Burbot-freshwater cod

Burbot-freshwater cod

The burbot has the chin barbel and pelvic fins with only a few rays typical of the cod family. The body is long, petering out at the tail, and there are two dorsal fins, the first quite short, the second long-based, extending nearly to the tail. The anal fin is also long. Overall, the burbot is rather like a ling, but smaller.

A burbotless Britain

Now thought to be extinct in Britain, the burbot has the distinction of being the only native fish no longer found in our rivers. It was never widespread, being confined to the rivers of Yorkshire, the Trent system and the rivers of East Anglia.

This was a distribution typical of the freshwater species which just made it to England before the sea flooded the land-mass of the present North Sea. Paradoxically, considering it never was widespread in Britain, and has now probably disappeared, the burbot is one of the most widely distributed of all freshwater fishes. Its world range extends from western Europe right across the northern land-mass of Europe, Asia and North America. eggs (large specimens may have as many as three million). They are shed close to the bottom and lie there until hatching.

What happened?

Why has the burbot seemingly died out in temperate Britain when it can tolerate, and even breed in, ice-covered waters?

The reasons are not really known, but are probably a combination of circumstances. Pollution was certainly one – the Trent, once a burbot stronghold, became severely polluted early in the 20th century. The British population lived in a series of isolated rivers, every one altered – and so further isolated – by weirs, locks, abstraction and industrial use. The widely separated small groups, no longer able to mingle,

A chilly life-style

Despite this range, the burbot isn’t seen by many people. A few anglers may catch it when fishing through holes in the ice or at night in summer, and researchers catch it in traps set on lake and river beds.

Most active in the half light of dawn and dusk, it feeds at night. During the day it lies up in holes in the bank, under tree roots, in crevices under rocks and, in lakes, simply half-buried in the mud. Its food consists mainly of bottom-living invertebrates — insect larvae, crayfish and molluscs. Larger burbot eat bottom fish – ruffe, gudgeon, bullhead and loaches.

The burbot spawns in winter, from December to March. Over the northern parts of its range this means that it spawns under the ice. Adults gather in small groups of up to 20 individuals, usually in fairly shallow water over gravel or stone.

The females produce a huge number of gradually became less viable.

Finally, the British climate is probably too warm. Cold winters are not the norm — as they are in, say, Sweden or Canada – and our cold snaps in winter are often punctuated by warmer spells. These conditions are unsuitable for a fish capable of surviving for months under a foot or two of ice.