Bullhead - Cottus gobio

Alternative names
Miller's Thumb

The European Bullhead is a small fish, with a large mouth, large pectoral fins, prominent eyes and a wide flattened head; hence the common names 'Bullhead' and 'Miller's Thumb'. They are brownish in colour with mottling or barring, and pale undersides. During the spawning period males become black in colour with a white-tipped dorsal fin, and females become plump. They rarely grow to more than 10 cm long. 

Identification difficulty

Occurs in freshwater streams, rivers and lakes with hard stony substrates and shows a preference for fast flowing, shallow water bodies. The large pectoral fins enable Bullheads to hold their position in fast flowing water. 

When to see it

All year round but most readily seen around dusk. 

Life History

They lay their eggs in March and April, and the male guards the eggs until they hatch (although once they hatch he may eat a few of the youngsters if they come close enough). 

UK Status

The Bullhead is widely distributed in England and Wales but in Scotland is only known from the Forth and Clyde catchments.  It is less common in the rest of Europe. Red Data Book species.

VC55 Status

Fairly common in Leicestershire and Rutland where it is widely distributed in both smaller and larger rivers; found especially in the Soar, Gwash, Chater, Swift, Charnwood streams including Black Brook, Rothley Brook, Wreake, Eye, Langham Brook, eastern and western Sence, Mease/Gilwiskaw, Hooborough Brook, Gaddesby Brook and Sibson Brook.

Leicestershire & Rutland Map


Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map

Species profile

Common names
Miller's Thumb, Bullhead
Species group:
Records on NatureSpot:
First record:
11/09/1997 (Environment Agency)
Last record:
09/04/2023 (Bell, Melinda)

Total records by month

% of records within its species group

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