Effects of Salinity on Growth, Digestive Enzyme Activity, and Antioxidant Capacity of Spotbanded Scat (Selenotoca multifasciata) Juveniles

As a euryhaline fish species that inhabits estuarine and coastal regions, the spotbanded scat (Selenotoca multifasciata) experiences growth influences during its larval stage due to variations in salinity. Here, we evaluated salinity required by early-stage spotbanded scat juveniles to achieve the highest growth performance, digestive enzyme activity, survival, and antioxidant capacity. We reared spotbanded scat juveniles (all 0.50 ± 0.05 g) in 0–35‰ salinity gradients for 50 days and recorded their survival rate every 10 days. After 50 experimental days, we measured morphological data, stomach and intestinal digestive enzyme activities, and liver antioxidant enzyme activities and malondialdehyde contents. In general, 5–15‰ salinity led to 100% survival. The 5‰ salinity group demonstrated the highest values for the following measures: final wet body weight; weight gain rate; specific growth rate; growth percentage; average daily gain; stomach amylase and lipase specific activities; and intestinal amylase, lipase, trypsin, and pepsin specific activities. However, stomach trypsin and pepsin activities did not demonstrate significant between-group differences (all p > 0.05). The 25‰ salinity group demonstrated the highest liver superoxide dismutase and glutathione peroxidase activities and malondialdehyde content. Finally, the 0‰ salinity group demonstrated the highest liver catalase activity. Thus, spotbanded scat juveniles demonstrate the highest survival rates, growth performance, and digestive enzyme activity at 5‰ salinity and the strongest oxidative stress responses at 25‰ salinity.