Investigation of the impact of stocking density on the production of Oreochromis niloticus fry in hapas

Abstract

The aim of this study was to determine the stocking density that maximises the commercial production of O. niloticus fry in hapas at Lake Harvest Aquaculture.  The study was conducted over a period of nine weeks.  Three stocking densities of 4500 (A), 8000 (B) and 11500 (C) fry/hapa with four replicates each were used in the study.  The stocking density of 4500 was used as the control.  Fry were fed with a mixture of fry meal (40% Crude Protein) and crumbles (30% Crude Protein) in a ratio of 1:2 respectively using the Lake Harvest Aquaculture Feed Chart.  Weekly random fry sampling was done, with a sampling intensity of 60% for all replicates to determine average body weight per treatment.  The average body weight was used to determine fry growth, feed conversion ratio and the computation of fry survival rates after the final harvest.  Data was tested for normality using the Kolmogorov-Smirnov (p<0.05). A one way analysis of variance was computed for all variables at 5% level of significance.  Stocking density had no significant influence on fry growth (p=0.603), fry survival, (p=0.774) and feed conversion ratio (p=0.304).  Since the stocking densities used in this study did not influence fry growth, survival and feed conversion ratio, we conclude that the current stocking density at the farm was low and rather conservative.  Consequently, we recommend that Lake Harvest Aquaculture use a stocking density of 575 fry/m³in order to increase fry production.  For a more convincing validation of this study, it would be necessary to conduct a replica of this study with much higher stocking densities for the optimization of fry production at Lake Harvest.

Keywords : Oreochromis niloticus, Fry, Feed conversion ratio, Hapa, Stocking density