Abstract: In order to explore the survival and underlying mechanism of hybrid grouper under pure oxygen and controlled atmosphere during waterless live transportation, this study investigated the changes in stress levels, serum biochemical indices, metabolites and antioxidant system in hybrid grouper in an environment simulating waterless live transportation, and it also evaluated the survival of the fish. The results showed that the survival time of grouper was (13.88 ± 1.00) h in modified atmosphere without water, which was significantly longer than that in pure oxygen environment ((10.90 ± 0.66) h) (P < 0.05). The levels of blood urea nitrogen (BUN), uric acid (UA) and creatinine (CREA), and the activity of acid phosphatase (ACP) showed an increasing trend with waterless survival time. The activities of aspartate aminotransferase activity (AST) and alanine aminotransferase activity (ALT) also increased steadily and reached the peak level at 10 h in pure oxygen atmosphere, which were (262.22 ± 1.54) and (232.05 ± 1.87) U/L, respectively, and significantly higher than those in modified atmosphere (P < 0.05); however, the activities of alkaline phosphatase (ALP) and peroxidase (POD) decreased gradually. Glycogen levels in the muscle and liver of dormant fish under cold stress was significantly decreased by 17.65% and 27.34% compared with the normal control group (P < 0.05). Lactic acid contents in muscle and liver increased significantly and returned to the normal level after resuscitation. The lactate dehydrogenase (LDH) activity in muscle fluctuated, the LDH activity in liver increased significantly (P < 0.05), and the level of malondialdehyde (MDA) showed an upward trend during waterless stress, all of which were significantly higher than those in the normal control group (P < 0.05). The activities of catalase (CAT) and superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and the level of glutathione (GSH) in muscle and liver increased gradually, and decreased after resuscitation. The changes of the related indicators in the pure oxygen group were significantly greater than those in the modified atmosphere group, indicating that the modified atmosphere environment effectively alleviates kidney and liver damage as well as oxidative stress damage in grouper, has a strong regulatory effect on the energy metabolism, antioxidant system and immune defense system of grouper, and maintains its normal physiological metabolism under low temperature and waterless stress.

Key words: grouper (♀Epinephelus fuscoguttatus ×♂Epinephelus lanceolatus); modified atmosphere; waterless live; survival; mechanism