Effects of Hydrogen-Rich Water on Antioxidant Capacity, Immune Response, and Gut Microbiota in Juvenile Snakehead (Channa argus)

Hydrogen-rich water (HRW) has growth-promoting, antioxidant, anti-inflammatory, and microbiota-modulating properties; however, its effects on juvenile snakeheads (Channa argus) remain underexplored. In this experiment, we investigated the effects of HRW on the antioxidant capacity, immune response, and gut microbiota of juvenile snakeheads. A total of 360 fish (15.32 ± 0.50 g) were randomly assigned to three groups: a control group (aerated water), a low-hydrogen group (H1, 280 ± 50 ppb), and a high-hydrogen group (H2, 550 ± 50 ppb). The results revealed that, compared with the control group, H1 significantly reduced serum levels of total protein, triglycerides, glucose, and urea nitrogen (P < 0.05). In the liver, H1 upregulated tir-2 expression and downregulated tnf-α expression (P < 0.05). Furthermore, serum SOD activity was significantly increased in both H1 and H2 groups compared with the control (P < 0.05), while serum CAT activity was significantly elevated only in the H2 group (P < 0.05). No significant alteration was detected in intestinal morphology (P > 0.05), and similarly, digestive enzyme activity did not change significantly (P > 0.05). Regarding gut microbiota, the H1 group increased the relative abundance of Actinobacteria (P < 0.05); at the genus level, it decreased the abundance of Acinetobacter and Pseudomonas, while increasing the abundance of Agathobacter, Faecalibacterium, and Anaerostipes (P < 0.05). In summary, our findings revealed that optimal HRW supplementation enhances immunomodulatory and antioxidant functions and improves intestinal health, thereby establishing HRW as a promising functional water conditioner for sustainable aquaculture applications.