hardin 1985 aquacultural-engineering

7/28/2019 Hardin 1985 Aquacultural-Engineering

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Aquacu l tura l Eng ineer ing 4 (1985) 85-92

T e m p e r a t u r e a n d S i z e E f f ec t s o n th e A c c u r a c y o fE s t i m a t i n g P o s t la r v a l S h r i m p P o p u l a t io n sM.P. HardinCedar Bayou Research Laboratory, PO Box 1396, Baytown, Texas 77520, USA

D.L. Hutchins , G.W. Chamberla inTexas Agricultural Extension Service and Experiment Station, Texas

A&M University, PO Drawer Q, Port Aransas, Texas 78373, USAandD.V. AldrichDepartment of Wildlife and Fisheries Sciences, Texas A&M University,Building 11, Fort Crockett, Galveston, Texas 77550, USA

A B S T R A C TT h e co m m o n p r a c ti ce i n e s t i m a t in g p o s tl a rva l p en a eM s h r i m p p o p u l a t i o n sfor s tock ing po nds is vo lum et r i c subsampl ing wi th subse quen t ex t rapo la -t ion . Th i s proeedure can lead to cons iderab le undercoun t ing , wh ich , i f no trecogn i zed , w i l l resu l t i n overs tock ing wi th accompanying under f eed ingand depressed growth . Pos t larva l b lue shr imp P e n a e u s s t y l i r o s t r i s co u n t sd er i ved f r o m vo l u m e t r ic s u b s a m p l in g i n a co n t a in er o f kn o w n vo l u m e a n dshr imp d ens i t y were che cke d for accuracy . C oun t s were ma de o f th rees izes o f shr imp (4 , 6 and 10 .5 m m to ta l l eng ths ) a t f o ur t em pera tures (18 ,22 , 26 and 30C) . Water t empe ra ture and shr imp s ize bo th had h igh lys ign if ican t (p < 0 .00 01) e f f ec t s on the mea n ca tch , wh ich t ende d todecrease wi th increasing shrimp s i zes and water temperatures .T h e p o p u l a t i o n e s t im a t e s r a n ged f r o m 1 0 0 % o f t h e a c tu a l p o p u l a t i o nf o r 4 m m p o s tl a rva e a t 1 8 C to 5 7 % f o r 1 0 .5 m m p o s tl a rva e a t 3 0 C.

INTRODUCTIONAn accurate technique of estimating postlarval shrimp populations priorto stocking ponds is of practical interest to aquaculturists in bothresearch and commercial production.For example, stocking density and percent survival in pond experi-ments cannot be calculated without an accurate idea of the initial

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


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86 M. P. Hardin , D. L . Hutchins , G. I . Chamber la in , D. V. Aldr ichp o p u l a t i o n . F u r t h e r , t h e l a r g e q u a n t i t i e s o f c o s t l y p o s t l a r v a e u s e d i nc o m m e r c i a l c u l t u r e c r e a t e a n e e d f o r a q u i c k a n d a c c u r a t e m e t h o d o fe s t i m a t i n g t h e i r n u m b e r s .

I n t h e p a s t , p o s tl a rv a e h a v e e i t h e r b e e n c o u n t e d e n t i re l y b y h a n d o rt h e p o p u l a t i o n h a s b e e n c a l c u l a te d v o l u m e t r i c a ll y a s a p r o d u c t o f t h ee s t i m a t e d s h r i m p d e n s i t y a n d t h e w a t e r v o l u m e o f t h e i r c o n t a i n e r . F o rt h e l a t t e r t e c h n i q u e , s h r i m p d e n s i t y i s d e r i v e d f r o m t h e m e a n n u m b e rc a u g h t i n s e v er a l s m a l l - v o l u m e a l i q u o t s t a k e n f r o m a h i g h l y c o n c e n -t r a te d p o p u l a t i o n . T h e s e s m a ll v o l u m e a l i q u o ts h a ve c o m m o n l y b e e nc o l l e c t e d w i t h e i t h e r a b e a k e r o r , m o r e r e c e n t l y , a s p r i n g o p e r a t e dp i p e t t e . S o m e p o n d s t u d i es th a t h a ve e m p l o y e d v o l u m e t r i c e s t im a t i o no f i n i t i a l p o p u l a t i o n s h a v e g i v e n f i n a l sh r i m p su rv i v a l f i g u re s s i g n i f i -c a n t l y g r e a t e r t h a n 1 0 0 % ( B e r r y , 1 9 7 6 ; T r i m b l e , 1 9 8 0 ; C h a m b e r l a i ne t a l . , 1 9 8 1 ) .

