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FOOD AND FEEDING PATTERNS OF THE SOUTHERN BROWN SHRIMP Penaeus subtilis PEREZ-

FARFANTE,1967 (CRUSTACEA, PENAEIDAE)

BY

©ALBERTO JORGE PINTO NUNES, B.S<. M.S<.

A THESIS SUBMITrED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL FULFlLLMENT OF THE REQUIREMENTS FOR THE DEGREE

OF DOCTOR OF PHILOSOPHY

DEPARTMENT OFBIOLOGY FACVLTY OF SCIENCE MEMORIAL UNIVERSITY OF NEWFOUNDLAND

OCTOBER. 1999

ST.JOHN'S NEWFOUNDLAND

©

Permission basbeengranted to the National Library of Canada to microfilm this thesis and to lend or sell copies of the film.

The author (copyright owner) has reservedother publication rights. and neither the thesis nor extensive extracts from it may be printed orotherwise reproduced withouthislher- wriuen permission.

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ABSTRACT

Penaeid shrimp farming consONtes the most imponant aquaculture sectorin economic value.Inrecent years however, the activity has faced slower progress in production despite a rapid intensification of production methods. The description and quantification of the food and feeding patterns of cultured penaeids may improve resource-usc efficiency and conserve inputs critical tothe sustainabiJity aCthe activity.

This thesis investigated the food and feedingpatternsof Pmanu suINt/is under laboratory-controllcd and culture conditions. Vidco-RCOrding of shrimp feeding beh.avioun was used toenrniDefoodhaodlin&efficieucyandsize selectivity. Shrimp feedinglevels in response to food dispersal methodweredetermined through qwmtitativc analysis of stomach contClltsand stable carbon isotope mass spectrometry. Theabundance of polychaclcs was used to study the effects of shrimp prMa!ion, stocking density and supplemental feeding. Partial integration ofdata was carried out using STELLAIIID.

Results indicated that Pnwevs subtilis feed nwUpulation was inversely related to foodparticlesize.with Luge peUets beingless preferred thansmall ones. Within the feed size range examined,shrimpsize had no significant efl'ed onbaudlingefficiency.Feed broadcastingwas a more effective methodinrqardstoshrimp food intake, resu.l.ting in a greatcr access and a higher consumption offoodmnongthe cultured shrimppopulation,a lower number of empty stomachs and a greater OCCWTence of feed inP. subtilisdiet.

Ingestion of food was a function of shrimpbodyweighLFeeding intensity increased

..

progressivelywithshrimpsize.but inverselyinpcrccntaIe terms. Forqut c1ear.ux:e nates peaked 3 h after food recovery. while the bulk of faeceswas produced within I h.

Polychaete~wasaffected by higher shrimp stoclcing densities.Artificialfceding promoled higher polychaete levels, althoughwasDOtcapable:of aJleviatiDgshrimpgrazing pressureatincreased stockingdensities.

Results indicalcdthatcrumbles and broken pellets may be more advantageous in the culture ofPertaew suhti/is. Feeds should be broadcast eVenly over lite culturearea.

and administered regularly al continually reduced amounts. Rations should vary in accordance to estimates ofP. subli/is body weighl and account for the initial polychaele abundance and shrimp stocking densities.

Iv

ACKNOWLEDGEMENTS

I Msh to express sincere gratitude 10 my supervisorDr.Jay Parsons. His guidance, friendship, intellectual views and discussions throughout all stages ermy Doctorate were of great contribution andart:very much appreciated. I am alsolhankfu.ItoDr.Stephen Goddard(SultanQaboosUniversity. Department of Fisheries). who stimulated my inltial interestinpenaeid feeding cco'ogy and supervised thefirstyear of my SlUdics.

AspeciaJdebeof gratitudeisowedtoDr. Tereu CristinaGcsteir.a(lnstitutode Ciencias do MM. GECMAR Grupo de Estudos deCaawioMarinbo), whosepencvCRDCC and hardwork have helped me10 succ::essfilllyconduct allof my graduate field investigationsinBrazil. I amabo grateful 10Dr.Anthony Dickinson (Memorial University of Newfoundland, International Programmes) who provided mewiththe opportunity 10 continue my graduate studies at Memorial, again devoting all means ofsupportand confidence in mywork.

Manythankstothe following people for their valuabk assislance, helpful COmmcrlll and encouragement:Dr.CarlosAmlrRochaprovided. friendlyworkingenvironment at lnstitutode Cifncias do MarJUFC. supplying laboratory space and some of the land tnlnSpOlUtion; Francisco da Costa (Fran) made helpful remarks dwlog construction of the aquarium system;Mr.GeraJdo Cicero Borba (AgribnmdsPuri.nado Brasil LtdL. 810 LourcnlFo da Mat&. PE, Brazil) and Ms. AnaC.Guerrelhas (AqualCC Industrial Pecuiria Ltda., Canguarctama. RN, Brazil). respectively, donated formulated shrimp feed and

Penaeus subri/is post.latvae for one of the studies; JerryPulchandirected the carbon isotope mass spectrometry aDalysi5; LauraHalfyudaDdKeithRideout provided valuable infonnation and tniniDg on feed cbemical analysis; shrimp farm owners.Mr.LivinioJ.

Sales (Artemisa Aquiculnua S.A., Acar.ui, CE, Brazil),Mr. Luis C. Ak1atz and Mr.

Fernando C. Sandoval (Tccnario Tccnologia de Camarlo Uda...Arcs.RN, Brazil) pennitted thework to be conducted in lheir operations. gently providing accommodations andlogistical support; Pedro Carlos Martinsshared his experiences on polychaete dynamics; Pedro SU1Liva and Arlinda CeluJar helped during transport of live shrimp, sea water. feed and other heavy equipment aDd material to and from the field site; Thales Andrade aided during set up of laboralory and field studies; Wilson Franklin gave experienced consultation on polychaete taxonomy; Zelia Madeira arranged the filming syslem for shrimp feeding behavioural trials. The helpful hand of numerous other people.

including !he efficient services of thestaffatCAPESIMEC. Memorial Univemty. Marine Institute,lnstituto de CiiDcias doMar. Artcmisa and TecnarIo, are also very much appnx:iated.

My Ph.D. studiesinCanadaWC!'efunded by the Brazilian FederalMinisuyof Education, FW'ldat;ioCoordenarlodeAperfci~entode Pessoal de Nivel Superior (CAPESIMEC. Ph.D. Grant N° BEX2S03J9S-6. Brasilia, OF, Brazil). The Canadian International Development Agcocy (CIDA) through the Canadian Centrefoe-International Fisheries. Training and Development of Memorial University of Newfoundland supported the first year of theprogramme. Field and laboratory workinBrazil was made possible by financial assistance from the Brazilian Federal Ministry of Science and Technology.

Consellio Nacional de Desenvolvimenlo Cientifico e Tecnol6gico (CNPqlMCT. Grant N°

vi

301682195.0, Brasilia, OF, Brazil) and Banco do Nordeste, Fund for Scientific and Technological Development (BNlFUNDECIISNDCT. Fortaieza. CEo Brazil). Their financialsuppon isgratefully acknowledged.

Itis alsoapleasure 10recognisethedevoted time and valuable input made by Drs.

Anthony Diclcinson and Richard Haedrich. membcn of my Supervisory Comminee, in the finaldr.lftsofthisthesisandduringallstagesof my Doctoral programme. Finally,on a more persooa.I note. I wish 10thankthe unrc:servedundersraoding,patience and incentive of all my family, especially my wife, Calia Melo.whoenswedIhada stable environment to live and work during all my graduate years.

This thesis contains material published in peer-reviewed journals, magazines and conference proceedings. PortionsofChapter I were published in World Aquaculture (1998.

29: 27-37). A preliminary and modified version ofOlapter 2 was publishedinthe Boletim do Instituto de Pesca, (1997, 24: 11-20). Chapters 2 and 3 as they stand, were publishedin the Marine and Freshwater Behaviour and Pbysio'ogy (1998,31: 193-213) andinthe Journal oftbe World Aquaculture Society (1999, 30: 331-348), respectively. Cbapters 3 and 4 were presented at the Aquaculture Brazi1'98Mectinl(Recife,Brazil), with abstracts publishedinthe conference proceedings. Chapter 4 has been acc.c:pted for publicationin the joumal of Aquaculture. Both Chapters5and 6 arc currently UDder review in the joumal.s ofAquaculture and AquacultunlEngineering.respectively.

