Abstract: In this work, the effects of water temperature and salinity on transportation stress in live grouper were studied. The response surface methodology (RSM) was used to optimize the two parameters. The results showed that different severities of stress reaction in grouper could be induced by different transportation temperatures with the highest survival rate occurring at 15 ℃. The concentration of serum cortisol and blood glucose and the expression level of HSP70 at 15 ℃ were significantly lower than those at 21, 27, and 30 ℃. Excessively lower (5‰) or higher salinity (40‰) could induce acute stress reaction in grouper, leading to injury or even death. The survival rate at 20‰ salinity was significantly higher than at the other salinity levels, whereas the concentration of blood glucose was significantly lower at 20‰ salinity. Besides, the concentration of serum cortisol and the expression level of HSP70 in at 30‰ were significantly lower than at the other salinity levels, while the suitable salinity range reduced the stress response of fish. The optimum water temperature and salinity were 16 ℃ and 26‰, respectively, as determined by a combination of single factor method and response surface methodology. In experiments conducted under these conditions, the serum cortisol level was (15.83 ± 1.07) ng/L, and the blood glucose concentration was (1.93 ± 0.17) mmol/L.

Key words: grouper, water transportation, transport stress, response surface analysis