Genetic Basis of the Antioxidant and Serum Enzyme Activities of the Large Yellow Croaker Larimichthys crocea Under Stress in an Experimental Simulation of Natural Winter Water Cooling

Antioxidant and serum enzyme activities of the large yellow croaker (Larimichthys crocea) were analyzed to investigate the influences of genotype and water temperature. The activities of four antioxidant factors (peroxidase, catalase, total antioxidant capacity, and superoxide dismutase [SOD]) in the muscle and liver, as well as six serum enzymes (alkaline phosphatase, lipase, aspartate aminotransferase [AST], adenosine deaminase, γ-glutamyl transpeptidase (GGT), and alanine aminotransferase), were measured at natural water temperatures (20, 16, 12, 10, and 8 °C). Analysis of the antioxidant enzyme activities showed that genotype, temperature, and genotype × temperature interactions had different influences on the two tissues. In muscles, the impacts of these three effects on antioxidant enzyme activity were extremely significant, while in the liver, only the genetic effects were extremely significant and the temperature effect was insignificant. SOD exhibited the highest and the most stable activity and the best performance in terms of both activity and stability in both tissue types. Temperature, genotype, and genotype × temperature interactions all had a prominent impact on serum enzyme activity. The indicators that were the top performers in terms of activity, stability, and the optimal balance of both were AST, GGT, and AST, respectively. Our findings provide a theoretical basis for breeding with low-temperature tolerance based on antioxidant factors, reliable tolerance indicators, and the evaluation and early detection of low-temperature stress using serum-based enzyme biomarkers.