TREATMENT WITH SAPONINS FROM TRIGONELLA FOENUM- GRAECUM AND QUILLAJA SAPONARIA INFLUENCES SEX RATIO IN NILE TILAPIA (OREOCHROMIS NILOTICUS) LARVAE

Nile tilapia production is one of the most rapidly increasing aquaculture industrial sectors worldwide. Mixed sex culture is not sustainable on a long term basis because of the high rate of reproduction, increasing feeding competition in ponds and low harvest of large individuals. The most common method to prevent unwanted reproduction and subsequent overcrowding is an all male culture which is mainly achieved by synthetic hormone treatment with 17-a-methyl-testosterone (MT). Since the application of synthetic hormones in animal feed is prohibited in many countries, including the whole of the EU, due to environmental and health concerns, endocrine active plant derived substances with a similar effect could serve as a substitute for MT. In previous experiments saponin supplementation in fish diets has shown a potential to influence sex ratio and reproduction success