Determine optimal diet for rearing black tilapia (Oreochromis niloticus) in Bafgh brackish water

Tilapia is one of African native fishes has been introduced to many thermal and temperate regions in the world for second part of twentieth century. First, intensive culture system dependes on complete and wide information in nutrition requirements, specially protein as most expensive nutrient; second, the importance of tilapia in future of Iran; and third, lipid as first non-protein energy source that is so influent and it’s unsufficient values affect negatively on growth and protein requirement, make us to investigating the protein and lipid requirement of Nile tilapia Oreochromis niloticus to achive a convience diet causing most economical interest by maximum growth and minimum feed conversion ratio. This experiment performed in Bafgh Inland Saline Water Fish Research Station. It was planned in four protein (15, 22, 29 and 36%) and three lipid (5, 9 and 13%) levels in factorial system. Thirty six 300 l tanks with 150 l water and 3 l/min water flow used for 12 treatments with triplicates. 15 male Nile tilapia fingerlings (13.94±0.88 g) kept in every tank and fed near satiation during 8 weeks experiment. There was any significant different in survival in all treatments. Growth performance (WG & SGR), feed and protein efficiency (FCR & C and PER & PCE respectively) improved with increasing proein level until 29%, however, significant positive effect was not observed by lipid increasing. Then, best economical protein and lipid level for convinienc growth performance and protein and lipid efficiency is 29 and 5% respectively. In 5% lipid, maximum growth and protein efficiency appears between 33.9 to 35.3% protein according to the mathematical method (polynomiyal curve)