leclercq 1985 aquacultural-engineering

7/28/2019 Leclercq 1985 Aquacultural-Engineering

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Aquacu l tu ra l Eng ineer ing 4 (1985) 299-304

S h o r t C o m m u n i c a t i o nP r e l i m i n a r y T e s t s o f a n A e r a t e d T a n k S y s t em f o rTi l ap i a C u l t u r e *

A B S T R A C TA s imp le t an k s y s t em , u s ing a r t if i ci a l ae ra t ion t o supp ly oxyg en an di n c o m i n g w a t e r t o d i l u t e m e t a b o l i c b y - p r o d u c t s a n d o t h e r w a s te s , w a stested. Blue t i lapia, Oreochromis aureus, w e r e g r o w n u n d e r a w i d e r an geo f l oads, 7 -31 kg l i t e r - l m in - l , and dens i ti e s , 19 -77 kg f i sh m -3 cu l t u reu n it . A v e r a g e y i e l d r a n ge d f r o m 6 - 1 0 k g m - 3 c u l t u re u n i t p e r m o n t h .A p p r o x i m a t e l y 1 4 - 2 0 m 3 o f w a t e r w as u s e d f o r e a ch k il og r am o f f i s hp r o d u c e d .

INTRODUCTIONIn 1982, a preliminary st udy of an aerated tan k culture system fortilapia was conducted in an effort to develop fish culture methodssuitable for arid lands by minimizing the water requi rements of flowingwater culture systems. The tanks are aerated to supply oxygen, andwater is provided to dilute and remove metabolic by-products andother wastes. Although complex recirculating systems use even lesswater, they were not considered appropriate for the conditions exist-ing in Kuwait at that time. This paper presents the results of the pre-liminary study.

*KISR serial number 1323/ICLARM contribution number 153.299

Aquacu l tu ra l Eng ineer ing 0144-8609/85/$03.30- Elsevier Applied SciencePublishers Ltd, England, 1985. Printed in Great Britain


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300 D i d i e r I. L e c le r c q , K e v i n H o p k i n sMATERIALS AND METHODS

Three experimental units were constructed and operated during thesummer of 1982. The units were situated under 60-70% agriculturalshade netting at Salmiya, Kuwait. Each unit consisted of a 450-litercircular fiberglass tank with sloped bottom, turn -down pipe and externalairlift for aeration (Fig. I). The ar rangement of the airlift and drainallowed partial settling of suspended solids. These solids were removedby lowering the drain pipe for a few seconds daily. The water supplycame from brackish water (3-5 ppt) wells located in the desert nearKuwait City. This water is normally used primarily for irrigation ormixing with the distilled water f rom desalination plants. Water tempera-tures in the tanks varied between 30 and 35C. The air supply wasprovided by the main blower of the research station. Water velocityalong the edge of the tank was maintained at about 10-15 cm s -] byadjusting the angle of the PVC elbow at the top of the airlift.

Two hundred and fifty blue tilapia, O r e o c h r o m i s a u r e u s , weighingan average of 67 g each, were stocked into each culture tank (37 kgfish m -3 tank volume; 53-58% of the fish were males). The water flow

F i g . 1 .

Brock shWater In let - - ~ I

~ O v e r f l o w

1 .4 r n | ~ " - , , ~ B a t t o r n S c r e e n I / ' - - - ' 1 1_ _ o _ ~ . . _ _ _

L _ ~ Air S u p p l y . . ~ FSchematic diagram of an aerated 450-liter circular fiberglass tank used for

tilapia culture in Kuwait, 1982.


