The Patagonian toothfish (Dissostichus eleginoides), also known as Chilean sea bass, mero, and icefish,[2] is a species of notothen found in cold waters (1–4 °C or 34–39 °F) between depths of 45 and 3,850 m (150 and 12,630 ft) in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around most Subantarctic islands.

[4][5] The Patagonian toothfish was first formally described in 1898 by the Swedish zoologist Fredrik Adam Smitt with the type locality given as Puerto Toro at 55°24'S, 68°17'W on the Chilean part of Tierra del Fuego.

[8] The Patagonian toothfish has a streamlined, fusiform body that has a depth that fits into its standard length 5 to 6.4 times.

[1] Patagonian toothfish spawn in deep water (around 1,000 m) during the austral winter, producing pelagic eggs and larvae.

As juveniles in shallow water, toothfish are primarily piscivorous, consuming the most abundant, suitably sized local prey.

With increasing size and habitat depth, the diet diversifies and includes more scavenging of squid, fish, and crustaceans.

[3] In turn, toothfish constitute a small part of the diets of sperm whales, southern elephant seals, and colossal squid.

[12][13][14] As most toothfish fisheries are managed in accordance with Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) regulations and conservation measures, CCAMLR adopts an "ecosystem approach", which requires that all other living resources of the Southern Ocean are treated as an integrated system where effects on predator, prey, and related species are considered, and decisions on sustainable harvesting levels are made based on sound, internationally peer-reviewed scientific advice.

[15] The Patagonian and the Antarctic toothfishes are sometimes sold under the culinary name "Chilean sea bass" in the United States and Canada.

[citation needed] In the UK, the approved commercial designations for D. eleginoides and D. mawsoni are "icefish" and "toothfish".

[18] This has created some confusion, as a genuine "icefish" (Champsocephalus gunnari) caught in subantarctic waters does not resemble toothfish in any way.

[21] This is a result of requirements for legal operators to use mitigation devices or approaches, such as: In 2011, the CCAMLR Scientific Committee Chair, David Agnew, was quoted as saying, "levels of seabird mortality are negligible in most areas", with the one region yet to achieve these "near zero" results, having reduced seabird interactions by over 98% from their peak levels, and have continued to improve each year.

[42][43] France regulates Patagonian toothfish in the waters surrounding the French islands in the South Indian Ocean, with scientific oversight from the National Museum of Natural History.

The Falkland Islands, a self-governing British Overseas Territory, also has a toothfish fishery and was awarded MSC certification in 2014.

[45][46] Combined, over 50% of all legally harvested toothfish is independently assessed and certified by the MSC as being from sustainable and well-managed fisheries.

[49] The TAC for the industrial fleet is determined each year by the Chilean government based on biological studies carried out by both public and private, scientific bodies.

[48] In the late 1990s to early 2000s, illegal, unreported and unregulated (IUU) fishing for toothfish nearly collapsed some fisheries in the Southern Ocean.

However, since 2005, because of CCAMLR member nations, government patrol vessels, NGOs, media exposure, and trade and port state measures, IUU fishing has been all but eliminated from within countries' EEZs, and until 2015, a relatively small portion of IUU fishing still occurred in high seas areas.

This included the Sea Shepherd campaign, "Operation Icefish", which pursued one of the vessels, the Thunder, for 110 days before it was scuttled.

[56] Operations by the Royal New Zealand Navy, the Royal Australian Navy, Interpol, and governments of Spain, Thailand, Malaysia, and Indonesia all combined to successfully apprehend, arrest and prosecute all of the remaining 6 IUU vessels fishing illegally for toothfish on the high seas.

This measure, combined with additional surveillance by member nations' catch documentation schemes, has played a significant part in the reduction of IUU fishing for toothfish.

All vessel VMS data must be reported to the centralized CCAMLR system, with confirmation to USA required that it has occurred, for any products from those boats to be imported into the United States.

An open reply noted that sea birds had been protected in toothfish fisheries globally and that IUU fishing was virtually eliminated.