Growth and survival of Nile tilapia fingerlings in net cages without supplemental feed in Laguna Lake, Philippines

Abstract

Oreochromis niloticus fingerlings were stocked at densities of 50, 100, 150 and 200 fish/m super(2) in fixed net cages in Laguna Lake, Philippines. These were reared without supplemental feed on 1 April-30 July 1980, 5 August-3 December 1980, and 19 December 1980-19 April 1981. Water temperature, dissolved oxygen, chloride level and pH for the three periods were measured outside the net cages. Growth rates were highest at 50 and 100 fish/m super(2) reared between April and July when phytoplankton biomass was high with a peak production observed in June (65.5 g/m super(2)), and zooplankton biomass ranged from 9.3 to 32.68 g/m super(2). Under these conditions, fish initially weighing 1.6-1.7 g grew to a marketable size of 106-124 g in four months. Those stocked at 150 and 200 fish/m super(2) had lower weights but still weighed over 80 g. None of those in the other two rearing periods exceeded 50 g after four months. Survival and fish yield during April-July were also higher than for those reared during the other periods.