The changes of the intestinal microbiota of large yellow croaker (Larimichthys crocea) during overwintering period

Large yellow croaker aquaculture in Zhejiang region is mainly conducted in net cages. During the overwintering period, large yellow croaker in net cages face dual stressors of low temperature and starvation. However, the adaptive response mechanisms of large yellow croaker to overwintering in net cages are still unclear, and whether there are differences between males and females has not been reported. In this study, intestinal tissue samples and intestinal contents samples of large yellow croaker cultured in net cages in Zhoushan were collected to systematically investigate the changes in intestinal barrier function, immune response, and intestinal microbiota of males and females during the overwintering period. Analysis of intestinal microbiota showed that the diversity and richness of intestinal bacterial communities in males were more susceptible to the influence of the overwintering period; during the overwintering period, the dominant status of Proteobacteria, Firmicutes, and Bacteroidetes did not change; the changing trend of relative abundance of Firmicutes in the intestinal microbiota of males was opposite to that of females; while Proteobacteria and Bacteroidetes showed an initial increase followed by a decrease in both males and females. The analysis of functional genes of intestinal microbiota showed that there were no significant changes in functional genes during the overwintering period for both males and females. In conclusion, during the overwintering period, the intestinal structural barrier of males may be damaged, and their immune function may decrease, while the immune function of females shows an increasing trend; the response and changes in intestinal microbiota and its function are different between males and females during the overwintering period. These findings provide a reference for studying the regulation of low temperature and starvation stress during the overwintering process in yellow croaker aquaculture in net cages and lay a foundation for precise regulation of yellow croaker growth and health during the overwintering period through intestinal microbiota.