Effect of pond fertilization and feeding level on productivity of nile tilapia (Oreochromis Niloticus) in Ghana

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Fish farmers have the desire to increase productivity but are constrained by the high cost of formulated feeds. This study quantified the performance of fish cultured in fertilized ponds and fed half the recommended ration of formulated feed and the cost-effectiveness of using inorganic fertilizers to improve productivity of tilapia raised in ponds. The study was conducted at the Renewable Natural Resources Management fish farm, Kwame Nkrumah University of Science and Technology (KNUST), located in Kumasi. In all, four 200m2 and two 300m2 ponds were used. Three of the ponds were unfertilized while the other three were fertilized. Ponds were dried, mud scooped out and limed before filling with water. Ponds were stocked with all-male tilapia (Oreochromis niloticus) fingerlings of average size 2g at 2fish/m2. Ponds were fertilized with Mono Ammonium Phosphate (MAP) at 2g/m2 and Urea at 3g/m2 strictly according to the phytoplankton abundance and Secchi-disk readings. Fish in the unfertilized ponds were fed 3-6% of their body weight twice daily with a 30-33% protein extruded feed. Fertilized ponds were fed half (1.5 – 3%) of the recommended ration whilst unfertilized ponds were fed strictly according to response. The results of the study showed a comparable growth of 202.9±23.8g and 204.2±36.3g between half ration and full ration ponds respectively. A similar observation was recorded for the Total Weight Gain (kg), Specific Growth Rate (%/day), Feed Conversion Ratio and Feed Intake with corresponding values of 101.7±35.6kg; 101.9±34.0kg, 1.2±0.2; 1.2±0.2, 1.2±0.3; 1.1±0.2, and 0.6±0.3; 0.7± 0.5 for half and full ration ponds, respectively. Total cost of production showed no significant difference (p=0.9888) between the half ration (GHȻ 1,621.1) and full ration (GHȻ 1,615.8) treatments. A total of profit estimated at GHȻ 596.7 and GHȻ 631.9 was realized for the full ration and half ration treatments, respectively. The results of this study indicate that farmers could increase their pond productivity, reduce production cost, and increase profit through fertilization and feeding at half ration with formulated feed. It is however, worth noting that to achieve best results, feeding strictly according to response is recommended.
A thesis submitted to the Department of Fisheries and Watershed Management of the College of Agriculture and Natural Resources. in partial fulfilment of the requirements for the degree of Master of Philosophy in Aquaculture, 2014