In 1937, the English ichthyologist John Roxborough Norman described the toothfish in a formal description. He gave its type locality as MacRobertson Land at 66°45’S, 62°03’E in Antarctica. The specific name was given for Douglas Mawson who led the Australasian Antarctic expedition from 1911-1914.

The Antarctic toothfish is a species of notothen native to the Southern Ocean. It is often mistakenly referred to as an Antarctic cod, which is consistent with the misnaming of other notothenioid fish as rock cods though it belongs to a different taxonomy order from codfish. This name follows from a confusion between two genera of true cods, COD and NOTOTHEA. Notottenoid fishes are not closely related to cods, which are in another taxonomic order.

The Antarctic toothfish is known as “Dissostichus mawsoni”. The common name for this fish is “toothfish,” which refers to the fact that it has a biserial dentition in its upper jaw, which gives it a shark-like appearance. This fish lives in the southern oceans at temperatures below 60°S.

The species was first described by Achille Valenciennes in 1837, as Brama diacanthus, but was later reclassified into the genus Dissostichus. The generic name, Dissostichus is from the Greek dissos (twofold) and stichus (line) and refers to the presence of two long lateral lines.

The Antarctic toothfish, Dissostichus mawsoni, has a partially cartilaginous skeleton which makes it lightweight. This fish also lacks a swim bladder and fat deposits serve as an energy source during migration. The Antarctic toothfish is neutrally buoyant due to its ability to store large amounts of fat in the body.

Antarctic toothfish can locate prey in low light conditions and have lateral lines and visual systems well adapted to their environment. They also have a well-developed sense of smell, which is why they are easily caught by baited hooks.

Body structure

The Antarctic toothfish species has a broad head, an elongated body, long dorsal and anal fins, large pectoral fins, and a rudder-like caudal fin. They typically move slowly but can reach bursts of speed when threatened by predators such as seals.

The Antarctic toothfish is a large, predatory fish. Growing to 1.7m in length and weighing 135 kg (298 lb), the Antarctic toothfish is the largest of the Antarctic fishes. This size allows it to compete with other predators for food, such as penguins, seals, and squid.

Antarctic toothfish, also known as the Chilean sea bass, is one of only five notothenioid species that are neutrally buoyant. As adults, they reach lengths of 100 to 120 cm and are able to spend time above the bottom without expending extra energy because of their neutrally buoyant state. They feed on both bottoms and mid-water-dwelling prey.

The olive-brown flathead catfish is a small fish that blends in well with its surroundings. The body and fins are mottled in a pattern that makes it very difficult to see, especially in the sponges and corals where it spends most of its time hiding from predators.

Diets

Antarctic toothfish feed on shrimp and small fish, which is also the main diet of Adélie penguins. Sperm whales eat large Antarctic toothfish, and the bottom-dwelling variety feeds on grenadiers. Toothfish also eat other smaller fish species and skates.

Habitat

The Antarctic toothfish live in the cold waters of the Southern Ocean. They are found around or near the Antarctic continent, but also as far north as Norway. They mainly live at depths between but have been caught as deep as. The largest toothfish ever caught weighed and measured long.

Reproduction

Antarctic toothfish are relatively fast-growing when young, but then growth slows later in life. They reach about one-third of maximum size after 5 years, and half maximum by 10 years, after which growth slows considerably. They spawn sometime during winter. Large, mature, older fish have been caught among the seamounts of the Pacific-Antarctic.

The maximum age recorded for an Antarctic toothfish is 48 years (McClanahan and Friedlander, 2002). It takes 13 years for the males to mature and 17 years for the females (Kotze et al., 2000; McClanahan and Friedlander, 2002). At maturity, they may not spawn every year.