Effect of rearing temperature and hormone treatment on sex ratio, survival and body weight of Oreochromis niloticus fry

Abstract

The present experiment was carried out to investigate the effect of rearing water temperature in combination with or without hormone application on masculinization of newly hatched O. niloticus fry. Nile tilapia fry (0.025 g) were reared in three levels of temperature 25, 30 and 35°C and in each rearing temperature fry were fed diet with or without supplementation of 60 mg 17α-methyltestosterone (MT) for 7, 14, 21 and 28 days. O. niloticus fry fed diet without MT and reared at different water temperature 25, 30 and 35°C significantly increased the male ratio from 48.67 to 48.67 and 65.33% after one week; 48.67 to 64.00 and 72.67% after two weeks; 48.67 to 68.67 and 77.33% after three weeks and 48.67 to 80.67 and 84.00% after four weeks, respectively. While fry fed diet supplemented with MT with increasing rearing water temperature from 25 to 30 or 35 °C significantly increased male percentage from 58.00 to 84.67 and 86.00% after one week; 67.66 to 93.33 and 96.67% after two weeks; 79.00 to 97.33 and 98.67% after three weeks and 85.67 to 98.00 and 99.33% after four weeks. Mortality rate for O. niloticus fry reared at different water temperature 25, 30 and fed diet without MT significantly increased from 10.33 to 14.00 and 14.33% after one week; 10.33 to15.33 and 15.00% after two weeks; 10.33 to 15.33 and 15.17% after three weeks and 10.33 to 15.83 and 16.83% after four weeks. But, supplementation of O. niloticus feed diet supplemented with MT and increasing rearing water temperature from to 30 or 35°C significantly increased mortality rate from 14.67 and 14.00% after one week; 16.00 and 15.67% after two weeks; 15.33 and 15.67% after three weeks and 16.00 and 17.33% after four weeks of treatment. The highest fry body weight was recorded for fry group administrated with MT and reared at water temperature of 35°C and the opposite trend was observed with fry group reared at the lower temperature (25°C) and fed diet without MT.

Effects of 17ß-estradiol Hormone on Growth and Sex Differentiation in the Mozambique Tilapia (Oreochromis mossambicus, Peters, 1852)

“…Water quality during the course of the experiment was within the recommended parameters for Tilapia species as suggested by Philippart and Ruwet, 1982;Azaza et al, 2008 andSoltan et al, 2013. No statistical difference was observed in average water temperatures between all treatment groups (p>0.05) which were all around 28 °C (Table 2). Dissolved oxygen (Table 2) stayed within acceptable limits as well (DO-4 mg/L or higher) as per the recommendations of Azim and Little, 2008;Iwama et al, 1997 andRappaport et al, 1976.…”