ToCatia

TABLE OF CONTENTS

POI'

ABSTRACT •••..•....••...•.••. iii

ACKNOWLED<;EM.ENTS .

TABLE

or

CONTENTS...

LIST OF TABLES..

LIST OF FIGURES .

LIST OF ABBREVIATIONS AND SYMBOLS...

LIST OF APPENDICES...

CHAPTER 1: GENERAL INTRODUCTION....

1.1General Considcr2tions...

1.2Rationale andResearch Objectives . CflAPTER 2: rOOD HANDLING EFFICIENCY AND PARTICLE SlZE SELECTIVITY BY THE SOUTHERN BROWN SHRIMPPrlf._s.btilis FED A DRY PELLETED FEED...

2.1 Introduction...

2.2Materialsand Methods . 2.2.1 Classification of Shrimp and Feed Size 2.2.2 Feed Proximate Chemical Analysis . 2.2.3 ExperimentalDesien and Apparatus . 2.2.4 Feed Manipu.lation and Size Selectivity...

"'I nU

"",I

11 II 14 14 IS 10 19

2.2.5 Feeding Behavioural Analysis

22.6 Statistical Analysis... . .

2.3ResuJLs ...••..•

2.3.1 Chemical Composition of Feed .

2.3.2 Feed Handling... . _ .

2.3.3 Feed Panicle Size. . H.

2.3.4 Shrimp Size . 2.35Timelnlerval . 2.3.6 Feed Panicle Size Selection...

2.4 Discussion...

2.4.1 Effects of Feed Particle Size...

2.4.1.1 Capture Efficiency.

2.4.1.2 Consumption Efficiency....

2.4.2 Effects of Shrimp Size and Tune interVal 2.5 Conclusions....

CHAPTER 3: FEEDING LEVELS OF THE SOUTHERN BROWN SHRJMPPelfuIIS sMlitiJisIN RESPONSE TOFOOD DISPERSAL...

3.1Introduction...

3.2 Materials and Methods....

3.2.1 Study Site and Experimental Design . 3.2.2 Pond Preparation, Stocking and Management . 3.2.3 Shrimp Collection and Stomach Content Analysis....

20 21 22 22 22 24 21

2.

3.

3.

3.

3.

40 42 44

4<

45 41 41 50 53

32.4 Statistical Analysis...

3.3Re:sults...

3.3.1 Waterand Sediment Analyses

55 55 55 3.3.2 Relationship between the Wet Weight of meEmpt)·Proventriculus

andthePost.Qrbill..lCarapaceLen&thofPenoeus suhtiJis... S8

3.3.3 Growth Detennination. .

3.3.4 Feeding Method ..

3.3.STime ofFeed Distribution...

3.3.6 Relative Source of Food in Shrimp Stomach Contents...

3.4 Discussion...

3.4.1Polycb.aeteAbundance...

3.4.2 Sediment QuaJity...

3.4.3 Relative Amount of ArtificiaJ FoodinPeNlelU subti/is Stomach Contents...••...••••.•..•...

3.4.4 Effects of Feed Dispersal Method on Growthand Food Intake of

PenoelU subtilis .

3.4.5Panemsof FoodIntakewithShrimpBodySize . 3.4.6 Foodlntakeas a Response 10 Time of Fccding. . 3.SConclusions...

CHAPTER 4: SIZE-RELATED FEEDING AND GASTRIC

EVACUATION MEASURES FOR THE SOUTHERN BROWN SHRIMP Penaeus sub/ilis...

61

6'

67 68 73 73 74

7'

76

7.

80 82

84

84 87 87 88 9) 96 97 98 102 107 11) 116 116 118 121 122

4.2 Materia.ls and Methods.. _ .

4.1 Introduction _ _.

42.1 Collectioo of Shrimpand Size Classification 42.2 Apparatusand Experimental Design 42.3 Indices of Food Ingestionand Egestion...

4.2.4Statistical Analysis...

4.3 Results.

4.3.1Maximum MeaL..

4.3.2 AppeliteRevivaL.

4.3.3 Ingestion Rale...

4.3.4Faecal Production and Evacuation Rates...

4.4 Discussion...

4.4.1 Relationship of AmOWlt of FoodEalmwithShrimp Size...

4.4.2 Foregut Evacuation. AppetiteRevivaland Food Adminis1lation...

4.4.3 Implications to Penaeid Feeding Strategies....

4_5 Conclusions...

CHAPTER 5: EFFECTS

or

THE SOUTHERN BROWN SHRIMP, PvraellSsllbtiJis,PREDATION AND ARTIFICIAL FEEDING ON THE

POPULATION DYNAMICS OF BENTHIC POLVCHAETES IN A

TROPICAL MESOCOSM... 114

5.1Introduct.ion... 124

5.2 Malerials and Methods... 127

5.2.1 Study Site and Experimental Design.... 127

5.2.2 Pond Preparation... 131

5.2.3 Shrimp Stocking, Feeding and Pond Management... 132 5.2.4 Polychaete Collection, ExaminationandIdentification... 134

5.2.5 Soil Analysis... 136

5.2.6 Statistical Analyses.... 137

5.3 Results... 138

5.3.1 Shrimp Growth and Survival, and Water and Soil Quality... 138

5.3.2 Polychaete Analysis... , 142

5.3.3 Trends over theRearingCycle... 146

5.3.4 Effects ofShrimpPredation..,,, 148

5.3.5 Effects of Artificial Feeding... . ISS

5.3.6 Family Classification and Abundance... 156

5.4 Discussion... 160

5.4.1 Environmental Parameters and Shrimp Performance... 160

5.4.2 Polychaete Families... 161

5.4.3 Polychaete Population Panems... 163

5.4.4 Impact of Penoeus subti/is Predation on Polychaete Abundance... 166 5.4.5 PolychaeteGrowthInteractionswithArtificial Feeding.., 168

5.5 Conclusions... 170

CHAPTER 6: A COMPUTER-BASED STATISTICAL MODEL OF THE FOOD AND FEEDING PAlTERNS OF THE SOUTHERN BROWN

SHRIMP Pe""ellS slIbtiJis . 6.1 Introduction....

6.2 Materials and Methods...

m

172 174

174 175 6.2.2.1 Penaeus subli/is Ingestion and Evacuation Rates... 175

6.2.2.2 Effects of Shrimp Predation on the Population Dynamics of

Polychaetes... 180

6.2.1 Model Development, Simulation, and StatisticalandSensitivity Analysis...

6.2.2 Model Structure and Parameter Estimation...

6.2.2.3 Penaeus subtilis Feeding Response to Feed Dispersal... 187

6.3 Results... 191

6.3.1Shrimp Hourly Feed lngestion.... 191

6.3.2 Polychaete Population Dynamics... 196

6.3.3 Shrimp Feeding Levels in Response to Feed Dispersal... 202

6.4Discussion.... 206

6.4.1Simulations of Shrimp Feed Ingestion.... 206

6.4.2 Simulations on Polychaete Population Dynamics.... . 208

6.5Conclusions . 210

CHAPTER 7: GENERAL DISCUSSION... 212

7.1 Significance and Implications of Results to Penaeus $ubtilis Culture... 212

7.1.1 Feeding Rates and Feeding Frequency... 212

7.1.2 Food Particle Size and Feeding Methods... 214

7.1.3 Patterns in the Availability ofNatura1 Food...

BIBLIOGRAPHY...

APPENDICES....

