Abstract

The effects of stocking density (0.1, 0.5, 1 and 1.5 fish.m^-2) on the nutritional value of the natural food source (total suspended solid (TSS) and sediment), diet quality and growth performance of fingerlings of Oreochromis niloticus were studied in ponds. The nutritional value of TSS expressed in terms of hydrolysable organic matter (HOM) and total amino acids contents decreased with increasing stocking density. The quality of the sediment resource was not affected by the densities treatments. The percentage of HOM, total amino acids and the total amino acids-energy ratios of the food ingested by O. niloticus decreased with increasing stocking density. Digestibility of total organic matter (Ash free dry weight, AFDW) and total amino acids decreased with increased density (P<0.05), which ranged from 52.7 ±19.3% to 29.8 ± 14.7% and 60.4 ± 24.5% to 39.7 ± 16.8% respectively. There was a positive correlation between fish daily gain and dietary total amino acids, total amino acids-energy ratios, digestibility respectively. The high density (1 fish.m-²) negatively affects food nutritional quality and growth performance of tilapia. Densities less than 0.5 fish.m^-² seem to be more adequate to obtaining the highest fish yields in practice of extensive aquaculture.

Key words: Oreochromis niloticus, stocking density, natural food, nutritive value, growth, extensive aquaculture.