Introduction
With more than 4500 species, Australia has one of the world's largest and most diverse fish faunas. The freshwater component, however, is the smallest for any continent of a similar or larger size. Currently, only 283 described freshwater species are known from our waters, of which 258 are native to Australia. These numbers reflect both the historical isolation of Australia from other temperate regions and its intimate association with the most diverse marine fauna in the world, that of the tropical Indo-West Pacific. In addition, Australia has a long history of aridity in all but a few, relatively small freshwater areas along its continental margin.
Almost a quarter of Australia's fishes are found nowhere else. Although more than two-thirds of these occur at tropical latitudes, 60% of the endemic species live in temperate southern waters, more than three times that of the tropics. Most Australian fishes live in coastal waters and on the continental shelf. Australia's aquatic environments are diverse, including desert springs and alpine streams, mangrove swamps and coral reefs, seagrass meadows and turbulent coastal kelp forests, estuarine sponge gardens and sandy surf beaches, and rock pools and the deepsea.
Like fishes everywhere, the vast majority of Australian species have restricted geographical distributions which are determined by their biology, behaviour and historical origins. In most cases, these distributional ranges conform to a number of generalized bioregions around the coastline and to rather regular depth intervals.