EFFECTS OF STOCKING DENSITIES ON GROWTH AND SURVIVAL OF JUVENILE NILE TILAPIA Oreochromis niloticus (Lin, 1758) IN HAPA NETS

Abstract

A study was carried between October 2008 and February 2009 to evaluate the effect of varying stocking densities on the growth and survival of Nile tilapia Oreochromis niloticus stocked in a pond of 100m2 and average depth of 1.5m at Chebarus fish farm, Kesess Location, Uasin Gishu County. Tilapia juveniles of mean weight 20±2 g were obtained from University of Eldoret fish farm. The juveniles were randomly stocked at 30, 60 and 90 fishm-3 respectively. The fish were fed twice daily at 9.00 am and 3.00 pm with formulated feeds of 40% crude protein. Fifteen, thirty and forty-five fingerlings were sampled from the 30, 60 and 90 fishm-3 respectively and analyzed for growth every fourteen days. Physical-chemical parameters like pH, temperature, water depth, total ammonium nitrates and dissolved oxygen were also measured fortnightly using standard procedures. Results showed significant differences (p< 0.05) in daily weight gain, specific growth rate, final weight, relative growth rate, feed conversion ratio and survival for all the treatments. Apart from the dissolved oxygen and Total Ammonium Nitrates, all the physical chemical parameters showed no significant differences (p> 0.05). There was a major decrease in the levels of dissolved oxygen with increase in stocking density, with the hapa nets containing 90 fishm-3 recording the lowest levels of oxygen. Overall, the fingerlings in 30 fishm-3 had relatively higher survival and growth rates compared to fish stocked at 60 and 90 fishm-3. Low stocking densities of 30 fishm-3 stocking are recommended for rearing fish in hapa nets.