i n g t r a n s m i t t e d t o th e c a g e f r a m e w o r k d i r ec tl y .

O n e o f t h e b i g ge st p r o b l e m s e n c o u n t e r e d b y f is h f a rm e r s w h o u s e dt h e m a r i n e e n v i r o n m e n t fo r c a g e c u l t u r e w a s t h a t o f n e t fo u l in g b ya l g a e a n d m u s s e l s ( M i l n e , 1 9 7 6 ) . F o u l i n g a n d m u s s e l s m a k e t h e n e th e a v ie r , i n c r e a se s t h e d r a g s i n c u r r e n t s a n d p r e v e n t s t h e e x c h a n g e o fw a t e r . T h e n e t s a r e r e p l a c e d 2 - 3 t i m e s a y e a r . N e t s a r e d r i e d a n ds c r u b b e d o n l a n d a n d r e u s e d a g a in . A b i o lo g i c a l m e t h o d o f c o n t ro l l in gf o u li n g o f th e c a g e n e t i s r e c o m m e n d e d b y p u t ti n g d o c t o r f is h Siganusfitscescens, r u d d e r f is h Girella punctata, m u l l e t M ugil cephalus, etc. , incages .

G e n e r a l l y t h e p r o d u c t s o f fl o a ti n g c a g e s a re S p a r i d a e1 5 - 2 0 k g m - 3 a n d g r o u p e r Epinephelus 8 - 1 5 k g m - 3.

C O N C L U S I O NI n T a i w a n , m a n y s e a f a r m s h a v e b e e n s e l e c t e d t o u t il iz e t h e c o a s t a lw a t e r s o f t h e s h o r e . I n g e n e r a l , c o n c r e t e p o n d s w i t h n e c e s s a r y f a c i l i -ti es f o r w a t e r c i r c u la t i o n a n d r e p l e n i s h m e n t h a v e b e e n c o n s t r u c t e d o nt h e s h o r e f o r i n t e n s i v e c u l t u r e o f s h ri m p s o r f o r p r o d u c t i o n o f s e e d s o fm a r i n e s p ec i es . C o n c r e t e p o n d s f o r s h r i m p o r s e e d c u l t u r e a r e lo c a t e do n t h e s h o r e n o t o n l y b e c a u s e t h e a n i m a l s n e e d t o b e m a i n t a i n e d i nw a t e r o f g o o d q u a l i t y b u t a ls o a c o n t i n u o u s f r e s h w a t e r s u p p l y is n e c e s -s a ry f o r s o m e c u l t u r a l s p e c i e s o r t h e i r li v e b a it s. E a r t h e n p o n d s o n t h es h o r e a r e c o m m o n l y u s e d f o r e x t e n s i v e c u l tu r e o f s h el lf is h e s, m il k fi sh ,s h r i m p , Gracilaria or po l yc u l t u r e ( T ang , 197 6 ; C he r t , 197 7 ).

O n m a n y s it e s a l o n g t h e w e s t c o a s t o f T a i w a n , a c t i v it ie s a r e r e-s t ri c t e d t o f a r m i n g o f s h e l lf i sh e s o n t h e s a n d y b e a c h e s o f t h e i n t e r t i d a lz o n e , e i th e r by s o w i n g s e e d s o n t h e b o t t o m o r b y h a n ~ n g o u t s tr in g so n t h e f a r m i n g p a r k s. T h e o r i g in a l m e t h o d s o f o y s t e r c u l tu r e c o n s i s t e do f d r i v in g b a m b o o s ti ck s in t o t h e b o t t o m a n d h a n g i n g st ri ng s h o r i z o n -t al ly w i t h i n th e i n t e r t i d a l z o n e . B u t c u l tu r a l a r e a s w i t h a c c u m u l a t i o n o fs e d i m e n t s a r o u n d t h e b a m b o o s t i c k s w e r e r e g a r d e d a s u n s u i t a b l e f o ro y s t e r c u l t u r e a n d t h is m e t h o d h a s d i m i n i s h e d i n i m p o r t a n c e . It is v e r y


