Wels Catfish

The wels catfish is the giant of European rivers — a broad-headed, whiskered, olive-black predator that can outweigh a person, hunts almost blind in the dark using taste and electricity, and in a few places has taken to ambushing pigeons on dry land.

Overview

The wels is native to central and eastern Europe and western Asia, in large slow rivers, oxbows, lakes, and reservoirs, and it tolerates brackish water in the Baltic and Black Seas. Over the past century it has been widely introduced for angling into western and southern Europe — France, Spain, Italy, and increasingly the UK — where warmer summers and nutrient-rich rivers let it grow fast and dominate. It is nocturnal, resting by day in deep holes, undercut banks, and among sunken timber, and hunting from dusk.

Built to hunt in the dark

A wels catfish barely uses its small eyes. Instead it relies on:

• Barbels — two long ones on the upper jaw and four shorter on the lower — and skin covered in taste receptors, letting it taste its surroundings;
• A powerful sense of smell;
• The lateral line, sensing water movement and pressure;
• Electroreception, detecting the fields around living animals.

It feeds by suction ambush, opening its huge flat mouth to pull in a rush of water and prey. Diet ranges from fish, crayfish, and frogs to water voles, rats, ducklings, and — for the largest individuals — almost anything that enters the water.

The pigeon hunters

In several French rivers, wels catfish have been filmed and studied performing a striking behaviour: partially stranding themselves on gravel bars and banks to snatch feral pigeons that gather there. The fish rushes into a few centimetres of water, grabs a bird, and flips and wriggles back to the depths. Only a minority of attempts succeed, but the behaviour is deliberate, repeated, and appears to spread socially — an example of a fish learning a novel foraging strategy on land.

Reproduction

Wels spawn in late spring and summer in warm, weedy shallows. The male builds a crude nest in vegetation, the female lays hundreds of thousands of sticky eggs, and the male guards them and fans them until they hatch, then continues to defend the young for a time.

Status

The wels catfish is Least Concern and increasing. In its native range it is a valued part of the fish community and a prized angling species. Where it has been introduced, it is regarded as an invasive predator that reduces populations of native fish, amphibians, and ground-nesting and drinking birds, and its continued spread — helped by illegal stocking and climate warming — is a growing management concern.