Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

摘要: Two consecutive experiments were conducted to study the effects of stocking density on growth, food utilization, production and farming profitability Nile tilapia (Oreochromis niloticus) fingerlings (initial mean weight: 16.2 ± 0.2 g) fed Azolla, as a main component in diet. In experiment 1, fish hand-fed twice daily with three isonitrogenous (28.5% crude protein) isocaloric (14.5 kJ g−1) diets A30, A35 A40 containing 30%, 35% 40%Azolla, respectively, for 90 days. Diets formulated by mixing Azolla locally available by-products. No significant differences found growth parameters (P>0.05). Total investment cost was significantly higher A30 (P 0.05). 2, densities, 3 5 m−2, assigned treatments T1, T2 T3 respectively. Fish diet A40. The final weight (89.53–115.12 g), gain (0.81–1.10 g day−1), specific rate (1.90–2.20% day−1) apparent conversion ratio (1.29–1.58) affected density, difference Yield annual increased increasing ranging from 7.10 0.90 25.01 1.84 kg are−1 28.79 3.66 101.42 7.48 kg are−1 year−1, between all densities (P<0.05). Higher resulted gross return lower production, variations net However, both 5 m−2 produced same values. On basis values economic return, it concluded that could be raised at 3 fish m−2 improve generate profit nutritional security poverty alleviation rural areas.