Sustained Swimming Performance And Physiology Of Lateolabrax Maculatus And Sebastes Schlegeli

The maximum sustained swimming speed (MSSS) of Lateolabrax maculatus and Sebastes schlegeli were examined according to Brett's method at different temperatures(5, 10, 15, 20, 25℃).The absolute values of the MSSS were directly proportional with the body length (BL) of Lateolabrax maculatus and Sebastes schlegeli. But the relative values of the MSSS were inverse proportional with BL. And the MSSS was significantly affected by the environment temperature. The MSSS of Lateolabrax maculatus and Sebastes schlegeli were directly proportional with the environment temperature at the range of 5~25 ℃. The MSSS of Lateolabrax maculates and Sebastes schlegeli at 20℃ were not significantly different from those at 15℃. And there were also differences in the swimming ability of each species at the same body length and the same temperature. The swimming coefficient(k) of Lateolabrax maculates at different temperatures were concluded by analyzing tail beat frequency and stride length at different speeds.The plasma glucose, plasma lactic acid, muscle glycogen and muscle lactic acid of Lateolabrax maculatus and Sebastes schlegeli were also investigated in the swimming experiment at 5 ℃, 15 ℃ and 25 ℃. At each temperature, five groups were used (immediately after, 2h after, 12h after, 24h after swimming exercise and non-exercise control group) for each species. For the group of immediately after exercise at 5℃, the concentration of muscle glycogen in Lateolabrax maculatus was lower than that of the control group, but the concentrations of muscle lactic, plasma lactic acid and plasma glucose were higher than those of the control groups. The concentrations of plasma glucose and muscle glycogen in Sebastes schlegeli were lower than those of the control group, but the concentration of plasma lactic acid and muscle lactic acid were not significantly different from those of the control group. At 15℃, lower concentration of plasma glucose and higher concentration of plasma lactic acid than those of the control group were found in Lateolabrax maculatus of immediately afterexercise group, but the values of muscle glycogen and muscle lactic acid were not significantly different from those of the control group. In Sebastes schlegeli, significantly higher concentrations of plasma glucose, plasma lactic acid and muscle lactic acid than those of the control groups were found(P<0.05), with no significant variance in muscle glycogen found. At 25°C, the concentrations of plasma glucose, plasma lactic acid, muscle lactic acid in Lateolabrax maculatus increased immediately after the swimming exercise, but the concentration of muscle glycogen was not significantly different form the control group. In Sebastes schlegeli, significant increase in the concentration of plasma glucose and plasma lactic acid(P<0.05) and slight decrease in the concentration of muscle glycogen were found; no significant changes in the muscle lactic acid level were monitored after the swimming exercise. The levels of blood sugar, blood lactic acid, muscle glycogen and muscle lactic acid in both Lateolabrax maculatus and Sebastes schlegeli nearly recovered 24h later after the swimming exercises.From the research results of Lateolabrax maculatus and Sebastes schlegeli, two relationship models between the MSSS, temperature and body length were established respectively. Based on the models, the suitable size of each fish species for the net-cage culture can be decided according to their MSSS, environment temperature and water current data in certain area.