GROWTH PERFORMANCE AND PRODUCTION OF OREOCHROMIS NILOTICUS USING POLYCULTURE SYSTEMS AND FERTILIZERS

Abstract

Nile tilapia (Oreochromis niloticus) with an average weight of 40,0 g were reared with Sarotherodon galilaeus (initial weight of 5L0 g) and Clarias gariepinus (initial weight of 73.0 g) at three different combinations of monoculture, duoculture and polyculture systems. The fishes were stocked in seven earthen ponds with varied areas at a density of 4 fish/ m2 during 210 days and fed on wheat bran. Some rearing ponds were fertilized weekly with a mixture of triple superphosphate and urea. At the end of the rearing period, the polyculture combination gave better growth rate and production for O.niloticus than in duoculture and monoculture systems. The average monthly increments were 21.lg and 29.0 g in ponds 2,3 (polyculture ponds), while in duoculture and monoculture, 18.7 g in pond 6 and 16.6 g in pond 4 were obtained. The specific growth rate and percentage weight gain reached their highest values for O.niloticus (0.85, 4.98 in pond 3 and 0.73, 3.64 in pond 2) using polyculture combination. On the other hand, O.niloticus showed better growth rate when cultured with Clarias gariepinus than with S.galilaeus. Its average weight was 131.0 g in pond 6 (O. niloticus with Clarias gariepinus and 128.5 g in pond 7 {O.niloticus with S.galilaeus). It was also observed that in the fertilized ponds, maximum growth in weight and production were recorded (0.379, 0.165 and 0.158 kg/m2 for the three fish species respectively). In pond 3 (fertilized), the average final weight was 244.0 g for O.niloticus, 188.5 g for S. galilaeus and 332.0 g for Clarias gariepinus. The food conversion ratio has also the optimum value (3.14) for O.niloticus reared in polyculture system and fertilized pond.