The Patagonian toothfish (Dissostichus eleginoides), also called Chilean sea bass and mero, is a type of notothen fish. It lives in cold waters (1–4 °C or 34–39 °F) at depths between 45 and 3,850 meters (150 and 12,630 feet) in the southern Atlantic, Pacific, and Indian Oceans and the Southern Ocean. It is found on seamounts and continental shelves near most Subantarctic islands.

The average weight of a Patagonian toothfish caught for sale is 7–10 kilograms (15–22 pounds), depending on the fishery. Some large adults may weigh more than 100 kilograms (220 pounds). These fish can live up to 50 years and grow as long as 2.3 meters (7.5 feet). Multiple commercial fisheries catch Patagonian toothfish, as described below.

A closely related fish, the Antarctic toothfish (Dissostichus mawsoni), lives farther south along the edges of the Antarctic shelf. A fishery certified by the Marine Stewardship Council operates in the Ross Sea for this species. The Antarctic toothfish is sometimes sold as Chilean sea bass.

Taxonomy

The Patagonian toothfish was first described in 1898 by the Swedish zoologist Fredrik Adam Smitt. The location where the species was first identified is Puerto Toro, located on the Chilean part of Tierra del Fuego at coordinates 55°24'S, 68°17'W. Smitt also created a new group of fish called Dissostichus, and the Patagonian toothfish is the only species in this group. The name "eleginoides" means the fish has a shape similar to another fish called Eleginops.

Description

The Patagonian toothfish has a streamlined, torpedo-shaped body. The depth of its body is about 5 to 6.4 times the length of its body. It has a flat head with a wide, flat area between the eyes. The snout is longer than the diameter of the eyes. The mouth is large and extends past the middle of the eye. The upper jaw has two rows of teeth, with the outer row containing larger, canine-like teeth. The lower jaw has a row of spaced, canine-like teeth. Additional canine-like teeth are found at the joint where the upper and lower jaws meet. There are two lateral lines made of tubed scales: one on the top of the body and another along the middle of the sides. The upper lateral line has 88–104 scales, while the lower line has 61–77 scales. The first dorsal fin has 8 to 10 spines. The second dorsal fin and the anal fin each have 28 to 30 soft rays. The tail fin is slightly notched. The pectoral fins are large and fan-shaped. The head and body are covered in ctenoid scales, except for the front of the head. This species can grow up to 215 cm (85 inches) long, though most are around 70 cm (28 inches). The heaviest recorded fish weighed 200 kg (440 pounds). Its overall color is brownish-grey with darker spots.

Distribution and habitat

The Patagonian toothfish lives in the southeastern Pacific and southwestern Atlantic Oceans. It is found along the coast of Patagonia in southern Chile, in Argentina, and on the Falkland Islands. It has also been seen near Macquarie Island in the southwestern Pacific Ocean, at South Georgia in the Southern Ocean, and on sub-Antarctic islands and underwater mountains in the Indian Ocean region. One fish was found in the Davis Strait near Greenland in the northwestern Atlantic Ocean. Scientists believe this fish traveled more than 10,000 km (6,200 mi) and passed through tropical areas in deep, cold parts of the ocean. Young fish live near the ocean surface but move closer to the ocean floor at depths between 150 and 400 m (490 and 1,310 ft). Adult fish live in deeper water, often more than 1,000 m (3,300 ft) below the surface.

Biology

Patagonian toothfish lay their eggs in deep water, about 1,000 meters below the ocean surface, during the winter in the Southern Hemisphere. These eggs and the young fish that hatch from them live in open water. When the young fish are about 1 year old, they move to shallower water near the ocean floor, around 100 meters deep. They stay in this habitat until they are 6 to 7 years old, after which they slowly move to deeper water.

As young fish in shallow water, Patagonian toothfish mainly eat other fish. As they grow larger and move to deeper water, their diet changes. They begin eating more squid, fish, and crustaceans that they find on the ocean floor. In turn, Patagonian toothfish are sometimes eaten by sperm whales, southern elephant seals, and colossal squid.

Most Patagonian toothfish fisheries are managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). This group uses an "ecosystem approach," which means it considers how all living things in the Southern Ocean interact. Decisions about how many fish can be caught are based on scientific studies reviewed by experts to ensure the ocean’s ecosystem remains healthy.

Fisheries and fisheries management

The Patagonian and Antarctic toothfish are sometimes sold in the United States and Canada under the name "Chilean sea bass." This name was created in 1977 by a fish seller named Lee Lantz. He wanted a name that would attract buyers in America. He tried names like "Pacific sea bass" and "South American sea bass" before choosing "Chilean sea bass." In 1994, the U.S. Food and Drug Administration approved "Chilean seabass" as an official name for Patagonian toothfish, and in 2013 for Antarctic toothfish.

