Effects of open-pond density and caged biomass of Nile Tilapia (Oreochromis niloticus L.) on growth, feed utilization, economic returns and water quality in fertilized ponds

Abstract

The effects of open-water and caged fish density on growth, feed utilization, water quality and proftability were investigated to assess the feasibility of a small-scale rotational system for production of Oreochromis niloticus (L.) in fertilized ponds. Hand-sexed male fingerlings averaging 18.6 and 29.9 g were stocked in open water and cages, respectively in four treatments with open-pond:caged tilapia ratios of 300:0 (control), 150:150 (L), 300:150 (H1) and 300:300 (H2). The ponds in L and H1 contained one cage, two cages in H2, and the control ponds had no cages. Each cage contained 150 fish, which were fed daily at 1.5% body weight for 125 days. All ￠sh in the open water except the control fish were not fed. Growth of open water tilapia was significantly (Po0.05) higher in L than in control. Feed utilization, dawn DO and economic returns were significantly better (P<0.05) in caged than control ponds. Growth of tilapia in L was significantly lower (P<0.05) in cages than in open water. Fingerling production was significantly lower (P<0.05) in L than in other treatments. In conclusion, cage-cum-open-pond integrated treatment (L) was optimal for O. niloticus production in fertilized ponds. However, the system could not rotate and needed further fine-tuning to rotate