Dorsal spines (total): 0; Dorsal soft rays (total): 13 - 21; Anal spines: 0; Anal soft rays: 12 - 23; Vertebrae: 46 - 58. Without prominent keel; no median notch in upper jaw. Gill cover without radiating bony striae. No distinctive dark spots on body or fins. Overlaps C. harengus in White Sea, but distinguished by fewer vertebrae (usually 52 to 55; cf. usually 55 to 57) and fewer post-pelvic scutes (10 to 14; cf. 12 to 16). Dark blue to olivaceous above, shading to silver below (Ref. 27547). Precaudal vertebrae: 29-31-32; caudal vertebrae: 19-22-22 (Ref. 265).
Source: FishBase. Whitehead, P.J.P. 1985 . (Ref. 188)