fish identification help please?

Hi
I'm trying to identify a fish I saw at St Abbs last weekend, at Pettico
Wick, to be exact. Any takers??
It was in a hole so all I could see were it's head and pelvic fins.
Size of the head, a couple of inches across. The head was wider than it
was deep, similar aspect ratio to a dogfish.
Colour sort of dark olive to grey, no spots or markings.
Single barbel under the lower jaw.
Eyes black and more to the front of the head than a dogfish, for example.
Pelvic fins were fleshy, not rayed.
Skin looked smooth.
Cheers
Graham