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Preliminary tests o a n aerated ta nk syste m fo r t i lapia culture 30 1t o e a c h t a n k w a s s e t d i f fe r e n t l y , 3 , 5 o r 7 w a t e r e x c h a n g e s p e r d a y , top r o v i d e i n i ti a l l o a d s o f 8 - 1 8 k g l i t e r -1 ra i n - 1 ( l o a d i n g o r l o a d is t h e r a t i oo f fi s h b i o m a s s t o w a t e r f l o w ; M e l a r d a n d P h i l ip p a r t , 1 9 8 1 a ) . T h e fi shw e r e s u c c e s si v e ly f e d t h r e e d if f e r e n t 4 0 - 4 8 % p r o t e i n f e e d s , a c c o r d i n gt o f e e d a v a i la b i li ty . T h e f e e d in g r a te w a s a p p r o x i m a t e l y 3 % o f b o d yw e i g h t p e r d a y . F e e d w a s d e l i v e r e d b y a d i s c f e e d e r w i t h f i rs t f e e d i n ga t 0 8 3 0 h . E a r ly i n th e e x p e r i m e n t , f e e d in g f r e q u e n c y w a s e v e r y1 5 r ai n, b u t l o w d i s s o lv e d o x y g e n ( D O ) le v el s w e r e e n c o u n t e r e d w i t ht h is v e r y f r e q u e n t f e e d in g s o th e n u m b e r o f f e e d i n g s w a s r e d u c e d t ot h r e e p e r d a y ( 0 8 3 0 , 1 2 0 0 a n d 1 5 0 0 h ). E a c h o f th e t h r e e e q u a l f e e d in g sl a s t e d 2 0 m i n .

T h e e x p e r i m e n t l as te d f o r 1 1 8 d a y s . E v e r y t h r e e o r f o u r w e e k s , t h ef is h w e r e a n e s t h e t i z e d w i t h 1 5 m g l i t e r -~ q u i n a l d i n e ( d i ss o l v e d ina c e t o n e a n d a l c o h o l ) , t h e t a n k s w e r e d r a in e d , a n d t h e f is h w e r e w e i g h e da n d c o u n t e d . D i s s ol v e d o x y g e n w a s m e a s u r e d b e f o r e t h e f i rs t f e e d i n gt h r o u g h o u t t h e e x p e r i m e n t b y a n o x y g e n m e t e r ( Y e l l o w S pr in g s I n st ru -m e n t ) . O c c a s i o n a l ly , d ie l f lu c t u a t i o n s in D O w e r e m o n i t o r e d b y c o n n e c t -in g a n o x y g e n m e t e r t o a c h a rt r e c o rd e r . A m m o n i a a n d p H w e r e m e a s u r e di n f r e q u e n t l y w i t h a B a u s c h a n d L o m b w a t e r a n a l y si s k i t.

R E S U L T S A N D D I S C U S S I O NA s u m m a r y o f l o a d s , d e n s i ti e s , y i e ld s a n d w a t e r u t i li z a t i o n a t t a i n e dd u r in g t h e e x p e r i m e n t is s h o w n i n T a b l e 1. T h e m e a n l o a d s , 1 5 - 2 7 k gl i te r -1 m i n - 1, a r e c o n s i d e r a b l y h i g h e r t h a n t h e 9 - 1 0 k g l i te r -1 m i n -1a t t a i n e d in a e r a te d t r o u t r a c e w a y s ( B r o w n a n d G r a t z e k , 1 9 8 0 ) . T h em a x i m u m d e n s i t ie s ( 6 3 - 7 8 k g m -3 c u l t u r e t a n k ) a n d y i e ld s ( 6 - 1 0 k gm - 3 c u l t u r e t a n k p e r m o n t h ) a r e s u b s t a n t i a l b u t a re lo w e r t h a n t h et il a p i a d e n s i t i e s o f 1 0 0 - 1 2 0 k g m -3 c u l t u r e t a n k a n d y i e l d s o f 2 6 k g m - 3c u l t u r e t a n k s p e r m o n t h a t t a i n e d b y M e la r d a n d P h il ip p a r t ( 1 9 8 1 b )in r a c e w a y s . H o w e v e r , t h e a e r a te d t a n k u t i li z e d w a t e r m u c h m o r ee f f i c i e n t ly t h a n t h e i r r a c e w a y s , 1 4 - 2 0 m 3 w a t e r u s e d p e r k g f is hp r o d u c e d v e r s us 4 8 - 1 0 8 m 3 k g - l . P o n d s y s t e m s in K u w a i t a r e e s t i m a t e dt o r e q u i r e a b o u t 1 3 m 3 o f w a t e r p e r k g fis h p r o d u c e d b e c a u s e o f th ev e r y h i g h e v a p o r a t i o n r a t e s ( H o p k i n s e t a l . , 1 9 8 4 ) . A m a j o r a d v a n t a g eo f t h e a e r a t e d t a n k s o v e r p o n d s is t h a t a l m o s t a ll o f th e w a t e r f r o m t h et a n k s c a n b e r e - u s e d f o r a g r ic u l tu r e w h e r e a s m o r e t h a n 6 0 % o f t h e


