EFFECTS OF STOCKING DENSITY ON THE GROWTH, SURVIVAL AND YIELD PERFORMANCE OF NILE TILAPIA (Oreochromis niloticus, Linn. 1858) IN AN INTEGRATED CAGE-CUM-POND CULTURE SYSTEM
Charles C. Ngugi*, Gladys Kuria, Kwamena Quagrainie, and Sammy Macharia
*Kenyatta University, Department of Agricultural Resource Management
P.O. Box 43844 - 00100, Nairobi, Kenya
Email:
Abstract
Rural pond culture in Kenya is moving from subsistence to small-scale commercial culture of fish. Small-scale commercial farmers are utilizing improved management practices such as stocking densities, feeding regimens, and feed nutrient to enhance their economic returns (Quagrainie et al., 2009). There are several aquaculture systems in use among them being pond culture, cage culture but most recent is the integrated pond cum cage culture. This culture has been developed and practiced using combination of catfish-tilapia and tilapia-tilapia (Yang Yi et al., 1996). The integrated system allows the open pond water to utilize cage wastes as fertilizers, generating natural food in the pond. The integrated system is environmentally friendly because less waste nutrients are released to the public water systems.
We investigated the appropriate stocking density for rearing O. niloticus in cage-cum-pond fish culture that enhances optimal growth and increases fish yield in a 1300m2 earthen pond using 9 cages each with a volume of 1 m3. The cages had a frame made from PVC pipes covered with a half inch netting material. Hand sexed male O. niloticus fingerlings averaging 60g from the Mwea Aquafish Farm hatchery were stocked in the cages and the open pond water respectively. Prior to stocking, the pond was fertilized with 20kgN ha-1 wk-1 and 5kg P ha-1 wk-1 using Urea and Di-ammonium phosphate; a standard procedure. After 30 days, the rate of Urea application was lowered to 10kgN ha-1 wk-1 as a measure to correct ammonia builds up in the pond. Cages were stocked at varying densities of 50, 75 and 100 fish per m3. Fish were fed with commercial floating feeds containing 17.60% crude protein reared for 180 days.
At the end of the trials, fish were harvested and total yield determined. A partial enterprise budget was evaluated for economic gains. Preliminary results showed that low density stocking favoured growth and that in all cages fish weight doubled within 30 days. This information will be useful to small scale fish farmers who stand to benefit from two crops in one pond.