Aquaculture Collaborative Research Support Program and AquaFish CRSP Technical Sessions at

Aquaculture America 2007San Antonio, Texas, USA

26 February – 2 March 2007 Session Organizer: Dr. Hillary S. Egna

Proceedings Assembled by Briana Goodwin

Edited by Jenna Borberg2017

AquaFish Innovation Lab Management Office Oregon State University

Strand Agriculture Hall

Corvallis, Oregon USA 97330

Program activities are funded in part by the United States Agency for International Development

(USAID) under CA/LWA No. EPP-A-00-06-00012-00 and by participating US and Host

Country institutions.

The mission of the AquaFish Innovation Lab is to enrich livelihoods and promote health by

cultivating international multidisciplinary partnerships that advance science, research, education,

and outreach in aquatic resources. Bringing together resources from Host Country institutions

and US universities, the AquaFish Innovation Lab emphasizes sustainable solutions in

aquaculture and fisheries for improving health, building wealth, conserving natural environments

for future generations, and strengthening poorer countries’ ability to self-govern.

Acknowledgements

The AquaFish Management Entity acknowledges the contributions of researchers and the

support provided by participating US and Host Country institutions, including the associated

collaborators involved in this work. The editors acknowledge the contributions of Ford Evans,

Kat Goetting, Stephanie Ichien, and Amanda Hyman.

Disclaimers The Feed the Future Innovation Lab for Collaborative Research on Aquaculture & Fisheries is funded under USAID Leader with Associates Cooperative Agreement No. EPP-A-00-06-00012-00 and by the participating US and Host Country partners. The contents of this document are the responsibility of the authors and do not necessarily reflect the views or endorsement of USAID or the United States Government.

This publication may be cited as:

AquaFish Innovation Lab. November 2017. Aquaculture Collaborative Research Support Program Technical Sessions at Aquaculture America 2007. AquaFish Innovation Lab, Oregon

State University. Corvallis, Oregon, USA.

AquaFish Innovation Lab

College of Agricultural Sciences

Oregon State University

Strand Agriculture Hall

Corvallis, Oregon 97330-1643 USA

TableofContentsPREAMBLE ................................................................................................................................... 1Aquaculture CRSP Session Agenda ............................................................................................... 2Aquaculture CRSP Session Abstracts and Presentations ................................................................ 3

Assessment on the use of tilapia as biomanipulators in shrimp farming in Negros Occidental, Philippines .................................................................................................................................. 3Markets for Honduran tilapia ...................................................................................................... 4Susceptibility of the White Spot Syndrome Virus (WSSV) to ultraviolet (UV) light in a recirculation system type raceway .............................................................................................. 5Intensive larviculture of South American catfishes Pseudoplatystoma fasciatum and Pseudoplatystoma coruscans ...................................................................................................... 6Aquaculture waste management in China ................................................................................... 7Tilapia farming: a comparison of enterprise profitability among Ghanaian farmers ................. 8Use of dietary phytochemicals as a new method to sex-reverse Nile tilapia – aqueous plant extracts versus synthetic steroids ................................................................................................ 9Stocking ratios of tilapia Oreochromis niloticus and African catfish Clarias gariepinus and their effects on yield and profitability in earthen ponds ........................................................... 11Assessment of riparian buffers for protecting streams from small and large scale agricultural developments in Kenya ............................................................................................................. 12Coliform bacteria concentration in two coastal lagoons of the Mexican Pacific Ocean with oyster growing .......................................................................................................................... 13

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PREAMBLE

AquacultureAmerica2007SanAntonio,Texas,USA

26February–2March2007SessionsorganizedbyDr.HillaryEgna

The2007WorldAquacultureSociety’sAquacultureAmericawasheldinSanAntonio,TexasFebruary26toMarch2.OnMarch2,Dr.Egnamoderatedawell-attendedCRSPsessionfeaturing10presentationsonCRSPglobalsuccessesinproduction,healthandsafety,marketing,andcapacitybuilding.

