Tench

An introduced bottom feeder of slow and still water with plenty of weed and a soft bottom. It eats midge larvae, mudeyes, mayfly nymphs and small crustaceans. It is easy to recognise once you have seen one. It is not a fly target, but it does take small food off the bottom. Do not put it back: Tasmania and Victoria encourage anglers to keep it, and South Australia requires it.

Fishes of Australia gives its range as the Murray–Darling Basin in New South Wales, South Australia and Victoria, and the Derwent River in Tasmania. The Inland Fisheries Service is more specific for Tasmania: common throughout the Derwent system, the South Esk and Macquarie rivers, and the midlands. PIRSA says it is established in the River Murray and the Onkaparinga River in South Australia, and asks anglers to report it anywhere else.

In this guide tench are recorded in the Macquarie River in Tasmania from 1990 to 2010, in the Merri River in Victoria from 1985 to 2017, and in the Murrumbidgee River in a 1949 record. The Inland Fisheries Service also names the South Esk. These are records of the fish being present, not fisheries for it.

Fishes of Australia describes slow-flowing or still water, often with a muddy bottom and abundant aquatic plants, in backwaters, lagoons and deep sheltered holes. The Inland Fisheries Service adds that in Tasmania it lives in lakes at a range of altitudes as well as slow sections of river.

It feeds on the bottom. Fishes of Australia lists mainly aquatic insects, naming chironomids, mudeyes and mayflies, along with small crustaceans, some molluscs, worms and plant material. The Inland Fisheries Service mentions algae and small invertebrates. Most fish are 10 to 30 centimetres, Fishes of Australia says, with a maximum around 70 centimetres; the Inland Fisheries Service gives a common length of 300 millimetres in Tasmania.

The concern is competition. PIRSA says tench compete with native species for food, and the Victorian Fisheries Authority says they can affect other recreational species.

The European carp is the usual confusion, and the mouth settles it. The Australian Museum describes carp as having two barbels at each corner of the mouth, large scales and strongly serrated spines in the dorsal and anal fins. A tench, in Fishes of Australia’s description, has a single small barbel at each corner, scales so small and embedded the skin looks smooth under a heavy coat of mucus, a short, high, rounded dorsal fin, and that orange-red eye. Both are introduced.

Goldfish are another introduced relative, but the Australian Museum notes that goldfish have no barbels at all.

There is no fly fishery for tench in Australia, and none of the agency sources describe one. The fish’s diet is the only real guide. A fish that eats chironomid larvae, mudeye and mayfly nymphs off a weedy bottom may take an imitation of them fished slowly where it feeds. A small Bloodworm, a Pheasant Tail Nymph or a Gold-Ribbed Hare’s Ear Nymph, crawled along the bottom on a slow figure-of-eight retrieve near weed, is the obvious thing to try.

If one comes up, keep it. Check the rules for the state you are in, and do not carry it alive to another water.

Spring and summer. Fishes of Australia says tench mature at three to four years and spawn in spring and summer, with each female laying 300,000 to 900,000 small adhesive eggs in three or four batches about two weeks apart, in shallow water, usually on weed. The larvae hatch after three to six days. The Inland Fisheries Service describes adults gathering in large schools in the shallows to breed. That output matters: NSW DPIRD notes that once pest fish are established in a waterway they are very difficult, if not impossible, to remove.

Look at the mouth. One small barbel at each corner and tiny scales hidden in slime is a tench; two barbels at each corner and big obvious scales is a carp.

In South Australia, no. In Victoria and Tasmania the authorities ask you not to. Moving a live tench to another water is illegal in Victoria without approval, and spreading it is how it got where it is.

In Tasmania’s midlands rivers and the Derwent system, where the Inland Fisheries Service calls tench common, and in slow, weedy backwaters of the Murray–Darling in Victoria, New South Wales and South Australia.