Effects of triploidy induction on growth and masculinization of red tilapia [Oreochromis mossambicus (Peters, 1852) X Oreochromis niloticus (Linnaeus, 1758)]

The present study aims to evaluate the effects of triploidy induction by temperature-shocks (Heat shock at 41o C for 5 minutes and Cold shock at 9o C for 30 minutes of duration, starting 4 minutes after fertilization) on growth parameters and the sex ratios in progenies of three different red tilapia brood stocks under tank culture condition for 120 days. A significant difference in total yield (P < 0.05) was recorded in favour of the heat-shocked induced triploid groups. Total average body weight of male fish in all the groups showed more weight gain than the females, during the culture period (P < 0.01). Statistical analysis of the total weight gain among the sexes revealed that there was no significant difference between the average weights of male belonging to various groups, whereas in females the heat-shocked group showed a significant increase with respect to that of diploid females (P < 0.05). Red tilapia subjected to heat-shock treatment showed positive correlation (P < 0.001) with sex ratio, where skewness towards male progenies (84.1%) were observed as compared to cold-shocked and control groups. Highly significant difference in ovary weight and GSI was assessed between triploidy induced females and diploid females of the control group (P < 0.001). The impact of heat shock and cold shock induction of triploidy on the performance and masculinization is discussed in detail.