Wickins 1985 Aquacultural-Engineering

7/28/2019 Wickins 1985 Aquacultural-Engineering

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Aqu acu l t u ra l E ng i neer ing 4 (1985) 155-174

Am m onia P roduct ion and O xidation During the Cul tureof Marine Pra wns and Lobsters in LaboratoryRecirculat ion System sJ . F . W i c k i n s

Ministry of A griculture, F isheries and F ood , Direc torate of Fisheries Research,Fisheries Experim ent Station, Conw y, Gw ynedd LL32 8UB , UK

A B S T R A C TD at a ob t a i ned dur i ng t he cu l tu re o f t rop ica l p raw ns Penaeus sp. andEuropean lobs ters Homarus gamm arus (L.) in 20 laboratory recirculatT"onsys t em s over a nu m ber o f y ear s were used t o ob t a i n gros s e s ti m a t e s o f( a ) t he ra te s and d i urna l pa t t e rns o f am m oni a exc re t ion , ( b ) f oo d u t il iza -t ion an d was tage , an d (c ) n i t r i f i ca t ion ra tes in b io logical f i lt ers . Am m on iaexcre t ion in Penaeus m onodo n decreased w i th increase in an ima l s i ze f ro m0 . 9 3 t o 0 . 3 0 m g N g -~ day -1 a t 1 . 6 a nd 2 7 g l iv e we i gh t , r e spec t iv e l y. Largel obst e rs ( 30 0 g ) e xc re t ed 0 . 3 m g N g -x day -1 . Peak exc re t i on t i m es wereappro x i m a t e l y 3 , 9 an d 15 h a f t e r a s ing le m orn i ng f e ed f o r p rawn s anda f t e r 6 a nd 12 h f o r lobste rs . U nea t en f o od so li d s am ou n t ed t o 11%( l obst e r s) a nd 32% ( praw ns ) o f t he da i l y ra t i on and , f o r 4 g an i m a ls , on l y69% ( l obs t e r s ) and 45% ( prawns ) o f t he f ood n i t rogen i n t he da i l y ra t i onwas con ver ted in to crus tacean f l esh . N i t r i f ica t ion ra tes ranged f ro m O. 03t o 0 . 4 3 g N o x i d i z e d p e r m 2 o f f i lt e r m e d i a s u rf ac e p e r d a y. S o m e e v id e n c ef or pe r i od i c i t y i n n i t r i f y i ng ac t i v it y was also f o un d and i s d i s cus sed inrelat ion to the publ ished l i terature.

I N T R O D U C T I O NE c o n o m y o f w a t e r d u r in g t h e c o m m e r c i a l c u lt u r e o f a q ua t ic or g a ni sm sis f r e q u e n t l y a c h i e v e d t h r o u g h r e - a e r a t i o n o r r e - o x y g e n a t i o n . W h e r ec l o se c o n t r o l o f o t h e r s p e c if ic e n v i r o n m e n t a l f a c to r s , p a r t i c u l a rl yt e m p e r a t u r e , is r e q u i r e d , th e w a t e r m a y b e r e c y c l e d b e t w e e n t h ec u l t u r e t a n k s a n d s p e c ia l iz e d w a t e r t r e a t m e n t u n i t s. P e r c o l a t i n g b i o-

155O Crown Copyright, 1985.


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15 6 J. F. Wickinsl o g ic a l f il te r s a r e a m o n g t h e t r e a t m e n t u n i t s w i d e l y u s e d in r e c i r c u la t i o ns y s t e m s b u t f a c t o r s g o v e r n i n g t h e i r d e si g n a n d p e r f o r m a n c e i n h e a v i lys t o c k e d s e a w a t e r s y s t e m s a re n o t w e ll u n d e r s t o o d ( T i ew s , 1 9 8 1 ).

B e s id e s o x y g e n d e p l e t i o n , m a j o r c h a n g e s o c c u r in a m m o n i a , n it r it ea n d n i t r a t e le v el s o f r e c y c l e d s ea w a t e r . U n d e r e x t r e m e c o n d i t i o n s ,p r o d u c t i o n o f w a s te m e t a b o l i te s b y m i c r o o r g a n i sm s i n t h e s y s te m c a ne q u a l o r e ve n e x c e e d t h a t f r o m t h e c u l t u r e d o r g a n i sm s ( M o f f e t t a n dF i s h e r , 1 9 7 8 ; W i c k in s , 1 9 8 2 ) .

T h e s u c c e s sf u l d e s ig n a n d o p e r a t i o n o f s u i ta b l e w a t e r t r e a t m e n t u n i tsd e p e n d s u p o n k n o w l e d g e o f t h e c u l t u r e d a n i m a l s ' f ee d i n g b e h a v i o u r,e x c r e t i o n p a t t e r n s a n d t o l e r a n c e t o r e c y c l e d w a t e r . S i n c e o x i d a t i o n o fw a s t e s i s a c c o m p l i s h e d b y m i c r o b i a l s l i m e s i n b i o l o g i c a l f i l t e r s , t h en u t r i t io n a l a n d e n v i r o n m e n t a l r e q u i r e m e n t s o f t h o s e s li m e s h a v e a ls ot o b e m e t . T h e m e t a b o l i c a c t iv i ty o f a ll t h e o r g a n i s m s w i t h i n t h ec u l t u r e s y s t e m w i ll v a r y a c c o r d i n g t o t h e f e e d i n g p r a c t i c e s a d o p t e d , a n du n l e s s t h e s e a r e in s y m p a t h y w i t h t h e p h y s i o l o g i c a l a n d b e h a v i o u r a lr e q u i r e m e n t s o f t h e c u l t u r e d s p e c ie s , f o u l i n g a n d u n n e c e s s a r y l o a d s w i llb e p l a c e d o n t h e t r e a t m e n t u n i t s. E v e n s o, c o n s i d e r a b l e a d v a n c e s h a v eb e e n m a d e d u r i n g t h e la st d e c a d e i n w a t e r t r e a t m e n t m e t h o d s f o r t h ei n te n s i v e c u l t u r e o f f r e s h a n d b r a c k i s h w a t e r f i s h ( T i e w s , 1 9 8 1 ).

