The Xisha Islands in the South China Sea represent a significant spawning, feeding and nursery ground for a diverse range of fish species. This study involved two surveys, one conducted during the spring of 2021 and the winter of 2022, using environmental DNA (eDNA) metabarcoding to understand the relative abundance and seasonal variation of fishes in this area. A total of 354 fish species were identified, of which 236 species of Perciformes were the most prevalent. Additionally, 283 fish species were found to be reef-associated. The dominant families in the Xisha Islands were the Labridae and the Acanthuridae. The most abundant species in both seasons were Chlorurus sordidus and Acanthurus triostegus. The rare fish species, such as Regalecus russelli, was identified. The composition of the fish community showed significant differences between the two seasons, yet exhibited a relatively consistent pattern between the various islands and reefs. Of the fish species identified, 189 have historical records in the Xisha Islands, while 165 have no historical records but are consistent with their anticipated geographical distribution. This brings the total biodiversity of fish species in the Xisha Islands to 881, which represents an 18.73% increase. Our findings indicate that eDNA metabarcoding has the potential to serve as a non-invasive approach for the monitoring of fish biodiversity in ecologically sensitive marine environments.
 

fish, environmental DNA, the Xisha Islands, species diversity monitoring, seasonal variation