N o n e t h e l e s s , i n b o t h r e s e a rc h f a c i li ti e s a n d c o m m e r c i a l h a t c h e r i e st h e r e is r o u t i n e u s e o f t h e v o l u m e t r i c t e c h n i q u e f o r c o u n t i n g l ar gen u m b e r s o f p o s tl ar v a e ( M o c k a n d M u r p h y , 1 9 7 0; P a r k e r a n d H o l c o m b ,1 9 7 3 ; P h il ip B o e i n g , S E M A C U A , G u a y a q u i l E c u a d o r , p e r s o n a l c o m -m u n i c a t i o n ; E d w a r d D . S c u r a, A q u a t i c F a r m s , K a n e o h e H a w a ii ,p e r s o n al c o m m u n i c a t i o n ) . A ls o , m o s t m a j o r c o n t r a c to r s f o r p ur c h a s e o fw i l d - c a u g h t p e n a e i d p o s t l a r v a e u s e d i n t h e e x t e n s i v e m a r i c u l t u r ei n d u s t r y i n E c u a d o r a c c e p t v o l u m e t r i c a l ly d e r iv e d p o p u l a t i o n e s t im a t e s( a l t h o u g h s u c h e s t i m a t e s a r e g e n e r a l l y b e l i e v e d t o b e c h r o n i c a l l y l o w ) .H a n d c o u n t i n g t h e e n t i r e p o p u l a t i o n h a s t h e a d v an t a g e o f c o m p l e t ea c c u ra c y , b u t is a t r e m e n d o u s i n v e s t m e n t o f t i m e a n d la b o r a n d m a yi n c u r g r e a t e r h a n d l i n g m o r t a l i t y . F o r t h e s e r e a s o n s i t s a p p l i c a t i o n h a sb e e n l i m i t e d t o s i t u a t i o n s i n v o l v in g l o w s t o c k i n g n u m b e r s (W illis a n dB e r r i g a n , 1 9 7 7 ; F u r n e s s , 1 9 7 8 ) .T h e p u r p o s e o f th i s s t u d y w a s t o t e s t th e a c c u r a c y o f v o l u m e t r i cc o u n t i n g u n d e r c o n s e r v at iv e c i r c u m s t a n c e s a n d t o d e t e r m i n e c o n d i t i o n sf o r m a x i m i z i n g a c c u r a c y .

M A T E R I A L S A N D M E T H O D SA p p r o x i m a t e l y 1 0 0 0 0 f ir s t d a y p o s tl a rv a e o f b l u e s h r i m p P e n a e u ss t y l i r o s t r i s w e r e o b t a i n e d f r o m t h e T e x a s A & M M a r ic u l tu r e R e s e a r c hL a b o r a t o r y . T h e s h r i m p w e r e t r a n s p o r t e d t o t h e C e d a r B a y o u M a r ic u l-t u r e R e s e a r c h L a b o r a t o r y , w h e r e t h e e x p e r i m e n t s w e re p e r f o r m e d .


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Estimating p ostlarval shrimp populations 87T h e i n it ia l t o t a l m e a n l e n g t h o f t h e s h r i m p w a s 4 m m . A l l m e a s u r e -

m e n t s w e r e m a d e t o t h e n e a re s t 0 .5 m m u n d e r 10X m a g n i f i c a t i o n f r o mt h e t i p o f th e r o s t r u m t o t h e t i p o f t h e t e ls o n . F o r e a c h e x p e r i m e n t5 0 0 p o s t l a r v a e w e r e c o u n t e d i n d i v id u a l l y a f te r b e i n g c a u g h t o n h a n d -s i ze d p i e c e s o f 1 .5 m m m e s h s c r e e n . T h e s e w e r e r e l e a se d i n t o a l - l i t e rp l a st ic b e a k e r c o n t a i n i n g 5 0 0 m l o f s e a w a t e r , r e s u lt in g in a d e n s i t y o f1 p o s t l a rv a m 1-1. T h e w a t e r t e m p e r a t u r e w a s a d j u s t e d b y p a r t ia l lyi m m e r s in g t h e b e a k e r in w a r m o r c o ld w a t e r b a t h s .

