Stress response of olive flounder, Paralichthys olivaceus and Japanese croaker, Nibea japonica on changes of water temperature

In this study, we investigate the physiological response of olive flounder, Paralichthys olivaceus and Japanese croaker, Nibea japonica , on a series of rising water temperatures (WT). At 1, 9, and 17 days, WT increased from 23 ℃ (control) to 26, 29 and 32 ℃ within 6 hours, respectively, and then maintained for 96 hours. At 5, 13, and 21 days, WT decreased from each WT to 23 ℃ within 6 hours and was maintained at 23 ℃ for 96 hours. Blood were collected at 0, 1, 5, 9, 13, 17, 21, and 60 days. In both species, hematocrit, red blood cell and hemoglobin of stressed groups were lower than non-stressed group at 13 days. The osmolality of stressed group was lower than non-stressed group at 21 and 60 days. In olive flounder, hemoglobin of stressed groups was lower than non-stressed group at 21 and 60 days, respectively, but osmolality of stressed group was higher than non-stressed group at 9 days. In Japanese croaker, hematocrit, red blood cell and hemoglobin of stressed groups were higher than non-stressed group at 21 and 60 days, respectively, and osmolality of stressed group was higher than that of non-stressed group at 1 day. At 1, 17, and 21 days, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) of stressed group were higher than non-stressed group in olive flounder. In Japanese croaker, AST and ALT of stressed group was lower than non-stressed group at 17, 21, and 60 days. The cortisol of olive flounder increased with increasing WT, but those of Japanese croaker increased with decreasing WT. In both species, the glucose increased with increasing WT. After changing WT, lactic acid of olive flounder and Japanese croaker were not significantly different. The physiological response of olive flounder increased directly to the increase in WT, and Japanese croaker contrasted with olive flounder.