A Partial Economic Analysis for Nile Tilapia Oreochromis niloticus L. and Sharptoothed Catfish Clarias gariepinus (Burchell, 1822) Polyculture in Central Kenya
Gichuri, W. M
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Aquaculture development in Kenya has been hampered by lack of targeted feeds. Chemical fertilizers can enhance natural food production and thus indirectly provide protein to complement energy-rich cereal brans used as feed. Consequently, an experiment was conducted at Sagana Fish Farm in central Kenya to realize least-cost combinations of rice bran and fertilizer. Twelve 800 m2 (0.08 ha) ponds were stocked with juvenile (32 g) Oreochromis niloticus L. at 2 m−2 and Clarias gariepinus (Burchell 1822) (fingerlings of 4.6 g) at 0.2 m−2. Four treatments, calculated to approximate isonitrogenous conditions, were applied in triplicate as follows: (1) urea and diammonium phosphate (DAP) to provide 16 kg of N ha−1 week−1 and 4 kg of P ha−1 week−1; (2) urea and DAP applied to give 8 kg of N ha−1 week−1 and 2 kg of P ha−1 week−1, plus rice bran fed at 60 kg ha−1 day−1; (3) rice bran fed at 120 kg ha−1 day−1; (4) rice bran as in treatment 3 and fertilizer as in treatment 2. Ponds were sampled monthly to measure fish growth, and drained completely after 20 weeks. A partial economic analysis indicated minimal net profits of K.Sh. 18 851 (US$ 251), K.Sh. 9895 (US$ 132), K.Sh. 3299 (US$ 44) and K.Sh. 7015 (US$ 94) for treatments 1–4, respectively, because of high feed and seed costs.