Mass culture ofTilapia zillii [Cichlidae] in pond ecosystems

The culture ofTilapia zillii (Gervais) in 18 and 34 cm deep, 5.5×7.6 m earthen ponds at 3 initial stocking densities, 6, 9 and 12 pairs, revealed an optimum 9 pair initial density for the maximum production of fry after 104 days. However, biomass increase was significantly greater at the 6 pair stocking density and in deeper ponds. Pond depth had no significant effect on size and weight gain of parental fish. Nest and brooding tube construction was variously influenced by pond depth and stocking density. Partial shading of ponds, while not affecting the maximum water temperature, did apparently reduce fish biomass production, the average length and weight of fry, and the average depth of nests. An estimated 1 million fish could be produced in 104 days from 190 similar ponds with a water surface equivalent to 0.8 hectares. This would be equivalent to ca. 725 kg fish biomass production and would require ca. 1,900 kg of catfish pellets or their equivalent. Possible ways to increase rearing efficiency are discussed.