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The design of coastal aquaculture O'stems in Taiwan 251d i f f i c u l t t o o b t a i n a d e q u a t e s p a c e f o r o y s t e r f a r m i n g . U n t i l 1 9 7 5 f l o a t -i n g h a n g i n g o y s t e r s o n r a f t s o r l o n g - l i n e s p r o d u c e d e x c e l l e n t r e s u l t s ,w h e n t h e o y s t e r c u l t u r e s w e r e m o v e d t o t h e w a t e r o f th e s u b l it to r a lz o n e. T h e t e c h n i q u e s a n d m a t e r ia ls h a v e b e e n i m p r o v e d , a n d p r o d u c -t io n o f o y s t e r m e a t i n c r e a s e d fr o m 1 3 8 5 0 t o n n e s in 1 9 7 5 to 2 5 9 5 0t o n n e s in 1 9 8 3 . O n t h e n o r t h e a s t c o a s t o f T a i w a n , c o n c r e t e p o n d c o n -s t r u c t i o n o n t h e r o c k y t i d a l z o n e f o r s m a l l a b a l o n e c u l t u r e h a s b e e nd e v e l o p e d f o r s i x y e a r s . B e c a u s e p o n d c o n s t r u c t i o n h a s r u i n e d t h en a t u r a l s c e n e r y i n t h a t a r e a , a l m o s t a l l t h e a b a l o n e f a r m s w e r e c l o s e da n d n o m o r e p o n d s w e r e a l l o w e d t o b e b u i l t o n t h e n o r t h e a s t c o a s t .T h e p r o d u c t i o n o f a b a l o n e s w a s 4 9 8 t o n n e s in 1 9 8 1 a n d d e c r e a s e d to2 2 1 t o n n e s i n 1 9 8 3 . A t p r e s e n t , s m a l l a b a l o n e h a s b e c o m e a m a j o rs p e c i e s r e l e a s e d i n t o p r o t e c t e d s e a a r e a s f o r r e s o u r c e s u p p l e m e n t i nT a i w a n . T h e f l o a ti n g c a g e s a r e o f s m a l l s iz e s a n d s t r o n g f r a m e s m a i n l yb e c a u s e o f t h e ty p h o o n a n d m o n s o o n s e a s o n s i n T a i w a n . S o fa r o n l y af e w f a r m e r s o p e r a t e f l o a t i n g c a g e s i n t h e c o a s t a l a r e a s o f t h eP e s c a d o r e s .

L i m i t a t io n s i n t h e u s e o f th e a r e a b e y o n d t h e m e a n h ig h w a t e r l ev e la t n e a p t id e f o r p o n d c o n s t r u c t i o n a r e a s s o c i a te d w i t h te c h n i q u e d if fi-c u lt ie s a n d c o s t o f c o n s t r u c t i o n o f p o n d s o n s a n d y a n d r o c k y a r e as .U n l e s s t h e r e is a si g n i f ic a n t b r e a k t h r o u g h i n t e c h n o l o g y o f ti d al l a n df a r m i n g d e v e l o p m e n t , t r a d i t io n a l s h e l lf is h f a r m i n g a n d m i n i s c a le c o n -c r e t e p o n d s f o r h i g h - v a lu e m a r i n e s p e c i e s w ill c o n t i n u e t o b e o p e r a t e din t h e n e a r f u t u r e a s t h e a d v a n t a g e s o f fl o a ti n g t e c h n i q u e s a n d d e v e -l o p m e n t o f n e w t e c h n i q u e s o f fl o a t in g c a g e s a n d r a ft s r e v e a l t h e p o t e n -ti al o f s e a f a r m i ng .W a v e a c t i o n d a m a g e t o c u l t u r e s y s t e m s , i n t e r f e r e n c e w i t h m a n a g e -m e n t , m a i n t e n a n c e a n d h a r v e s t i n g a r e s e r i o u s p r o b l e m s f a c e d i n t h eu s e o f o f fs h o r e w a t e r f o r c u l t u r e in T a i w a n . D e v e l o p m e n t o f n e w t e c h -n i q u e s , m a t e r i a l s a n d w a t e r b r e a k e r s h a v e b e c o m e t o p i c s f o r f u t u r ee x p l o r a t i o n .