215 217 258

32

LIST OF TABLES

p. . . Table 2.1: Proximate composition of Cannulated diet usedinthe study. Feed

sizes refuto crumbles arless than I mm length by 1.90 mm diameter (Pj ).broken pellets of 1.31 mm length by 2.31 mm diameter (P2) and pellets of 5.50 mm length by 2.38 mm diameter (p}). Results are presented as mean:!:standarddeviation. derived from three replicates of each sample:. Common letter'S denote no significant difference among pelletsatthea - O.OS level by Scheffc's Multiple Range Test. 2J Table 2.2: Handling efficiency indices forPClIDeus subtillsseparately fed three

feedparticle sizes. Results are presented as mean ±standard deviation. Numbers in parentheses indicate minimum and maximum values. Common letters denc)(c no significant difference among pellets at the a" 0.05 level by Schc:ffc's Multiple: Range: Test... 28 T.bk 2.3: Handlingefficiency indices for fow groups sizes of PC_lIS subtUis

fedthree feed panicle: sizes. Results are pn:ser1ted as mean±standard deviation. Numbers in parentheses indicate minimum and maximum values. Conunon letten within each column denote: no significant difference among shrimp size groups at thea ..0.05 level by Schcffe's Multiple Range Test...

nl

Table 2.4: Handling efficiency indices for two time interva.ls(T0-4andT..,) when PenaelUmblilis was exposedtofonnulated food. Ta..refers to theinterval starting attimdetection offoodupto4min.T.., COITe$pOOds tolhcinterValbetween4 to 8 min after firstfood detection by shrimp. Results are presentediiSmean±standard deviation. Numbcn in parentbcses indicate minimumandmaximum values..•...

Table 3.1: Chemicalanalysis of bonom samplesfromthegroW-oUI pond after a 89-<1 growth cycle. Results are presented as means±standard deviation for treaunents feed broadcast and feed concentration. Hest data indicate contrasts between lreattnents....

37

59 Table3.1: Comparison of shrimp biometric data among culture periods(d)and

feeding methods. Results are reported as means±standard deviation for nindividuals. Numbers inparenlhescsindicate minimumand maximum values.Pvalues present degree of significance forposI.

orbital carapace length (CL,inmm)by feeding method. OW refers to

shrimpwetbodyweight (g)... 62

Table3.3: Gro\lo"thrate, survival, final biomassandfood conversion ratios of PenoelU subrUisfortreatmentsfeedbroadcastandfeed concentration over a 89..d rearing cycle. Data presented as means±standard deviation....

Table 3.4: Carbonisotopic data [mean±standard deviation' (n^b- 8)J of

IVii

64

Penaeus subtiJis stomach contents (ouCs<:) throughout the rearing period for tre3ttnents feed broadcast and feed concentration. Each value represents a mixture of the stomach contents from a total of 27 shrimp.Ol3Cof artificial food(OIlCJand polychaetes(.s13Cn) were.

22.770±0.002"" and ·17.109±0.006%0. respectively...

Table 4.1: Rate of appetite revival (AR. g of dried feed consumed/shrimplh)± s.d. and appetite revival index (ARl. g of dried feed consumed/shrimp BWIh)::tS.d. for four size groups of Penaeus subtiUs at five time intervals (n denotes total number of observations for each shrimp size class). Shrimp body weight (BW. g) presented as mean:l:s.d., with numbers in parentheses indicating minimum and maximum values.

Non.significant time periods (horizontal comparisons for AR) and shrimp size groups (vertical comparisons for ARJ) are shown in the last column and last line, respectively...

Table 4.2: Ingestion rate (IR. g of dried feed consumedlshrimplh)±s.d. and ingestion rate index (lRl, g of dried feed consumed/shrimp BWIh)::t s.d. for four size groups ofPel1Q(!ussubti/is for three I·h rations delivered at consecutive 1.5 h periods (n denote total number of observations for each shrimp size class). Shrimp body weight (g) is presented as mean±s.d.• with numbers in parentheses indicating minimum and maximum values. Non-significant time periods (horizontal comparisons for lR) and shrimp size groups (vertical

70

lOS

comparisons for IRI) are shown in the last eolumn and last line.

respectively...

T.ble 5.1: Meanfinalgro\\1b (g) and survival.(%.values in parentheses) of Penaew SUblHis for treatmenu SNF (shrimp and no foed) and FS (feedandshrimp) at four stocking densities....

T.ble S.l: Finalchemical composition and relative representation of particle size: of sedimentfrompond bottom of enclosures FNS (feed and no shrimp). NFNS (no feedandno shrimp), SNF (shrimp and no feed) andFS(feed and shrimp). Last colwnn indicates significance level of one·wayANQV A ...

Table 5.3: Polychaete density (mean numberJm²xItr-:t s.d.) at the bottom of FNS. FS. SNFand NFNS enclosures. Valuesinparenlheses indicate minimumand maximum values (n refers to number ofobservations for each treatment).Commonletters denoce noo-significant differences at thea -O.OS level by Scheffe's Multiple Range Test. Lowercase and uppercase letters refer to vertical and horizontal comparisons, respectively .

T.ble 5.4: Numerical representation of pol)'chaetes (numberJm2)±s.d.) by family over a62-dshrimprearin~cycle (n refers to number of observations at each cuhwe period). Each observationrepresentSa mixture of five to six substrate samples of 306 em). Common letters denote non-significant differences at the a. - O.OS level by Scheffe's

109

139

14)

144

114

190

IS.

Multiple Range Test. Lowercase 'etters indicate borizonuJ comparisons among alhure periods for each family, while uppen:asc Icners refer toverticalcomparisons amoDS familiesateachcukure period...

Table 6.1: Percentage daily increaseinthe number of polychaetcsperm¹in response to shrimp stocking density and feeding regime as observed by Nunes and Parsons (in press)...

Table 6.1: POwef" functions obtained between PenDeus subtilis stomacb weight (SW, ing) and shrimp body weight(BW,ing)inrelation to time of day and feed dispersal method..Allequationswere significantatthe 0.1%level (r is the coefficient ofCOfTelatiOD, Drefers to number of observat.ioos and Eq. provides the referencenumbertotheequation).

Data from Nunes and Parsons (1999)....

Table 6.3: Percentage occutT'eOCe(%)of artificial foodinPenaeus subtiJ;s slomach contCDts (3O-min after feed distribution) overan8O-d production cycle. Daucompiled from Nunes and Parsons (1999)... 191 Table 6.4: Sensitivity a.naJylis ofthe total amount of consumed(Fe)and uoeateo

(FII)feed 10 model parameter variability.Thesensitivity index (Equation 6.1) was uJa.llated for theCDtireparametervariability raDgc_..

Table 6.5: Onc-at-a-time sensitivity analysis offinalpolycbae-.~population (number/m¹)tomodel parametersbased on afixed percentage

197

variatioD. Negative values indicate reduction in final polychaete density....

Table6.6: Sensitivity analysis of the total amount of feed consumed(Tl)to model parameter Variability. The sensitivity index (Equation 6.1) was calculated for the entire parameter variability range...

201

20'

LIST OF FIGURES

P. . . Figur~1.1: Annual estimatedvalue (USS x Ilt). annual production(kgx 10"')

and annual compounded growth rate(%)of the penaeid shrimp farmingindusuy since 1984. Data compiled from FAD (1999)...

Figure: 1.2: A conceptual model of nutrient flow in a tropical semi-intensive pcnacidshrimppood. Formulatedfoodis used to supplement the shrimp's natural diet (Nunes and Parsons. 19983)...

Figure: 1.3: AconcepNaI model of shrimp feeding patterns in a semi-intensive culture system.Themodel is represented by three components: M.

management;CA. cultured animal; and, CE, cuJture environment.

Relationships are indicated by arrows (fine arrows, within components; thick arrows. between components). Sourc:e: Nunes andParsoos (19984)....

Figure 2.1: Schematic diagram of apparatus used to record Pe_us SUblilis

feeding behaviour... 18

Figure: 2.2: Comparison of meanAC, PC and PI for three feed particle sizes(PI - crumbles of lessthanI mm length by 1.90 mm diameter, P2 ., pelletsof 1.31 nun length by 2.31 nun diameter; and,p) -pellets of 5.50DUDlength by 2.38 mm diameter) fed toPenaeus subti/is.

