Author : Iwan Suyatna

Summary : A field study was conducted in Sampaloc lake, San Pablo City, Laguna, on June-September 1990. It aimed to determine the growth of Nile tilapia (O. niloticus) by cage culture under different stocking densities and supplemental feeding. Stocking densities of 50, 75, and 100 fish/m (superscript3) were used and feeding levels included fine rice bran and mixed feed (50 percent fine rice bran and 50 percent commercial feed), and a control without feeding. The physico-chemical and biological parameters in and outside the experimental fish cages showed that water temperature, pH values, and dissolved oxygen concentraions were well within the optimal limits for tilapia culture. However, natural fish food organisms appeared to be poor. The analysis of variance on feeding and stocking densities and their interactions on the growth of O. niloticus indicated significant differences. On the other hand, mean weight gain sampled biweekly for various treatments were significantly different. Results indicated that the control without feeding gave lowest growth at all stocking densities followed by fine rice bran and mixed feed, respectively. Of the three stocking densities, the highest stocking rate gave the highest productivity while lower stocking densities resulted in better individual daily weight increment for treatments stocked at 50 pcs/m (superscript 3) with no feeding (control), with feeding rice bran, and mixed feed. The congestion of too many commercial cages in the vicinity of the experimental site affected the growth efficiency of O. niloticus.