Differs from all species of Cottus in Europe by the dorsal fins usually separate in both sexes. Other characters useful to distinguish the species from other Cottus in Atlantic drainages include: relatively elongated body; first dorsal fin low, slightly rounded or regularly slanted; caudal peduncle stout (length 14-20% SL; depth 8-9% SL and 1.5-2.4 times in its length); no prickling in adults; eye diameter 19-26% of HL; interorbital distance 0.9-1.2 times in eye diameter; last anal-fin ray connected to body by a membrane at most along 1/4 of its length; last dorsal-fin ray connected to body by a membrane along 1/2-4/5 of its length; no membrane between pelvic fin and body; pelvic-fin ray 1 straight and slender; lateral line complete (Ref. 55856).