Growth and nutrient conversion of white shrimp Litopenaeus vannamei (Boone) and Nile tilapia Oreochromis niloticus L. in an integrated closed recirculating system

We investigated the eiects of the stocking density of white shrimp (Litopenaeus vannamei )o n shrimp and tilapia growth and nutrient conversion in an integrated closed recirculating system both with and without Nile tilapia (Oreochromis niloticus). A 2 � 3 factorial design involving tilapia presence/ absence and shrimp stocking densities of 40, 80 and 120 m � 2 was applied, using a tilapia:shrimp ratio of 0.025. There were no signi¢cant interactions between tilapia presence and shrimp stocking density in terms of shrimp growth performance or feed utilization. The presence of tilapia had no eiect on the shrimp growth rate, survival rate or total weight gain (%). Shrimp growth declined signi¢cantly with increased shrimp stocking density, but the growth of tilapia was not signi¢cantly diierent among the three shrimp densities tested. The conversion of feed nitrogen and phosphorus into total harvested animal biomass was signi¢cantly higher in the presence than in the absence of tilapia. The nutrient conversion rate at the lowest shrimp density (40 m � 2 ) was signi¢cantly higher than at the highest density tested (120 m � 2 ).