The Effect of Water Temperature on Antioxidant and Digestive Flexibility in Miiuy croaker, Miichthys miiuy

Miichthys miiuy is a marine fish with high commercial value that is extensively cultured in China. Seawater temperature is an important factor that affects the cultivation of this fish. However, whether and how seawater temperature affects enzymatic activity during cultivation remains unclear. We treated M. miiuy with average body weight of 232.59 ± 48.79 g with four seawater temperature treatments (13.0, 20.0, 24.0, and 30.0 °C) for 12 days, and measured activities of liver antioxidant enzymes (SOD and CAT) and intestine digestive enzyme (lipases, amylase, and trypsin) at the beginning and end of the treatment. Temperature had a significant effect on the activity levels of antioxidant enzymes. SOD activity decreased from 13.0°C to 24.0°C, and increased at 30.0°C, where SOD activity was highest in samples placed in 30.0°C seawater, and lowest at 24.0°C. There were no clear trends in the CAT activity pattern with increasing temperature, and highest CAT activity levels were observed at 20.0°C and lowest levels were observed at 24.0°C. The activity rates of digestive enzymes were also significantly affected by temperature. However, there were no clear trends in activity pattern with increasing temperature, similar to CAT. Lipase activity was highest at 24.0°C, and amylase activity was highest at 24.0°C. Trypsin activity was similar across the different temperature treatments after 12 days of culturing. The present study investigated the effects of seawater temperature over time on the activities of antioxidant and digestive enzymes in M. miiuy, and the results will help develop better culture practices for M. miiuy.