The creek was flowing gently, the water cool and clear with a touch of tannin. The late spring algae was yet to take hold on the rocky bottom and the summer storms were yet to cloud the waters with sediment and debris. Sliding into the water I donned a pair of goggles to be instantly amused by a small turtle scuttling away from me along the bottom to hide unconvincingly amongst rocks a little further upstream. I frog-kicked my way over to a partly submerged log of a grand River She-oak that had fallen and bridged the junction of a small tributary.

As I neared the she-oak log, a dark shape whipped out with speed and intent directly towards me. My heart stopped and my mind raced. I tried to shake off the primeval flight or fight response and rationalise what was the hell was going on. I was swimming in a freshwater creek, what could possibly want to have a go at me? The serpentine shape came within a metre of me and saw me stall and back paddle; it seemed content with its successful defence. It turned and with a powerful splash shot back to the shelter of the log.

With my curiosity piqued, I clambered out of the water to try for a closer look at this creature from the safety of dry land. Lomandra had sprung from crevices in the she-oak log, so it must have laid there for some time. Its position had created an eddy of the main flow that was shallow and well protected. In the middle of the eddy sat what looked like a wheel barrow load of clean pebbles and gravel in a carefully constructed low mound almost two meters across. This was the nest of the native Fresh Water or Eel-tailed Cat fish (Tandanus tandanus). The nest’s creator, a 60 cm mature male, was incessantly tending to the nest and patrolling the surrounding territorial waters.

Eel-tailed Cat fish are fascinating animals. As its common name suggests the long dorsal n that runs seamlessly around the tail and beneath the body gives this fish a characteristic eel-like appearance. This trait easily distinguishes it from its cousin the Fork-tailed Cat fish (Ariopsis grae ei) whose distribution overlaps the Eel-tailed Cat fish from saltwater into freshwater systems. While most commonly observed individuals are around 40 cm in size, the Eel-tailed Cat fish can grow quite large, with some specimens weighing up to 7 kilograms and reaching 90 cm in length.

Male Eel-tailed Cat fish raise and protect their young in large circular nests as shown in this image taken at Enoggera Creek, Brisbane.

Eel-tailed Cat fish can vary considerably in their colouring, which can be grey, olive, brown, red-brown or charcoal. This wide variation in colour is probably a camouflaging response to the bedding material composition of the water body in which they live. The colouring is commonly mottled with a pale underside. The skin is tough, smooth and scaleless. Around its thick, fleshy mouth are the classic cat fish ‘whiskers’ or barbels. These barbels contain tastebuds that assist them in finding food such as worms, snails, yabbies, shrimp, insect larvae and small fish in murky waters.
I now count myself lucky in my encounter, as the Eel-tailed Cat fish is not all bluff when it comes to the defence of their nests and territories. They are equipped with very sharp serrated dorsal and pectoral fin spines which can be locked into place so that they stick outwards. These spines can inflict an extremely painful and mildly venomous sting if delivered to an animal the cat fish considers a threat. Henry Lawson confirms this in a 1901 short story; “There was the cat fish, with spikes growing out the sides of its head, and if you got pricked you’d know it”. The venom is generally much weaker than that of marine cat shes. Venom from a sting delivered by an Eel-tailed Cat fish is unlikely to cause pain for more than an hour or two. To treat a cat fish sting, soak the affected area in hot but not scolding water (ideally 45°C) for up to 90 minutes. Wounds should also be treated to prevent bacterial infection.

Breeding takes place from late spring to mid-summer when the water temperature rises to between 20°C and 24°C, and is preceded by males creating nests. Males have been observed constructing their nests using their broad head to bulldoze loads of gravel and pebbles into a low circular mound. They then use their tail and pectoral fins to flush sand and silt away creating a clean pile 60 cm to 2 metres across, distinct from the rest of the creek bed. Males will pick up individual pebbles in their mouth and move them around for finer renovations to the nest.

In water bodies such as sandy creeks or clay dams where there is an absence of pebbles, males have been known to use twigs, leaves and small pieces of woody debris to construct their nests.

Some male Eel-tailed Cat fish have been observed returning to the same nest site each year to give it a spring clean to encourage prospective mates. If a female is suitably impressed by the male and his nest structure, a complex courtship ritual ensues. The male and female circle and weave about the nest for some time until the female arches her body, agitates her pelvic fins and releases tens of thousands of eggs (about 3 mm in size) above the nest. The male fertilises the eggs, which settle into the gravel of the nest. Fertilised eggs are guarded by one of the parents (usually the male) and are aerated by fanning with their tail until the eggs hatch about a week later. After hatching, the fry leave the nest to take refuge from predators amongst snags and aquatic vegetation.

Eel-tailed Cat fish are common in freshwater rivers, creeks, lakes, dams and billabongs in South East Queensland. Eel-tailed Cat fish are also residents of coastal catchments from northern Queensland to central New South Wales. Once common throughout the warmer waters of the Murray-Darling basin, populations have significantly diminished. The introduction of European Carp is implicated as a contributor of this decline due to direct competition for food (European Carp and Eel-tailed Catfish have similar feeding habits) and carp interfering with catfish nest sites.

Keep an eye out for Eel-tail Cat fish and their nests in your local creeks and water bodies this spring and enjoy their fascinating antics.


Allen GR, Midgley SH & Allen M (2002) Field Guide to the Freshwater Fishes of Australia. Western Australian Museum.

Gomon MF & Bray DJ (2011) Freshwater Cat fish, Tandanus tandanus, in Fishes of Australia, accessed 01 Aug 2014, http:// www.

Johnson, J (2014) Manager, Ichthyology Queensland Museum, pers. comms.

Lawson H (1901) The Loaded Dog, in Joe Wilson and His Mates. Blackwood.

Morris SA, Pollard DA, Gehrke PC & Pogonoski JJ (2001) Threatened and Potentially Threatened Freshwater Fishes of Coastal New South Wales and the Murray-Darling Basin. Report to Fisheries Action Program and World Wide Fund for Nature. NSW Fisheries.

NSW Department of Primary Industries (2007) What sh is that?

Queensland Museum (2007) Wildlife of Greater Brisbane. Queensland Museum.

Article by Scott Sumner Land for Wildlife Officer Brisbane City Council

All photographs by Gunther Schmida. Visit for more impressive photographs and information on freshwater fish. This website also offers excellent eld guides on freshwater fishes, geckos, snakes, turtles and other Australian wildlife for download.

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