Decapod Crustaceans of the North West Shelf, a Tropical Continental Shelf of North-western Australia

The North West Shelf is a tropical continental shelf with a highly diverse fauna of epibenthic decapod crustaceans. The 357 taxa of epibenthic crustaceans, including 308 decapods, recorded from four sites are more than reported from any other continental shelf. The dominant taxa were amphipods, portunid crabs, xanthid crabs, palaemonid shrimps, hermit crabs, crangonid shrimps, sergestid shrimps, and majid crabs, in decreasing order of abundance. The most diverse family was the leucosiid crabs, containing 39 species. The number of crustacean species collected was similar at both 40 m and 80 m depth, and only 35% of the most common species differed in abundance between the depths. The abundances of 30% of these common species appeared to be related to particle size of the sediment or to the biomass of large sedentary fauna. The abundance of 45% of the most abundant, mainly small, species differed between two sampling times 6 months apart. The abundance of many decapod crustacean species was related to depth, sediment type, bottom type, or sedentary fauna. It is concluded that the epibenthic decapod fauna at 40 and 80 m depth on the North West Shelf is a broadly distributed assemblage with high diversity, some environmentally determined pattern and, in smaller animals, significant seasonal variability.