The study was carried out to evaluate the effect of varying stocking densities on the growth, survival, and yield of tilapia (Oreochromis niloticus Linnaeus 1757) at the freshwater reservoir (average depth, 1.7 m) of the University of Agriculture Abeokuta, Nigeria, for a period of 3 months. Tilapia juvenile with a mean weight of 29 +/- 4.81 g were randomly (Complete Randomized Design) stocked at 50, 100, 150 and 200 specimen per cage (1 m(3)) were fed with commercial feed (34.55% Crude Protein). 20% of stocked fish was sampled for growth forthnightly. Profit index of the fish harvested under each treatment was evaluated. Relevant physico-chemical parameters like pH, conductivity, temperature, water depth and dissolved oxygen were also monitored forth nightly. The experimental fish and fish carcass (before the experiment and at harvest) from each treatment were analysed in replicates for their proximate composition. There were no significant differences (P > 0.05) in daily weight gain, specific growth rate, final weight, relative growth rate, feed conversion ratio (FCR), survival, protein efficiency ratio for all the treatments. However there were significant differences (P < 0.05) in fish production (harvest), profit index, crude protein, crude fat, and ash composition of the fish carcass (at harvest). As stocking density increased, the crude protein content of the fish carcass decreased indicating an inverse relationship. The stocking density of 150 juvenile/cage with a final weight of 82.74 g per fish, feed conversion ratio of 2.15, survival of 99.35% and fish production of 24.79 kg/cage was considered best on the basis of the profit index of 2.01 compared with the range of 1.45 to 1.82 for the other three treatments.
