The Patagonian toothfish (Dissostichus eleginoides), also called Chilean sea bass and mero, is a type of notothen fish that lives in very cold waters (1–4 °C or 34–39 °F). It is found between depths of 45 and 3,850 meters (150 and 12,630 feet) in the southern Atlantic, Pacific, and Indian Oceans, as well as the Southern Ocean. These fish live near seamounts and continental shelves around many 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). There are several commercial fisheries that catch Patagonian toothfish, as described below.

A closely related species, the Antarctic toothfish (Dissostichus mawsoni), lives farther south near 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 under the name Chilean sea bass.

Taxonomy

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

Description

The Patagonian toothfish has a smooth, torpedo-shaped body. The body’s depth is about 5 to 6.4 times shorter than its length. It has a flat head with a wide, flat area between the eyes. The snout is longer than the width 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, sharp, pointed teeth. The lower jaw has a row of spaced, sharp, pointed teeth. Additional sharp, pointed teeth are found at the joint where the upper and lower jaws meet. There are two lateral lines made of scales with small tubes: one along the top of the body and another along the middle of the sides. The upper lateral line has 88 to 104 scales, while the lower line has 61 to 77 scales. The first dorsal fin has 8 to 10 spines, and the second dorsal fin has 28 to 30 soft rays. The anal fin also has 28 to 30 soft rays. The tail fin is 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 in) in length, though 70 cm (28 in) is more common. The maximum recorded weight is 200 kg (440 lb). The 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 southern coast of Chile near Patagonia, in Argentina, and the Falkland Islands. It has also been seen near Macquarie Island in the southwestern Pacific Ocean, at South Georgia in the Southern Ocean, and around the sub-Antarctic islands and seamounts in the Indian Ocean sector. One fish was found in the Davis Strait in the northwestern Atlantic Ocean near Greenland. 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 Patagonian toothfish 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 below 1,000 m (3,300 ft).

Biology

Patagonian toothfish lay eggs in deep water (about 1,000 meters) during the austral winter. These eggs and the young fish that hatch from them float in the water. When the young fish are about 1 year old, they move to shallower water near the ocean floor (around 100 meters) and stay there until they are 6–7 years old. At that age, they slowly move to deeper water. As young fish in shallow water, toothfish mainly eat fish, choosing the most common prey that is the right size. As they grow larger and move to deeper water, their diet changes to include more squid, fish, and crustaceans that they find on the ocean floor. Toothfish are also eaten by sperm whales, southern elephant seals, and colossal squid.

Most toothfish fisheries are managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). CCAMLR uses an "ecosystem approach," which means it considers how all living things in the Southern Ocean interact. This includes looking at how changes affect predators, prey, and other related species. Decisions about how many toothfish can be caught are based on scientific research reviewed by experts from around the world to ensure fishing is sustainable.

Fisheries and fisheries management

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

The name "Chilean sea bass" was created in 1977 by a fish seller named Lee Lantz. He wanted a name that would attract American buyers. 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 allowed "Chilean sea bass" to be used as another 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 has caused some confusion because a real fish called "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.

Fishing for toothfish is managed by an organization called CCAMLR in the area that covers Antarctica and the waters between 45°S and 60°S. Some fishing areas within the territorial waters of islands like Crozet, Prince Edward, and Marion are managed separately by the countries that own those waters, but they follow CCAMLR rules. Toothfish fishing near the coasts of Argentina, Chile, and Uruguay is managed by those countries, but they still follow the CCAMLR Catch Documentation Scheme, which tracks the movement of toothfish from when they are caught to when they are sold.

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

In 2011, David Agnew, the chair of the CCAMLR Scientific Committee, said that seabird deaths from fishing are very rare in most areas. One region still has some interactions with seabirds, but it has reduced them by over 98% since their highest levels and continues to improve each year. However, interactions with marine mammals like sperm whales, orcas, fur seals, and elephant seals are more common and can sometimes be deadly.

Trawling usually catches smaller toothfish, which affects how many fish can be legally caught each year. CCAMLR has banned trawling in high seas areas and in exploratory fisheries.

To protect toothfish and the ocean environment, CCAMLR uses systems to monitor fishing activities. These systems help ensure that fishing is done in a way that does not harm fish populations or ecosystems.

The Coalition of Legal Toothfish Operators, Inc. (COLTO) is a group of toothfish fishermen who represent about 80% of all legally caught toothfish worldwide. Seven of the fisheries that 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 (CCAMLR Statistical Division 48.3) became the first toothfish fishery 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 (CCAMLR Statistical Division 88.1 and 88.2) was the second toothfish fishery to be certified by the MSC as sustainable in 2010. It was recertified in 2015. This fishery mainly catches Antarctic toothfish, which is closely related to Patagonian toothfish.

The Heard Island and McDonald Islands fishery (CCAMLR Statistical Division 58.5.2) 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 fishery.

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

France manages Patagonian toothfish in the waters around the Kerguelen Islands and the 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 recertified 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. The Falkland Islands are not in the CCAMLR area, but their fishing rules match those of CCAMLR. 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 split into two groups. The "artisanal fleet" uses small boats to fish 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 amount of fish allowed to be caught by the industrial fleet is decided each year by the Chilean government based on scientific studies. Since 2006, the artisanal fleet has caught between 1,558 and 2,091 tonnes of fish each year.

Argentina’s toothfish fishery is managed by the Argentine Federal Fisheries Council, which follows 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, part of the Ministry of Agriculture, Forestry, and Fisheries. South Africa supports all CCAMLR conservation rules. Two boats owned by two companies catch fish in this area. After too much illegal fishing in the late 1990s, the amount of fish allowed to be caught has slowly increased as fish populations recover.

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