Remi Masson / European bullhead (Cottus gobio) camouflaged among rocks and aquatic plants, Ain, Alps, France

Remi Masson / Two European bullhead fish (Cottus gobio) hiding among rocks in small river, Ain, Alps, France

Remi Masson / European bullhead (Cottus gobio) on riverbed of small river, Ain, Alps, France, May.

Henley Spiers / European bullhead (Cottus gobio) portrait, River Otter, Devon, England, UK.

Emanuele Biggi / Bullhead (Cottus gobio) adult fish underwater in small alpine stream, Italy, July.

Emanuele Biggi / Bullhead (Cottus gobio) adult fish underwater in small alpine stream, Italy, July.

Brian Bevan / Bullhead millers thumb (Cottus gobio) resting amongst stones, Befordshire, UK, November. Controlled conditions.