T h e r a te a n d t e m p o r a l p a t t e r n o f e x c r e t i o n i n f a n n e d c ru s ta c e a ns p e c i e s a re g e n e r a l l y l es s w e l l d o c u m e n t e d t h a n t h o s e f o r fi s h. I na d d i t i o n , f e e d i n g i s o f t e n l es s e f f i c i e n t i n c a p ti v e d e c a p o d s d u e t o t h e i rv a ri ab le r e q u i r e m e n t f o r f o o d w i t h i n t h e m o u l t c y c le a n d t h e ir h a b i to f e x t e r n a l m a s t i c a t i o n ( W i c k in s , 1 9 7 6 a , 1 9 8 2 ) . I n t h i s p a p e r , d a t ao b t a i n e d o v e r a n u m b e r o f y e ar s d u r i n g t h e c u l t u r e o f t r o p i ca l p r a w n sPenaeus s p p . a n d E u r o p e a n l o b s t e r s Homarus gammarus ( L . ) i n l ab o ra -t o r y -s c a le r e c i r c u l a t io n s y s t e m s w e r e u s e d t o e s t i m a t e ( a) t h e ra t e s a n dd i u r n a l p a t t e r n s o f a m m o n i a p r o d u c t i o n , ( b ) f o o d u t il iz a t io n a n dw a s t a g e , a n d ( c ) g r o ss n i t r i f i c a t i o n r a t e s i n b i o lo g i c a l fi lt e rs . S o m ee v i d e n c e f o r p e r i o d i c i t y i n n i t r i f y i n g a c t i v i t y w a s a l s o f o u n d a n d i sd i s c u s s e d i n r e l a t i o n t o p u b l i s h e d l i t e r a t u r e .

M E T H O D SE x c r e t i o n m e a s u r e m e n t sM e a s u r e m e n t s o f a m m o n i a e x c r e ti o n w e re m a d e o n 16 i n t e r m o u l tp r a w n s (Penaeus monoclon) o f 1 . 5 - 2 7 g l iv e w e i g h t h e l d a s p o p u l a t i o n s


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A m m o n i a p r o d u c t i o n a n d o x i d a t i o n d u r i n g p r a w n a n d l o b s t e r c u l t u r e 157o r a s i n d i v id u a l s i n t a n k s ( 2 8 1 8 1 6 c m w a t e r d e p t h ) a t d e n s i t ie s o f3 9 6 - 5 9 5 g m - 2, i .e . 1 - 1 0 p r a w n s p e r t a n k . F i l t e re d s e a w a t e r w a sd e l i v e r e d t o t h e t a n k s a t 5 l i tr e s h -1 g i v in g 7 5 % r e p l a c e m e n t i n 2 h .E f f l u e n t f r o m e a c h t a n k w a s c o l le c t e d in a v e ss e l f r o m w h i c h s a m p l e sw e r e t a k e n f o r a n a l y s i s e v e r y h o u r f o r 2 4 h p e r i o d s . E a c h v e s se l w a se m p t i e d a n d c l e a n e d a f t e r t h e s a m p l e s h a d b e e n t a k e n . T h e p r a w n sw e r e e i t h e r s t a r v e d f o r 2 d a y s a n d t h e n f e d w i t h m u s s e l o r s t a rv e d fo r3 d a y s p r i o r t o m a k i n g e a c h d e t e r m i n a t i o n . T h e r e s u l t s g a ve i n f o r m a -t io n o n w e i g h t - s p e c if i c e x c r e t i o n r a te s a n d o n t h e p a t t e r n o f e x c r e t i o na f t e r a s i ng le f e e d i n g p e r i o d . T h e p a t t e r n o f e x c r e t i o n i n t w o l o b s t e r s( 3 0 0 g liv e w e i g h t ) f e d w i t h s h r i m p w a s d e t e r m i n e d b y d i f f e r e n c e sb e t w e e n w a t e r s a m p l e s ta k e n f r o m t h e in l e t a n d o u t l e t o f e a c h in d iv i-d u a l l o b s t e r r e a ri n g c o m p a r t m e n t ( B e a r d e t a l . , i n p r e p . ) a n d a l so b ym e a s u r i n g t h e a c c u m u l a t i o n o f a m m o n i a i n s t a ti c w a t e r t es ts .C u l t u r e s y s t e m sO b s e r v a t i o n s w e r e m a d e o n 2 0 r e c i r c u la t i o n s y s t e m s ( 8 7 5 - 1 0 6 2 7 l it re sc a p a c i t y ) o p e r a t e d f o r p e r i o d s o f 2 8 - 3 5 2 d a y s ( F ig . 1). T h e s y s t e mc o n t a i n e d s t o c k s o f a d u l t o r r a p i d l y g r o w i n g j u v e n i l e m a r i n e p r a w n s o rl o b s te r s . D a t a f r o m s y s t e m s in w h i c h e x p e r i m e n t a l t r e a t m e n t s o rm a l f u n c t i o n e i t h e r c a u s e d m o r t a l i t y o r s e v e r e ly r e d u c e d g r o w t h ra te sw e r e n o t u s e d . S a li. ni ty a n d t e m p e r a t u r e , r e s p e c t i v e l y , w e r e 2 0 -3 4 ~ /o o

I ~ i u t m o o ~ m v ~ ~ r, s ~u di ~

' " "+ + i + !)+

T a n k d r a i n .A i r

Fig. 1. The general arrangement o f tanks and water t reatm ent uni ts in labo ratoryrecirculation systems.


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TABLE1

TVum(eoCueT

aWaeTem

UsnhLaoyRcaoSem(TTw

CumRenoSemCannLeaeMak(L

~ Oo

Nmosyem

1

1

1(L1

2

1

4

1

3

1

3(L

1

Nmoas

3

1

1

1

4

1

4

1

3

1

3

1

Tasyemvum

16

857239

2926

1

1410109

8

Tavumowencue1

6

5

7

1

2

8

8

4

3

5

4

taTavumoweem2

161

42

155

6

5

6

6

3

4

usa

Temuvuma

2b

1

2

8

5

2

4

4

5

6

4

5

apcaohsyem

vum

Pcanfevum(e2

2

7

10

1

2

2

1

1

8

1

7

Fema(L=mo

L

P

P

L

L

L

L

P

P

L

P

L

4%vdP=pac

9%vd

Hacoofe(m31

1

9

2

1

1

1

1

1

2

1

1

m3d

M

cfaoD=-

WW....

D

D

-

W

-

daom

ehpeue

feW=syhcwn

Dspafoao

-

~

~

.

.

.

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~

-

Cuabomsyem(k0726183

203504022012192100020008

aInuvumopcanfe

bAmsreenwerevnnsaea


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Am m on ia product ion and oxidation during prawn and lobs ter cu lture 159and 28 -+ 2C for prawns and 28-32~/0o and 20 + 2C for lobsters.Partial water changes were made once or twice each week. Furtherdetails of the systems and their management are given in Table 1, andby Beard and Forster (1973), Beard e t a l . (1977), Richards and Wickins(1979), Sedgwick (1979), Beard and Wickins (1980) and Wickins andBeard (1978).

