The effect of dietary protein to energy ratio and stocking densities on fish production, food web enhancement and economic benefit of gift Nile tilapia aquaculture in ponds

In non-lined ponds, natural food complements dietary P/E. We assessed the effect of lowering dietary PIE ratio with an increasing stocking density on performance of tilapia, food web enhancement and impact on pond nutrients. The experiment was conducted in a 2x2x2 factorial design: diet (CP:CE ratio 19 vs. 14 g.MJ-1); feeding level; and stocking density (2 vs 3 m-2) in 40 farmers' ponds. Biomass gain increased with a decreasing dietary PIE ratio and increasing stocking density). A negative accumulation of N and P in pond water was noticed for low stocking density ponds. Nitrogen gain in fish was higher for low P/E diet and also influenced by feed per square meter. At low P/E diet, the contribution of natural food to fish production was higher than for the high P/E diet. Net profit increased by lowering the dietary P/E ratio of the diet (2070 vs 1072 US$ ha-1 83 day-1).