Values (n) on top of ban indicate number of observations. Venical

30 bars representstandardcnot. Common letters within each figure dcoote DO significant diffcrmce at the a • 0.05 level by Sc.heffe's Multiple Range Test. AC • Dumber ofattemptStocapturefeed particles;PC -number of feed particles conducted successfully to thepre-oral cavity; and, PI=number of movemeDts performed by the mouthparts which may have led 10 ingestion of food... 25 FigUR 2.3: Comparison of mean AC, PC and PI for four group sizes (01 -

1.148 - 3.760 g shrimp(n=29); 01 -4.387·6.995 g shrimp (n

=

31);OJ"7.1t7 •9.B55g shrimp(n -31); and,O.=10.057 • 13.715 g shrimp (n ,.. 30n ofPCNHUSsubtilis. Values (n) on top of bars indicateDumber of observations. Vertical bars representstandard error. Commonletterswithin each figure denote no significanl difference atthe a - 0.05 level byScheffl~'sMultiple Range Test.

AC=0-number ofattemptstocapturefeed particles;PC -number of feedparticles conducted successfully to the prc-oral cavity; and, PI - number ofmovementsperfonned by the mouthparts which may have led to ingestion offood.__ .

Figure 2.4: Mean variation in thehandlineefficicocy indices for Pcnacus sublillsin response to mean shrimp body weight and feed particle size. CER..,CaptweEfficiency Ratio; IER.., Ingestion Efficiency Ratio; and, Mel, ManipuJation Capacity Index...

Figure 2.S: AC. PC and PI as a function of the time interval at which images 33

\o\'ereanalysed. TOot refen tothe interval starting at

rust

detection of foodbyPrnoew $ubtilis up to4min.Tu colTeSPOnds to the interval between 4 to 8 min aftertimfooddetection by shrimp. n values indicate number ofobservations

Figure 2.6: Mean relative PC (number of feed particles conducted successfully to the pre-oral cavity) for four group sizes (Gl - 1.201 - 3.100g shrimp; G2 -4.178 - 6.303 g shrimp; G] ., 7.224 - 9.302 g shrimp;

and.G~""10.347 - 16.493 g shrimp) ofPenoeus subti/is exposed simultaneously to three feed particle sizes (PI=crumbles of less thanImIDlengthby1.90 mm diameter; P2 ., pelletS of 1.31 mm length by2.31 mm diameter,and. p] -pellets of 5.50 mm lengthby 2.38 mm diameter). Values (n) on top of bars indicate number of shrimp analysed. Common letters denote no significant difference at the( l=-0.05 level by Scheffe's Multiple Range Test (comparisons

withingroups only)... . 38

Figure 3.1: Geographical location of the study siteinNE Brazil, Slate of Rio

Grandedo None... 48

Figure 3.2: Schematic plan of the grow-oucpond.indicating location of

enclosures and feeding trays 49

Fip", 3.3: Daily fluctuationsinwatertransparency (em) over the grow-out cycle ofPe1llUw subtilis. Culture period (d) is the number of days after post-larvae stocking .

....

56

Figure 3.4: Mean polyehaete density±standarderror (n - 3) in the pond sediment of six endosures WJde1" two feedingmethods (feed c:onc:entralcd and feed broadcast) during a 89-<1 grow-out eyde of Pentnus subtilis. Values from the sample size of 75.43 em^lwere

eonverted tom² 57

66 Filure 3.5: Relationship betweenwetweight of empty stomach. W£s (g) and

post-orbital earapac:e length. CL (mm) of PenDew subli/is... 60 Figure 3.6: Mean stomac:h content weight (g) 30-min after feeding of Pe1fO.eus

subti/is for two methods of feed disaibution (broadcast and eoneentrated) over a 89-<1 cultwe period. Numbers on top of bars indicate results&omtwo-tailed I-tests .

Figure 3.7: Panem of food intake of Penaeus subli/is at thn:c feed distribution times (0600. 0930 and 1430 h) over the eourse of a 89-<1 rearing eyde. Culture: period (d) represenu the number of days of rearing after stocking grow-outpond withpost-larvae .

Figure 3.8: Relative 0CC'W'T'enCCof formulated versus oatura1 food in the stomach of Pe_us subtilis, 3()..min after feed distribution, as indicated by stable carbon isotope mass$peCtrome1l)'analysis.

Results are presented for feed broadcastina (A) and feed concentration(8)over six samplingperiods...

69

71 Figure 4.1: Lay-out of the dosed aquarium system usedinthestudy... 89 Figure 4.2: Maximum meal. ingestion rate, appetite revival and fa«al

101 production of Penaeus sub,ilis as a function of shrimp size (n refers to number of observations). Common letters denote no significant difference at the a '" 0.05 level by Scheffe's Multiple Range Test... 99 Figure 4.3: Relationship between maximum meal (MM. g of dried feed

consumed/shrimp) and wet body weight (BW. g) of Penoeus subtilis. Negative and null values were not considered...

Figure 4.4: Relationship between the rate of appetite revival(AR,g of dried feed consumedlshrimplh) and wet body weight (BW. g) of Penaeus sub,ilis. Doned lines indicate point where AR valuesstarttodecline in the curve. Negative and null values were not considered... 103 Figure 4.5: Rate of appetite revival (AR) and appetite revival index (ARI) for

Penaeus subtilis as a function of feeding time(h).Feeding times refer to time foodwasgiven following a satiation meal (t=0; n referstonumber of shrimp observed at eacb timeperiod).Common leners denote no significant difference atthea =0.05 level by

$cheffe's Multiple Range Test....

Figure 4.6: Ingestion rate (rR) and ingestion rate index (lRI) for Penaeus subtilis as a function of ration given. Meals were delivered for I h at consecutive 1.5 h periods. following a l-b satiation ration (n values indicate the number of shrimp observed at each feeding period).

Common leners denote no significant difference at the a=0.05 level by $cheffe's Multiple Range Test. .

104

108

114 Figure 4.7: Relationship between ingestion rate (IR. g of dried feed

consumcdlshrimplh) andwetbod)'wei&ht (BW, g) ofPe_us SIlblilisfor threemeals(M\.M2andM)given at 1.5bconsecutive time periods.Dottedlinesindicate pointwhereIR valuesstanto declineinthecurve.Negati~andnull values were not considered... III Ftgure 4.8: Faecalproduction rate (FP) and faecal production index (FPI) for

Pe_us subtilis as a function of time(h).Times refer to period of faeces collection following a satiation meal (t .. 0),withn values indicating the numbet'" of shrimp observed at each time period.

Common letters denote no significant difference at the a .. 0.05 level by Scbcffc's Multiple Range Test...

Figure 4.9: Stomach clearance rate for four size groups (01 ..3.707±.0.593g;

G2 .. 5.914±.0.990g BW; G) -7.987::1: 1.719 g BW;04 '"'13.803::1:

2.604 gBW)ofPenaeus sublilis at three time interVa1s (T" T2and Tl ) as indicatedbythe stomacb repletion index (%). Time intervals refer to period after food collection (To; n indicates tolal number of shrimp sacrificed for each corresponding sizegroup). Common letters (comparisons among groupsfor each time period) and numbers (comparisons among time periods for each group) denote nosignificant difference at thea ,.0.05level by Scheffe's Multiple

RangeTest . 115

Figure 5.1: Gcographicallocation oftbc study site in NE Brazil, State of Ceara.... 128

FiguR 5.2: Arrangement of enclosW'eS ingrow~utpondusedfor the study.

Shrimp stocking density(S.10, IS or 201m^l)andrespective fceding regimearcindicated by numbersnexttoeach enclosure(FNS ,.

feed.DOshrimp; NFNS - nofeed.no shrimp; SNF ,. shrimp, no feed; FS - fccd"shrimp) .

FIgU.R 5.3: Daily mean physical and chemical water quality parameters(i.~.•

pH. salinity. dissolved oxygen, temperature and water visibility) of shrimp pond enclosW'eS over the rearing cycle of Perraeus subliUs.

Measurementsweretakenatleast onceaday. Rainfall data provided by Funda\:lo Cearense de Metcorologia eRccursos Hidricos (FUNCEME)...

Figure 5.4: Overall mean polychaete density(numbcrfm~x 102) and biomass(g of dried polychetcslm¹)inrelation to therearingperiod. Common lettersinparenthesesindicate OOQ-significant differencesatthea - 0.05 level by Scheffi's Multiple Range Test. Uppercase Ic:ners refer to comparisons for biomassandlowc:rcasc Ic:ners for density.

