Abstract:
The present study was conducted over a 40 days period based on a 3 × 3 factorial design with three rearing densities (D1 = 100, D2 = 200, and D3 = 300 fish/m3) and three levels of feeding rates (25%, 30%, and 35% of body weight) using feed having 36.8 crude protein (CP) to study the effects of stocking density and feeding levels on the growth and survival of fry Oreochromis niloticus L. cultured in hapas in an earthen pond. Fish of average initial weight 1.1 g ± 0.03 were stocked at three different rates: 6, 12 and 18 fish per hapa (30×40×50cm about 60 litre each). Fish of each density were fed on the above experimental diets till satiation twice daily, 6 days a week, for 6 weeks.
The growth parameters were inversely affected by stocking density and feeding level with positive effect on their interaction. The average final weights varied significantly (P < 0.05) and varied at D1 from 2.30 to 4.23 g, at D2 from 2.80 to 2.97 g and D3 from 2.63 to 2.90 g. Fish stocked at 100/ m3 with feeding level 25% exhibited the highest average weight gain (3.17 ± 0.03 g) whiles; fish stocked at 300/ m3 with feeding level 35% recorded the lowest average weight gain (1.60 ± 0.07 g). The lowest feeding rate with lowest stocking density recorded the best feed conversion ratio, protein efficiency ratio and relative growth rate, with significant differences. Condition factor and fish survival in different experimental groups were significantly affected by rearing densities and protein levels. The overall results recorded here reveal that the best growth performance of Oreochromis niloticus was obtained when the fish were fed on the 25% of body weight diet and when reared at a stocking density of 100 fish/ m3.