T h e b e a k e r w a s t h e n i n s e r t e d i n t o a s t y r o f o a m s le e v e t o h e l p m a in -ta in t h e e x p e r i m e n t a l t e m p e r a t u r e . W a t e r t e m p e r a t u r e a n d v o l u m e w e rec h e c k e d a p p r o x i m a t e l y e v e r y 3 - 5 m i n t h r o u g h o u t e a ch e x p e r i m e n t a n dc o r r e c t e d a s n e e d e d . P u r e o x y g e n w a s b u b b l e d c o n t i n u o u s l y i n t h eb e a k e r .

A H e n s e n - S t e m p e l a u t o m a t i c p i p e t t e ( W i ld li fe S u p p l y C o ., S a g i n aw ,M i c h ig a n ) w a s u s e d t o s u b s a m p l e . T h e p i p e t t e t a k e s a 10 m l v o l u m e o fw a t e r b y m e a n s o f a s p r in g - o p e r a te d p lu n g e r. O p e r a t i o n o f t h e p i p e t t eis v e r y q u i c k , r e q u i r i n g l es s t h a n 1 s t o t a k e a n a l i q u o t . T h i s p i p e t t e h a sb e e n r o u t i n e l y u s e d b y T e x a s A & M U n i v e r s i ty s ta f f t o s u b sa m p l ep e n a e i d e g g s a n d n a u p l i i, b u t i t s e f f i c i e n c y w i t h p o s t l a r v a e w a su n k n o w n .E a c h a l i q u o t w a s f ir s t d i s c h a r g e d i n t o a p l a s t ic d is h t o c o u n t a n dr e c o r d t h e n u m b e r o f c a p t u r e d p o s tl a rv a e . H e a l t h y sh r im p w e r e t h e nr e t u r n e d t o t h e b e a k e r . S h r i m p m u t i la t e d b y t h e p i p e t t e ( a p p r o x i m a t e l y2 0 % o f t h o s e c a p t u r e d ) w e r e r e p l a c e d f r o m r e se r ve s . T o a c h i e v e an e v e nd i s t r i b u t i o n o f p o s t l a r v a e in t h e b e a k e r , t h e w a t e r w a s v i g o r o u s ly s ti rr e di m m e d i a t e l y p r i o r t o t a k in g e a c h 1 0 m l s u b s a m p l e . T o p r e v e n t c o n c e n -t r a t io n o f t h e p o s t l a r v a e i n t h e m i d d l e o f t h e b e a k e r , st ir ri n g w a s d o n ein a s i d e - to - s i d e t h e n f r o n t - t o - b a c k m a n n e r . A t ig h t l y r o l le d t ie d p la s t i cb a g s e r v e d as a s o f t , s t i f f s t ir r in g r o d . 3 0 a l i q u o t s w e r e t a k e n f o r e a c h o ft h e t e m p e r a t u r e s ( 1 8 , 2 2 , 2 6 a nd 3 0 C ) . F r e s h b a t c h e s o f 5 0 0 p o s t-l a r v a e w e r e u s e d a t e a c h t e m p e r a t u r e .