129

140

Numberof observationsateach culture: periodarcindic.alcdby N (biomass) andn(density). lWW" cycles are shown on the bottom.... 147 Figure 5.5: Differences in total mean polychaete density (numberfm²x 102)+

standarderror (s.c.)andbiomass(gof dried polychaetcslm1) • s.e.

among treatments FNS (feed and no shrimp), NFNS (no feed and no shrimp), SNF (shrimp and no feed) and FS (feed and shrimp).

149

1S3 Number ofobscrvatio~are indicated by N (biomass) and n (density). Common letters (uppercase refers to biomass and lov.-en:ase refers to density) denotenosignificant difference at thea.

:<0.05level by Scbeffi's Multiplc RangeTCSt..••.

Fipre S.': Changes in mean polychaete density (number/m!xIo!)±s.c. in enclosures with (SNF and FS) and without (FNS and NFNS) shrimp and with (FNS and FS)andwithout (SNF and NFNS) feed. Days represent cultureperiodafter shrimp stocking(D.-t>.Numbers nelCt 10lines indicate level of significancc from two-tailcd t-tests... lSI Filure5.7: Comparison of tota! mean polychaete density (nwnbcr/m2 x 102)±

s.c. in relation to four shrimp and (or) feed densities among treatments FNS (feed andDOshrimp). FS (feed and shrimp) and SNF (shrimp andnofeed). Feed density refer to fcedingregimeused fO("

eacb respective shrimp stocking density (number of shrimplm!).

Values (n) ontop of bars indicate Dumber of substrate samples analysed.Commonlc:uersdenotenosignifiant diffc:rc:nce at thea. - O.OSIcvel by Scbcffi's Multiple Range:Tcst...

Figure 5.8: Frequency(%)andoccunence(%)of polychactcs by family over a 62-<1 rearingcycle ofPcnaeus subtilisinpond enclosures. 157 FieuR6.1: Structure and sectors ofPcnacus sublitamodel of ingestion and

evacuation tales. Note the relationships bctw«n components... 176 Figure6.2: Structure and sectors ofthc model on the effects of shrimp predation

on the popuJation dynamics of polyc:baetes. Note the relationships betweencompooeots...

Fipre 6.J: Structureand sectors of the model 00 Pe_wsubtilis response to feed dispersal (shrimp feeding response sector only). Sector on shrimp population same as presented onFigure 6.2...

Figure 6.4: Simulations ofPenaew subtilis feed ingestion (dFS/dt. gIh) in response loftedralian (R. glshrimp),feedingfrequency (F. number of feedings/d) andshrimpbodyweight(BW.g).FeandFuindicate the results of the100al Qmou'ltoffeedcOflS1Uf'red(gId)and theIOtal amounl ofUJWaunfeed (gId), respectively

Fipre 6.5: Simulationof the changesinpal)ICNxte population per",1after shrimp predation (dPdldl. number/m²)over a cultureperiod(d) in response to initial polychaete density(Dpi. number/m²),feeding regime(Fr,dimensionless). stvimp stocking density(D,number/m²) and total culture area(A,hal. Dottedlines (control) represent simulations without shrimp and feed supply .

Figure 6.6: Simulatiooof the clwtges in the total stomach weight of a shrimp population(PSW,kgldltotal culture areainm²)during agrowth period(d)inresponse to time of the day. fcedingmethod(Fm.

dimensionless)IIICIshrimp stoeking density(D. number/m2). Tf indicates the results of total amount of feed consumed (kg) for each ploned curve. Total culture area(A)was10 ha...

181

188

193

198

203

LIST OF ABBREVIATIONS AND SYMBOLS

~... dimensionless fraction from Table 6.3 at timei A... dimensionless fraction genenued bySell00

dimensionless value given byRg+1

\II... polychaete individualdryweight given as 0.7 x lD'l g statistic:a11evel of significance

SlJc.... SoC ofanificialfood

S^1J

c.... slle

of natural food (represented by benthic polychaetcs) OllC""...

slJe

ofshrimpstomach contents

~m.... micron

A... IOtaJarea

AC... number of anempts (successful or WlSUccessful) to capture feed particles a.d... anno domini

ANOVA... Analysis of Variance AR... mean appetiterevivalme ARI... mean appetite revival rate index Broad.... feed dispersal treatment BW... shrimp wet body weight

c...

c.v .

CA . CE . CER . Cfo ..

CFr . CL...

Cn....

Cone...

Const...

d .

D .

df.. . Di·..

DO ..

Dp . Dpi ..

Dr .

dl ...

EDTA...

coefficient of variance cultured animal culturedenvironment capture efficiencyntio

dried weight of feed offered/control aquarium dried weight of feed recovered from control aquariums shrimp post-orbital carapace length

ccntimetre(s) polychaetefrequency feed concentration treatment constant

day(s) initial shrimp density degrees of freedom

number ofdays (i+1)after shrimp stocking dissolved oxygen

increaseinpolychaetedensity

initialnumberofpolychaetesper m²prior to shrimp stocking shrimp daily ration

day of shrimp stocking time interval between calcuiatiolU ethylene diarninc tetra-acetic (acid)

Eq.

F .

F .

L..

f.. ..

FC..

Fe Fi...

FL.

Fm ...

FNs....

Fo FP...

FPI...

fr...

Fr...

Fr....

Fs. __

FS...

Fu...

g....

equation Fstatistic fecdiDgfrequency polychaete occurrenceindex relativcapernueoflcns dryweight of feed consumed lotal amount of feed consumed pre..establishcd feeding intervals proportion ofdried feedkminwater feeding method

enclosureswithfeedsupply,but withoutshrimp dried weight of feed offered/shrimp faecal production rate mean faecal production rate index dried weight of faeces recovered dried weightoffeedrccovcm1 fecdingregjmc

amount of feedinstomach az timei enclosureswith shrimpand feedsupply tola!amount of uneaten feed gram(s)

juvenile shrimp of a specific body weight range

G2... juvenile shrimp ofaspecificbodyweight range

GJ ••• pre-adult shrimp ofalowerbodyweighl raoge

G.... adult mrimp ofa highCl'"bodyweight range GE... gastric evacuation rate

h... how(s)

ha... bectarc(s) IER.... ingestion efficiency ratio

Ip... average daily percentage increase in polychaele abundance IR... mean ingestion rate

00... mean ingestion rale index kg... kilogram(s)

left L... litre(s) LD... lightand dark

M managemCtlt

MANOVA.. Multiple Analysis of Variance MeL. rnu.ipulation capacityindex mg... milligram(s) min... minute(s) MM... mean maximum meal

millimetre(s) MML. mean maximum meal index

N N'...

NFNS...

N... total number of individuals sampled from aspeci6c shrimp size group sampled

n...

tota.! number of enclosures

control enclosures without feed supply and shrimp n....be,-

Np•.. number ofenclosures with each specific polychaetc family Np... number ofpolyehaetcs preyed per shrimpBW Npm... number ofpolychactcsgrazedperm¹ NR... number of shrimp alivcperlotal culturearea Nsm... changes in number of shrimp perm^l P degree:ofsignificance

p... tota.! number of each specific polychaete family P'... total numbeT ofpolychaetcs observed in all samples Ps... totalshrimppopulation size per culturearea PI... feed crumbles

Pl... broken feed pellets Pl... pellets PB... polychaete biomass

Pc... dimensionless fraction of.polychaete contribution to shrimp's diet pc... number of feed particles conducted successfully to the pre-oral cavity

Pd.... polychaete population per m^Zafter shrimp predation PD... polychaele density

pers. obs... penonalobservation

Pl... number of movements performed by the mouthparts which may have led to ingestion of food placed successfullyinIbe pre-oral cavity PL...

Pmax . Pmin . PSW . PVc. .

shrimp post-larvae maximum output value minimum output value total sJuimp population slomach weight polyvinyl chloride

coefficienl of statistical com:lation R... feedratic'l

R.... right

Rg... polychaete daily population factor

Ri... amount of food ingested by shrimp after food administration Ro... relative OCCWTCOce ofcarbon from artificial food

second(s) S... percentage shrimp survival

S... south

s.d... standard deviation slandarderror

Se... change in the degree of gastric evacuation

SG... shrimp growth SI.... sensitivity index

SNF... enclosures with shrimp and without feed supply SW.... .. shrimp stomach weight

time

TOo4 ••• time betweenfin1detection of food up 10 4 min T44... interval between 4 10 8 min after first food detection

Tf.... total amount offeedconsumed

Tj ••• time (i) after initialfood exposure

Tr... total amount of food administered toshrimp SlUdentl·tcst

W... watts

W ....

