The Atlantic halibut is a ground dwelling flatfish and member of the flounder family, found on sand, gravel or clay bottoms at depths to 500 fathoms in the extreme. It is right-eyed, with its upper surface being a uniformly dark chocolate, olive or slate color, and can be almost black. The underside is pale. It is among the largest flatfishes in the Atlantic with a gaping mouth, sharp, curved teeth and a concave edged tail fin. Though both of its ventral fins are alike, its two pectoral fins are of different shapes, the one on the upper (eyed) side of the fish being obliquely pointed while the fin on the lower side is rounded. Halibut are fast swimmers, unlike other flatfish species.
Depending upon location, up to seven million eggs are produced by spawning females in batches, the average age at maturity believed to be 10 years. Juvenile fish feed on invertebrates. Fish larger than 12 inches to 31 inches consume invertebrates and fish, and halibut over 31 inches feed almost exclusively on fish. Full grown females can grow to 150 pounds, while males tend to be smaller.
Juvenile Atlantic halibut are quite localized, being found in apparently well-defined nursery grounds and in coastal areas 66 to 197 feet deep with sandy bottoms. Adults are found over sand, gravel or clay substrates and at depths of 328 to 2300 feet.
The native habitat of the Atlantic halibut is the temperate waters of the northern Atlantic, from Labrador and Greenland to Iceland, the Barents Sea and as far south as the Bay of Biscay. Found as far south as off the coast of Virginia in the United States.