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AquacultureCRSPSessionAgendaThursday,March1,2007,08:30-12:30

08:30 AssessmentontheuseoftilapiaasbiomanipulatorsinshrimpfarminginNegrosOccidental,

Philippines RemediosBolivar

08:45 MarketsforHondurantilapia SuyapaTriminioMeyer09:00 SusceptibilityoftheWhiteSpotSyndromeVirus(WSSV)toultraviolet(UV)lightina

recirculationsystemtyperaceway PabloGonzález-Alanis09:15 IntensivelarvicultureofSouthAmericancatfishesPseudoplatystomafasciatumand

Pseudoplatystomacoruscans MariaCéliaPortella09:30 AquaculturewastemanagementinChina WiminWang09:45 Tilapiafarming:acomparisonofenterpriseprofitabilityamongGhanaianfarmers SteveAmisah11:00 Useofdietaryphytochemicalsasanewmethodtosex-reverseNiletilapia–aqueousplant

extractsversussyntheticsteroids GustavoRodriguez11:15 StockingratiosoftilapiaOreochromisniloticusandAfricancatfishClariasgariepinusandtheir

effectsonyieldandprofitabilityinearthenponds CharlesNgugi11:30 Assessmentofriparianbuffersforprotectingstreamsfromsmallandlargescaleagricultural

developmentsinKenya ErnestTollner11:45 ColiformbacteriaconcentrationintwocoastallagoonsoftheMexicanPacificOceanwith

oystergrowing GuillermoRodriguez-Dominguez

3

AquacultureCRSPSessionAbstractsandPresentations

AssessmentontheuseoftilapiaasbiomanipulatorsinshrimpfarminginNegrosOccidental,Philippines

RemediosBolivar*,PhilipS.Cruz,MerlinaN.AndalecioandKevinFitzsimmonsFreshwaterAquacultureCenter-CollegeofFisheries,CentralLuzonStateUniversity,ScienceCityofMuNuevaEcija3120,Philippines

Theuseoftilapiaasbiomanipulatorsinshrimpfarming,oralsoknownasgreenwatertechnology,hasplayedanimportantroleinthecurrenteffortsinthePhilippinestocontrolluminousbacteriadiseasecausedbyVibrioharveyi.Atpresent,greenwatertechnologyismostextensivelyusedbyshrimpfarmersintheislandofNegros,inthecentralpartofthePhilippines.Whilethecontributionoftilapiaasabiomanipulatorishighlightedintheliterature,themechanismofactionisnotwell-understood.Thisstudywasconductedmainlytoassessthecontributionoftilapiaingreenwatersystem.Thedataweregatheredcamefromshrimppondspracticingbasicallytwoproductionsystems:a)greenwatersystem(probiotics+tilapia)andb)closed/semi-closedsystem(probioticsalone).Therewasnodifferencebetweenluminousvibriocount(p<0.05)inbothsystemsandthatwaterqualitywasfoundtobesimilar(p<0.05).Becausethegreenwatersystemutilizesabiggerreservoirtoraisethetilapiabiomass,thenetshrimpproductionwaslower.Intermsofdirectcostofproduction,however,thegreenwatersystemwasaround10-15%lowerthantheclosed/semi-closedsystemduetothesignificantlylessaerationrequired.Also,ingreenwatersystem,therewasamorestableplanktonenvironmentduringtheearlymonthsofculture,whichpromotedbettersurvivalofshrimps.Variouspathwaysarepresentedinthecontrolofluminousbacterialgrowthinshrimppondsbygreenwatertechnology,namely:a)feedingonorganicwastesandconversiontofeces;b)selectiveforagingtoincreasethedominanceofbeneficialphytoplankton;c)bioturbation;andd)releaseinthewatercolumnofantimicrobialsfrommucus.Thecombinedactionsofthesepathwaysandnotjustanysingleeffectarebelievedtoberesponsiblefortheoveralleffectivenessofthegreenwatertechnology.

