| The body is usually covered in a heavy coat of slime, which gives the species its other common names of "Slipperys" or "Slimies". The River Blackfish can be distinguished from the similar-looking Two Spine Blackfish by the larger number of dorsal spines - six to thirteen. It has been known to grow to be as large as 60 cm in length and weighing 5.5 kg, but it is usually seen at sizes up to 45 cm.
River Blackfish are ambush predators. They hunt at night and feed on aquatic insects, crustaceans and sometimes other fish.
The species can be found in freshwater streams, rivers, lakes and reservoirs of southern Queensland, eastern New South Wales, Victoria, Tasmania and South Australia. They prefer a habitat with lots of rock cover, log snags and debris.
Spawning season is Spring and Summer. Female River Blackfish lay up to 1,000 large, sticky eggs amongst boulders and submerged logs. After fertilisation, the male fish stays to guard the eggs. The eggs take about sixteen days to hatch. On hatching, the baby fish are still attached to their egg case and remain attached for about five weeks until they have used up their yolk sac and can start eating with their mouth. It is thought that by staying attached, the tiny fish gain some protection from being swept away by strong currents. The father continues to protect them for some time after hatching, but they are still vulnerable to predators such as crayfish and dragonfly nymphs.
In the past fifty years, the number and range of River Blackfish have declined. It is thought that this is the result of river clearing, dam building and other habitat degradation. All fish in Girraween National Park are protected, and in Queensland the River Blackfish is a protected species. The catching or possession of these fish anywhere in the state is totally prohibited. If caught, River Blackfish should be released unharmed.
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