Basically solitary rather than a schooling fish. Inhabits rocky bottoms but may occur among floating seaweed. Migrates considerable distances in an annual cycle between deeper waters in winter and shallower waters in summer. Colour variable, usually bluish-grey, yellow-green or yellow-brown. Spawning males are reddish on sides, fins and ventral surface. Feeds on ctenophores, medusas, small crustaceans, polychaetes, jelly fish and small fishes. Valued for their eggs, which make an inexpensive caviar. Eaten in Nordic countries, marketed fresh or smoked. Male flesh is most demanded and roe is sold fresh.
Throughout the north of 45º N latitude (Portugal and southern Bay of Biscay) in appropriate habitats to Spitsbergen, including Iceland. Elsewhere, known from western Greenland, Hudson Bay, and the coasts of North America as far south as Maryland.