F e e d i n g a n d c a l c u la t i o n s o f ' l o a d'Food was given once each day in the morning and was adjusted so thatsome remained uneaten the next day. Generally a 50:50 mixture offresh mussel M y t i l u s e d u l i s L. and frozen shrimp C r a n g o n c r a n g o n (L.)was given but where pellets were fed to the prawns these were obtainedfrom the Taiyo Gyo G yo Co. Ltd of Japan (Sedgwick, 1979). Deter-mination of gross food utilization was made from the differencebetween the blotted weights of fresh food supplied and of the uneatenfood removed by hand-net the next day (Beard and Forster, 1973). Tofacilitate comparisons between diets and between species, the foodand animal biomass data were converted to values representing theirnitrogen content. To this end the approximations of water and nitrogenconten t of the mussels and shrimps (annual means), pellets and juvenilelobsters and prawns shown in Table 2 were used.

TABLE 2I te m Water g N kg -1 dry weight Referen ce

(% ) ( N-Prtein~6.25 /

Myti lus edul is 83-0Crangon crangon 72-0Pelleted feed 5-0Juvenile lobsters 67-5Prawns (Penaeus 73-0spp.) (mean value)

93.9 Dare and Edwards (1975)100.6 This paper80-0 Sedgwickt al. (1979)107-0 Beard, Richards andWickins (in prep.)125.5 Guary et al. (1974),Gerhardt (1978), thispaper


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160 3". F . W i c k i n sFor example, if a populat ion of 100 g biomass of prawns (mean

weight 5 g) were fed daily with 37.5 g mussel, plus 37.5 g shrimp, thegross amount of nitrogen given would be calculated thus:Mussel: 37.5 X ( 1 0 0 - - 8 3 )100

= 6-37 g dry wt, which contains - -Shrimp: 37.5 ( 1 0 0 - - 7 2 )I00

= 10-50 g dry wt, conta ining

6.371000 93-9 = 0.598 g N, plus

10.501 0 0 0 X 100.6 = 1.056 g N, giving

Total: 1.056 + 0.598 = 1.65 g N (fed per 100 g prawns held per day)The gross nitrogen load on nitrifying filters (the estimated amount oftotal ammonia nitrogen to be oxidized) was derived (see below) frommeasurements of food consumption and biomass increase during short(2-4 week) intervals for six populations of 10-488 prawns, and inter-mittently over a 2-year period for nine individual lobsters. To simplifythe calculation, growth was assumed to be linear during such short inter-vals and results were expressed as average nitrogen values for groups ofsimilar sized animals. The nitrogen load, or nitrogen not incorporated intocrustacean flesh, included that excreted by the cultured animals butnot that contained in those fragments of cast exuvia removed andweighed with the uneaten food. Many exuvia were wholly or partlyeaten and their nitrogen conte nt thus recycled.

An example of the calculation of gross increase in nitrogen contentfor a population of prawns (mean weight 5 g) whose biomass increasedby 227 g (from 258 to 485 g) in 28 days was:

(100 - - 73)227 X (100)= 61.29 g dry weight, which contained - -

representing

61-291 0 0 0

7.69 = 0.27 g N day -l28

125.5 = 7-69 g N


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A m m o n i a production and oxidation during prawn and lobster culture 161The total weight of nitrogen fed (less that removed as uneaten food)was 4.99 g day -~ and the difference 4.99 -- 0-27 = 4.72 g N day -~ wasthe gross nitrogen load on the ni trifying filter.Freq uen cy o f sampling and ana ly t i ca l m ethod sIn each system, measurements of temperature, salinity and pH weregenerally made two or three times per week and ammonia and nitriteonce or twice each week before feeding and routine water changes. Theanalytical methods used were those described by Wickins and Helm(1981). Additionally, measurements of ammonia nitrogen, nitritenitrogen and oxygen were made at hourly intervals for up to 10 24-hperiods in a 7245 litre lobster culture system over an 8-month period.Samples were taken from the water inlets to individual lobster compar-ments and, since the water flows to compartments and biological filterwere in parallel (Richards and Wickins, 1979), the samples were alsorepresentative of the water supplied to the nitrifying bacteria in thefilter.

In this paper the term 'ammonia nitrogen' refers to the sum ofionized (NH~-N) and unionized (NHa-N) ammonia nitrogen and isdesignated, for convenience, total NH4-N.

RESULTSExcret ion o f to ta l ammonia n i t rogenSpecific ammonia nitrogen excretion rates for the prawn Penaeusm o n o d o n decreased with increase in animal size from 0.93 to 0.30 mgN g-~ day -~ at 1.6 and 27 g live weight respectively (Fig. 2). Largelobsters (300 g) excreted on average 0-3 mg N g-i day-~ but no datawere obtained for post-larval and juvenile lobsters.

Similar patterns of excretion were observed both for prawns and forlobsters (Fig. 3). Ammonia excretion in prawns fed between 08.00 hand 10.00 h was greatest between 11.00 h and 13.00 h and, in smallprawns (1-16 g), peaked again at 18.00 h. For all prawns a further peakoccurred at 24.00 h. Excretion was lowest from 01.00 h until feedingbegan again after dawn. Peak excretion times for lobsters fed at 09.00-10.00 h were 16.00 h and 22.00 h, although the first peak was not asmarked as that for prawns.


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162 J . F . W i c k i n s

I

I

EE

I -

2.0 IO

1.01 O

0 .5

0.25

0.10 I i I I I J5 10 15 20 25 30Live weight (g)

Fig . 2 . The l ive weigh t spec if ic amm onia excre t ion ra tes o f Pen a eu s m o n o d o n ( e ) .The regression line is:

in N = in 1-002 -- 0 .045 W(r = 0 .93 , deg rees o f f reedom = 12 , P '~ 0 .001)

whe re N = mg to ta l NH4-N g -1 day -1 and N = live we igh t (g) . Fo r compar i son ,d a t a f o r Penaeus indicus (o ) (Ge rha rd t , 1978) and Macrobrachium rosenbergii (x )

(Wickins, 1976a) are included.P r a w n s s t a r v e d f o r 3 d a y s e x h i b i t e d s i m i l a r b u t l o w e r p e a k s to

p r a w n s f e d o n c e a f t e r 2 d a y s s t a r v a t i o n . F o r u p t o 7 h a f t e r t h e m e a lt h e f e d p r a w n s e x c r e t e d 5 0 % m o r e a m m o n i a n i t r o g e n t h a n t h e s t a rv e dp r a w n s b u t t h i s d i f f e r e n c e f e l l t o a r o u n d 3 0 % a f t e r 2 4 h .F o o d u t i l i z a t i o n a n d w a s t a g eF o o d w a s t e dT h e w e i g h t o f f o o d r e m a i n i n g u n e a t e n 2 4 h a f t e r fe e d i n g w as d e te r -m i n e d f o r t h r e e p o p u l a t i o n s o f p r a w n s a n d e i g h t g r o u p s o f i n d i v i d u a l l y


