Establishment of Tilapia Spawning Families Providing a Continuous Supply of Eggs for in vitro Fertilization

Three hybrid tilapia ( Oreochromis mossambicus ± O. niloticus ) spawning families were established in three separate culture tanks to provide a continuous supply of fresh gametes. An ovulation event, resulting in a natural spawn, an artificial spawn or oocyte resorption, occurred with a mean of every 1.4 days among 19 females, though only a few females demonstrated periods of evenly spaced 10 to 20 day maturation-ovulation cycles. Ovulation events/female/year were similar among the three spawning families: 13.1, 17.5 and 13.4/female, as were mean interovulation intervals (23.6, 21.9, and 23.9 days). Estimated fertilization rates, both natural and as a result of strip-spawning, were highly variable. Rates from natural spawns ranged from a mean per female of 25.7 to 57.3%, and from artificial spawns from 47.8 to 58.8%. Establishment and active management of spawning families of tilapias proved to be an effective procedure for obtaining a continuous supply of gametes for manipulative genetic research.