A l l o f t h e p o s t la r v a e w e r e t h e n d i v id e d b e t w e e n t w o 3 8 0 - l i te r a q u a r i aa n d f e d b r i n e s h r i m p n a u p l i i d a i l y . A f t e r 1 w e e k , m e a n l e n g t h h a di n cr e a se d t o 6 ra m . F o l l o w i n g m e t h o d s d e s c r i b e d a b o v e , t h e e x p e r i m e n tw a s r e p e a t e d a t t h e sa m e f o u r te m p e r a t u r e s . Y e t a n o t h e r r e p e t i t i o n a tt h e se t e m p e r a t u r e s w a s p e r f o r m e d a f t e r a s e c o n d w e e k o f g r o w t h in th ea q u a r i a h a d in c r e a s e d m e a n s h r i m p l e n g t h to 1 0 .5 m m .M e a n s a n d s t a n d a r d d e v i a t i o n s w e r e c a l c u l a te d f o r t h e n u m b e rc a u g h t p e r a l i q u o t a t e a c h te m p e r a t u r e a n d si ze . T w o - w a y a n a ly s is o f


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88 M. P. Hardin, D. L. Hutchins, G. W. Chamberlain, D. V. Aldrichv a ri an c e ( A N O V A ) w a s p e r f o r m e d o n t h e d a t a t o c h e c k f or s ig n if ic a n td i f f e re n c e s a m o n g t r e a t m e n t le ve ls . T h is w a s f o l l o w e d b y D u n c a n ' sm u l t ip l e r a n ge t e s t ( D M R ) t o i d e n t i f y s p e c i f ic s i g n if i ca n t d i f f e r e n c e sa m o n g m e a n s . C a t c h v a ri ab i l it ie s a m o n g t r e a t m e n t s w i t h d i f f e r e n tm e a n s w e r e c o m p a r e d u s in g c o e f f i c i e n ts o f v a r ia t io n ( S o k a l a n d R o h l f ,1 9 6 9 ) .

R E S U L T S

A c a t c h o f 1 p o s t l a r v a m 1-1 , o r 1 0 p e r a l i q u o t w a s a v e r a g e d a t t h e 1 8 Ct e m p e r a t u r e w i t h t h e 4 m m l e n g t h ( F i g . 1). H o w e v e r , m e a n c a t c hd e c r e a s e d w i t h i n c re a s in g s iz e a n d t e m p e r a t u r e . C a t c h w a s le a s t w i t h1 0 .5 m m l e n g th s a t 3 0 C . A N O V A i n d i c a t e d h i g h l y s ig n i fi c a n t di f-f e r e n c e s in m e a n s b e t w e e n le v els o f b o t h f a c t o rs ( f o r t e m p e r a t u r e :F = 1 0 . 4 8 , d e g r e e s o f f r e e d o m = 3 , p < 0 . 0 0 0 1 ; f o r l e n g t h : F = 4 0 . 2 4 ,d e g r ee s o f f r e e d o m = 2 , p < 0 . 0 0 0 1 ) . S p e c if ic si gn if ic a n t d i ff e r e n c e sa m o n g m e a n s , a s i so l a te d b y D M R , g e ne r al ly o c c u r r e d b e t w e e nt e m p e r a t u r e s o f 1 8 a n d 2 2 C a n d s iz e s o f 4 - 6 m m ( F ig . 1).

IM EA N CATCH

Fig. 1. M ean catch of 4.0-1 0.5 m m length postlarvae at 18, 22, 26 and 30C.Means having the same letter are not significantly different (p < 0.05).


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Estimating postlarval shrimp populations 89A n a c c u r a t e e s t i m a t e o f p o s t la r v a l d e n s i t y w a s t h u s o b t a i n e d w i t h

4 m m s iz e p o s t l a r v a e a t a ll f o u r t e m p e r a t u r e s . H o w e v e r , d e n s i t y w a su n d e r e s t i m a t e d w i t h l ar g er p o s t la r v a e , p a r t i c u l a rl y a t t h e h i g h ert e m p e r a t u r e s . S p e c i f i c a l ly , a t 1 8 C , t h e m e a n c a t c h d e r i v e d f r o mr e p e a t e d s u b s a m p l in g o f 6 a n d 1 0. 5 m m p o s tl a rv a e u n d e r e s t i m a t e d t h ea c t u a l d e n s i t y b y 1 6% . A t 2 2 - 3 0 C t h e i n d i c a t e d d e n s i t y f o r t h e s a m es iz e g r o u p w a s 3 1 - 4 3 % le ss ( r e s p e c t i v e l y ) t h a n t h e a c t u a l d e n s i t y .

