THE EFFECT OF PREDATION OF AFRICAN SHARPTOOTH CATFISH (CLARIAS GARIEPINUS) ON THE GROWTH PERFORMANCE OF TILAPIA (OREOCHROMIS NILOTICUS).

Excessive proliferation of Tilapia has been a major problem of the fattening process in semi intensive culture. The control of the overpopulation of Tilapia by Catfish (African Sharptooth Catfish) is practiced over the world. This study was conducted to determine the best size and the best stocking ratio of Catfish and Tilapia. Catfish was stocked with different sizes of Tilapia in three ratios 1:10, 2:10 and 3:10 (Catfish: Tilapia) in outdoor concrete tanks (T/C1, T/C2, and T/C3) with replication. The two species were also raised in monoculture (T1 and C1). The fish were fed in all the tanks during 180 days of experiment. The parameters of water quality were monitored every 10, 20, and 30 days. The average daily gain (ADG) did not vary significantly in monoculture and polyculturesystem during the two years of experiment. The growth parameters of Tilapia and Catfish increased significantly (p < 0.001) in polyculture system from 90 to 180 days. The best growth rate was observed in T/C2 with ratio 2:10 where the highest values of average daily gain were also foundfor Tilapia (1.416 ± 0.014) and Catfish (3.69 ± 0.07). Water quality parameters have shown a significant variation (p < 0.001) of pH, dissolved oxygen, salinity, turbidity and critical survival values were observed over a period of 30 days. The study showed that polyculture of Tilapia and Catfish can be used to reduce the overpopulation of Tilapia and allowfarmersto obtain the best growth performance for both Tilapia and Catfish in semi-intensive farming.