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Ammonia production and oxidation during prawn and lobster culture 1635 o . - J r " 4 , , o , ,

g " ' , l l

3 0 (

2 o - , t \\ .~. ' ~ - ~ . , . ~ _ . o . . ~ . . ~ . ~' ~ 1 0 . ~. ( b )

0 . ' I 4 0 0 ' , / 2 = 0 0 4 1 0 ' ' ~ 0 ' '8 0 0 1 0 0 0 1 2 0 0 1 1 8 0 0 1 8 0 0 2 0 2 2 0 0 2 0 0 0 4 0 0 0 6 0 8 0 0 1 0 0 0Time

Fig. 3 . The temporal pat tern of am mon ia excret ion rate. In Penaeus monodon,(a) 1-1 0 g l ive we ight , n = 9 ; (b) 16-17 g, n = 3; (c) 27 g, n = 4; and in Homarus

gammarus, (d) 300 g, n = 4.

h e l d l o b s t e r s o v e r p e r i o d s o f 1 6 a n d 9 8 w e e k s , r e s p e c ti v e ly . T h e w e tw e i g h t o f f o o d r e m o v e d f r o m p r a w n t a nk s r a n g ed f r o m 0 t o 2 6% ( m e a n1 1% , n = 2 7 7 ) o f t h e d a il y r a t io n a n d f ro m l o b s t e r c o m p a r t m e n t s f r o m4 t o 6 6 % ( m e a n 3 2 % , n = 9 5 ) . T h e t o t a l 'w a s t a g e ' o f n i t r o g e n w a s a ls oe s t i m a t e d b y d e t e r m i n i n g t h e p e r c e n t a g e o f f o o d n it r o g e n ( t h e d a i lyr a t io n ) n o t c o n v e r t e d t o f l es h n i t ro g e n , in o r d e r t o a c c o u n t f o r t h a t l o s tb y l e ac h in g a n d f r a g m e n t a t i o n o f f o o d , a s w e l l a s t h a t l e f t u n e a t e n . T h ed a il y r a t io n v a lu e s w e r e a v e r ag e d o v e r 2 - 4 w e e k p e r i o d s t o c o i n c i d ew i t h m e a s u r e m e n t s o f a n i m a l b i o m a s s . T h e r e s u lt s, w h i c h a re s p e c if ict o t h e f e e d i n g m e t h o d s u s e d ( se e D i s c u ss i o n ), s h o w e d t h a t l os se s w e r ea g ain g r e a t e r f o r p o p u l a t i o n s o f p r a w n s t h a n f o r i n d i v id u a l ly h e l dl o b s t e r s . W h e n p l o t t e d a g a i n st a n im a l s iz e , h o w e v e r , t h e p e r c e n t a g e o ff o o d n i tr o g e n n o t c o n v e r t e d t o fl e s h n i t r o g e n i n c r e a s e d s l i g h tl y w i t hs i z e a c c o r d i n g t o t h e r e g r e s s i o n e q u a t i o n s :P r a w n ( 0 . 3 - 1 2 g liv e w e i g h t ) : % = 4 8 . 3 5 + 1 . 75 I4'( r = 0 - 9 9 , d e g r e e s o f f r e e d o m = 2 4 , P "~ 0 - 0 0 1 ) (1 )L o b s t e r ( 0 - 2 - 2 0 0 g l iv e w e i g h t ) : % = 3 0 . 8 6 + 0 . 1 8 I4I( r = 0 - 6 1 , d e g r e e s o f f r e e d o m = 8 4 , P "~ 0 . 0 0 1 ) (2 )w h e r e W = m e a n l iv e w e i g h t ( g ).

F o r 4 g p r a w n s a n d l o b s t e r s, r e s p e c t iv e l y , w a s t a g e w a s a p p r o x i m a t e l y5 5 a n d 3 1 % o f t h e d a i l y r a ti o n .


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164 J. F. WickinsGross fo od consumptionThe difference between the dally food ration and the amount recoveredthe following day represents the food consumed not only by thecultu red species but also by heterotrophic microorganisms (microbialbiomass) in the culture system. It includes that lost through dissolution.The gross consumption per 100 g of animals held, measured in 11culture trials with prawns and lobsters, decreased with increasing sizeaccording to the regression equations:Prawns:

Lobsters:

In y = In 0.963 -- 0-306 In x(r = 0.81, degrees of freedom = 22, P ,~ 0-001)

(3)

lny = In 0.203 -- 0-317 ln x (4)(r = 0.60, degrees of freedom = 95, P '~ 0.001)

where y = g N consumed per 100 g o f animals held per day and x =mean live weight (g). The slopes were not significantly differen t (P >0.05).Gross nitrogen loadThe difference between the food consumed within a recirculationsystem and that incorporated in the tissues of the cultured speciesrepresents a load on the water t reatment plant.

The calculated amounts of nitrogen to be oxidized (see Methods) fordiffe rent sizes o f animal and di fferent husbandry practices are shown inFig. 4.

Taking two widely separated examples from the prawn data, feedinga population of 25 prawns of mean weight 4 g (i.e. 100 g biomass) willproduce at best (pelle ted feed, low stocking density) 0.35 g N day -1,95% confidence limits 0.25-0.48 g, and at worst (fresh foods, highstock dens ity) 0.87 g N day -x, 95% confidence limits 0-60-1.29 g, to beoxidized by the filter. For lobsters of similar size the figure was 0-05g N per 100g held per day -1, 95% confidence limits 0.03-0-09 g.A general estimate of the proportion of this nitrogen that is excreted asammonia nitrogen in prawns may be obtained by comparing the dailyamo unt of ni trogen to be oxidized (Fig. 4) with that excret ed by


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A m m o n i a p r o d u c t i o n a n d o x i d a t i o n d u r i n g p r a w n a n d l o b s t e r c u l t u r e 1652 . 0

1 . 0

t -

~ 0 . 2

0 . 1o

0 . 0 2

F i B . 4

x ( a )

~ x (b ) o(c )

o

o oOO OO O0 0 5 o o g , . . L _ ,

o O O O ~ d OO - - ( t l )

, , I I . . . . . . . . . . 1I l O 1 0 0Live weight ( g )

Exam ple s o f the d i f fe rences in the g ross n i t rogen load on b io log ica l f i lt e r sdue to d ie t , feeding f req uen cy, anim al s ize and spec ies .

