Cold Tolerances of F₁ Tilapia Hybrids

The tolerances of 3 F₁tilapia hybrids of Oreochromis niloticus(♀)×Oreochromis aureus(♂) to cold temperatures were studied.By artificially lowering the tank water temperature, the death rate, semi-lethal low temperature (LT₅₀), and cumulative survival rate of the fish were monitored to determine the abilities of the F₁ tilapia hybridsto survive in cold temperatures. There were significant differences in their cold tolerances among the 3 F₁ hybrids. Aiao began to die soon after the water temperature was reduced to 9.6℃, ranging from 9.6℃ to 7.5℃. For Xiang'ao, the lethal temperature ranged from 9.4℃ to 6.7℃; and, it was 8.9℃ to 6.3℃ for Jiao tilapia. LT₅₀ of Aiaowas 8.63℃; that of Xiang'ao, 8.23℃; and, that of Jiao, 7.60℃. It appeared that Jiao was a significantly more hardy tilapiathan either Aiao or Xiang'ao (P < 0.05).