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MarketsforHondurantilapiaSuyapaTriminioMeyer*andDanielE.MeyerAguacultureOutreachProgramPanamericanAgricultureSchool,ZamoranoP.O.Box93Tegucigalpa,Hondurassmeyer@zamorano.edu

TheHonduranmarketsfortilapiapresentthreecomponents,theexportmarkettotheUnitedStatesofAmerica,thedomesticmarket,andthelessimportantbutgrowingmarketintheneighbouringCentralAmericancountries.TheexportoffreshtilapiatoNorthAmericabecameimportantbeginningaround1996whenalargecommercialfishfarmbeganexportingfreshtilapiafilletsfromnorthernHonduras.Severalyearslaterasecondfarmbeganexportoftilapiafillets.Honduranexportsoffreshfilletssurpassed6,572MTwithavalueofUSD41,315,394for2005atanaverageFOBpriceofUSD6.28/Kg.Itisexpectedthatfor2006theseamountswillbesurpassedandHonduraswillbethesecondmostimportantexporteroffreshfillettoNorthAmericaafterEcuador.TheexportoffilletshasprovokedanimportantchangeintheperceptionoftilapiaamongHonduransandCentralAmericansingeneral.Traditionallytilapiahasbeenperceivedasafishusedprimarilytoassistruralfamiliessufferingfromextremepovertyandpoornutrition.Sincethecommencingofexports,thefishisnowverymuchappreciatedandappearsinalmosteveryfishdisplaycaseinpublicmarketsandsupermarketsacrossthecountry.Itisalsoveryprominentonrestaurantmenus.OverthepasttenyearstherehasbeenaproliferationofrestaurantsofferingtilapiainHonduras.Theserangefromwhitetableclothrestaurants,locallyoperatedUSfast-foodfranchisesandsimpleroadsideeateries.Someoftheroadsideeateriesmaintainlivefishintankstoassureafreshproductfortheirclientele.PricesforaKgoflivefishrangebetweenUSD1.73to2.30andforcleanfish(intheround)fromUSD2.30to2.90.Locally,freshorfrozenfiletaveragepriceisUSD7.00/Kg.PreparedtilapiainrestaurantsissoldinHondurasatpricesranginguptoUSD12.22,avaluethatsurpassesthepriceforthefinestmarinefinfishfilletsonthesamemenu.Localdemandfortilapiahasstimulatedgreaterproductionamongsmallandmedium-scalefishfarmersinHonduras.TheincreasedlocaldemandhasresultedfromthepublicitygiventotheexportoffilletsfromHondurasandtheavailabilityoftheproductinthelocalmarketsandsupermarkets.SeveralHonduranfishfarmersareexportingtheirfish(fingerlingsforstockingpondsandprocessedfishforconsumption)toneighbouringcountriesinCentralAmerica.ElSalvadorandGuatemalaaretwogrowingmarketsfortilapiawherepricesaresuperiorofthoseinHonduranmarkets.

5

SusceptibilityoftheWhiteSpotSyndromeVirus(WSSV)toultraviolet(UV)lightinarecirculationsystemtyperaceway

PabloGonzález-Alanis*,MarioHern,EnueE.Sicairos-Ruelas,AbundioGonz,FranciscoM.Guzm,DonaldV.Lightner,andKevinM.FitzsimmonsEnvironmentalResearchLaboratoryTheUniversityofArizona,Tucson,Arizona85706pabloglz@email.arizona.edu

