Abstract:

We assessed fish communities using bottom gillnet surveys in 7 coral reefs (Beijiao Reef, Huaguang Reef, Jinyin Island, Dongdao Island, Langhua Reef, Yuzhuo Reef and Yongxing Island) of the Xisha Islands in May, 2003 and analyzed species composition and diversity, dominant species, and community pattern using the software Primer. A total of 146 fish species belonging to 31 families and 10 orders were collected during the survey. Fishes in the coral reefs were dominated by the typical tropical species, including members of the families Scaridae, Chaetodontidae and Lutjanidae. According to the Index of Relative Importance (IRI), the six most dominant fish species were Myripristis murdjan, Lutjanus kasmira, Paracaesio sordidus, Caesio diagramma, Axinurus thynnoides and Hexanchus griseus, respectively. Shannon-Wiener diversity indices (H') ranged from 1.91 to 3.33 among reefs, with an average of 2.81. Overall, diversity indices for the Xisha Islands were higher than those found in the East China Sea, the Yellow Sea and the Bohai Sea, all of which are found at a higher latitude. The spatial pattern of fish communities was analyzed using hierarchical clustering and non-metric multidimensional scaling. Two major groups based on fish assemblages were indentified, with group I located in the Yongle Islands and Group II in the Xuande Islands. ANOSIM and RELATE tests showed significant differences (R=0.685, P=0.029<0.05) in fish assemblages between these groups and the community pattern were quite stable (R=0.958, P=0.003<0.01).

Key words: fish, species diversity, community pattern, bottom gillnet, coral reef, Xisha Islands