Abstract:During April, 2007, Upper incipient lethal temperature (UILT50) of two coastal copepod species (Calanus sinicus Brodsky and Labidocera euchaeta Giesbrecht) in a subtropical bay were carried out in laboratory under heat shock for 15 min, 30 min and 45 min at different acclimation temperature. The results showed that: (1) The 24-h UILT50 of two copepod species decreased with increasing exposure duration at the same acclimation temperature; (2) The 24-h UILT50 of two copepod species increased with rising acclimation temperature at the same exposure time, but this increase lessen and tended towards fixed temperature; (3) The Ultimate upper incipient lethal temperature (UUILT50) of C. sinicus was 317℃, 31.0℃, 30.3℃, under heat exposure for 15 min, 30 min, 45 min, respectively. The UUILT50 of L. euchaeta was 36.5℃, 36.0℃, 35.4℃, under heat exposure for 15 min, 30 min, 45 min, respectively; (4) The 24-h UILT50 of C. sinicus was significantly lower than the 24-h UILT50 of heat exposure for the same time under same acclimation temperature. Thus, according to these data from experiment suggested that entrainment-induced mortality of marine copepod mostly due to such acute thermal shock varies with the range of temperature increase of the cooling water, the acclimatization temperature or acclimation temperature of the species, the exposure time to stress conditions experienced during passage through condenser conduits and discharge canals, and the thermal tolerances of entrained species to acute temperature shock.