Water temperature (WT) is a major environmental factor of metabolic rate in fishes, and directly affects food intake, ammonia excretion, oxygen consumption, growth, and survival. Thus, the purpose of this study was to investigate the change of oxygen consumption (OC) and hematological response of olive flounder, Paralichthys olivaceus on WT changes. In Exp. I, WT increased from 20°C to 29°C within 18 hours, and then maintained at 29°C for 96 hours. WT decreased from 29°C to 20°C within 18 hours, and maintained at 20°C for 24 hours. In Exp. II, WT decreased from 20°C to 11°C within 18 hours, and maintained at 11°C for 96 hours. WT increased from 11°C to 20°C within 18 hours, and maintained at 20°C for 24 hours. The Exp. III maintained that the Exp. I and II was consecutively.
In Exp. I, the oxygen consumption increased from 116.7 mg O2 kg-1hr-1 to 317.5 mg O2 kg-1hr-1 with increasing WT. After, OC decreased to 130.3 mg O2 kg-1hr-1 with decreasing WT. In Exp. II, the OC decreased from 96.5 mg O2 kg-1hr-1 to 71.3 mg O2 kg-1hr-1 with decreasing WT, and increased to 96.7 mg O2 kg-1hr-1 when WT was increased to 20°C and maintained during 24 hours. In Exp. III, the OC, when the WT was maintained at 20°C for 48 hours, was found to be 117.1 mg O2 kg-1hr-1. OC was 226.1 mg O2 kg-1hr-1 during 3 days at 29°C, and was decreased to 108.4 mg O2 kg-1hr-1 during 3 days maintenance of WT to 20°C. When WT was decreased to 11°C, and maintained for 3 days, OC was decreased to 54.4 mg O2 kg-1hr-1. After, OC, when WT was kept for 48 hours after increased to 20°C, was increased 110.2 mg O2 kg-1hr-1. In Exp. I, cortisol, glucose and AST (aspartate aminotransferase) values of olive flounder were increased with increasing WT. In Exp. II, Cl-, osmolality, AST and ALT (alanine aminotransferase) values were significantly changed during experimental period. Glucose value was increased, and cortisol values was decreased with decreasing WT. But cortisol and glucose values were no significant differences between the initial and the final of experiment. In Exp. III, hematocrit, cortisol, glucose and AST were significantly increased, and Cl-, osmolality and ALT were significantly decreased during experimental period. The other parameters were not significantly changed. Exp. III is likely more stressful environment to olive flounder than Exp. I and Exp. II. The results of our study would be useful for evaluating current culture procedures of olive flounder, and also for developing techniques to minimize stress during aquaculture.