SUSTAINED SWIMMING ON THE ENDURANCE TIME AND PHYSIOLOGICAL METABOLISM OF ACANTHOPAGRUS SCHLEGELI AND SCIAENOPS OCELLATUS

It has become possible to set up deep-water cages in the open ocean in response to the further development of the marine aquaculture industry. In these conditions, fish encounter strong currents and waves, and ensuring their wellness becomes a crucial part of the farming process, so studying the endurance of farmed fish species is necessary. However, there are few studies on the ability of fish to swim continuously in constant current mode. Breeding of black snapper and American redfish is currently expanding into more open waters, so its endurance swimming ability needs to be assessed to ensure farmed yields and fish farming welfare. At 20℃, we tested the endurance swimming ability of two fish with no significant differences in body length (P>0.05). First, determine the endurance swimming time at different flow rates, and then choose the speed when the endurance swimming time is 150min to carry out the endurance swimming experiment. Black snapper and American redfish were tested for 0, 30min, 60min, 90min, 120min and 150min at constant swimming speeds of 3.15 and 4.32 BL/s, respectively. Measure the concentrations of metabolites in the muscle, blood, and liver of the fish at six-time points, ensuring that each time point produces three sets of valid data. At 0 and 150min, the concentrations of fish liver glycogen, back muscle lactic acid, and blood glucose were significantly different between the experimental groups (P<0.05), but the concentrations of muscle glycogen was not (P>0.05). A bivariate correlation analysis revealed that liver glycogen concentration decreased and dorsal muscle lactate and blood glucose increased with increasing fatigue. Gray-scale correlation analysis and principal component analysis showed that blood glucose and liver glycogen concentrations were the main factors affecting fatigue. However, the concentration range of black sea bream was larger than that of American redfish. Our experimental results concluded that: (1) American redfish have stronger swimming abilities than black snapper, and black snapper and American redfish are unsuitable for culture at flow rates exceeding 3.15 and 4.32 BL/s, respectively. (2) Liver glycogen concentration limits the endurance swimming ability of both fishes, and the results also provide a reference for the study on swimming and metabolism in other fishes.