Fish
European Bullhead
Cottus gobio · also called miller's thumb
Under a flat stone in a clear Welsh stream, a European bullhead lies motionless, its mottled body invisible against the gravel as it waits for a shrimp to pass.
Overview
The European bullhead, Cottus gobio, is a Least Concern fish of clear, stony streams, rivers, and lake shores across Europe. Its flat head, ambush hunting, and guarding fathers make it one of the most characteristic small fish of clean upland waters.
A fish with a miller’s thumb
The old name miller’s thumb comes from the fish’s broad, flat head, said to resemble the thumb a miller would flatten by testing flour between finger and thumb.
Status
Least Concern, though sensitive to pollution.
European Bullhead: common questions
Why is it called the miller's thumb?
It is named for its broad, flat head, which resembles a miller's thumb, flattened by testing flour.
Why does the bullhead stay on the bottom?
It has no swim bladder, so it rests on the bottom and moves in short darts rather than swimming continuously.
Who guards the eggs?
The male, who prepares a nest under a stone and guards the eggs until they hatch.
Where is the European bullhead found?
It lives in clear, stony streams, rivers, and lake shores across Europe.