Change of physiological stress and flesh quality of Megalobrama amblycephala during suitable waterless keep alive conditions

Abstract: Currently circulation mode of freshwater fish was water transport. Commercial cost and several transportation procedures, including catch, temporary culture, transport shake, loading, unloading and distribution, induced harmful stress in fish, caused injury and even death. Related research showed the loss cost accounted for about 10% of the total cost in China, which was 20 times that in developed countries. Therefore, waterless keep alive transport of freshwater fish was more and more taken seriously. Hibernated temperature, packing method, survival time and survival rate of four seasons fish live in waterless environment were researched in order to investigate the effects of physiological stress and flesh quality of Megalobrama amblycephala during suitable waterless keep alive condition. Fish were examined at different time points: living in normal temperature (control), waterlessly keeping alive for 14 h (waterless) and then recovering in normal temperature for 24 h (recover). Blood biochemical items including cortisol (COR), glucose (GLU) and lactic acid (LAC) concentration, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activity were determinated and flesh quality indicators such as water holding capacity, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), texture and free amino acids were studied. The results showed: suitable living temperature of Megalobrama amblycephala for waterless keep alive was (14.8±0.2)℃(at winter), and then dropped (2℃/h) living temperature to 2℃ (hibernated temperature). The hibernated fish were packaged in moist wood-shavings but without added water by plastic bag (120 cm×90 cm) and oxygen-rich atmosphere (80% O2), finally plastic bag was sealed and placed at 2℃ for 14h, survival rate reached 100% after (14.8±0.2)℃ (normal temperature) recovery 24 h. Blood COR and LAC concentration, AST and ALT activity of fish keep alive 14h in waterless were significantly higher than normal level (control) (P<0.05), while blood GLU concentration and ALP activity were significantly lower than normal level (P<0.05). After recovery 24 h, most blood biochemical values returned to normal level, except for blood AST activity was still significantly higher than normal value. Protein and fat content, TVB-N, TBA and the water holding capacity of fish flesh were not influenced in low temperature waterless environment, but the fish flesh hardness and chewiness were significantly decreased (P<0.05). Free amino acids Ser, Glu, Gly, Val and Arg of fish flesh at waterless were significantly higher than normal value (P<0.05), concentrations of Ile, Leu, Tyr, Phe at waterless were not significantly change with normal , however, after recovery 24 h, them were significantly higher than normal (P<0.05). In conclusion, the stress induced by the cold and waterless condition in fish can be eliminated 24 h after recovery, and the changes of fish tasting quality are not significant. The results provide a reference for the application of waterlessly keeping alive in transportation of live freshwater fish.