length of the range. None of the river capture events that allowed native fish of the Murray-Darling system to cross into and colonise these East Coast river systems seem to have formed permanent linkages. The colonising Murray-Darling fish in these East Coast river systems have therefore become isolated from their parent species, and due to isolation, the founder effect, genetic drift and natural selection, have become separate species (see allopatric speciation). Examples include: Golden perch (Dawson–Fitzroy river system, central Queensland). Eel-tailed catfish (several rivers, northern New South Wales). However, note recent genetic research which now indicates eel-tailed catfish colonised east coast drainages in multiple colonisation events relatively recently (by evolutionary standards) and may subsequently have colonised the Murray–Darling system via an east-to-west river capture event, contrary to usual west-to-east capture events listed here. Macquarie perch (Hawkesbury-Nepean rivers, Shoalhaven River, southern New South Wales). River blackfish (multiple rivers, Victoria). Murray cod, whose eastern species/subspecies are: Eastern freshwater cod (Clarence River system, northern New South Wales. It was also found in the Richmond River system in New South Wales but that population is now extinct.) Brisbane River cod (Brisbane River system, southern Queensland. That population is now extinct, and its exact taxonomic status is not known.) The Mary River cod (Mary River, southern/central Queensland.) The mountain galaxias species complex (multiple rivers, southern Queensland, New South Wales, Victoria). Olive perchlet (Ambassis agassizii), western carp gudgeon (Hypseleotris klungzingeri), pygmy perch (Nannoperca australis) and Australian smelt (Retropinna semoni) also appear to have made crossings into coastal systems, the last two species seemingly many times as they are found in most or all coastal streams in south eastern Australia as well as the Murray-Darling system. Unfortunately, with the exception of eastern freshwater cod and Mary River cod, it has not been widely recognised that these coastal populations of Murray–Darling native fish are separate species and their classifications have not been updated to reflect this. Many are threatened and two, the Richmond River cod and the Brisbane River cod, have become extinct. See also Lake capture Niger River Misfit stream References Rivers Biogeography Fluvial geomorphology Hydrology