Effects of Low-Salinity Environments on Growth, Antioxidant Response, and Intestinal Microorganisms of the Largemouth Bass (Micropterus salmoides)

Abstract

This research revealed that low-salinity environments have positive effects on largemouth bass (Micropterus salmoides), with the study finding that low-salinity levels can have beneficial impacts on this species. A 8-week experiment was conducted using four salinity gradients S0, S1, S2, S3 (0, 2, 4, 6 psu), and biochemical indicators and 16S rRNA sequencing were analyzed. Results showed relatively good growth performance at S0 and S1, and no significant antioxidant stress response at S3. Na+–K+–ATPase activity was significantly lower in the S2 group. The diversity showed no significant differences between the treatment groups. However, with increasing salinity, the proportion of potentially pathogenic bacteria in freshwater decreased significantly while that in the seawater increased. Indicator species analysis showed a significantly higher abundance of positive microbial species in the 4 psu group. In conclusion, although growth performance decreased at 4 psu, antioxidant damage was relatively small and disease risk was significantly reduced, indicating a positive effect on the largemouth bass.