Differs from other species of Cottus in the North Sea and Atlantic basins by the combination of the following characters: no distinct transverse bands on pelvic fin; prickling on body extending backwards to caudal peduncle in juveniles and most adults; sometimes absent in large males; first dorsal fin marbled or black in nuptial males; eye diameter 18-21% HL; interorbital distance 0.7-1.9 times in eye diameter; last anal-fin ray connected to body by a membrane along 0.1-0.90 of its length (Ref. 55856).