Screening of enzyme activity for assessing the condition of larvae in the seven-band grouper Epinephelus septemfasciatus and devil stinger Inimicus japonicus

摘要

We conducted screening tests to determine whether enzyme activity is a suitable biomarker for assessing the physiological condition of marine fish larvae. The rearing experiments consisted of three trials, of which two were conducted using the seven-band grouper Epinephelus septemfasciatus for a period of 5 days after hatching (DAH), and one was conducted using the devil stinger Inimicus japonicus for 10 DAH. The trials were conducted under three different rearing-tank environments (shallow tank, intermediate tank, deep tank) in a water volume of 100 l and an aeration rate of 50 ml/min. We determined survival, surface death, growth, and enzyme activities (trypsin, esterase, and alkaline phosphatase). The highest survival rates and lowest surface deaths in both species occurred among the larvae grown in the deep tank. There was a significant and negative correlation between survival at 5 DAH and alkaline phosphatase activity at 0 DAH in the seven-band grouper. The same correlation was found between survival at 10 DAH and trypsin and alkaline phosphatase activity at 1 DAH in the devil stinger. Based on these results, we conclude that the activity of a specific enzyme is a candidate for assessing the physiological condition of marine fish larvae.