Application of environmental DNA technology in marine ranching-case study of Bailong Pearl Bay Demonstration area in Beibu Gulf.

• A complete eDNA workflow was established for the Marine Ranching Demonstration area. • The artificial reef marine ranch demonstration area in Beibu Gulf has achieved remarkable results. • Environmental factors have different effects on fish in different habitats. • Fish diversity distribution in the different four areas was different and the overall fish community is changing to smaller species. Environmental DNA (eDNA) technology has emerged as a widely used method in resource monitoring. The purpose of this study was to assess the effectiveness of the eDNA approach in determining fish composition in the marine ranching of the Bailong Pearl Bay National Marine Ranching Demonstration Zone. Samples were collected from 12 sites in four different zones within Bailong Pearl Bay of the Beibu Gulf, and species diversity was analyzed through 12S rRNA gene amplicon sequencing. The results showed the collection of a total of 75 fish species, with Setipinna taty , Hypoatherina valenciennei , Trachurus japonicus , and Scatophagus argus identified as the dominant species based on the eDNA survey. Alpha and beta diversity index analyses revealed significant differences in composition and abundance of the different fish groups in Bailong Pearly Bay in July 2021. Furthermore, it was found that the artificial reef area and the natural sea area outside Bailong Bay harbored a more diverse fish population, which can be attributed to the positive effects of marine ranching construction. Mantel test correlation analysis demonstrated that phycoerythrin, salinity, and dissolved oxygen were the primary environmental factors influencing the structure of fish assemblages in different zones. The results indicated that eDNA can detect a greater number of species and uncover taxa that are rarely observed visually, thereby providing a comprehensive picture of fish diversity in the sample. This survey offers important technical support for the Bailong Pearl Bay National Marine Ranching Demonstration Zone, and the research findings provide valuable data for the development of marine ranching. [ABSTRACT FROM AUTHOR]