T h e l a t te r f i n d in g is i m p o r t a n t , s in c e t h e t e m p e r a t u r e a n d s iz e r a n ge so f 2 2 - 3 0 C a n d 6 - 1 0 . 5 m m a re t h o s e m o s t l ik e ly t o b e e n c o u n t e r e db y c u l t u r i s t s w h e n s t o c k i n g p o n d s . A 9 5 % c o n f i d e n c e i n t e r v a l a b o u t t h em e a n c a t c h ( N = 1 8 0 ) f o r t h e s e r a n g e s w a s e s t a b l i s h e d a s 6 - 4 7 0 . 3 7( 6 4 . 7 + 3 . 7 % a c c u r a t e ) . C o e f f i c i e n t s o f v a r i a t i o n w e r e l a rg e , r a n g in gf r o m 2 2 . 0 t o 4 7 . 3 % , w i t h l o w e r v a lu e s m o r e c o m m o n a m o n g t h es m a l l e s t si z e o f p o s t l a r v a e ( F i g . 2 ) .

D I S C U S S I O NR e d u c e d c a t c h e s a re p r o b a b l y d u e t o th e s h ri m p s ' a v o i d a n ce o f t h ep i p e t te . T h e p o s tl a rv a e r e m a i n e d a c t i ve t h r o u g h o u t t h e e x p e r i m e n t a n d

F i g . 2 .

t C O E F F I C I E N T O F V A R I A T I O N 54 Z 3i i

I

,,I

g X 4 0 x a

3 ~

Co efficients of variation for the m ean catche s (Fig. 1) o f three sizes ofpostlarvae at four temperatures.


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90 M. P. Hardin, D. L. Hutchins, G. W. Chamberlain, D. V. AMrichwere observed to jump back from any object thrust into their immediatevicinity. Reaction times would be expected to decrease with increasedtemperature, since shrimp are poikilotherms. Increased size wouldfurther enhance their ability to avoid something as limited in effectiverange as the pipette.

The high variation from aliquot to aliquot in the number of post-larvae captured is typical for the volumetric counting technique. Thisindicates that patchy distributions persist in a contained population ofpostlarvae, even after vigorous mixing. The practical significance is thatif thoroughly mixed populations of postlarvae were not obtained underour conservative, small-scale conditions, then good mixing would beeven more difficul t when sampling from large containers.

In summary, at temperatures ranging from 18 to 30C, volumetricestimation is a fairly accurate technique for counting live postlarvalshrimp that do not exceed 4 mm in length. Density estimates for thelarger postlarvae (such as those used to stock ponds) are underestimatedby a relatively standard factor dependent on temperature and size.Data presented in Fig. 1 represent an index of the exten t of avoidancecapability of postlarval shrimp with increasing size and temperature.This phenomenon may often escape detect ion, since postlarval mortali-ties in ponds are commonly very high. If final populations are reducedto levels less than stocked populations, no initial miscounting wouldbe suspected.

A solution to underestimation could be to: lower water temperatureprior to sampling; use a larger volume subsampling device; or revise thepopulation estimate upward using experimental correct ion factors.

An example of the latter option based on 64.7% accuracy of thepresent experiment implies that the real population is 100/64.7 = 1.55times the estimated population.

Chilling the water prior to subsampling would be cumbersome inexecut ion, stressful to the postlarvae, and yield an estimate still lackingin complete accuracy. The use o f a larger volume sampling device, suchas a 25 or 50 ml pipette, is currently under investigation by Texas A&Mpersonnel. However, this modification would increase the number ofpostlarvae per aliquot, in turn increasing the time required to count abig population. Further, even the use of a 400-ml beaker in the Trimble(1980) study did not prevent a substantial underestimation of stockingdensity. Thus, some manner of correction factor seems necessary forthe volumetric counting technique.


