Fitting growth with the von Bertalanffy growth function : a comparison of three approaches of multivariate analysis of fish growth in aquaculture experiments

Abstract

Three approaches for multivariate analysis of fish growth in aquaculture experiments with Nile tilapia (Oreochromis niloticus niloticus L.) based on the von Bertalan¡y growth curve are presented and compared. The approaches are: an extended Gullandand- Holt (GH) plot, a forced extended GH plot and a multilinear regression analysis for the growth parameter K. All three models provide valuable insight into the major environmental factors in£uencing the daily growth rate and explain 28-46%of the variance of the observed daily growth rate of the used data set. For all three methods, the modelled parameter is significantly related to the net yield of Nile tilapia and can, therefore, be used for the predictive modelling of management scenarios. The extended GH plot loads the in£uence of environmental parameters upon L1, while the forced extended GH plot and Direct fitting of K load the in£uence on the growth parameter K. The latter ismore in the tradition of aquaculture research. But the forced extended GH plot and Direct fitting of K can only be applied if L1 of the cultured species is known, as the selected L1 in£uences the variance in the regression variables.