River Blackfish

A small-stream ambush feeder that eats after dark, holds under timber and undercut banks, and is usually caught on a worm. Native Fish Australia says most blackfish are taken on bait, with scrubworms the best option, that small dark lures fished close to the bank at dusk also work, and that wet flies have been used with success. The fish is secretive rather than shy: the trick is to get the fly within striking distance of cover, not to hide from it. Fish the last hour of light and the first hour of dark, in Victoria or Tasmania only, and check the closed season before you go.

Fishes of Australia gives the range as the upper reaches of most rivers in the Murray–Darling Basin, coastal rivers from the Cann River in eastern Victoria west to the Murray mouth in South Australia, and rivers across northern Tasmania. In Victoria it lives in the Murray tributaries and the south-flowing streams, though it is absent from many small coastal streams such as those of the Otways. Native Fish Australia notes that fish south of the Great Dividing Range, especially in south-eastern Victoria, often grow much larger than their northern relatives.

In Tasmania the Inland Fisheries Service gives the natural range as the Arthur River in the north-west along the north coast to the Ansons River on the east coast. Populations in the Huon and Derwent catchments, and a couple on the west coast, were translocated there.

In this guide the species is recorded in the Tasmanian midlands rivers: the Macquarie, the Meander, the South Esk and Brumbys Creek, with survey records from the 1980s to the 2000s. On the mainland there are older records from the Mitta Mitta in 1975 and the Merri River in 1981. These are records of the fish being found, not reports of a fishery.

Clear, gently flowing water with plenty of cover: logs, snags, woody debris and rocks, in the words of Fishes of Australia. The Inland Fisheries Service adds that blackfish favour the slower, well-oxygenated sections of a stream. In practice that means the tail of a run where it slows against a fallen tree, the root mat under an undercut bank, the gaps between big rocks in a pool.

The Victorian Fisheries Authority describes a carnivore that eats aquatic insects, molluscs, crustaceans, small fish and terrestrial invertebrates that fall in, with the diet changing from stream to stream. It also says most fish are under 30 centimetres and about 450 grams, though the species can reach 60 centimetres and 5 kilograms. The Inland Fisheries Service puts the Tasmanian fish commonly to 450 millimetres and up to 750 millimetres and 5.5 kilograms.

The twospine blackfish is the lookalike, and it shares water with the river blackfish in parts of the upper Murray. Fishes of Australia describes it as very similar, but with two (rarely one or three) slender dorsal-fin spines and a clear white edge to the dorsal, anal and tail fins, often with a dark stripe just inside it. It is a smaller fish, to about 30 centimetres, of clear upland streams in north-eastern Victoria, the ACT and south-eastern New South Wales, and it is listed Endangered in the ACT. In this guide it is recorded in the Cotter River and the Mitta Mitta. Victoria applies the same rules to both blackfish; New South Wales protects both. If you are not sure which you have, it goes back.

A small blackfish could be mistaken for a juvenile Murray cod at a glance, but the blackfish’s pelvic fins are reduced to a single ray sitting under the gill opening, as both the Australian Museum and Fishes of Australia note, and its long, low dorsal fin runs most of the length of its back.

Blackfish are a bait fish first. If you want one on fly, accept that you are fishing the edge of the method, and fish it the way the bait anglers do: close, in low light, slow.

Handle any fish you plan to release gently and wet. The slime coat is part of the fish.

Spawning is a late-spring and early-summer event. The Victorian Fisheries Authority says it begins when the water reaches about 16°C, and that the strongly adhesive eggs are laid in hollow logs and rock cavities, even in lengths of discarded PVC pipe. A female of 30 centimetres lays only about 500 eggs. The Inland Fisheries Service puts Tasmanian spawning around November and says the male guards the eggs until they hatch, about 16 days later. Fishes of Australia adds that the newly hatched larvae stay tethered to the egg case until the yolk is used, which keeps them from washing downstream. Few eggs and a guarding male are another reason the hollow logs in a stream matter.

In Victoria, outside the closed season and over the minimum size, and in Tasmania under the bag and size limits, yes. In New South Wales, South Australia and Queensland, no.

Because that is when they feed. The Victorian Fisheries Authority describes a fish that moves mainly at night, late evening and early morning, and spends the day in cover.

Count the slender spines at the front of the dorsal fin and look for a white edge on the dorsal, anal and tail fins. Two spines and white edges point to a twospine. If in doubt, release it.