High-intensity exercise training in large yellow croaker is a compromise between disease resistance and fish welfare

Exercise training is being applied to improving the productivity and welfare of farmed fish species. Nonetheless, research into whether exercise training improves disease resistance and immune function in fish is still at an early stage, and more studies is required. This study examined the impact of exercise training on growth performance, disease resistance and immune function of large yellow croaker (Larimichthys crocea). Juvenile fish underwent a 12 days training regime at 2–3 BL.s−1, followed by a parasite disease challenge test (Cryptocaryon irritans). Fish muscle RNA-seq analyses was used to evaluate the influence of exercise on juvenile immune function. The results showed that: (1) exercising at 2–3 BL.s−1 had no impact on the growth of juvenile croakers, however it induced an inflammatory response in croakers, leading to increased mortality in the treatment group (T) compared to the control group (C); (2) exercising also enhanced the resistance of T to C. irritans, resulting in a significant 17.6% increase in the survival rate of T compared to that of C; and (3) the RNA-seq analysis of the muscles demonstrated that differentially expressed genes (DEGs) between T and C were primarily involved in regulating the expression of genes related to muscle development and immunity in croaker; (4) enrichment analyses using KEGG and GO revealed that the DEGs were significantly enriched in pathways related to metabolic processes and biosynthesis. In conclusion, it is suggested that exercise training with high water speed induces an inflammatory response in the large yellow croaker, compromising the welfare of the fish. However, this stimulates the expression of immune-regulation-related genes and pathways, thereby improving the disease resistance of exercising individuals. Our study reveals that exercise training can improve disease resistance of large yellow croaker, which has significant implications for the sustainability of the croaker aquaculture industry.