Bullhead (Cottus gobio)  

Description: 
Length: 7 – 11cm
They range from an olive / brown colour to nearly black and have a wide flat topped head with a slender body. They are also known as 'miller's thumbs' because millers were said to develop broad thumbs from rubbing grain.

They have no swim bladder, so dart from place to place on the bottom of the river bed. Their flat underbelly enables them to lie close to the bottom of the river where the current is weaker, and to hide in small gaps between stones. Bullheads are common throughout England and Wales, though rare in Scotland and Europe.


Diet: freshwater macroinvertebrates (small aquatic insects). The small, flattened body of the Bullhead enables it to feed on insects that are beyond the reach of larger fish.

Spawning: April and May.
The adult fish search for a suitable spot under the stones where they clean out the silt and debris which may otherwise choke the freshly laid eggs and starve them of oxygen.

The females lay 200-250 eggs (2mm diameter) on the underside of stones, although sometimes in the sand on the river bed. The male guards the eggs, fanning them with his fins to ensure a constant supply of well oxygenated water, until the fry hatch out three weeks later.