Abstract
Genetic data were collected from eight allopatric populations of the common freshwater catfish, Tandanus tandanus. Catfish sampled from the New South Wales (NSW) mid-northern coastal rivers of the Bellinger, Macleay, Hastings and Manning exhibited fixed allelic differences from T. tandanus from the type locality (Namoi River) at four enzymatic loci (GPI-1*, EST*, UMB-1* and UMB-2*), suggesting that, collectively, catfish from these four river systems constitute an undescribed species of Tandanus. Catfish from the northern coastal rivers of NSW (Tweed, Richmond and Clarence) displayed a complex pattern of population structure that was not fully resolved by the present study. More work is needed on the complex assemblage of populations of eel-tailed catfish in the eastern coastal drainages of Australia.