( a ) P rawns , f r e sh foods , one feed pe r day , po pu la t io n> 50 m -2 , regression :In y = In 1 .21 - - 0-23 In x ( r = 0-89, degrees o f f reed om = 24, P ~ 0-001) .(b) Prawns, pe l le ts, on e feed per day, popu la t ion > 50 m -2 , regression: l n y =In 0-94 - - 0 .29 In x ( r = 0 .81 , degrees o f f reed om = 17, P ~ 0 .001 ) .

(c ) Prawns, pe l le ts , two feeds per day, po pula t ion < 20 m -2 , regression: l n y =In 0-58 - - 0-37 In x ( r = 0-99, degrees of f reed om = 3 , P ~ 0 .001) .

(d) Lob ste rs , f resh food s, one feed per da y, indiv idua l ly he ld anim als , regression:In y = In 0 .06 - - 0 .14 In x ( r = 0-66, degrees o f f reedom = 85, P ~< 0 .001) .

P . m o n o d o n ( F ig . 2 ). A s s u m i n g t h a t a m m o n i a n i t r o g e n is 7 5 % o f t h et o t a l n i t r o g e n e x c r e t e d b y p r a w n s (s e e D i s c u s s io n ) , th e n t h e t o t a ln i t r o g e n e x c r e t i o n f r o m , f o r e x a m p l e , 2 5 4 g p r a w n s w i l l b e 0 - 0 8 4 +0 - 7 5 = 0 . 1 1 2 g N 1 0 0 g -~ d a y - 1, o r a b o u t 1 3 - 3 2 % o f t h e t o t a l , d e p e n d -i ng o n d i e t a n d s t o c k i n g d e n s i ty . T a b l e 3 i n d i c a t e s t h a t e x c r e t e d n i t r o g e nb e c a m e a m o r e i m p o r t a n t c o m p o n e n t o f g ro ss n i t r o g e n lo a d w h e n t h ep r a w n s w e r e f e d m o r e e f f i c i e n t l y w i t h p e l le t s ( b u t s ee D i s c u ss i o n) .

F o r la rg e 3 0 0 g l o b s t e r s t h e p r o p o r t i o n o f t o t a l n i t r o g e n e x c r e t e dw a s e s t i m a t e d t o b e a b o u t 1 3% o f t h e g r o s s n i t r o g e n lo a d . N o c o m p a r -a b l e d a t a w e r e a v a il a b le f o r p o s t - l ar v a l a n d j u v e n i l e l o b s t e r s .


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166 J. F. l~ickinsTABLE 3Excreted Nitrogen as a Percentage of Total Nitrogen Load in Marine RecirculationSystems

De nsity Fo od Feeds Mean live weight ( g)(m-2) per day 0 .8 4 .0 10 .0 20 .0 300

Prawns >50 Fresh 1 10.3 12 . 8 12.0 9.1 -Prawns >50 Pelleted 1 12-8 17 .7 17-7 - -Prawns


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Ammoni a producti on and oxi dation during prawn and lobster cultur e 167

o ~ 6 . 5Et '4o

6 .0 I I I I I I I I I0 . 2 5o~E

Z-r

Z 0 . 0 I I

Fig. 5.

I-&Ev

zIg

Z

0 . 1 0

0 . 0 5

0 . 0 I I I | I I | I I0 8 O 0 1 2 O 0 1 6 O 0 2 0 O 0 2 4 O 0 0 4 O 0 0 8 O 0 1 2 O 0 1 6 O 0T i m e ( h )

The diurnal f luctuat ion s o f o xyg en, a m m onia and ni tr i te n i trogen leve ls ina laboratory 7 24 5 l i tre lobster culture system .

b a c t e r ia l a t t a c h m e n t , t h a t is , t h e s p e c i f i c s u r f a c e a r e a o f t h e f i lt e rm e d i u m .

T o e n s u r e t h a t e a c h f il te r w a s w o r k i n g w i t h i n it s n i t r if y i n g c a p a c i t y ,o n l y d a t a c o l le c t e d w h i l e a m m o n i a a n d n i tr i te n i t r o g e n c o n c e n t r a t i o n sr e m a i n e d b e l o w 0 - 8 m g l i tr e -~ f o r se v e ra l m o n t h s w e r e u s e d . T h e r o u t i n ep a r ti al w a t e r c h a n g e s o n l y r e d u c e d t h e n i t r o g e n l o a d s l ig h t ly a n d o n l yo n o n e o r t w o d a y s e a c h w e e k . F o r e x a m p l e , i f t h e r e c ir c u la t in g w a t e rc o n t a i n e d 0 . 2 m g N H 4 - N l i tr e -~ a n d t h e r e p l a c e m e n t w a t e r 0 - 0 3 m gl it re - ~ , t h e n a w e e k l y r e n e w a l o f 5 0 0 l it r e s o f w a t e r f r o m a 1 0 0 0 l it rec a p a c it y s y s t e m w o u l d r e m o v e 5 0 0 X ( 0 . 2 - 0 . 0 3 ) = 0 . 0 8 g N H 4 - Nw e e k -~ . T h i s l o s s is i n s ig n i f ic a n t c o m p a r e d w i t h t h e n i t r o g e n l o a d i n g , a si ll u s tr a t e d b y t h e d a il y p r o d u c t i o n o f ' l o ad ' n i tr o g e n f r o m a t y p i c a ls y s t e m c o n t a i n i n g 2 k g o f 1 0 g p r a w n s fe d m o d e r a t e l y c a r e fu l ly ( F i g . 4 ,l i n e ( b ) ) , v i z. 0 - 4 8 X 2 0 = 9 . 6 g N o r 6 7 - 2 g N w e e k - ~. I n F i g . 6 t h ee s t i m a t e d g r o s s n i t r i f i c a t i o n r a te ( g N o x i d i z e d m - 2 d a y - ~ ) is p l o t t e da g a i n st t h e g r o w t h r a te o f t h e c u l t u r e d a n i m a l e x p r e s s e d a s t h e d ai lyi n cr e a se in n i t r o g e n c o n t e n t o f t h e t o t a l p o p u l a t i o n h e l d . O v e r al l,n i t r i f i c a t i o n r a te s i n c r e a s e d f r o m 0 - 0 3 t o 0 - 4 3 g N m - 2 d a y -~ a n d


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168 J . F . W i c k i n s

A

EzOI

o "

Z

0.5

0.2

0. 1

0.05

0.02

J

I I0.01 0.1 1.0G r o w t h r a t e (gNd -1)

Fig. 6. The relat ion be twe en est im ated gross ni tr i f icat ion rate in plast ic mediaf il ters and g rowth rate o f cul tured prawns. Minimum input concen t rat ion o fam mon ia n it rogen 0 .1-0 .3 mg l i tre- l ; hydraul ic load 153-18 2 m 3 m - 3 da y -~ .

s h o w e d n o t e n d e n c y t o d e c r e a s e w i t h i n c re a s in g a ni m a l g r o w t h ra te , a sm i g h t b e e x p e c t e d i f t h e n i t ri f y in g c a p a c i t y o f t h e f i lt e r w e r e e x c e e d e d .

