Bioenergetics-based Models To Estimate Growth,Feed Requirement And Waste Output Of Gibel Carp(Carassius Auratas Gibelio)and Grass Carp(Ctenopharyngodon Idellus)

Aquaculture nutritional models play a vital role in the management of fish culture operations.This paper mainly studied the growth trajectory of grass carp(Ctenopharyngodon idella)and carassius auratus gibelio(Carassius auratas gibelio)at different growth stages,determined the energy reqiurement of these two kinds of fishes in different environments and constructed a combined nutritional model based on bioenergetics.This combined model comprised a growth model,a feed requirement model and waste(nitrogen and phosphorus)output model,and provides a theoretical basis for improving the quality and reducing the pollution output of fish culture operation.The research comtents were as follows:The growth rate of gible carp and grass carp at different growth stages was calculated by specific growth rate(SGR),daily growth coefficient(DGC),thermal-unit growth coefficient(TGC),average daily growth(ADG)growth models baised on the data from two fish farms in Jingzhou,Ningbo(china)and published studies.The least squares method was used to optimize the growth coefficient within each growth stage and to choose the best growth model.Feed requirement of fish in different growth stages was determined by digestible energy requirement(DEreq).Feed requirement was estimated based on digestible energy requirement(DEreq),calculated from the summation of retained energy(RE),basal metabolism energy(HeE),heat increment of feeding(HiE),and urinary and branchial(UE+ZE).All estimated by compiling and analysing data from published studies.The waste outputs were estimated using a nutrient mass balance approach.Feed requirement model simulations were compared with the results from a growth trial based on gibel carp and grass carp were fed with 35%,28%crude protein for different growth stages,respectively.The result shows that gibel carp has 3 growth stages in its life cycle:from first-feeding<13.5 g(Stage 1);from 13.5 to 175.5 g(Stage 2);and>175.5 g(Stage3)and the modified TGC models produced a better fit of the growth trajectory of gibel carp and grass carp than other growth models(SGR,DGC,ADG)in practical aquaculture culture operations.Values predicted for body weight and feed conversion rate(FCR,feed:gain)by the models were highly correlated to the observations from the growth trial.The digestible energy requirement is about1.94×10~7 kJ for 1t gibel carp with the body weight of 0.5-500g,total solid wastes(TSW)output of gible carp was estimated at about 282 and 419 kg per tonne of feed fed and per tonne of fish produced,respectively.The digestible energy requirement is about 1.43×10~7 kJ for 1t grass carp with the body weight of 0.5-1500g,total solid wastes(TSW)output of grass carp was estimated at about 405 and 511 kg per tonne of feed fed and per tonne of fish produced,respectively.These results indicate that the combined model can effectively estimate the growth,feed requirement and waste output in the actual culture operations of grass carp and gibel carp,and could be a valuable tool for the differential listing,reduce the cost of feed and feed waste,pollution assessment in fish culture operation.