Bacterialandviraldiseasesarecommonproblemsinaquaculture.Theuseofflow-throughsystemsfrequentlyrepresentsariskofcontaminationresultingindiseasesthatimpacttheindustry.Nowadays,theuseofdisinfectionmethodsinwaterisacommonpracticetoavoidtheintroductionofpathogensandtoreducepathogensincontaminatedsystems.Whitespotsyndromevirus(WSSV)isashrimpdiseaseresponsibleforsubstantialeconomiclossesinmanycountries.SeveralstudiesontheinactivationofWSSVbyUVlighthaveassessedtheefficacyoftheirunitsbyeitherexposinginfectedtissueorvirusstocksolutiondirectlytoastaticUVlightirradiationfordifferentperiodsoftime.Noneofthesestudieshadbeentestedonrunningwater.Aviralchallengeisnecessarytodeterminethevirucidaleffectivenessofthesystemat4L/minflowrate.AchallengemodelwasdevelopedtoobservetheinactivationoftheWSSV.Thepresentstudywasconductedtodetermineifthespecificpathogenfree(SPF)indicatorshrimpmighttakeWSSVfrominfectedwatereffluentaftertreatmentwithUVlight.SPFLitopenaeusvannamei,2.5-gravg.wt.,wereacclimatedto25ppt.artificialseawater.Onceacclimated,theyweredistributedinfourpairsoftanks(25/tank).Eachpairoftankshadoneinfectedtankbyinjectionandonenon-infected.Watereffluentfromtheinfectedtankwaspumpedandtothenon-infected,andreturnedtotheinfectedtankbygravity.TwopairsoftankshadUVlight(G15T8)toirradiatethewatereffluentbeforepasstothenon-infectedtank.Theothertwopairsoftanks(controlgroup)hadnoUVlightirradiationtothewatereffluent.MoribundanddeadshrimpwerecollectedandfrozentodetermineifinfectedwithWSSVbyusingPCR.After5weeks,thetankswithwaterinfectedwithWSSVandtreatedwithUVdidnothaveanymortality.ThetanksexposedtowaterinfectedandnottreatedwithUVresultedininfectedanddeadshrimp.Deadshrimpwerecountedandreplaced.ThisstudydemonstratedthatitispossibletoeliminatetheviralinfectivityeffectsoftheWSSVbytreatingthewaterwithUV.FurtherstudiesonflowrateandUVexposuretimewillbedonetodeterminetheUVlethaldosesrequiredtoinactivateWSSV.

6

IntensivelarvicultureofSouthAmericancatfishesPseudoplatystomafasciatumandPseudoplatystomacoruscans

MariaCéliaPortella Maria*,DaltonJ.Carneiro,MarcosA.Cestarolli,CarolinaFlores-Quintana,MarceloBorgesTesser,RosKiyokoJomori,CamiloGuerrero-Alvarado,ThomazJordAyres,MariaInezEspanholiG.Martins,JoMartinsPizauro,andKonradDabrowskiSaoPauloStateUniversity-AquacultureCenter,s/n,CEP14.884-900Jaboticabal,SP,Brazil.portella@caunesp.unesp.br

