Members of the family Cottidae are more commonly found in estuaries, and the freshwater bullhead is similar in appearance to common fish found in rock pools, such as gobies and blennies. Bullheads are often considered to prefer fairly fast-flowing upland rivers, although annual fish surveys undertaken by the Environment Agency suggest that this is not always strictly the case.

They are unmistakable from other freshwater fish: they have disproportionately large, flat heads and taper towards the tail. They are predominantly brown in colour, with black flecks which offer superb camouflage in Cornwall's often shady rivers. Bullheads grow to between seven and ten centimetres in length, although we have found some whoppers at up to 14 centimetres. They breed between March and April, laying tiny yellow eggs underneath stones, which the male fiercely guards for three to four weeks until they hatch. They hide in cracks and crevices between stones during the day and feed at night on crustaceans, other invertebrates and the occasional small fish. A bullhead is protected from predators by spikes on the gills and dorsal fins which make it very hard to swallow; in fact we have seen an unfortunate brown trout in a fatal lock with a bullhead stuck in its mouth.

The bullhead has been largely neglected in terms of annual surveys and little is known about its population densities and tolerance to biological and chemical factors. The Environment Agency's Fisheries, Ecology and Recreation section initiated surveys in 1997 which aim to understand the environmental factors needed to sustain Cornwall's wealth of "non-commercial" fish species such as lampreys, stone loaches, minnows, sticklebacks, eel and of course bullhead. We hope to understand enough about their population dynamics and specific environmental requirements to be able to plan for their favourable conservation.

The best place to find or see bullheads would be the freshwater tributaries of the upper Tamar, Camel, Fowey (including Lerryn) and Fal, although they can be found on most Cornish rivers including the very small tributaries. Although they are fairly inactive during the day, they can be seen and easily caught with a dip net, either with patience or by placing the net downstream and disturbing the river bed. If you do catch bullheads, please treat them carefully as they are protected and internationally rare. Wet your hands before holding them and quickly place them in a container. Do not leave them there for long, especially in direct sunlight, and always return the fish to where you caught them. Disturbance to bullheads must be avoided during their breeding season but at this time they are quite active and therefore fairly easy to watch. (The above recommendations should apply to all fish species when caught).

Cornish rivers are amongst the cleanest and most diverse in Britain. We need to look after and conserve them in order to maintain and encourage such an abundance of wildlife.

Happy hunting!

Paul Smith
Paul Smith, an environmental studies graduate, joined the Environment Agency in 1996 and works as a Conservation Officer in its Fisheries, Conservation and Recreation Section. In his spare time, he co-ordinates the Bodmin Area BTCV Group.