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302 D i d i e r 1. Lec l e rcq , Kev i n H o pk i nsT A B L E 1

Loads, Densities, Yields and Water Utilization in Aerated Tank Culture ofO reochrom i s aureus during 118 day Culture Period at Salmiya, Kuwait. Water

Temperatures Varied Between 30 and 35CWater exchan ge ra te

3 5 7Load (kg liter -1 min-1)a

Initial 19 11 8Mean 27 21 15Final 32 22 17

Density (kg m -3 culture tank)Initial 39 38 37Mean 54 58 58Final 63 75 78

Mean yield (kg m -3 culture tank/month) 6 9 10Water utilization (m 3 water used kg -~ fish produced) 14 15 20a The ratio of fish biomass to water flow.

water used in pond s (2 m deep + 3-6 m evaporat ion yea r -l) is 'los t'to the atmosphere.

Water flows obtained fro m the airlift ranged fr om 75 to 95 litermin -~, depen ding on inline air pressure and air use by oth er users onthe station. Air flow was not measured but can be estimated usingthe efficiency tables in Spotte (1979) to be twice the amou nt of watermoved. As the ret ent ion time in the airlift was very short (1 "7-2-00 s),oxygen transfer was low and the system was sensitive to increases inoxygen demand (Fig. 2). The DO levels during the day were closelyrelated to the frequency of feeding. Levels were highest in the earlymornin g before the first feeding (mean maxim un daily DO = 6-0 mgliter-x, partial pressure = 126-8 mm Hg ). At the onset of feeding,vigorous feeding activity by the fish caused a drop in DO. Dissolvedoxygen then started increasing at the end of feeding. Similar patternswere reported for a closed recirculating system (Rosenthal e t a l . ,1981). It was readily apparent that oxygen demand caused by almost


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Prel iminary tes ts o a n aerated tan k sys tem for t ilapia cul ture 3 0 3A 7 '

o

--~ 2_w I.r~

0

A

6 9 12 15 18 21 0 :5 6T i m e o f D o y ( h o u r )

Fig. 2. D ie l f luctua t ion in dissolved oxyge n conce ntrat ions in a tank containingapproxim ately 50 kg of f ish m -3 of tank volume. Traces w ere obtained using acont inuou s oxyg en moni tor . Trace A corresponds to three feedings per day and

trace B corresponds to fou r feedings per hou r from 083 0 to 1700 h daily.

c o n t i n u o u s f e e d i n g a c t iv i t y c o u l d n o t b e m e t b y t h e re l a t i v e ly i n e f f ic i e n ta ir li ft . F o r t h is r e a s o n , a f e e d i n g f r e q u e n c y o f t h r e e t i m e s p e r d a y w a su s e d f o r m o s t o f t h e e x p e r i m e n t a l p e r io d e v e n t h o u g h m o r e f r e q u e n tf e e d in g h a s b e e n r e p o r t e d t o y i e l d h ig h e r g r o w t h ( J a u n c e y a n d R o s s ,1 9 8 2) . I m p r o v e m e n t o f t h e a e r a t i o n s y s t e m o r i t s r e p l a c e m e n t b y as u i t a b l y d e s i gn e d o x y g e n a t i o n s y s t e m c o u l d p o s s i b l y a l lo w m o r ef r e q u e n t f e e d i n g .

T h e p H o f t h e i n le t w a t e r w a s s t a b l e a t 7 -9 + 0 "1 , b u t f l u c t u a t i o n so f th e p H w e r e i n d u c e d in th e c u l t u r e u n i t. T h e s e f l u c t u a t i o n s s h o w e dt h e s a m e d ie l p a t t e r n a s t h e D O , in d i c at in g t h a t t h e y w e r e c a u s e d b yh i gh e r r e s p i r a t o r y m e t a b o l i s m ( a n d C O 2 p r o d u c t i o n ) d u r i n g f e e di n g.T h e p H d r o p p e d t o 7 . 5 - 7 " 6 d u r i n g f e e d i n g b e f o r e r is in g a g a in a s t h eC O : w a s e l im i n a t e d .