InterestincommercialfarmingofthebaredsurubimPseudoplatystomafasciatumandthespottedsurubimP.coruscanshasincreasedconsiderablyinBrazilduringthepastfewyearsduetothequalityoftheirmeatandhighmarketvalue.However,larvicultureofbothspeciesisdifficultsincetheyexhibitcannibalisticbehavior.Thischaracteristicandthelackofanadequatefeedingmanagementduringlarvicultureresultinreducedsurvivalratesduringthisphase.In2000westartedanewlineofinvestigationattheAquacultureCenterfocusingonthedevelopmentofrearingtechniquesofthesesurubins,basedontheknowledgeoftheirmorpho-physiologicalcharacteristicsduringtheontogeny.Histologicalstudiesonthedevelopmentofthedigestivesystemofthebaredsurubimhaveshownthatthezymogenegranulesarevisibleinthelarvalpancreasatthe2nddayposthatching(DPH)andthedifferentiationofthesegmentsofthedigestivetubestartedatthe3rdDPH.At10DAHthefirstgastricglandswereobserved.Themucuscellsintheesophaguswereoftwotypes,onePASpositiveandanotherABnegative.Intheintestine,mucuscellswerePASpositiveandABmoderatelypositive.Parallelinvestigationfocusingontheactivityofdigestiveenzymes(trypsin,chymotrypsin,pepsin-like,amylaseandlipase,from1to53DPH)showedthatthepancreaticproteaseactivitieswerealreadydetectableatthetimeofendogenousfeeding(1-2DPH).Thetrypsinandchymotrypsinactivitiesincreasedafterthebeginningofexogenousfeeding(3rdDPH).Pepsin-likeactivityincreasedatthe10thDPH,correspondingwiththeappearanceofthefirstgastricglandsinthestomach.Weconcludethatbaredsurubimlarvaepossesswelldevelopeddigestiveenzymeapparatusandweaningthemtoartificialdietsisanachievablegoalatthisstage(10DPH).Themorphologicaldevelopmentoftheeye,chemo-,mechano-andelectroreceptorswasstudiedinthespottedsurubim.Theolfactoryorganandthetaste-buds(oralandextra-oralreceptors)developprecociouslyandquicklyduringtheearlylarvalstageandindicatethatchemoreceptionisofprimaryimportanceforthedetectionandcaptureofthefood.Thevisionisprobablyofsecondaryimportanceandtheelevatednumberofampullaryelectroreceptorsspreadintheepidermalsurfaceofthecephalicregionpointstotheimportanceoftheelectroreceptionforthelarvalbehavior.Additionally,themechanoreception(laterallineandthefreeneuromasts)developsinsurubimlatermetamorphosis.Basedoncombinedresultsoffeedingandlarvalgrowthunderlightanddarkcondition,werecommendrearingofsurubimlarvaeindarknessthroughoutmetamorphosis.SeveralexperimentswerecarriedoutinBrazilandUSaimingatthedevelopmentoffeedingtechniquesduringlarvicultureandfeedtrainingofthesurubins,usingliveanddrydiets.Theresultssuggesttheneedofartemianaupliiduringthefirst10days;afterthisperiod,theweaningtoformulatedfoodisfeasible.Cannibalisticbehaviorishighduringthetransition.

7

AquaculturewastemanagementinChinaCaoLing,WangWei-min,YangYi,YangCheng-tai,JamesDianaCollegeoffishery,KeyLabofAgriculturalAnimalGenetics,BreedingandReproductionofMinistryofEducation,HuazhongAgriculturalUniversity,Wuhan,430070,P.R.Chinawangwm@mail.hzau.edu.cn;yangyi@ait.ac.th

Thisreviewaimstoidentifythemajorcause,potentialcompromiseandmanagementstrategiesofaquaculturewasteincurrentChina.Aquacultureactivitiesarewellknowntobethemajorcontributortotheincreasingleveloforganicwasteandtoxiccompoundsintheaquacultureindustry.Themaincontaminantsofthewastewatereffluentaresuspendedsolids,ammonium,organicnitrogenandphosphorus.Aquaculturewastewaterdischargesmaycausemanyenvironmentalproblemstothereceivingwaters.Nutrientremovalisessentialforaquaculturewastetreatmenttoprotectreceivingwatersandforpotentialreuseofthetreatedwater.Therefore,itisapparentthatappropriatewastetreatmentprocessesareneededforsustainingaquaculturedevelopment.Anumberofphysical,chemical,andbiologicalmethodsusedinwastetreatmentappliedinaquaculturesystemshavebeenpresentedinthisreview.Theprinciples,advantagesanddisadvantagesofthecommonlyusedwastetreatmentsystemsareexamined.Amongwhichbiologicaltreatmenthasbeenconsideredthemostfeasibleapproachforenablingwaterreuse.Besides,newapproachesareintroducedasreferencesforthepotentialdevelopmentofwastetreatmentsysteminChina.