In the United Kingdom, the official names for D. eleginoides and D. mawsoni are "icefish" and "toothfish." This can cause confusion because a real "icefish" (Champsocephalus gunnari) found in subantarctic waters looks very different from toothfish.

In Singapore, the Patagonian toothfish is sold as a type of cod fish.

Commercial fishing of toothfish is managed by an organization called CCAMLR in the CCAMLR Convention Area, which covers the Antarctic continent and the waters between the 45th and 60th parallels south. Some fisheries near islands like Crozet, Prince Edward, and Marion are managed by the countries that own those areas, but they follow CCAMLR rules. Toothfish caught near Argentina, Chile, and Uruguay is managed by those countries, but they still use the CCAMLR Catch Documentation Scheme to track toothfish from when it is caught until it is sold.

In legal toothfish fisheries, the most common method is longlining, where a long line with many baited hooks is placed in the water. A small amount of toothfish is also caught using trawling, where a net is dragged behind a boat. For all legal fishing methods, the risk to seabirds is very low because rules require using tools or methods to reduce harm.

In 2011, David Agnew, the chair of the CCAMLR Scientific Committee, said that seabird deaths from fishing are very low in most areas. One area still working to reduce seabird deaths has cut interactions by over 98% since their highest levels and continues to improve each year. However, toothfish fishing sometimes harms marine mammals like sperm whales, orcas, fur seals, and elephant seals, and these interactions can be deadly.

Trawling usually catches smaller toothfish, which must be considered when calculating how many toothfish can be caught each year. This reduces the total number of toothfish available for fishing by trawling. CCAMLR has banned trawling in high seas areas and exploratory fisheries.

To protect toothfish, their habitats, and the ocean, CCAMLR uses systems to monitor fishing activities. These include requirements for fishing companies to follow rules and report their actions.

The Coalition of Legal Toothfish Operators, Inc. (COLTO) represents about 80% of the world’s legal toothfish catch. Seven of the fisheries COLTO members operate in have been certified by the Marine Stewardship Council (MSC) as sustainable and well-managed.

In 2004, the South Georgia toothfish fishery became the first to be certified by the MSC. It was recertified in 2009 and 2014. This fishery is managed by the UK overseas territory of South Georgia and the South Sandwich Islands.

The Ross Sea fishery was the second toothfish fishery to be certified by the MSC in 2010 and recertified in 2015. It mainly catches Antarctic toothfish, a close relative of the Patagonian toothfish.

The Heard Island and McDonald Islands fishery was certified by the MSC in 2012 and recertified in 2017. It is managed by Australia and follows CCAMLR rules. Two Australian companies operate four fishing vessels in this area.

The Macquarie Island toothfish fishery is located in Australian waters outside the CCAMLR Convention Area but follows similar rules. It was certified by the MSC in 2012 and recertified in 2017. Two Australian companies are allowed to catch fish in this area.

France manages Patagonian toothfish around the Kerguelen and Crozet Islands in the South Indian Ocean. These fisheries are monitored by the National Museum of Natural History. Six companies based in Reunion Island are allowed to fish there. The Kerguelen fishery was certified by the MSC in 2013 and again in 2018. The Crozet fishery was certified in 2017.

The Falkland Islands, a British Overseas Territory, also has a toothfish fishery. It was certified by the MSC in 2014. Though the Falklands are not in the CCAMLR area, their fishing rules match CCAMLR standards. A single longline boat catches the total allowed amount of fish each year.

More than 50% of all legally caught toothfish comes from fisheries that have been certified by the MSC as sustainable and well-managed.

The Chilean toothfish fishery is divided into two parts. The "artisanal fleet" uses small boats north of 47°S in Chilean waters. Six larger boats in the "industrial fleet" fish south of 47°S in Chilean waters and on the high seas. The total allowed catch for the industrial fleet is set each year by the Chilean government based on scientific studies. Since 2006, the artisanal fleet’s catch has ranged between 2,091 and 1,558 tonnes annually.

Argentina’s toothfish fishery is managed by the Argentine Federal Fisheries Council, following advice from the National Fisheries Research Institute. Five boats catch the total allowed amount of fish each year.

The Prince Edward and Marion Islands toothfish fishery is managed by South Africa’s Branch Fisheries. This area follows all CCAMLR rules. Two boats from two companies catch the total allowed amount of fish each year. This fishery’s catch was reduced after too many fish were caught illegally in the late 1990s, but catches have started to increase as fish populations recover.

The global toothfish catch is about 30,000 tonnes, with around 80% of this coming from COLTO members.