2Aquaculture and Aquatic Resources Management

The purposes of the study, consisting of two experiments, were to determine the upper limits to tilapia production utilizing supplemental feeding and appropriate fertilization regimes for controlling nutrient addition and maintaining good water quality. In order to test these, Nile tilapia fingerlings were stocked at 3, 6, and 9 fish m-2. The fish were supplementally fed to 50 % satiation during culture of 155 and 194 days for experiments 1 and 2, respectively. While ponds were fertilized at fixed rates (4 kg nitrogen and 1 kg phosphorus per hectare per day) throughout experiment 1, ponds in experiment 2 were fertilized at various rates to balance nutrient contents of feeding wastes, bringing nutrient loading to the same levels as in experiment 1. The experiments were conducted at the Ayutthaya Freshwater Fisheries Station, Thailand. Growth, survival, yield, and water quality were evaluated during both experiments. Growth continued in a linear fashion throughout the experiments. Survival also differed significantly among treatments in both experiments, with lowest rate at the highest density. Feeding rates averaged 1.86 % and 1.65 % of the body weight per day in experiments 1 and 2