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    • Conference paper

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

      Z Basiao & A San Antonio - In JL Maclean, LB Dizon & LV Hosillos (Eds.), The First Asian Fisheries Forum. Proceedings of the First Asian Fisheries Forum, 26-31 May 1986, Manila, Philippines, 1986 - Asian Fisheries Society
      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.
    • Article

      Hatchery production of Oreochromis niloticus L. at different sex ratios and stocking densities 

      AM Bautista, MH Carlos & AI San Antonio - Aquaculture, 1988 - Elsevier
      The influence of various sex ratios and stocking densities on hatchery production of Nile tilapia, Oreochromis niloticus L., was studied in land-based (concrete tanks) and lake-based (hapa nets) systems. In both hatchery systems, egg and fry production was maximum at a sex ratio of 4:1 females to males and a density of 4 females per m2.

      Seed production varied significantly among treatments at different periods of the year. In concrete tanks, significantly high seed production of 12.98 and 11.77 eggs and fry per spawner per day was obtained in March and August, respectively. In hapa nets, irrespective of sex ratios, 10.18 seeds per spawner were collected daily in March.

      In relation to the broodstock density in concrete tanks, significantly bigger daily harvests of 13.41 and 13.00 eggs and fry per spawner were produced in late February and March, respectively. In hapa nets, daily harvests of 8.95 and 7.74 eggs and fry per spawner were the highest seed production levels which occurred in April and March, respectively.

      Seed production was significantly higher in concrete tanks than in hapa nets while insignificant differences (P>0.05) were found among sex ratio and broodstock density treatments.