Environmental DNA Metabarcoding as a Promising Conservation Tool for Monitoring Fish Diversity in Dongshan Bay, China

Dongshan Bay is a typical subtropical semi-enclosed bay characterized by abundant fish resources. We aimed to assess fish diversity and its seasonal variation in Dongshan Bay and to provide a scientific basis for the sustainable management and conservation of the fishery’s resources. In this study, we employed environmental DNA (eDNA) metabarcoding technology to analyze fish diversity in the bay during winter 2023 and summer 2024. A total of 76 fish species were detected across 12 sampling sites, with 43 species identified in summer and 45 species seen in winter. Overall, 13 species were detected in both the winter and summer. Non-significant differences were observed in Alpha diversity among the sampling sites. Fish species richness at the HXH2 site was the lowest among all the sampling sites for the reason that this sampling site was near to the effluent outlet of the Zhangzhou nuclear power plant and notably influenced by the thermal discharge. In general, fish diversity and abundance were higher in winter than in summer. RDA test analysis revealed that water temperature and dissolved oxygen were the primary environmental factors influencing fish distribution in summer. In winter, the influence of various factors is relatively balanced, with chlorophyll and Blue Green Algae Phycoerythrin (BGA PE) having a relatively greater impact than other factors. Our results offer valuable insights into enhancing fish diversity management in Dongshan Bay.