Gill cover (operculum) without radiating bony striae (cf. Sardinops, which has dark spots along the flank).
Pelvic finrays 8 (as in Sardinella lemuru of southern Japan, which has strong fronto-parietal striae on top of head and a pair of fleshy outgrowths on the hind border of the gill opening).
No distinctive dark spots on body or fins.
Can be confused with: Overlaps C. harengus in White Sea, but distinguished by fewer vertebrae and post-pelvic scutes (usually 52 to 55 and 10 to 14; cf. usually 55 to 57 and 12 to 16).