T h e n i tr a t e r e s u lt in g f r o m n i t r if i c a t i o n w a s m a i n t a i n e d b e t w e e n3 a n d 5 5 m g N O 3 - N l i tr e -~ , m e a n l e v e ls , b y d i l u t i o n , w h i c h r e s u l t e d i no n l y a s l o w i n c r e a s e i n n i t r a t e l e v el s o v e r t h e c u l t u r e p e r i o d .

D e s p i t e t h e r e gu l a r, p a r t i a l w a t e r c h a n g e s a n d c a r e f u l c o n t r o l o ft e m p e r a t u r e , s a l i n it y a n d p H , c y c l i c f l u c t u a t i o n s i n b io l o g i c a l f i lt e rp e r f o r m a n c e w e r e o b s e r v e d i n 25 tr ia ls m a d e u n d e r d i f f e r e n t lo a dc o n d i t i o n s i n 2 0 s e p a r a t e s y s t e m s . T h e m a g n i t u d e o f t h e f l u c t u a t i o n si n a m m o n i a a n d n i t r it e l e v e ls w a s ir re g u l a r, b e t w e e n 0 .1 a n d 0 . 6 m gN l it re -1 , a n d o c c u r r e d i n s y s t e m s w i t h m a t u r e , w e l l - e s t a b l is h e d n i t ri f y -i ng f i lt e rs . T h e m e a n i n t e r v a l b e t w e e n t h e f l u c t u a t i o n s w a s 3 -5 w e e k s ---s t a n d a r d e r r o r = 0 .1 , n = 1 1 4 f o r a m m o n i a a n d 3 . 9 w e e k s - + s t a n d a r de r r o r = 0 - 2 , n = 8 8 , f o r n i t r i te n i t r o g e n . T h e f r e q u e n c y d i s t r i b u t i o n so f th e o b s e r v e d in t e r v a ls f o r a m m o n i a a n d n i t r i t e a r e s h o w n i n Fi g. 7 .


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Ammonia production and oxidation during prawn and lobster culture 169

40-

F i g . 7 .

3 5 -

30 -

25 -

20-

15 -

10 -

5io l

25

20

15

10

( a )

(b )

2 3 95 6 7 8In te rva l (weeks)

I 110

T h e f r e q u e n c y d i s t r i b u t i o n o f f l u c t u a t i o n s i n p r e - f e e d ( a ) a m m o n i a a n d( b ) n i t r i t e l eve ls i n 2 0 l ab o r a t o r y r ec i r cu l a t i on sys t em s .


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170 J. F. lCickinsDISCUSSION

F o o d w a s ta g e a n d e x c r e t io nMost of the culture systems discussed in this paper contained stocksof crustaceans that were being grown either for breeding or to deter-mine maximum growth rates in captivity (Arnstein and Beard, 1975;Beard e t a l . , 1977; Wickins and Beard, 1978; Richards and Wickins,1979; Beard and Wickins, 1980). A mixture of fresh mussel and frozenshrimp was the best diet available for this purpose, but the dailypreparat ion of the mussel meats and the manual feeding methods usedwere so time-consuming that only one feed per day was practicabledespite the wastage this caused; 11 and 32% of the daily ration forprawns and lobsters, respectively, were removed uneaten. The lowerfigure for prawns is misleading because considerable fragmentation anddispersal of food occurred in the prawn cultures due to communalfeeding, feeding behaviour and, doubtless, the high temperaturesinvolved. Overall, more than 50% of the nitrogen in the daily ration wasnot converted into prawn flesh. A similar value (58%) was reported fortrout grown from 48 to 134 g (mean weight) in recycled water (VanToever and MacKay, 1981). Greater wastage by juvenile prawns wasfound by Gerhardt (1978) who fed 0.5-4.0 g P e n a e u s i n d i c u s witha pelleted diet at 2-5% of the live weight per day for 2 months. Uneatenfood fragmented and was oxidized within the sub-gravel filter. Approxi-mately 80% of the food nitrogen given in his experiments was notconverted into prawn flesh and represented the nitrogen load on thefilter. Although the present experiments were not designed to testfeeding f requency and water exchange rates, Fig. 4 illustrates howfresh foods, infrequent feeding and high stocking densities can placea high gross nitrogen load on water treatment units in the recirculationsystems that contained prawns (see also Wickins, 1976a, 1982). Morefrequent feeding with pelleted diets is known to improve growth inprawns (Sedgwick, 1979) and at low population densities seems likelyto reduce the risk of fouling.

The conclusion that excreted nitrogen becomes a more importantcomponent of gross nitrogen load as prawns are fed more efficientlywith pellets (Table 3) must be viewed with some caution, since theestimates were based on the assumptions that (a) ammonia nitrogenis 75% of excreted nitrogen (Snow and Williams, 1971; Gerhardt, 1978)


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Ammonia product ion and ox idat ion dur ing prawn and lobs ter cul ture 17 tand (b) similar excretion rates occurred in prawns reared on differentdiets and stocking densities. This assumption is debatable since,although excretion rate in juvenile M a c r o b r a c h i u m r o s e n b e r g i i appearednot to be influenced by diets of plant, animal or pelleted material(Nelson e t a l . , 1977), excretion in C r a n g o n f r a n c i s c o r u m was shown tobe influenced by diet (Nelson e t a l . , 1979).N i t r i f i c a t i o n

Diurnal variations in the chemistry of recycled water (Rosenthal, e t a l . ,1981) dictate the time when samples must be taken to obtain thespecific informat ion required. The measurements presented here wereobtained from samples collected prior to feeding and water changes andrepresent, for example, min imum levels of nitrogen to which the micro-organisms in the biological filter are exposed. They do not representthe peak levels to which animals might be exposed in the culture tankswhich, although higher, rarely exceeded 0.7 mg total NH4-N litre -1,1-0 mg NO2-N litre -1, and 75 mg NO3-N litre -1 (see also Wickins, 1976b,1981). Knowledge of the varying diurnal demands made on watertreatment units allows appropriate periodic adjustments to be made,for example, to aeration rates and hydraulic load to mechanical andbiological filters. To check for the occurrence of harmful levels ofmetabolites, the time of sampling for each substance must be deter-mined in relation to feeding times.

