The Bullhead (Cottus gobio), is a small fish which is native to the UK. It has a large mouth, large eyes and a flattened head. During the mating season, they become black in colour. Pink and yellow eggs are found in clumps underneath rocks. They can live upto 5 years , are nocturnal and live among stones and thick water weeds.
The bullhead is a small demersal fish that lives both in cold, clear, fast-slowing small streams and in middle-sized rivers. It also occurs on gravelly shores of cold lakes. Further, it thrives in diluted brackish water of the Northern Baltic Sea. Its food items include benthic insects and crustaceans.