DIVERSITY AND COMMUNITY STRUCTURE OF DECAPOD CRUSTACEANS AT HYDROTHERMAL VENTS AND NEARBY DEEP-WATER FISHING GROUNDS OFF KUEISHAN ISLAND, TAIWAN: A HIGH BIODIVERSITY DEEP-SEA AREA IN THE NW PACIFIC

Kueishan Island (northeastern Taiwan) is an important deep-water fishing ground and is world famous for its unique hydrothermal vents that extend from shallow to deep waters. The global scale community structure of deep-sea fauna has received scant attention, thus the present study investigated the biodiversity and community structure of decapod crustaceans in these unique vent and non-vent regions of Kueishan Island. The fauna was sampled with 24 quantitative benthic trawls and with additional monthly surveys of bycatch and commercially important species collected over a year by commercial trawlers. We recorded a total of 51 families, 119 genera, and 202 species of decapod crustaceans. Brachyura was the most diverse group, representing 34% of the species, followed by Caridea (20%), Dendrobranchiata (20%), and Anomura (18%), while Astacidea, Achelata, Polychelida, and Axiidea had lower abundances (8% combined). Multivariate analyses revealed significant differences in species composition between the vent and non-vent regions. Some species were recorded at both regions but differed in abundance between the two habitats. The vent crab, Xenograpsus testudinatus Ng, Huang and Ho, 2000, had high abundance on vents but was not recorded in non-vent regions. Comparisons between the community structure of Kueishan Island with Tosa Bay, Sagami Bay, and Suruga Bay, Japan, indicated that Kueishan Island has the highest average taxonomic distinctness and variation in taxonomic distinctness among these deep-water regions. Our results suggest that Kueishan Island is a species-rich, deep-water ecosystem not dominated by a specific taxonomic group.