Determination on the cold tolerance of NEW GIFT Nile tilapia，GILI tilapia and Blackchin tilapia

Abstract:

Cold tolerances of three tilapias（NEW GIFT Nile tilapia，GILI tilapia and Blackchin tilapia）to low temperatures naturally decreased in Shanghai area were studied and the average lethal temperature of 50% individuals has been calculated continuously for 3 years. It is found that low lethal water temperatures ranged from 7.5℃ to 5.8℃，and the average lethal temperatures of 50% individuals was 6.8℃ for NEW GIFT Nile tilapia in 2008. Meanwhile,behaviors of tilapias under decreasing water temperatures were observed. The range of low lethal water temperatures were 10.8-7.6℃，12.4-9.2℃ for NEW GIFT Nile tilapia and GILI Tilapia in 2009, and the average lethal temperatures of 50% individuals were 9.2 ℃ and 11.4 ℃. But they were 10.8-7.6 ℃，12.4-9.2 ℃ and 13.8-12.4 ℃ for NEW GIFT Nile tilapia，GILI tilapia and Blackchin tilapia in 2010. The average lethal temperatures of 50% individuals were 8.3 ℃, 12.5 ℃ and 13.1 ℃，separately，also there were significant differences among them. The comprehensive results showed that：water temperatures that began to die and 100% die were 11 ℃，5.8 ℃ respectively for NEW GIFT Nile tilapia, 12.4 ℃，9.2 ℃ respectively for GILI Tilapia，13.8 ℃，12.4 ℃ respectively for Blackchin tilapia. There were significant or highly significant species/strainspecific differences among these three genotypic tilapias in cold tolerance. The hybridization could improve cold tolerance to a certain extent.