8

Tilapiafarming:acomparisonofenterpriseprofitabilityamongGhanaianfarmersSteveAmisah*,KhalidSualih,andKwamenaK.QuagrainieKwameNkrumahUniversityofScience&TechnologyKumasi,Ghanasteveamisah1@yahoo.co.uk

Efficientmanagementofatilapiafarmcanmakethedifferencebetweenprofitsandlosseseveninyearswithunfavorablepricesandcosts.Farmmanagementinvolvesmorethanjusttakingcareofthebiologicalprocessesinvolved;itincludespayingcloseattentiontoeconomicandfinancialmeasuresofthefarmbusinessalso.Acomparisonismadeofeconomicandfinancialindicatorsof10fishfarmerseachintheBrong-AhafoandAshantiregionsofGhana,analyzingtheperformanceofthetilapiafarmbusinesses.Asurveywasconductedtoassesstheprofitabilityoftilapiafarmingintwogrowingregions-Ashanti&Brong-AhafoinGhana.Samplingwasnon-randomaidedbygovernmentdirectoryandbasedonabilityofrespondenttoprovideinformation.Atotalof10farmerseachfromAshantiandBrong-Ahaforegions(20farmers)weresurveyed.PerformanceindicatorsexaminedincludedOperatingProfit,NetIncome,NetProfit,ReturntoLandandCapital,Break-evenPrice,Break-evenProduction,andRateofreturntototalinvestment.ResultssuggestedthatfishfarmingintheAshantiregionwasmoreprofitablethanfishfarmingintheBrong-Ahaforegion.ProfitabilityintheBrong-Ahaforegionappliedtofarmersproducingfingerlingsforsale.Break-evenproductionaveraged913kgintheBrong-Ahaforegioncomparedto877kgfortheAshantiregion.Ashantiregionperformedbetterinmeasuresofprofitability.Farmerwhoconstructedtheirownpondshadpositivenetprofit.Ashantiregionbreak-evenpriceof$1/kgwaslowerthanbreak-evenpriceofBrong-Ahafooperations.Measuresofprofitabilityweregenerallybetterforfarmerswhoprovidedsupplementaryfeed.

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Useofdietaryphytochemicalsasanewmethodtosex-reverseNiletilapia–aqueousplantextractsversussyntheticsteroids

GustavoRodriguez*,LaineFrantzandKonradDabrowskiTheOhioStateUniversitySchoolofEnvironmentandNaturalResourcesColumbusOH43210*rodriguez-montes.1@osu.edu

Manystudieshavefocusedontheuseofchemicalsproducedbyplants(phytochemicals)assexsteroidendocrineregulators.Suchstudiesanticipatethatphytochemicalswillactasendocrinemodulatorsbychangingendogenoushormoneprofiles.Theseeffectscouldberelatedtotheiraromataseinhibitorycapacityamongotherunidentifiedmechanisms.Ifsuchactivityispreciselyexpressedbythesechemicals,theycouldprovideanovel(alternativetosyntheticinhibitors)modeofactiontoinducechangesinthephenotypicprocessofsexdifferentiationinfishgonads.Naturalplantchemicalswithexpectedsaferutilizationandhandlingissues,andpossiblylowertoxicityforbothfishandthesurroundingenvironment,areaveryattractivealternative.Weconductedafeedingtrialonfirstfeedingall-femaleNiletilapia(>80%female).Fishwererandomlydistributedintoglassaquariainarecirculationsystematatemperature262C,atthedensityof60fishperaquariumwiththreereplicatespertreatment.Experimentalcasein-gelatinbaseddietswerepreparedasfollows:control(CON),0.006%17(MT),1%spironolactone(SPIRO),alongwiththeaqueousextractsof0.1%(H100)and0.5%(H500)ofHibiscusmacranthusandmate(Ilexsp.),(M100andM500respectively),and0.5%ofmaca(Lepidiummeyenii)(MACA).Incaseofallplants,aqueousextractswereaddedtothedietsonthedrymatterbasis.Toobtainsuchaqueousextracts,20gofdryplantmaterialwassuspendedin1.5lofdistilledwaterfor12hours,filteredusingpaperfiltersandresultingsuspendedsolutionswerefreeze-driedtoobtaindrypowderextracts.Fishwerefedfor40d,withperiodicalweightgainestimationsat14and28dtoreadjustfeedingratiofrom20to8%.Fishperformancewasevaluatedintermsofthefinalindividualbodyweight,survival(%),specificgrowthrate(SGR,%/day)andfeedconversionratio(FCR).Thefinalsexwasdeterminedbymicroscopicanalysisofgonadsquashesattheendoftheexperiment.Resultsindicatedthatthesexratioofgeneticallyall-femaletilapiaisnotaffectedbytheinclusionofthetestedplantextracts;howevertheMTandSPIROgroupsexhibitedsignificantchangesinsexratio,100%and75%males,respectively(Fig1).SPIROaffectednegativelythesurvivalofexperimentalfish(49.5comparedtotheothertreatments(94.3Nosignificantdifferenceswereobservedinthefinalindividualbodyweight(0.71g),SGR(10.6%/day)orFCR(0.94amongdietarygroups.