We shrimp SIOn'laCh food contents wet weight WF.S... . shrimpstomach wet weight, without food contents Ws.·.· . shrimpstomach wet weight, including existing food coDtcnts

253

LIST OF APPENDICES

AppeDdix A: Variables, type and description of components in the feed management sector.Type refers10the following: V=variable with value set byuser.C=command; I - integration.... 25 I Appeadix B: Variables,typeand description of componentsinthe shrimp

intema.l feeding control sectOT.Type referstolhe following: V= variablewithvalue set by user; C

=

command; I "" integration; R ., pre-established relationship....

Appendix C: Variables, type and description of componentsinthe feed loss sector.Type refers10the following; V "" variablewithvalue set byuser; C '" command; [=integration...

Appendix D: Variables, type and description of components in the shrimp populationsectOT.Type refers to the following: V ., variable withvalue setbyuser;C -command; I=integration; Repre- established relationship....

AppCDdiJ: E: Variables, type and description of componentsinthepolychaete population seclor. Type referstothefollowing; V=variable with value set by user, C ., command; I '"' intcaration; R '"' pre- established relationship...

Appeadis. F: Variables. typeand description of components in the shrimp

U%Viii

255

256

257

grazinapressure sector.Type refCt"lii to the following: V - variable with value setbyuser, C -command;I .,integration; R

~pre-established relationship; Cons - constant...

Appendix G: Variables. type and description of componentsintheshrimp feedingresponsesectM. Type refet"5 to the following: V -

258

variable with value setbyuser;C - command; I ,.. integration; R '"" pce-established relationship or value 261 Appendix H: Presentationof models in theSTELLACl

n

envirorunent,

software version 3.0.7 for Windows . 267

CHAPTER 1 GENERAL INTRODUCfION

1.1 Geaeral CoasidentioDS

Aquaculture is the fastestgrowiDgfood production systemintheworld.expanding at an estimated annual me of loe..- since 1984 (FAD. 1997).In1997, theindustry contributedwith27.6% aCthe global aquaticoutput,gcneratillg ]6.0 million mt of more than300species of finfish,sbellfish and aquaticplanuvalued al USS 50.3 billion (FAD, 1999). Despite itsLowoverall volume representation (only 2.6%), peaaejdshrimp'is the most imporuotculturedgroupinmoncwy tenns,ac.eouobDgaIooein 1997for12.0%or USS 6.1 billion of thetoWestimated value generated by the aquaculture KCtor (Figure 1.1).

Historically, cultivation ofmarineshrimp originatedthousandsof years agoin the Medilerraneao region (Brown, 1983)andto the 15thceDtutya.d.inlndooesia(Ling, 1977). Nowadays, the activity bas modernised and is DOW established in Ova'"SOcoumries

In.c^name"shrimp" isusedbcRtocio=dcthefamiliesPa.adIe"ud'-PrPaIacmmIidae CHohbuis.1910),wbicbCIQCUfin mariDt,l;SlUarincaa:l6ab waters.PaIaeicIKlaXCDOIDic classificationadopted inthiswortinac.cordaDee10Percz·F~(1911) IIIlIdDaI1et al. (1990).

A recent change in nomenclature hasbeenproposedfor the Pmacoidc:anshrimp(PeIu-Farfame and Kcnslc:y, 1997),butithasDOtyetbeen widely aeceplCd.

700 ---,

'€" .

w

600r

^5001----400--

'"

~

³⁰⁰

I~

j200-

100

~

I

..-LLL.J.,..l-LLL,.LJ-L-4~10 -o-Growth Rate

GiIiIilProduction

100 , - - - ----, 40

~ ~ ::::j~:~~:: ~ I

:5

50 \.. 15 ;:Q

~ ^{40 10 ;.}

i: ~j :~

10 1 4

OJ.WUO.....,.UiL~--'-'L.1._

Year

Figure1.1:Annual estimated value (USS x 10·), annual production (kg x 10·) and annual compounded growth rate(%)of the penaeid shrimp farming industry since 1984. Oatacompiled from FAO (1999).

(Rosenberry, 1998) located in both tropical and sub· tropical areas aroWld the globe. With its increasing demand and economic value (Figure: 1.1), fanned penaeid shrimp production has grown 81.7% since 1984. The sector now constitutes almost half (47.3%) of the world penaeid landings, with over 86% of its total volume represented by only four species(PenCleu5 ",onodan, P. vannCl",ei, P. chinensis and P. ",erpiensis).

Inrecent years however, the sustainabilitY of the activity has been questioned. The industry has shown relatively slower rates of development, with substantial production declines in some instances (Figure 1.1). Contradictorily, these reducing patterns have been associated with over·intensificatioD of production driven primarily by market forces and competitive use of the resources (FAO, 1997, 1(98).Inmarine shrimp farming, this rapid trend towards more intensive forms of husbandry has resulted in overloading the carrying capacity of the aquatic environment, creating self.pollution problems and disease outbreaks. These and other environmental·related difficulties have caused sudden losses and discontinuous progressinproduction a.,d the industry now faces constant scrutiny for its ecological impacts. These constraints are now recognised as the major obstacles for further expansion oflhe activity (FAO, 1998).

2Sustainable development iiithemanaaement and conservation ofthenarunl resourcebaseand the orientation of technological and institutional change in such • manner as to ensurethe attainment and continued satisfaction of human n«<Is for present and future generations. Such sustainable development is environmentally non-dcgrading, technically appropriate, economically viableandsocially acceptable (FAO, 1988),

1.2 Rationale.ad Researcb Objectives

At present. the bulk of marine shrimp production is still derived from extensive and semi-intensive culture systems, operating under low shrimp stocking densities and with cilber some orDOexternal food provision. Under these conditions.. natural productivity acts as a major food source, and although lower yields are achieved, these systems are considered more sustainable than intensive ones (phillips, 1995; Tacon and De Silva.

1997;Nunes and Parsons, 1998a).

In less intensive production systems, environmental control, manipulation and management arc intended primarilY to relieve nutrient limitations of the ecosystem to the cuhured animal. to achieve maximum yield with a minimum quantity of external input and ecological impact. Semi-intensive systems are characterised by a complex food web structure and netWork of relationships (Figure 1.2). The Datura.I diet of the shrimp is supplementedwithinputs of formulated food.. Fertilisation promotes natura.! productivity and water quality is enhanced byincreasedwater exchange rates, thereby allowing higher stoclcing densities and improved yields.

The functioning of the system involves chemical, biologicalandphysical processes that interact with thepond.biotaina continuousstaleof flux, and tends to be accompanied by physiological and behaviounl responses from the cultured species.

Water quality characteristics may change significantly over 24-h periods. mainly due to respiration and photosynthesis. Penaeid shrimp may alter food web structure through predation, while displaying ontogenetic variationsintheir feeding patterns. Some

Figure 1.2: A conceptual model or nutrient flowina tropical semi-intensive penacid shrimppond.Formulated food is used to supplement the shrimp's natural diet (Nunes and Parsons, 1998a).

Penaew spp. for example, may modify their diet during the rearing cycle, which often involves a shift from detritus source dependency to more animal-based sources at large!"

body sizes.Innature, these dietary altentions are apparenLly associated with the change in habitat aspcnac:idsgrow.

Inthis changing environment, feeding patterns ofpeoaeidsarestructuredonthree elements: its own behavioural and physiological cues; the physical, chemical and biological components of the culture system; and, the elements that comprise a feed management regime (Figure 1.3). The way these structural elements change over time, are controlled, and their inter-relationships have yet tobedescribed completely or quantified. As a consequence, only a portion of the organic matter and nutrients in pelleted feeds that enter the system is convened to shrimp flesh and removed from ponds at harvest. The remainder may either be consumed or recycled by thepondbiotic community; flushed from the system with water exchange; or deposited in thepond sediment acting as a source of organic pollution. Little isalsoknownabout the faclors that dictate the abundance aDd productivity of important shrimp prey speciC$ in aquaculture ponds, impairing attempts IOwards maximisation ofnatunl food use.

