Diagnostic features
Body elongate, somewhat compressed. Snout a little pointed, upper jaw reaching to about eye centre, lower jaw projecting;  teeth on jaws small, vomerine teeth minute.  Gillrakers 33-44 (48).  Dorsal fin (with 10-14 rays) origin behind midpoint of body and about over pelvic fin bases, a low adipose fin behind it; pectoral finrays 16-21.  Scales very small, cycloid, 170-220, lateral line complete and reaching to caudal peduncle; males develop a midlateral ridge of elongate scales along flanks at spawning time.  Colour on the back, transparent olive to bottle green; below, the sides are silvery and the belly is silvery-white. The edges of the scales have dusky specks. 

Geographical distribution
North Atlantic and tributary parts of the Arctic; in the eastern Atlantic, from Spitsbergen and Jan Mayen Is., southeastern Greenland, Iceland, White and Barents Seas, northern Norway southward to Trondheim Fjord in abundance, occasionally to Oslo Fjord and Faroes; in the western Atlantic, from southwestern Greenland, Hudson Bay, and northern Labrador, southward to Newfoundland (including the islands of St. Pierre and Miquelon), the Gulf of St. Lawrence, northern Nova Scotia, and occasionally to the eastern part of the Gulf of Maine; Arctic coast of Alaska and Canada (Bathurst Inlet, Coronation Gulf, and Welcome Gulf); in the North Pacific southward to the Strait of Juan de Fuca in the east and to Korea and northern Japan in the west.


Capelin - Geographical distribution

Habitat and biology
Marine, littoral to neritic and epibenthicon fishing banks down to 300 m. They feed almost exclusively on small planktonic crustaceans. This fish spawns in late spring and early summer (different populations) in large schools in the shoreline, or in very shallow water, to lay adhesive eggs on beaches and banks. The eggs are buried in the gravel and hatch in 2 to 3 weeks.  Mature males have the base of the anal fin strongly convex, the fins generally larger and their margins rounder, and two distinct lines of lanceolate scales on flanks (mid-lateral and between pectoral and pelvic bases), also small nuptial tubercles on fins (especially on the paired fins). The capelin rarely live longer than five years.

Size
Attains a maximum size of 23 cm. Males are slightly larger than females in each year class. 

Fisheries
Is extremely abundant in the Arctic parts of the North Atlantic and forms a major constituent of the diet of many larger fishes, sea-birds, and cetaceans, as well as the human inhabitants of the region. Most common fishing techniques are "small pelagic purse seining" and Capelin purse seining".