The estimates of the overall nitrifying performance of percolatingfilters obtained in this study are likely to substantially underestimatetrue nitrification rates which could be as much as two to three timeshigher. This is because two assumptions are inherent in the estimatesof gross nitrification rate: firstly, that the microbial biomass within thesystem contains only a small amount of the nitrogen in relation to thegross nitrogen load, and secondly, tha t the nitrifying organisms areevenly distributed throughou t the filter medium.

The assumption that the microbial biomass contains relatively littleof the nitrogen would seem reasonable for the filters which containedplastic med ium which had a high propor tion o f voids (93%). In contrast,graded gravel medium (nominal maximum size 2-5 cm) which hasa similar specific surface area to the plastic medium ( ~ 160-200 m 2 m -3)contains 40-50% voids and is thus more likely to support greaterquantities of microbial biomass (Wickins and Helm, 1981). However,


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17 2 J . F . W i c k i n st h e m i c r o b i a l f i lm a t t a c h e d t o t h e s u r f a c e s w i t h i n p e r c o l a t i n g f il te r su n d e r g o e s p e r i o d i c , p a r t ia l s l o u g h in g , s o m e o f t h e f r a g m e n t s b ei n gw a s h e d f r o m t h e f i l t e r a s s u s p e n d e d f i l m - h u m u s s o li ds . S h o r t - t e r m ( n o n -s e a s o n a l ) c y c l i c s l o u g h i n g a n d v a r i a t i o n s i n f i l t e r e f f i c i e n c y ( B r u c e a n dM e r k e n s , 1 9 7 3 ) a re w e l l - k n o w n o c c u r r e n c e s i n w a s t e w a t e r t r e a t m e n tp l a n t s, a n d p e r i o d i c i t y r an g e s f r o m a b o u t 1 4 t o 3 0 d a y s ( H e u k e l e k i a na n d C r o s b y , 1 9 5 6 ; S a n d e r s , 1 9 6 6 ; L . F . R e y n o l d s , 1 9 7 4 , p e rs . c o m m . i nH o w e l l a n d A t k i n s o n , 1 9 7 6 ). I n t h e l a b o r a t o r y m a r i n e fi lt e rs , a s i m i la rp e r i o d i c i t y ( 2 4 - 2 7 d a y s ) i n p r e - f e e d a m m o n i a a n d n i tr i t e le v els w a so b s e rv e d f o r w h i c h n o e x p l a n a t i o n m o r e s u it a bl e t h a n s l ou g h i n g c o u l db e o f f e r e d . T h e o c c u r r e n c e o f s u c h s l o u g h i n g w o u l d l e a d t o th e lo s s o fa n u n k n o w n a m o u n t o f n i tr o g e n ( m i c ro b i a l b io m a s s ) o v e r l o n g c u l t u rep e r i o d s .

T h e s e c o n d a s s u m p t i o n a b o u t e v e n d is t r ib u t i o n o f n it r if y i n go r g a n i s m s i s i n f a c t u n l i k e l y t o b e t r u e f o r d e e p f i lt e r s b e c a u s e h e t e r o -t r o p h i c m i c r o o r g a n i s m s c o m p e t e s u c c e s s f u ll y w i t h n i tr i fi e rs f o r s p a c ea n d w o u l d t e n d t o d i s p la c e n i tr i fi e r s t o t h e l o w e r r e g i o n s o f t h e f i lt er .T h e p r o p o r t i o n o f th e f i l t e r t h e y w o u l d o c c u p y is t h e r e f o r e u n k n o w nb u t p r e s u m a b l y w o u l d d e p e n d u p o n t h e a m o u n t o f o r ga n ic o x i d a t io no c c u r r i n g i n t h e f i l te r (S ~irn er, 1 9 8 1 ) . A n y o r g a n i c o x i d a t i o n w o u l dt h u s l e a d i n t u r n t o o v e r e s t i m a t e s o f f i l te r n i tr i f y i n g c a p a c i ty .

F o r t h e s e r e a s o n s , a n d b e c a u s e r e m o v a l o f o rg a n i c m a t e r i a l b ys e p a r a te m e c h a n i c a l f i l tr a t i o n a n d f o a m i n g c a n a f f e c t f i lt e r p e r f o r m a n c e ,n o a t t e m p t w a s m a d e t o c a l c u la t e c a r r y in g c a p a c i t y . E x p e r i e n c e h a s

" s h o w n , h o w e v e r , t h a t p e r c o l a t i n g f i l te r s iz e s b a s e d o n n i t r i f i c a t i o n r a t e so f 0 - 3 - 0 - 5 g N m - 2 d a y -1 h a v e b e e n s a t i s f a c t o r y f o r l a b o r a t o r y c u l t u r es y s t e m s ( W i c k i n s a n d B e a r d , 1 9 7 8 ; R i c h a r d s a n d W i c k in s , 1 9 7 9 ) .I n d e e d t h e se s y s t e m s p r o v i d e d s u f f ic i e n tl y g o o d e n v i r o n m e n t s t o a l lo w :( a) f o u r s p e c ie s o f p e n a e i d p r a w n s t o b e r ea r e d t o m a t u r i t y w i t h i n 8 - 1 8m o n t h s a n d i n d u c e d t o s p a w n ( A r n s te i n a n d B e a rd , 1 9 7 5 ; B e a r d e t a l . ,1 9 7 7 ; B e a r d a n d W i c k in s , 1 9 8 0 ) ; ( b ) b a t c h e s o f l o b s t e r s to b e r e a r e d a t3 - m o n t h i n t e r v a l s , r e g a r d le s s o f s e a s o n , f r o m e g g t o m a r k e t si ze (c . 4 0 0g ) in l es s th a n h a l f t h e t i m e n o r m a l l y t a k e n b y n a t u r a l p o p u l a t i o n s( R i c h a r d s a n d W i c k i n s , 1 9 7 9 ) .

A C K N O W L E D G E M E N T ST h e a s si st an c e o f a s t u d e n t , M r R o m e o M ila n , w h o m e a s u r e d p r a w ne x c r e t i o n i s d u l y a c k n o w l e d g e d .


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Ammonia production and oxidation during prawn and lobster culture 17 3R E F E R E N C E S

Arns te in , D . R . & Bea rd , T . W. (1975) . Induced ma tu ra t ion o f the p rawn Penaeusorientalis Kish inouye in the l abora to ry by means o f eyes t a lk remova l . Aqua-culture, 5 , 411-1 2 .

Bea rd , T . W. & Fors t e r , J . R . M. (1973) . A g rowth expe r imen t w i th Penaeusmonodon Fab . in a c losed sys t em. ICES C.M., K: 39 , 6 pp . (mimeo) .