10

Fig1.Finalsexratioperdietarytreatment(Mean±SD,n=3;79-90fishperdietweresexed).

11

StockingratiosoftilapiaOreochromisniloticusandAfricancatfishClariasgariepinusandtheireffectsonyieldandprofitabilityinearthenponds

CharlesNgugi*,ElizabethNyanchiri,JosephRasowo,andJamesBowmanMoiUniversityDepartmentofFisheriesandAquaticSciencesP.O.Box1125,Eldoret,Kenya30100.cngugi@africaonline.co.ke

Mixed-sextilapiaculturetypicallyleadstooverbreeding,resultinginsmall-sized(stunted)fishthatareoflowvaluetoproducers.WhenstockedwithapredatorsuchastheAfricancatfish(Clariasgariepinus),largerfishandhigheryieldsareusuallyobtained.However,inKenyaNiletilapia:Africancatfishpolycultureisnotcommonlypracticed,largelybecausefishfarmerslackinformationonappropriatestockingratios,economicimplications,andtheanticipatedoutputsatharvest.ThisstudywasconductedtotesttheyieldsandprofitabilityofOreochromisniloticusandClariasgariepinusstockedatdifferentratiosinorganicallyfertilizedearthenponds.A182-daytrialofdifferentstockingratiosformixed-sextilapia/catfishpolyculturewasconductedin100m2earthenpondsatMoiUniversity,Eldoret,Kenya.Tilapia:catfishratiosof2:1,6:1,and19:1(wetweightbasis)weretestedalongsideatilapia-onlycontrol.Meandailygrowthrates,finalweights,andyieldsofmarket-sizeNiletilapiaweresignificantlyhigher(P<0.05)inthe2:1polyculturetreatmentthaninallothertreatments(Table1).Nosignificantdifferences(P>0.05)wereseenamongdailygrowthratesorfinalweightsofAfricancatfishamongthepolyculturetreatments(Table2),butgrossandnetcatfishyieldsvariedsignificantlywithstockingratios,withthehighestyieldsobservedinthe2:1stockingratio.Survivalamongtreatmentswasnotsignificantlydifferentforeithertilapiaorcatfish(Tables1,2).The2:1stockingratiowasthemostcosteffectiveandtheleastprofitablewastilapiastockedalone(Table3),suggestingthatKenyanfarmersstockingmixed-sexedtilapiacansignificantlyimprovetheiryieldsandincomebystockingAfricancatfishwithtilapiaataratioof2:1byweight.

12

AssessmentofriparianbuffersforprotectingstreamsfromsmallandlargescaleagriculturaldevelopmentsinKenya

E.W.Tollner*andHerbertSseganeDepartmentofBiologicalandAgriculturalengineeringUniversityofGeorgia,Athensbtollner@engr.uga.edu;706-542-3047