It is now recognised that efforts 10 improve resource-use efficiency, including naturally occuning pond food sources, and 10 conserve critical inputs, such as formulated foods, will become increasingly imponant in aquac:u.lture (phillips, 1995; Tacon, 1996;

Tacon and De Silva. 1997; Nunes and Parsons, 1998a). Studies on these subjects will undoubtedly lead 10 favourable implications in the long-tenn sustainability oftbe activity.

: <·---x--····--x---··)o:

: F'hysic:al ~ Biologic:al:

:_---_.---_.'

<- - - --+--> _••• -->

F'trfsiobgical 8et8Yiolnl ,-_

...

__

.. _---_._._.---_.-

'- ^...

^__

.---.

M

figure1.3: Aconceptual model of shrimp feeding pancms in a semi-intensiveC1I1ture system. The model is represclIed bythree components: M, management;

CA, cultured animal; and, CE, culture environment. RelationslUps are indicated by arrows (finc arrows, within components; thick arrows. between components). Source: NunesandParsons (1998a).

Inthe present study, a directanimalapproach was taken to investigate the various implications arising from commercial feeding practices (Figun: 1.3) onP~na~

(Faifant~~nat!llS)subtHis feeding. This species hasbeenextensively (:ulturedinmany partsofnonh-eastern Brazil since the mid 1980's (Nunes. I99S) and has also supported a significant offshore fisheries between the Guianas and Brazil. Due 10 ilS prominenl carnivorous feeding habit, combined with the lack of appropriale commerdal diets, attempts to imensify its productioninaquacullUfcsyslems have failed.

Although the diet of nearly40 species of pcnaeids has been dncnbed (Dall et al.•

1990),with numerous other publicationscoolaining descriptions of their feeding behaviour, very little information is available on their food and feedina patterns under culture <:onditioos.Innature,it is suggested Ihat physiological, morpbomeaical, spatial andlemporal factorssuchas age, sex, moultstage, mouthparts and chelae sizes, habitat, availability of food, time of day and night,seasonandtide govern and regulate penaeid feeding.

Thepresent study examined the food and feeding patterns ofPenaeIU suhtilis under laboratory-c.ontrolled and culture conditions. Data was interpreted in the <:ontcx( of penacid feeding ecophysiology and behaviour andpondecology. Together the results provide indications and alternatives which may lead to optimisation of the use ofboth natural and artificial foodin P.subtilis rearing systems. The objectives of thisresearch investigation are as follows;

I. Describe and dctennine the handling efficiency and particle size selectivity of Penaf!US subtHis fed a commercially fonnulaled food. Specifically, this study aimed to detcnnine bow significanl the effects of shrimp body weight and (or) feed particle

size are on shrimp handling capacity,intermsof food capture and ingestion success and ovenJl manipulation efficiency.lbe workalsoexaminedP. subri/is selectivity ac:cording to food particle size;

2. Investigate the feeding levels ofPeruJew subrilisin response to food dispersal method.Specifically,thisworkdetenniDcdshrimp feeding patterns and growth in relation to foodconcentration versus food broadc.asl over- a complete rearing cycle.

The study provided explanationsasto why and how food dispersal may affect shrimp feeding behaviouralresponses. The role of time of feed distribution on food consumption and the possible effects on pond sediment quality produced. by feeding method were also examined;

3. Define the effects and relationships of shrimp body size on quantitative feeding and evacuationparamet~ofPcnaewsubrilis. This work investigated and detennined the possible interactions betweenshrimpbody weight and maximum meal size, food ingestion.returnof appetite, faeeal production and gastric evacuation. The study presented mathematical models oftbe relationships observed and determined the time required for shrimp stomach emptying and appetite revival;

4. Investigate the impacts ofPenaeus subri/is predation and stocking density, and the growthpromoting effects of artificial feedingonthe populationdynamicsof benthic pllychaetes. This workaimedaIexamining polychaete population patterns (nwnber and biomass) relative to various culture conditions. such as variations in shrimp stocking density and absence or presence of food supply and shrimp predation over- a complete rearing cycle. The research evaluated the extent of the effects of these

parameters and defined possable enviromnenla.l inccnctioos. including polychaete abundanceand water and soil quality. and lunar cycles;

S. integme part of the data derived from this research investigation. structuretheminto a seriesof one-dimensiooal dynamic models andanalysethe results.Threemodels were developed and simulations wen: performed on the following:(I)PenontS subtilishourlyfeed intake in relation toshrimpbodyweight,feedr.iltionandfeeding frequency over a24-h time period;(il)shrimp population feeding levelsinresponse 10feed dispersal method over a production cycle; and. (iii) polychaete population dynamics in relation to shrimp stocking density, feeding regime and initial polychaete availability over agrowthcycle.

10

CHAPTER 2

FOOD HANDLING EFFICIENCY AND PARTICLE SIZE SELECTIVITY BY THE SOUTHERN BROWN SHRIMP

Penlleu••ubtiJis FED A DRY PELLETED FEED

2.1 IDtroduction

Inaquaculture systems. the mode of handling of dry pellctcd food byPellaewspp.

is thought to generate a significant loss of feed and leaching of nutrients (Goldblattet al., 1979; Csavas., 1994; Goddard, 1996a; Lawrence andLee. 1997). This is associated with the typical cylindrical shape (Dall, 1992)andsize of artificialfood (Goddard. 1996a;

Nunes, 19%a; Nuneset aJ.,1997a).Inpcnaeid shrimp, food capture and transfCT to the mouthparts is carried out by thefirstthreepainof chelate pen:opods (Hindley and Alexander, 1978; Nu.ncset aI.,1997&), as the sccood maxillipcd enditesopen 10 receive il (AlexanderandHindley, t98S). AI this stage. the third pair ofmaxillipcdsCODtr.Jct10 press food particles against the mouth (Hindley and Alc:x.andcr. 1978; Alexander CIal., 1980), where laceration aod trituration of food occur. This is acc::omplished by the mandibular gnathobases and the mandibles (Alexander ct 01., 1980). Ingestion is a rapid process [less than 20 s inP.mcrpicnsu (Alexander and Hindley, 1985»). and declines as

II

the foregutfillsto capacity (Dal!, 1967; Sick and Baptist, 1973; SickI!tal.,1973; Hill and Wasscnberg, 1987).

Under both culnan: and oatural conditions, juvenile and adult pcnacidshrimpare fq)Ortcd toconsume awKkrangeoffood particle sizes(R.ac.ek,1959;CoDdleyelaJ.,1972;

Marte, 1980; Suthers, 1984; Stoner and Zimmcrman, 1988;Reymondand~,1990;

NunesI!ta/.,1997b) and althoughsomeauthors reportlittleindication ofachangein diet withsize of shrimp (Sastralcusumah, 1971; Kuttyatnma. 1974; Hunter and Feller, 1987), variations associated with shrimp and relative prey size are often evident (Hall, 1962;

George, 1974; Leber, 1983; Wassenberg and Hill, 1987; Stoner and Zimmerman, 1988;

Reymond and Lagardere, 1990; Nuneset aJ.,1997b). These dietary variations are characterised by a decline in the consumption of small food items[e.g.,nematodes, foraminiferans (Stoner and Zimmerman, 1988; Nuneset aI., 1997b), harpacticoid copepods (Wassenberg and Hill, 1987; Stoner and Zimmerman, 1988; Reymond and Lagan:lere,1990;Nunese10/., 1997b)J,infavour oflarger ones[e.g.,bivalves(George, 1974; Marte, 1980; Wasseuberg and Hill, 1987), gastropods, ophiwoids (Wassenberg and Hill, 1987), polyc.t.aelcs (Reymond and Laprdere, 1990; Nunesel 0/., 1997b), chironomids (Reymond and lagardere, 1990) and amphipods (George, 1974; Stoner and Zimmerman, 1988)}asshrimp attain largerbody sizes.Hence, it is assumed thatas shrimp grow, they become capable ofmoreeffectivelycapturingandconsuming larger prey (Marte, 1980; Wassenberg and Hill, 1987; Stoner and Zimmerman, 1988; Nunes, 1995).