Beard , T. W. & Wickins , J . F . (1980) . The breeding ofPenaeus monodon Fabric iusin l abora to ry rec i rcu la t ion sys tems . Aquaculture, 2 0 , 7 9 - 8 9 .

Beard , T. W. , Wickins , J . F . & Arnste in , D. R . (1977) . The breeding and growth ofPenaeus merguiensis de Man in l abora to ry rec i rcu la t ion sys t ems . Aquaculture,10 , 275-89 .Bruce , A . W. & M erkens , J . C . (1973) . Fu r the r s tud ie s o f pa rt i a l t r e a tm en t o fsewage by h igh-ra te b io logica l f i l t ra t ion . War. Pollut. Control, 7 2 , 4 9 9 - 5 2 7 .

Dare , P . J . & Edwards, D. B . (1975) . Seasonal changes in f lesh weight and b io-chemica l com pos i t ion o f musse ls (Mytilus edulis L. ) in the C onw y e s tua ry , Nor thW ales. J. exp. mar. Biol. Ecol., 18, 89-97.

Gerha rd t , H . V . (1978) . Th e cu l tu re o f Penaeus indicus Milne Edwards in experi-m enta l c losed system s w i th special re fe rence to w ater qua l i ty . MSc Thesis ,Rhod es Un ive rsi ty , Graha mstow n , Sou th Af r i ca , 86 pp .

Gu a ry , J . C ., Kay ama , M. & M urakami , Y . (1974) . L ip id cla ss d i s t r ibu t ion and fa t tya c id c o m p o s i t i o n o f p r a w n , Penaeus japonicus Bate . Bull. Jap. Soc. Scient. Fish.,40 (10 ) , 1027-32 .

Heukelekian , H. & Crosby, E. S . (1956) . Sl ime format ion in pol lu ted waters . I I .Fac to r s a f fec t ing s l ime g ro wth . Sewage Ind. Wastes,2 8 , 7 8 - 9 2 .

How el l , J . A. & Atkin son , B . (1976 ) . S loughing of m icrobia l f ilm in tr ick l ing f il te rs .Wat. Res., 10, 307-15.

M offe t t , W. L . & F i she r , W. S . (1978) . Am mo nia p roduc t ion ra t e s ofArtemia salinaunde r va r ious cu l tu re cond i t ions . J. Fish. Res. Bd Can., 35, 1643-8 .

Nelson , S . G. , Knig ht , A. W. & L i , H. W. (1977 ) . The me tabol ic cost of fo od u ti liza-t i o n a n d a m m o n i a p r o d u c t i o n b y juvenileMacrobrachium rosenbergii(Crustacea :Pa laemonidae ) . Comp. Biochem. Physiol., 57A, 67 -72 .Ne l son , S . G . , S im mo ns , M. A . & Knigh t , A . W. (1979) . Am mo nia exc re tion by theben th ic e s tua r ine sh r imp Crangon franciscorum (Crustacea : Crangonidae) inre la t ion to d ie t . Mar. Biol., 54 , 25 -31 .

Richards, P . R . & Wickins , J . F . (1979) . M inis t ry of A gricul ture , Fisheries and Fo od ,Lo bste r Cul ture Research . Lab. L ea r . , Direc t . Fish . Res., L ow esto f t , (47) , 33 pp .

Ro sentha l , H. , A ndjus, R . & KrOner , G. (1981) . Dai ly var ia t ions o f wa ter qua l i typaram eters u nde r in tensive cul ture con di t ion s in a recyc l ing system . In : Aqua-culture in Heated Effluents and Recirculation Systems. Vol. 1, ed. K. Tiews,H een em an n Verlagsgesellschaft , Berlin, pp. 1 13-2 0.

Sanders , W. M. I l l . (1966) . Oxygen u t i l iza t ion by s l ime organisms in cont inuouscul ture . Air and Wat. Pollut. Int. J., 10, 253-76.


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174 J. F. WickinsS~'rner , E. (19 81) . Rem oval o f d issolved and pa r t icula te organic m at te r in h igh-ra te

t r ickl ing f i l te rs , l~at. Res., 15 , 671 -8 .Sedgwick , R . W. (1979) . Ef fec t o f r a t ion s ize and feed ing f requency on the g rowthand food conve rs ion o f juven i le Penaeus merguiensis de Man . Aquaculture, 16,

2 7 9 - 9 8 .Snow, N. B . & Wil l iams, P . J . le B . (1971) . A s imple method to de te rmine the O:N

ra t io o f sma l l ma r ine an ima l s . J. mar. biol. Ass. UK, 5 1 , 1 0 5 - 9 .T iews , K . (Ed . ) (198 1) .A quac u l tu re in Heated Effluents and Recirculation Systems,

Vols 1 and 2, He ene m an n Verlagsgesellshaft, Berl in.Van Toeve r , W. & MacKay , K . T . (198 1) . A m odu la r r ec i rcu la t ion ha tche ry and

rearing sys tem for s alm onid s uti l ising ecological design principles. I n: Aquaculturein Heated Effluents and Recirculation Systems, Vol . 2 , ed . K. Tiews, Heen em annVerlagsgesellshaft, Berlin, pp. 40 3- 13 .

Wickins , J . F . (1976 a) . Prawn bio logy and cul ture . In : Oceanography and MarineBiology: An Annual Review, Vol . 14 , ed . H. Barnes, Ab erdeen Universi ty Press ,p p . 4 3 5 - 5 0 7 .

Wickins , J . F . (1976 b) . The to l e rance o f wa rm wa te r p rawns to r ec i rcu la t ed wa te r .Aquaculture, 9, 19-37.

Wickins , J . F . (1981) . Water qua l i ty requirements for in tensive aquacul ture :a review. In: Aquaculture in Heated Effluents and Recirculation Systems, Vol . 1 ,ed. K. Tiews, Hee ne m ann Verlagsgesellschaft, Berl in, pp. 17- 37.

Wickins , J . F . (198 2) . Op portu ni t ies for the fa rm ing of Crustacea in weste rntempera te regions. In : Recent Advances in Aquaculture, eds J . F . Mu ir and R . J .R o b e r t s , C r o o m H e l m , L o n d o n , pp . 8 7 - 1 7 7 .Wickins , J . F . & Beard , T. W. (1978) . Minis t ry of Agricul ture , Fisher ies and Food,Praw n Cul ture Research . Lab. Leaf l . Direc t . Fish . Res., Lo w esto f t , (42) , 41 pp .

Wickins , J . F . & Helm, M. M. (1981) . Sea water t rea tment . In : Aquarium Systems,ed . A . D . Haw kins , Academ ic Press, L ond on , pp . 6 3 -128 .

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Wickins 1985 Aquacultural-Engineering

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