Optimizing tilapia Oreochromis niloticus production in Senegal by reducing financial cost and time-consuming of gender determination

Abstract

Nile tilapia, Oreochromis niloticus, is the most important cultured fish species in Senegal, with male monosex populations being preferred over females because of their higher growth performance. Manual sorting of sexes is being used to obtain male monosex populations, but the technique is very laborious, wasteful, stressful to the fish and expensive, and it can be prone to considerable mistakes. The purpose of this pilot study was, therefore, to optimize the production of O. niloticus in the Maraye Farm (Saint-Louis, Senegal) by reducing the financial cost related to gender determination. This was achieved by orally administrating a dose of 6.02mg/ml of 17α-methyltestosterone (17α-MT) to sexually undifferentiated fry from the 4th to the 28th day post-hatching. The results showed that 12.5% of fry did not survive the hormonal treatment, probably due to changes in physicochemical parameters in the holding tanks, in particular sudden drops of the dissolved oxygen levels at the 10th day after the treatment. Although this study did not use a control group fed with commercial diet without hormonal supplements, control groups of previous studies exhibited around 50% male population. The hormonal treatments of this study showed a satisfactory sex reversal rate of 80%, indicating that the dose (6.02mg/ml) used is effective in inducing a sex reversal in O. niloticus. With such results, the hormonal sex reversal can be successfully used instead of the manual sexing to optimize the tilapia O. niloticus in the Maraye Farm. However, this can only be achieved by optimizing water quality and efficiency in feed conversion, as is evident from high mismanagement-related mortalities (40%) recorded before evaluating the effects of hormonal treatments.