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Estimating postlarval shrimp populations 91T h e c o r r e c t i o n f a c t o r o f 1 . 5 5 f r o m t h is s t u d y w a s u s e d to e s t im a t e

t h e s t o c k i n g p o p u l a t i o n s o f P. stylirostris p o s t l a r v a e u s e d in t h e 1 9 8 0C e d a r B a y o u p o n d e x p e r i m e n t s ( H a r d in , 1 9 8 1 ). H a r v e s t p o p u l a t i o n s int h e s e e x p e r i m e n t s r a n g e d f r o m 7 1 t o 1 0 0 % o f t h e c o r r e c t e d s to c kp o p u l a t i o n ( i m p l y in g t h a t u n c o r r e c t e d e s t i m a t e s w o u l d h a v e y i e l d e ds u r v iv a l s g r e a t e r t h a n 1 0 0 % ) . T h e u s e o f d i f f e r e n t s p e c i e s , s iz e s , t e c h -n i q u es , e q u i p m e n t , e t c ., m a y r e q u ir e e x p e r i m e n t a l c a l c u la t io n o fd i f f e r e n t c o r r e c t i o n f a c t o r s .

A C K N O W L E D G E M E N T ST h is re s e ar c h w a s f u n d e d b y t he H o u s t o n L i gh t i ng & P o w e r C o m p a n yt h r o u g h t h e D e p a r t m e n t o f W i l d li fe a n d F i sh e r ie s S c i e n c e s a n d T e x a sA g r i cu l tu r a l E x p e r i m e n t S t a t io n P r o j e c t 1 8 6 9 - 2 3 3 9 .

R E F E R E N C E S

Berry, R. (197 6). P ond study crustaceans. In: The Effects on Selected Organismsof Water Passing Through the Cedar Bayou Generating Station, Texas Agricul-tural E xperimen t Stat ion P roject Re port for 1975, pp. VII-1-VII-I 3 .Cham berlain, G. W,, Hutchins, D. L. & Lawrence, A. L. (198 1). M ono- and poly-

cul ture of Penaeus vannamei and P. stylirostris at differing percentages in experi-mental ponds. Proceedings World Mariculture Society, 12 (1) , 251-70.

Furness , G. N. (1978). Growth, survival , d is t r ibut ion and populat ion es t imates ofpenaeid shrimp in fertilized and unfertilized brackish water ponds receivingthermal effluen ts. M S Thesis, De partm ent of W ildlife and Fisheries Sciences,Texas A&M Universi ty.Hardin, M. P. (19 81 ). Considerations o f diet, stocking density, distribu tion, popula-t ion es t imat ion and ec onom ics in the pon d cul ture of b lue shrimp, Penaeusstylirostris (Stim pson ). M S Thesis, De partm ent of Wildlife and Fisheries Sciences,Texas A&M Universi ty, 155 pages.

M ock, C. R. & Mu rphy, A. (19 70) . Techniques of raising penaeid shrimp fro m eggto postlarvae. Proceedings Worm Mariculture SoeieO,, 1, 143-56.Parker , J . C. & Holco m b, H. W. Jr. (1 973). Gro wth and prod uct ion of brow n andwhite shrimp (Penaeus aztecus and P. setiferus) from experimental pond s inBrazoria and Orange counties Texas. Proceedings Worm Mariculture Socie~. , 4,2 1 5 -3 4 .Sokal , R. R. & Rohlf , F. J . (1969). Biometry, W. H. Freeman and Co., San Fran-cisco.


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9 2 M. P. Hardin, D. L. Hutc hins, G. W. Chamberlain, D. V. AM richTr i m b l e , W. C . ( 1 9 8 0 ) . P r o d u c t i o n t r ia ls f o r m o n o cu l t u r e an d p o l y cu l t u r e o f w h i t e

s h r i mp (Penaeus vannamei) or b lue sh r imp (Penaeus stylirostris) w i t h F l o r i d ap o m p a n o (Trachinotus carol inus) i n A l ab ama , 1 9 7 8 - 1 9 7 9 . Proceedings WorldMar icu l ture Soc ie ty , 1 1 , 4 4 - 5 9 .

Wi ll is , S . & Ber r igan , M. (1977 ) . E f fec t s o f s tock ing s ize and den s i ty on g rowth andsurvival of Macrobrachium rosenbergii i n p o n d s Proceedings W orld M aricultureS o c i e t y , 8 , 2 5 1 - 6 4 .

hardin 1985 aquacultural-engineering

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