Effects of water temperature in transportation on mortality and physiological indicators of Sepiella japonica

Restocking and releasing is an important means to restore the resources of Sepiella japonica, and the water temperature during the transportation process of restocking and releasing may affect its survival status. In order to optimize the transportation techniques for the adult enrichment and release of S. japonica, we conducted an experiment to simulate the transportation environment in laboratory and performed transportation experiments of adult S. japonica with different water temperatures (14, 17, 20, 23, 26, 29 ℃), and explored its mortality rate and liver physiological indicators. The results show that the water temperature in transportation affected the mortality rate significantly (p<0.05), and the mortality rates in 14 and 29 ℃ groups were higher, reaching 30.0% and 63.3%, respectively. Compared with 20 ℃ group, the glycogen content decreased significantly in 14 and 17 ℃ groups, but increased significantly in 29 ℃ group (p<0.05). The lactic acid content increased significantly in 23 and 29 ℃ groups (p<0.05). SOD decreased significantly in 17 ℃ group but increased significantly in 26 ℃ group (p<0.05). AKP decreased significantly at all water temperatures (p<0.05). With the change of water temperature, AST decreased initially and then increased, while ALT increased initially and then decreased. The mortality rate of squids was significantly positively correlated with glycogen, lactic acid content and AST activity in liver (p<0.05). In conclusion, too low or too high water temperature is not suitable for squid transportation at a density of 5 ind·L⁻¹, and it is recommended to control the water temperature between 17 ℃ and 26 ℃.