Testing of triploid tilapia ( Oreochromis niloticus) under tropical pond conditions

The aim of this investigation was to study the aquacultural potential of triploid tilapia in extensive pond culture under tropical conditions vs. traditional predator controlled cultivation of diploid tilapia. Triploidy was induced in Oreochromis niloticus by heat shock. Following a fry rearing period, a total of 2400 triploid and 1200 diploid tilapia were tested in two subsequent sets of experiments in 300 m 2 earthen ponds. Rice bran was administered as supplementary feed in addition to weekly fertilization of ponds. In order to estimate fish growth, sampling by seine took place twice a month. Twenty-five weeks after stocking (age of fish: 285 days) ponds were drained. While no differences in growth between triploids and diploid controls could be observed at age of maturation, triploids were significant heavier ( P < 0.01) than control fish at the end of the experiment. Triploid males exceeded body weights of respective controls on average by 66 ± 17%, whereas triploid females displayed an even higher increase in body weight compared to diploid ones (95 ± 27%). Gonadal weight and development in triploids were in general lower and retarded, respectively; however, in 15% of triploid females an extremely high gonadosomal index was observed. In this experiment, stunting was found to be prevented in ponds stocked with triploid tilapia. Thus, induced triploidy can be of great benefit in commercial tilapia culture.