Spatial and temporal differences in assemblages of demersal fishes on the inner continental shelf off Sydney, south-eastern Australia

Variations in assemblages of demersal fishes occurring in different depths of water (30, 60 and 100 m) on the inner continental shelf off Sydney are described. Assemblages comprised a diverse and abundant ichthyofauna; many species were of economic importance. Classification analyses showed that assemblages of demersal fishes at 30 and 60 m depth were most similar to each other and that they consistently differed from those at 100 m depth. This difference may reflect a change in the demersal ichthyofauna from a nearshore to an offshore assemblage. The depth-delineated differences between assemblages agree with those found in similar studies on demersal fishes in coastal waters elsewhere. The distributions and relative abundances of many species differed markedly among depths, but such differences were not always consistent between localities or throughout time. Despite this, some species showed some temporal affinity with a particular site and/or depth. The study confirmed spatial and temporal variabilities in the demersal fish fauna in coastal waters off Sydney; such heterogeneity must be considered when future studies are designed.