Found on continental and insular shelves and upper slopes down to at least 1,200 m (Ref. 247) and to as deep as 2,200 m (Ref. 55584). Epibenthic-pelagic (Ref. 58426). In the Arctic and boreal Atlantic, it occurs inshore in the intertidal and at the surface in shallow bays and river mouths during colder months, retreating to depths of 180-550 m when the temperature rises (Ref. 247). Feeds on pelagic and bottom fishes (herring, Atlantic salmon, Arctic char, capelin, redfish, sculpins, lumpfish, cod, haddock, Atlantic halibut, Greenland halibut and skates (Ref. 5951)), sharks and skates (Ref. 5578), seals and small cetaceans, sea birds, squids, crabs, amphipods, marine snails, brittle stars, sea urchins, and jellyfish (Ref. 247, 58240). Petromyzon marinus was reported to have been attached to S. microcephalus (Ref. 58185). Ovoviviparous (Ref. 205). Also utilized fresh and dried for human and sled-dog food (flesh is said to be toxic when fresh); eskimos also used the skin to make boots, and the sharp lower dental bands as knives for cutting hair (Ref. 247). A very sluggish shark (Ref. 28609).