The straying American catfish

The straying American catfish

The black bullhead occurs in Britain in just a few places. It was first imported into Europe from North America in the 19th century and, more recently, has been brought into Britain among goldfish stocks from Italy. British populations in the wild come from garden ponds, research laboratories and aquariums — people often dump them in the nearest river or stream if they are cleaning out the pond or if the fish grow too big for an aquarium.

The ‘British’ bullhead

For many years the black bullhead was mistaken in Britain for a very similar American catfish — the brown bullhead, which has not, in fact, been introduced to Britain at all. (Neither of these fish bears any relationship to the British native fish called the bullhead or miller’s thumb.)

The brown and black bullheads have a stout body, broad head and wide mouth and both have four pairs of barbels: one pair on the edge of the rear nostrils, another pair on the upper jaw and two other pairs on the lower jaw.

The black bullhead has a short-based dorsal fin, a slightly longer anal fin and a low, broad-based adipose fin situated just before the tail. Its small pectoral fins have a very sharp spine – which is capable of being locked rigid — on the outer edge. It has a dark back, greeny golden tinted sides and a yellow belly.

Painful pest

The black bullhead’s native habitat is the soft, muddy bottoms of lowland streams and lakes throughout the eastern region of North America – from southern Canada down to the extreme north of Mexico.

Both black and brown are common – as a result of introductions – throughout central Europe and around southern Europe and they are widely regarded as pests. Where the black occurs in Britain it has gained a similar reputation. It is fond of taking luncheon meat — usually intended for carp — and when it is caught the sharp spine on the pelvic fin makes handling it quite tricky and even painful.

Breeding and feeding

The breeding habits of this catfish are interesting. The female hollows out a depression on the bottom, then lays between 200 and 6000 eggs into it in a close packed mass (the number depending on the size of the female). Both parents guard and fan the eggs until they hatch, five days after being laid. Young bullheads swim around just below the surface in a tightly packed school accompanied by a parent. The school is startling to watch – it looks like a black blob moving around the lake.

The bullhead’s diet has not been studied in Britain but in North America – where there are in fact 37 native species of catfish — it eats aquatic insect larvae, crustaceans, snails, leeches, fish eggs and small fish.

It uses its barbels, which are equipped with sensory organs, to search out food. These organs are so sensitive that the fish has no need to take a bait into its mouth to assess its palatability.