The Atlantic wolffish (Anarhichas lupus), also known as the seawolf, Atlantic catfish, ocean catfish, devil fish, wolf eel (the common name for its Pacific relative), woof or sea cat, is a marine fish of the wolffish family Anarhichadidae. The numbers of the Atlantic wolffish in US waters are rapidly being depleted, most likely due to overfishing and bycatch, and is currently a Species of Concern according to the U.S. National Oceanic and Atmospheric Administration‘s National Marine Fisheries Service. Apart from their unique appearance wolffish are distinguished by the natural antifreeze they produce to keep their blood moving fluidly in their very cold habitat, involvement by both the male and female in brood bearing, and the large size of their eggs. They are also an important factor in controlling green crab and sea urchin populations, which can become overly disruptive to habitats if left unchecked. Wolffish population success is also an important indicator of the health of other bottom-dweller populations, such as Atlantic cod. The Atlantic wolffish has retained the bodily form and general external characteristics of small blennies (Blennioidei). The largest specimen recorded measured 1.5 m (5 ft) long and weighed almost 18 kg (40 lb). Its body is long, subcylindrical in front, compressed in the caudal portion, smooth and slippery, the rudimentary scales being embedded and almost hidden in the skin. Atlantic wolffish vary in color, usually seen as purplish-brown, a dull olive green, or blueish gray. An even dorsal fin extends the whole length of the back, and a similar fin from the vent to the caudal fin, as in blennies. The pectorals are large and rounded and the pelvic fins are entirely absent. Its obtuse, eel-like body type makes the fish swim slowly, undulating from side to side, like an eel. The Atlantic wolffish’s distinguishing feature, from which it gets its common name, is its extensive teeth structure. Its dentition distinguishes the Atlantic wolffish from all the other members of the family Anarhichadidae. Both the lower and upper jaws are armed with four to six fang-like, strong, conical teeth. Behind the conical teeth in the upper jaw, there are three rows of crushing teeth. The central row has four pairs of molars and the outer rows house blunted conical teeth. The lower jaw has two rows of molars behind the primary conical teeth. The wolffish’s throat is also scattered with serrated teeth.Atlantic wolffish inhabit both the west and east coasts of the Atlantic. In the west Atlantic, they are seen as far north as the Davis Strait, of the Canadian territory of Nunavut, populating the shores of Greenland, Newfoundland, and Nova Scotia, extending as far south as Cape Cod. Although they are seldom seen south of Cape Cod, there have been sightings in New Jersey. The most dense populations are in Georges Bank, the Gulf of Maine and the Great South Channel. In the eastern Atlantic, they range from Russia’s White Sea and Novaya Zemlya, through the Nordic countries and British Isles, to the Bay of Biscay. Atlantic wolffish are primarily stationary fish, rarely moving from their rocky homes. They are benthic dwellers, living on the hard ocean floor, frequently seen in nooks and small caves. They like cold water, at depths of 20 to 500 m (66–1,640 ft). They are usually found in water temperatures of −1 to 11 °C (30–52 °F). Since they can live in near-freezing waters (salt water only freezes at slightly below 0 °C or 32 °F), to keep their blood moving smoothly, they contain a natural antifreeze. Three related species (Atlantic, northern and spotted wolffish) occur in the north Atlantic. The northern wolffish has loose gelatinous flesh, but the other species are esteemed as food, both fresh and preserved. They are marketed in Britain as “Scotch halibut” and “Scarborough woof”, or, simply “woof” in other areas of the northeast coast, and are a popular ingredient in fish and chips.