T h e m a x i m u m c o n c e n t r a t i o n s o f u n i o n iz e d a m m o n i a ( N H 3 = 0 - 6 -0 . 7 m g l i te r - 1) w e r e e n c o u n t e r e d a t l o a d s o f 2 5 - 3 0 kg l i t e r -1 r a in -1.T h e r a ti o o f m o r n in g N H 3 t o a f t e r n o o n N H 3 w a s a p p r o x i m a t e l y 1 :2 ,w h i c h i s s im i la r t o o b s e r v a t i o n s b y R o s e n t h a l e t a l . , ( 1 9 8 1 ) o n N H 3 ina r e c i r c u l a ti n g s y s t e m .

A b r a s i o n o f t h e p e l v i c , p e c t o r a l , a n d t a il f in s w a s o b s e r v e d . T h e s ea b r a s io n s o c c u r r e d o n t h o s e f i n s o r i e n t e d t o w a r d s t h e c e n t e r o f t h et a n k w h i c h i n d ic a t e s th a t t h e y w e r e c a u s e d b y c o n t a c t b e t w e e n f is ha n d n o t b e t w e e n f is h a n d t a n k w a ll .


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304 Didier L Leclercq, Kevin HopkinsC O N C L U S I O N

T h e h i gh y i e ld s a t t a i n e d w i t h th e e x p e r i m e n t a l u n i t s s h o w t h e p o t e n t i a lo f a e r a t e d t a n k s f o r t il a p ia c u l t u r e . T h e s e s i m p l e s y s t e m s c o u l d p o s s i b l yb e m a d e m u c h m o r e e f f i c ie n t b y i m p r ov i ng th e a e r at io n s y s t e m s a n da d d i n g s im p l e s e d i m e n t a t i o n / m e c h a n i c a l f i l tr a t i o n .

R E F E R E N C E SBrown, E . E. & Gratzek, J. B. (198 0). Fish Farming Handbook, AVI Publishing

Co. , W estpor t, Conne ct icut.Hopkins, K., Hopkins, M., AI-Ameeri , A. & Leclercq, D. (1984). Ti lapia cul turein Kuwaut: a prel iminary economic analysis of production systems. Kuwait

Inst i tute for Scient if ic Research, Interim Report 1252 (unpublished).Jauncey, K. & Ross , B. (1982) . A Guide to Tilapia Feeds and Feeding, Inst i tuteo f A qu ac ultur e, University o f Stirling, Stifling, Scotland.

Melard, C. & Phil ippart , J .-C. (1981a). La production de t i lapia de consommationdans les rejets industriels d'eau chaude en Belgique. Cahiers d'EthologieAppliquee, 1, suppl. 2.

Melard, C. & Philippart, J.-C. (1981b). Pisciculture intensive du tilapiaSarotherodonniloticus dans les effluents thermiques d 'une centrale nucl6aire en Belgique.Aquaculture In Heated b~ffluents and Recirculating Systems, Vol. 2, ed. K.Tiews, H. Heeneman Gm bH & Co., Ber lin, 637-5 3.

Ro senthal , H., Andjus, R. & Ksuner, G. (198 1). D aily variat ions o f wa ter qual i typarame ters un der intensive cultu re in a recycling system. Aquaculture In HeatedEffluents and Recirculating Systems, Vol. 1, ed. K. Tiews, H. Heeneman G m bH& Co., Berl in, 112-20.

Spot te , S . (1979) . Fish and Invertebrate Culture: Water Management In ClosedSystems, 2nd Edit ion, Wiley, New York.D i d i e r I . L e c l e r c q *Kuwait Institute for Scientific Research,PO Box 24885 Safat, Kuwaita n dKevin HopkinstInternational Center for Living AquaticResources Management,MCC PO Box 1501 Makati,Metro Manila, Philippines

* Present address: France Aq uacu lture, CNEX O BP 337, 29 273 Brest, France.t Present address: Dept of Fisheries and Wildlife, Oregon State University, Corvallis,Oregon, 97331, USA.

leclercq 1985 aquacultural-engineering

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