Cold tolerance of three strains of Nile tilapia, Oreochromis niloticus, in China

Tolerance of three strains (GIFT, Sudan 78, Egypt 88) of Nile tilapia, Oreochromis niloticus, to naturally decreasing temperature was evaluated and determined in the Shanghai area. GIFT had been selected for increased body weight. Nile tilapia began to die when the water temperature dropped to 11 degreesC, and 100% mortality had occurred by 7.4 degreesC. Low lethal temperature ranged from 11 to 8.4 degreesC for the GIFT strain, from 9.8 to 7.4 degreesC for the Sudan 78 strain and from 11 to 7.4 degreesC for the Egypt 88 strain. The LD50 for low temperature among the three strains suggested that the GIFT line was less tolerant to low temperature than the other two strains and that there was no difference with respect to temperature tolerance between the Sudan 78 and the Egypt 88 strains. This has important implications for the application of genetically enhanced tilapia in cold climates when developed in warmer regions. (C) 2002 Elsevier Science B.V All rights reserved.