(Text by kind permission of Dr Cris Little)
The Black-faced blenny (Tripterygion delaisi) is a small fish that grows up to 9 cm in length. It lives on hard substrates in shallow waters, and seems to prefer shaded sites such as rock crevices and pier pilings. The male, pictured here in his full breeding colours of bright yellow body with blue edged fins and jet black head, is a rival to any tropical fish for gaudiness and would not seem out of place on a Red Sea reef.
Female black-faced blennies are much less conspicuous. Their bodies are grey to brownish with five vertical dark bars, but having the ability to mimic background colours they can be reddish against red weed. Being typical members of the triplefin blenny family (Tripterygiidae), the fish have two distinct features that allow easy identification. They have three dorsal fins (gobies have two and blennies one) and they have scaled bodies (true blennies are scaleless).
Where in Britain can you see this pretty fish? Well, here is the rub, black-faced blennies have a very limited distribution, sightings being reported only in the Channel Islands and a small stretch of the Dorset coast from Swanage west to Portland. It appears that the fish is a recent colonist of our coastline from its main population centre further south in the Atlantic and Mediterranean.