ThisresearchispartofaUSAIDprojecttoprotectFisheriesinLakeVictoria,theWorldssecondlargestsourceoffreshwaterfromAgriculturalPollution.Sedimentation,nutrientrunoff,andbiomassburninghaveinducedrapideutrophicationofLakeVictoria,leadingtodecreasedproductivityinthelakesfisheryindustry.TheprojectsiteistheNzoiariverbasin(Moibenwatershed)wheresoilerosiondegradesthelandanddrainsmillionsoffertilesoilintoLakeVictoria.DocumentedstudiesshowthatriverNzoiacontributesthemostsedimentloadingtoLakeVictoriafromtheKenyancatchmentmainlybecauseofitshighdischargeof118m3/s(48%ofthetotal).ThetotalsuspendedsolidscontributedbyNzoiaareinthemagnitudeof2,504,367tonnes/year.TheprojectevaluatestheimpactofstreamsidecultivationonwaterqualityusingGoogleEarthProasaremotesensingtoolformonitoringandextractingbasincharacteristics,theUniversalSoilLossEquation(USLE)forerosionprediction,andEnvironmentProtectionAgency(EPA)-SedimentDeliveryRatio(SDR)forpredictingsedimentyield.TypicalmapsareshowninFigure1.BoththeUSLEandtheEPA-SDRmodelsaredevelopedusingTKSolverprogram.Severalstudysiteshavebeenanalyzedwithvaryingriparianwidth(0-300m)andaripariancoverpercentof5%-75%oftherespectivecatchmentareas.Resultsforatypicalanalysesareshownbelow.Alsoapredominantlyrowcropagriculture(Sugarcaneproduction)zonewasconsidered.TypicalresultsoftheinvestigationareshowninTable1foroneofseveralsitesinvestigated.ThepreliminaryprojectfindingsindicatethatAgriculturalpollutionappearsnottobeasignificantproblemnow,butcouldbecomesowithtimeinthecaneproductionregion;asociallyworkablestrategyforimplementingriparianzonesmaybetoincreasethenominal30mthicknessbutallowlocaluseoftheriparianzones.IndustryandmunicipalwasteposeafargreaterdangertothefisherythantheAgriculturalPollution;andGoogleEarthProappearsusefulforinitialsurveys.

Figure1.ThreedimensionalelevationmapasdeterminedusingGoogleEarthPro.

13

ColiformbacteriaconcentrationintwocoastallagoonsoftheMexicanPacificOceanwithoystergrowing

GuillermoRodriguez-Dominguez*,E.GaxiolaCamacho,M.C.VelCuadras,J.A.Ruiz,GarcyJ.G.Olivo-Rojas,M.C.Haws,andJ.Supan*DepartmentofMarineSciences,AutonomousUniversityofSinaloa,PaseoClausenS/N.ApartadoPostal610,MazatlSinaloa,Mguirodom@yahoo.com.mx

InacoastallagoonoftheMexicanPacificOcean(CamichwherethereisaCrassostreacortesiencisoystergrowingandother(SantaMardelaReforma)wheretheCrassostreagigasoystergrowingisplanned,coliformbacteriaconcentrationswereanalyzed,inordertoknowiftheyclassifyasshellfishgrowingApprovedAreasaccordingwith:NOM-031-SSA1-1993(OfficialMexicanNorm).Foreachofthethreesamplingscarriedouton2006(February,JuneandSeptember)thirtywatersampleswerecollectedinTheCamichinlagoonandthirty-seveninTheSantaMardelaReformalagoon.Watersampleswereanalyzedforbacteriausingdilutiontestseriesofthreeglasstubes,recommendedby:NOM-031-SSA1-1993(OfficialMexicanNorm).InTheCamichinlagoon,medianandgeometricmeanofthebacteriaconcentrationexceededintwosampledatesthe70NMP/100ml(fortotalcoliformbacteria)and17NMP/100ml(forfecalcoliformbacteria)criteriaoftheofficialnormandconcentrationslowerthanstandardbutsoclosetothelimitwereobservedinFebruaryonly.Aninverserelationwasobservedbetweenthebacterianconcentrationandwatersalinitywhichchangedfrom29to4.FornoneofthethreesamplesrealizedintheSantaMardelaReformalagoon,coliformbacteriaconcentrationsexcededtheapprovedareacriteriafortheoystergrowing.Forthislagoon,watersalinityvariedfrom37to29.TheresultshavebeenshowedtothelagoonsuserstocreateanIntegratedManagementProgramwhichallowsasuitableadministrationofbasinresidualwatersandimprovethegrowingzonequality.