Large-scale patterns in species richness and composition of temperate riverine fish communities, south-eastern Australia

Riverine fish in New South Wales were studied to examine longitudinal trend s in species richness and to identify fish communities on a large spatial s cale. Five replicate rivers of four types (montane, slopes, regulated lowla nd and unregulated lowland) were selected from North Coast, South Coast, Mu rray and Darling regions. Fish were sampled during summer and winter in two consecutive years with standardized gear that maximized the range of speci es caught. The composition of fish communities varied among regions and river types, w ith little temporal variation. Distinct regional communities converged in m ontane reaches and diverged downstream. The fish fauna can be classified in to North Coast, South Coast, Murray and Darling communities, with a distinc t montane community at high elevations irrespective of the drainage divisio n. Species richness increased downstream in both North Coast and South Coas t regions by both replacement and the addition of new species. In contrast, species richness in the Darling and Murray regions reached a maximum in th e slopes reaches and then declined, reflecting a loss of species in lowland reaches. The small number of species is typical of the freshwater fish fau nas of similar climatic regions world-wide. Fish communities identified in this study form logical entities for fisheries management consistent with t he ecosystem-focused, catchment-based approach to river management and wate r reform being adopted in Australia.