Abstract
SectorofZoology–MarineBiology,DepartmentofBiology,UniversityofAthens,Panepistimiopolis,Athens,GreeceSummarySpecificgrowthrate,averagedailyfoodintake,grossconver-sionefficiency,plasmatotallipids,triglycerides,totalcholes-terolandglucosewereevaluatedannuallyinapopulationofEuropeanseabass(DicentrarchuslabraxL.)intensivelyrearedinfloatingmarinecages.Thesedataareaimedatimprovingproductivityandallowsmorepreciselimitstobeplacedonthehematologicalparameterswhichareanecessarypreconditionfortheassessmentoffishconditionandhealth.Specificgrowthrate(%),averagedailyfoodintake(%)andgrossconversionefficiencyshowedrelativelyhighervaluesinthewarmspringandsummermonths.Thespecificgrowthratecorrelatedbetterwiththeseawatertemperatureandtheaveragedailyfoodintake than with the photoperiod. The concentrations ofplasmatotallipids,triglyceridesandglucosewerehigherinsummer.Plasmatotalcholesterolconcentrationswerehigherduring the pregametogenesis and gametogenesis periods.Plasmatriglyceridescorrelatedbetterwithphotoperiodandplasmaglucosethanwiththeseawatertemperature.IntroductionClinicalmethodsformonitoringthephysiologicalconditionofteleostsexposedtoawiderangeofenvironmentalconditionshave been used extensively in the past. The levels ofbiochemicalvariablesinfishbloodhavebeenshowntobemainlyaffectedbyphotoperiod,watertemperature,dissolvedoxygen,salinity,qualityandrateoffoodconsumed(Courtois,1976;Alliotetal.,1984;Dheer,1988;AudetandClaireaux,1992;Audetetal.,1993;Vellasetal.,1994).Seabassmetabolicparametersshowdiurnalandseasonalchanges(Carrilloetal.,1982,1987;Gutierrezetal.,1984,1987;Perezetal.,1988;Fernandezetal.,1989;Pavlidisetal.,1997).Growthratesandfeedingratesofthisspeciesarecorrelatedwithsalinity,watertemperatureandphotoperiod(Alliotetal.,1983;ZanuyandCarrillo,1985;Hidalgoetal.,1987;Castritsi-CathariosandKavadias,1993;Begout-Anras,1995).Theproductionofseabass,amarinespecies,hasdramat-icallyincreasedandisintensivelyfarmedinGreeceandotherMediterraneancountries.Thesuccessfulfarmingofseabassrequiresagoodknowledgeofthefeedingstrategyasafunctionoftheanimalsizeandenvironmentalconditions.However,therearefewstudies(Castritsi-CathariosandKavadias,1993;Begout-Anras,1995)thatexaminetheinfluenceoffeedingrateandenvironmentalvariablesonthebiochemicalparametersofintensivelyrearedfish.Theaimofthepresentstudywastoinvestigatetheannualchangesofspecificgrowthrate(%),averagedailyfoodintake(%),grossconversionefficiencyandplasmabiochemicalparametersinfarmedseabassandtheeffectofnaturalfluctuationsofenvironmentalparameters(photoperiod, seawater temperature, salinity) on these. Inordertoachievethistarget:(i)annualnaturalfluctuationsofphotoperiod,seawatertemperatureandsalinitywereevaluated;(ii)specificgrowthrate(%),averagedailyfoodintake(%),grossconversionefficiencyandplasmabiochemicalparameters(totallipids,triglycerides,totalcholesterolandglucose)ofseabasswereevaluatedannually.Thegrowthandfeedingdataofthepresentstudywillenableaquaculturiststoimproveproductivitybyadjustingthefeedingratetotherealfishdemands,takingintoaccountthenaturalfluctuationsofthephotoperiodandtheseawatertemperature.Thebiochemicaldatawillenablefishphysiologiststoestablishmorepreciselimitsofhematologicalparametersfortheassess-mentoftheconditionandhealthofintensivelyculturedfish.Materialsandmethods
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