toothfish, common name for a genus (Dissostichus) of deep-water marine ray-finned fishes found in waters off S South America to Antarctica. The Patagonian toothfish, D. eleginoides, is the northerly of the two species; the Antarctic toothfish, D. mawsoni, is found only in circumpolar waters. The fish have thick scales, large eyes on the top of the head, and sharp teeth. The firm, bright white meat has made the fish a popular food fish since the 1990s; in the United States it is usually known as Chilean sea bass, but it is not related to the bass. The toothfish can take 10 years to reach sexual maturity, grow to weigh up to 200 lbs (90 kg), and live up to 50 years, but due to overfishing the average catch now measures about 2 ft (60 cm) long and weighs about 10 lbs (4.5 kg). Since 2000, however, increasing attempts have been made, with partial success, to regulate the catch.
Toothfish are classified in the phylum Chordata, subphylum Vertebrata, class Actinopterygii, order Perciformes, family Nototheniidae.