Sex reversal dynamics of Nile Tilapia (Oreochromis niloticus) and impact on growth performance

Nile Tilapia (Oreochromis niloticus) is one of the most economically important freshwater aquaculture species globally. However, reproduction during grow-out is a major problem that hinders fish growth. Therefore, production of all-male populations of tilapia has been developed to address the problem and is also identified as one of the most effective techniques of increasing tilapia growth. Various methods have been used to produce all males in Nile Tilapia i.e. use of hormone treatment (17-alpha-methyltestosterone), use of temperature shock and the recent YY technology. The latter two methods have limited documentation and usage in Kenya. The current study compared effectiveness of temperature and hormone sex reversed O. niloticus fry and influence on growth in hapa nets over a period of 3 months. Nile Tilapia fry of 3 days old after egg yolk absorption were sex reversed using hormone for 21 days and temperature shock for a period of 14 days. Hormone use involved making a dose of 60 mg kg(-1) of feed while temperature shock involved raising temperature from 28. to between 30. and 34.. Analysis of Specific Growth Rate using one-way analysis of variance, ANOVA, showed no significant difference between hormone and temperature induced sex reversed fish (F=0.0975, P=0.7705). Sex reversal efficacy rates of 91.18% and 92.86% were attained using 17-alpha-methyltestosterone hormone and temperature shock, respectively. The results indicate that temperature shock could be a replacement for Tilapia sex reversal without any negative consequences on growth.