Reef fishes of the Althorpe Islands and adjacent coasts of Central South Australia

Reef fish populations were surveyed by visual census from 2 - 20 m depth at a range of sites at the Althorpc Is, Haystack I., and nearby mainland reference sites. Mean densities ranged mainly from 0.13 - 0,18 m-2, and comprised mainly benthic carnivores, herbivores and omnivores. Densities are comparable to those elsewhere in SE Australia, but much lower than those in the eastern Great Australian Bight. Forty fish species were recorded at Althorpe Is, 28 at Haystack I. and 'fess at the other sites. Most species were too low in abundance to examine depth-related patterns, but the three most common species, blue-throated wrasse, herring cale and magpie perch, decreased in abundance with depth. The main faunal differences encountered were between mainland and island sites, and with depth. Biogeographically, the reef fish fauna was largely of widely ranging southern Australian temperate species, but included six species with SW Australian affinities, and three species with SE Australian affinities.