The eel-tailed catfish, Tandanus tandanus, is a freshwater fish native to the Murray-Darling river system of Australia. The scientific name for eel-tailed catfish comes from an aboriginal name for the fish - Tandan - which Major Mitchell recorded on his 1832 expedition.
It was originally found in most freshwater habitats of the Murray-Darling river system except for the upland, sub-alpine and alpine headwaters of southern tributaries. It is also present in speciated but undescribed forms in several east coast systems in northern New South Wales due to natural river capture events.
Eel-tailed catfish have a downturned mouth with fleshy lips surrounded by a number of "whiskers" which assist them with feeding. They are a solid, almost cylindrical, elongate fish, with the posterior half of their body tapering into a pointed eel-like tail. A continuous fin margin surrounds this tapering posterior half of the body. Their eyes are small. Colouration is variable but most commonly a mottled greyish-purple colour.