Fishes of three North West Shelf atolls off Western Australia: Mermaid (Rowley Shoals), Scott and Seringapatam Reefs

Abstract

The biodiversity of fishes on the Australian North West Shelf atolls is known to be the richest in the state. In recent years however, there has been minimal focus on comprehensive taxonomic fish surveys in this region. Since the atolls are subjected to an increasing frequency of pressures such as major cyclones, coral bleaching, tourism, fishing and natural resource exploitation, it is critical to monitor this region to have the information to safeguard the biodiversity for the future. To obtain current data that would complement ongoing quantitative surveys in the region, the Western Australian Museum undertook a taxonomic and semi-quantitative survey of the shallow water reef fishes and other major phyla at Mermaid, Scott and Seringapatam Reefs in September 2006. Thirty nine underwater visual surveys were conducted, supplemented by limited intertidal collecting, angling and surface observations. Analysis of the fish fauna across atolls demonstrated close similarities between North Scott, South Scott and Seringapatam Reefs, and, as a group, these reefs showed certain differences from the more southerly Mermaid Reef. Significant differences were found between lagoonal and outer reef slope habitats. At each atoll, the outer reef slope habitats were more homogeneous and had a greater diversity of fishes than the lagoon habitats, with South Scott lagoon housing a unique mix of both outer reef slope and lagoon species. Fish diversity was found to increase towards the northern atolls, supporting previous research in the region. The fish fauna at all four atolls had more in common with fish assemblages at equivalent clear-water reefs in Indonesia than with those on the northwest coastal mainland and, as such, are unique within Western Australian waters.