R E F E R E N C E SChe n, H . C . & Yang , H. H. (1979). Art i fi c ia l propaga t ion o f the aba lon e H a l -

io ti s d ivers ico lor super tex t , Ch ina F isheries Month ly , 314, 3-9 ( in Chinese) .Chen, T. R (1977). Aq uac u l tur e Prac tices" in Ta iwan , Fi sh ing News BooksLtd , England .


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252 S.-H. HuHu, S. H. (1980) . M arine cage cul ture in Penghu. Harvest Farm Magazine, 30(16) , 39- 42 ( in Chinese) .Hu, S . H. & Sheu, H. H. (1982a) . Studies on the increasing production ofcultured oyster C. gigas in Penghu - - L Growth o f oysters in long-l ineculture. An n. Col l. Rep . Penghu F ish . Lab . TFRI . , 2 . 1 7- 2 6 ( in Chinese ).Hu, S . H. & Sheu, H. H. (1982b) . Studies on the increasing production ofcultur ed oysters C. gigas in Penghu - - I I. Growth o f oys ters o f com bined tw oseeding a nd o f rotating culture. A nn . Col l . Rep. Peng hu Fish. Lab. TFRI. , 2 ,27-38 ( in Chinese) .Ku o, H. (1964) . Eco n o m ic M o l lu sc s o f Ta iwa n, JC RR Spec ia l Publ ica t ion No.38 (in Chine se).Li , Y. & Liao, I . C . (1979) . In t rod uc t ion to aqu acul ture in Ta iwan. Proc. W orld

MaricuL Soc., 1 0 , 2 2 9 - 3 7 .Liao, W. T. (1979 ). C ultu re o f small abalon e. Harvest Farm Magazine , 29 (4),30 -1 ( in Chinese) .Lin, Y. S. & Tang, H. C. (1980). Biological s tudies on cul tured oyster inPenghu. Bull. Inst. Zo ol , Ac ad em ic Sinica. 19 (2), 15-22.Milne, P. H. (1976 ). S elect ion of Si tes and D esign of Cages, Fishpen s and Ne tEnc losure s fo r Aquacul tu re . Advance in Aquacul ture FAO Technica lConference on Aquaculture, Kyoto, Japan. Fishing News Books Ltd, pp.4 1 6 - 2 2 .Tang, Y. A. (1976). Planning, Design and Construct ion of a Coastal MilkfishFarm. Ad van ce in Aqu acul ture FAO Technical Conference on Aquacul ture ,Ky oto, Japan. Fishing New s Books Ltd, pp. 1 04- 17.Tsai, W. S. & Hu, S. H. (1982). Cu ltivation o f groupers o f 'Intertidal Under-g ro u n d P o n d ' - - I n t rod u c t io n o f a n ew cul tu re me th o d . Ann. Coll . Rep.Penghu Fish. Lab. TF RI. , 2 , 10 3-7 ( in Chinese) .Tsao, H. C. (1984). Oy ster cul ture of subm ers ible ra ft me thod. Harvest FarmMagazine , 34 (4) , 16 -17 ( in Chinese).Tzeng, W. N. (1977). Studies on the grow th and rear ing envi ron m ent of theaba lone H aliotis diver soco lor supertext. C hina Fisheries M onthly, 292 , 2 - 7(in C hinese).Yen, J. L. & Y en, Y. E. (19 84). Cage cu l ture o f som e marine econom ic f i shes inPenghu. An n. Coll . Rep. Penghu Fish. Lab. TF RI. , 4 , 78 -8 5 ( in Chinese).

Hu 1986 Aquacultural-Engineering

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