Inother crustaceans, animalandfood particle sizearereported to affect food detection [copepods (Lillelund and Lasker, 1971)], food selectivity [copepods (Lillelund

andLasker, 1971; Wilson, 1973),crabs(Williams, 1982; RheinaJll, 1986), caridean shrimp(pihlandRoscnbng, 1984)], food capture and manipulation [copepods (Lillelund andLasker, 1971),crabs(Rbeinallt and Hughes, 1985; RheinaJU.. 1986; Boulding and Labarben.,1986). lobsters(Lau.1981; Lee. I99S»). rate and amount of food intake (copepods (Wilson, 1973; Richman"aJ••1977). euphausiid (Heyraud, 1979), cnab (RheinailtandHughes. 1985), lobsters(lau. 1987;Lee.1995»and energygain maximisation [crabs (ElnerandHughes. 1978)]. Although penaeidshrimpandprey size relationships havebeendescribed extensively (Leber. 1983; WassenbeTg and Hill. 1981;

Stoner and Zimmerman. 1988; Reymond andLagardCf'e, 1990; Nunes etaJ••1997b). linle isknownabout the ability of shrimp to manipulate different food particle sizes. As a result, optimal shrimp feed sizes for useinaquaculture have only been determined empirically (Akiyama, 1993). This information is essential 10 maximise feed use and shrimp feed intake, reducing the loss of feeds and nutrients in shrimp ponds. The prescot work investigated the food handling efficiency and size selectivity of juvenile and adult Pelfaeus SUblilufed threecommercial dried pelleted feed siZCiundeT laboratory conditions.

13

2.2 Materials aDd Methods

2.2.1Classilkatio. o(Shrimp ••d Feed Sin

Specimens ofPe"aeus subtiliswere collecled from nursery and grow-outpondsat a commercial marine shrimp farm (Anemisa AquicullUnl S.A) located on the north·

eastern coast of Braz.il, AcaraU. Ceari. Animals were uansponed alive in 50-L covered containers with cooled sea water (20 GC)andconstant aeration to a laboratory 4 h distanl from the sampling sile. Collected animals had been raisedinlarge ponds with access only to naturally occurring food organisms.

Inthe laboralory, shrimp were classified and arbitrarily divided into the following size groups according totheirwet body weight: Gl - 1.148 to 3.160 gjuvenile shrimp (2.217::l:0.769 g) (mean::l:standard deviation);Gol -4.118 to 6.995 g juvenile shrimp (5.644±0.734 g); GJ-1.035 to 9.855gpre-adult shrimp (8.315±0.177 g); and.G~­

10.036 10 16.493 g adull shrimp (ll.811::l:1.300 g). Groups were held sepU3tely in I,OOO-ltanks(area of 1.13m~)equipped with a biologjcal filteranda 5 em layer of 3·

mm sand on the bonom.The tanksystem bad a constanlairsupply andwasilluminated artificially under a 12:12 LD light cycle. Prior to the experimcot, shrimp were fedad libitumwith a diet composed offish nesh and fonnulaled dried feed for approximately 15 d.

Fonnulated diet used was a commercially produced shrimp dry pelleted feed(Ra~

Sibra para CamarOes; Sibra AquicuilUnl S.A., Propria. Sergipe. Brazil), consisting of

"

three different sizes: PI -aumblesoflcss than Immlength by 1.90::1: 0.32mmdiameter (::I:s.d.); P2 - broken pellets of 1.31::1: 0.35mmlength by 2..31::1: 0.09mmdiameter;and.

PJ - pellets of 5.50::I:1.48 mmImgth by 2.38%0.08 nun diameter. Pelletswen:

cylindrical inshapeand aumblesbadanirregular form. The feedwasformulated and processed to provide the same fmal chemical composition and texture for all sizes.Feed ingredients included: fish meal, soybean meal. wheat flour, agglutinated wheat flout. meat meal. bone meal. yeast, animal fat, manioc Gout, rice meal, peanut flour. oyster flour, fish waste meal.comflour. saltand mineral supplemcnL

2.2.2 Feed Proximate Cbemiul A. .lysis

Analyseswen:performed to assess if any possible differences in the chemical composition existed among the three feed particlesizesused in thestudy.followingthe methodology described by AOAC (1990). Moisture content was detennined by weighing three replicates of2gfor each of the samples anddryingat 105"Cfor 24 h. The loss in weight represented the moisture CODtenL Crudeproeeinwas detennined bythe Kjeldahl method [calculated as nitrogen (N)x6..251.and ash contentby burningina muBlefurnace at 660"Cfor 2 h. Lipidwas determined gr;avimetricalJy followingSoxhJctextrIlCtion using acetoneasthe SOIVeriL Nodinx:tmeasurements were made of carbohydrate. whichwas estimated by difference.

15

2.2.3 Experimeat.1 DtslgD .ad Appu.tull

Penae/U$IlbtiJisfeeding behaviour was examined wlth the aid of a video-<:amera (SharpCamcordc:rmodel VL-L63B, 43-mm diameter lens Fl.6 -F32,f-4.9 -S8.8nun.

xl2 power zoom, SharpdoBrasil S.A.,Manaus,AmazOnas, Brazil). Since m.ampulation of food by peoaeids is carried outunderits cephalothorax or thoracic region (Alexander and Hindley, 1985), the camera was installed below a glass aquariwn (IS em height by 24.Sem length byISem wldth, volume of3.76 L),where one shrimp at a time was introduced and allowed to feed.

The aquarium was suspended on a tnulSparent glass base attached to the top of a rectangular aluminium frame (74 em in height by 38 em length). On the bottom, a small can placed on a flat section of wood, held the video system in a vertical position (Figure 2.1).Hence., it was possible to adjust the vidco-camen. horizontally in response to the animal's locomotory movements within the aquariwnarea..A IS-Wwhite fluorescent light was attached to the top-left side of the frame and directed towards the aquariwn.The arrangement allowed detailed examination of the rapid food manipulation activity carried OUIby the feeding appendages ofPetIQft4subtiJis.The aquarium wascoveredwith adark sheetandthe water was constantly ac:rated. No substratum was placed on theaquarium bonom because bottom-image observations would not be possible. Sea water was maintained at 27.8 :!:O.S'"C(±s.d.;0 -198)temperature, 30±2%.( 0 :197) salinity and 8.08::l: 0.14 (0 -198) pH.

..

Fllure 2.1: Schematic diagram or apparatus used 10 recordPenaf!W subti/ufeeding behaviour.

17

Aeration

LightJ Da'"

Sheet Aquarium

Penaeus

SUbti:liS~=:b::~~!!!!~,-ll:

LFeed^•.. GIa. .•··•·

J'-I

Base

I

74

I an

Aluminium Structure

Cart

f--36an'---===--~

II

2.2.4 FeedMa.lpulatioD aDd Size Selectivity

Prior to feeding trials, shrimp were starved for 48 h. Animals were individually acclimated to the experimental light conditions and aquarium area and bottom for 48±27 min(:l::s.d.; n= 193). Only active and bealthy shrimp with completely functional pereopods and maxillipeds were used. Each specimen of Penaeus SUblilis was videotaped only once. If feed was not detected or no food consumption occurred within the first 5 min of exposure to food, recording was interrupted, and a newly acclimated shrimp used.

After recording of each shrimp, the water was discarded, and the aquarium washed and filled with new filtered sea water.

Filming was started by introducing a single feed size to a recently acclimated shrimp. Prior to feeding, formulated food was soaked in sea water for 2 min so that it would sink inunediately and completely in the aquarium. Food was always administered in excess,inequal quantities 10 all shrimp size groups (section 2.2.1). The amount of food offered bowever, varied according to feed particle size [1.008±0.007g PI(±s.d.), 1.008

±0.008gP2and 2.503

=

0.070g PJl.Onaverage, video·recording for handling trials lasted for 10.75 =4.83 min (n=158) from the time feed wasfirstoffered 10 the animal. A minimum of ten different shrimp of each size class exhibiting feeding behaviour responses,i.e.,capture, handlillg and consumption of food, were tested for each feed particle size.

Size selectivity experiments were carried OUI under identical conditions, except that all three feed sizes,i.e.,PI. P2and Pl, were administered simultaneously in equal

..