FEMINIZATION OF NILE TILAPIA Oreochromis niloticus (L.) BY DIETHYLSTILBESTROL GROWTH AND GONADOSOMATIC INDEX/Feminización de la tilapia del nilo Oreochromis niloticus (L.) mediante dietilestilbestrol. Crecimiento e índice gonadosomático

Abstract

Sex-reversal by exogenous hormones is the most common technique used to generate monosex populations of Nile tilapia (Oreochromis niloticus). However, this technique has provoked a negative perception in recent years. Because of this, alternative techniques have been developed, including the production of YY males. Although the nal product (for sale) is not administered hormones, the rst part of this technique still requires the feminization of XY fry by use of estrogens, including some of a synthetic nature, such as diethylstilbestrol (DES), an estrogen that has shown particularly excellent results in related species. The aim of this study was to evaluate the eect of increasing concentrations of DES (100, 200, 300, and 400 mg kg−1 ) during the fry stage on the sex proportion, growth and gonadosomatic index (GSI) of Nile tilapia. The 400 mg kg−1 concentration was the one that produced the highest proportion of females (91 %). However, increasing the concentration of DES provided through diet does not guarantee a 100 % feminization rate. Additionally, the growth, survival and GSI, showed a signi cant decrease (p < 0.05) in all groups fed with DES compared to the control group. It is possible that the anabolic eect of DES observed in other species is not present in Nile tilapia

Keywords

• Anabolic eect
• gonadal development
• sex-reversal