Species richness and geographical variation in assemblage structure of the freshwater fish fauna of the Wet Tropics region of northern Queensland

Abstract

A field survey of the freshwater piscifauna of the Wet Tropics region of northern Queensland was undertaken in August, September and October 1993. Sixty-six species of fishes, only two of which were exotic, were collected during the study, and reference to a further 12 species was found in the literature. The region contains two-thirds of the continent's fish genera and 40% of species. If the comparison is restricted to only those genera and species found in northern Australia, then the proportions increase to 80% and 55% respectively. Several species not previously recorded from Australia and one undescribed species from the family Percichthyidae, were collected. Ordination of the data set revealed a strong latitudinal gradient in assemblage structure, with the Bloomfield River and streams of the Cape Tribulation area and the Cardwell area containing the most distinctive faunas. The remaining seven drainages formed a homogenous group with little inter-basin separation, probably because they share similar hydrologies, water quality and contain a similar array of habitats. Discontinuities in river profile had a marked effect on assemblage structure.