Concept
The Antarctic toothfish (Dissostichus mawsoni) is a large, black or brown fish found in very cold (subzero) waters of the Southern Ocean near Antarctica. It is the largest fish in the Southern Ocean, feeding on shrimp and smaller fish, and preyed on by whales, orcas, and seals. It is caught for food and marketed as Chilean sea bass together with its sister species, the more northerly Patagonian toothfish (D. eliginoides). Often mistakenly called "Antarctic cod," the Antarctic toothfish belongs to the notothen family (Nototheniidae), a group of fish species abundant near Antarctica. The common name "toothfish" refers to the two rows of teeth in the upper jaw, thought to give it a shark-like appearance. The genus name Dissostichus is from the Greek (twofold) and stichus (line) and refers to the presence of two long lateral lines that enable the fish to sense prey. The species name, mawsoni, honors the Australian geologist Douglas Mawson who led the 1911-1914 Australasian Antarctic Expedition that explored the Antarctic coast and obtained the species' type specimen. The Antarctic toothfish was first formally described in 1937 by the English ichthyologist John Roxborough Norman with the type locality given as off MacRobertson Land at 66°45'S, 62°03'E in Antarctica. Fully grown, these fish (and their warmer-water relative, the Patagonian toothfish, D. eleginoides) can grow to more than in length and 135 kg in weight, twice as large as the next-largest Antarctic fish. Being large, and consistent with the unstructured food webs of the ocean (i.e., big fish eat little fish regardless of identity, even eating their own offspring), the Antarctic toothfish has been characterized as a voracious predator. Furthermore, by being by far the largest midwater fish in the Southern Ocean, it is thought to fill the ecological role that sharks play in other oceans. Aiding in that role, the Antarctic toothfish is one of only five notothenioid species that, as adults, are neutrally buoyant.