Bullhead

Bullhead, any individual of the acanthopterygian genus Cottus, which consists of some forty species of shore and freshwater fishes from the north temperate zone. They frequent rocky ground, lying between stones, and darting out with rapidity on their prey - small aquatic animals, notably crustacea. The River Bullhead (Cottus gobio), found in some British rivers, is from 3 inches to 4 inches long; brown, with dark spots on the upper part, and white beneath; but it undergoes many changes of colour after exertion or feeding. The "flesh, when boiled, is salmon-coloured, and delicate-eating. The species are also called Miller's Thumbs, from their broad flat heads.