Differs from other species of Cottus in North Sea basin by the combination of the following characters, none of them unique: no distinct transverse bands on pelvic fin; prickling on body absent or only under pectoral fin; base of first dorsal fin with faint black blotches at anterior and posterior extremities; depth of caudal peduncle 26-31% HL; lateral line complete; and unique molecular markers (Ref. 55856).