RECYCLING WASTEWATER OF INTENSIVE HYBRID CATFISH CULTURE FOR SEMI-INTENSIVE NILE TILAPIA CULTURE

An experiment was conducted in fifteen 5-m2 cement tanks for 90 days to determine the effects of water recirculation frequency on fish growth, water quality and nutrient recovery efficiency in an integrated recycling culture system, in which nutrient-rich water from hybrid catfish (Clarias macrocepharus x C. gariepinus) intensive culture tanks was recirculated to Nile tilapia (Oreochromis niloticus) semi-intensive culture tanks. There were three treatments: (A) catfish only without water recirculation; (B) water recirculation at 3-day interval; (C) water recirculation at 7-day interval. Results showed that water recirculation did not affect catfish growth and yield. Mass mortality of tilapia was observed in two of the three replicates in 3-day interval treatment. Tilapia growth and yield in 7-day interval treatment was significantly higher than that in 3-day interval treatment. Tilapia recovered 2.53 % N and 3.68 % P, and 3.12 % N and 4.47 % P from catfish wastes in 3- and 7-day interval treatments, respectively. The study demonstrated that tilapia can be cultured in an integrated recycling system to recover nutrients from catfish wastewater, and suggested that the ratio of catfish to tilapia can be lowered through either reducing catfish density or increasing tilapia culture area to allow tilapia reusing more nutrients contained in catfish wastewater