a genus of fishes of the family Nototheniidae of the order Perciformes. It is distinguished from other species of Nototheniidae by its large body and mouth, tusklike teeth, and very small scales.
There are two species, distributed in the waters around Antarctica. The Patagonian tootnfish (Dissostichus eleginoides) measures up to 193 cm long and weighs up to 70 kg. It is found at depths of 800 m along the shores of Argentina, the island of South Georgia, and the subantarctic islands of the Indian Ocean. The species is predatory. The antarctic toothfish (D. mawsoni), which is the same size as the Patagonian toothfish, lives off the shores of Antarctica and feeds on squids and small fish. It is the prey of the Weddell seal and the sperm whale. The antarctic toothfish is commercially valuable; its meat is extremely tasty and has a fat content of up to 30 percent.