The Patagonian toothfish (Dissostichus eleginoides), also called Chilean sea bass and mero, is a type of fish found in very 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, as well as the Southern Ocean. It lives near underwater mountains and along the edges of landmasses around many islands in the Subantarctic region.

Fishermen commonly catch Patagonian toothfish that weigh between 7 and 10 kilograms (15–22 pounds), though 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 operate to catch this species, as described below.

A closely related fish, 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, and it 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 part of Tierra del Fuego. Smitt also created a new genus called Dissostichus for this species. This makes the Patagonian toothfish the only species in the Dissostichus genus. The specific name eleginoides means "having the form of" or "similar in shape to" the fish Eleginops.

Description

The Patagonian toothfish has a streamlined, spindle-shaped body with a depth that is about 5 to 6.4 times its standard length. Its head is flattened, 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 along the upper part of the body and another along the mid-flanks. 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, and the second dorsal fin and the anal fin each have 28 to 30 soft rays. The caudal 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 total length, though 70 cm (28 in) is more common, and can weigh as much as 200 kg (440 lb). Its overall color is brownish-grey with darker blotches.

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 around the Falkland Islands. It has also been seen near Macquarie Island in the southwestern Pacific Ocean, at South Georgia in the Southern Ocean, and near the sub-Antarctic islands and seamounts in the Indian Ocean region. One fish was recorded 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 partly in the open ocean but move closer to the ocean floor at depths between 150 and 400 meters (490 and 1,310 feet). Adult fish move to deeper areas, living in places deeper than 1,000 meters (3,300 feet).

Biology

Patagonian toothfish lay their 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 this age, they slowly move to deeper water.

As young fish in shallow water, toothfish mainly eat other fish. 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 larger animals, such as 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). This group uses an "ecosystem approach" to protect the Southern Ocean. This means they consider how all living things in the ocean interact, including predators, prey, and other species. Decisions about how many fish can be caught are based on scientific research reviewed by experts from around the world.

Fisheries and fisheries management

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

The name "Chilean sea bass" was created by a fish wholesaler named Lee Lantz in 1977. He wanted a name that would appeal to 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 approved "Chilean sea bass" as an alternative name for Patagonian toothfish, and in 2013 for Antarctic toothfish.

In the UK, the official names for D. eleginoides and D. mawsoni are "icefish" and "toothfish." This has caused some 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 CCAMLR within the CCAMLR Convention Area, which covers the Antarctic continent and the waters between the 45th and 60th parallels south. Some fisheries in territorial waters within the convention area, such as those near Crozet, Prince Edward, and Marion Islands, are managed separately by countries that follow CCAMLR guidelines. Toothfish fisheries in the coastal waters of Argentina, Chile, and Uruguay are managed by those countries but still follow the CCAMLR Catch Documentation Scheme, which tracks toothfish from when they are caught until they are sold.

In legally managed 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 pulled behind a boat for short periods. For all legal fishing methods, the risk to seabirds is very low because legal operators use 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 rare in most areas. One region still has some interactions but has reduced seabird contact by over 98% from its 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 be deadly.

Trawling usually catches smaller toothfish, which must be considered during annual stock assessments by CCAMLR. This reduces the total amount of toothfish that can be legally caught by trawling. CCAMLR has banned all trawling in high seas waters and exploratory fisheries.

To protect toothfish, bycatch species, and marine ecosystems, CCAMLR uses systems to monitor fishing activities. These include requirements for fishing methods and tools that reduce harm.

The Coalition of Legal Toothfish Operators, Inc. (COLTO) is a group of toothfish fishing companies that represents about 80% of the legal toothfish catch worldwide. Seven of the fisheries COLTO members operate in are certified by the Marine Stewardship Council (MSC) as sustainable and well-managed.

Commercial fishing of Patagonian and Antarctic toothfish is managed by CCAMLR in most Subantarctic and Antarctic regions. However, fisheries within a nation's exclusive economic zone (EEZ) are managed by that nation, following CCAMLR guidelines.

In 2004, the South Georgia toothfish fishery (CCAMLR Statistical Division 48.3) became the first toothfish fishery certified by the MSC as sustainable and well-managed. 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 certified by the MSC in 2010. It was recertified in 2015. This fishery mainly catches Antarctic toothfish, a close relative of the Patagonian toothfish.

The Heard Island and McDonald Islands fishery (CCAMLR Statistical Division 58.5.2) was certified by the MSC in 2012 (recertified in 2017) and is operated by Australia under CCAMLR rules. Two Australian companies operate four vessels in this fishery.

The Macquarie Island toothfish fishery is within Australia's EEZ and outside the CCAMLR Convention Area but follows CCAMLR conservation rules. This fishery was certified by the MSC in 2012 (recertified in 2017). Two Australian companies are allocated fishing rights here.

France manages Patagonian toothfish in the waters around the Kerguelen Islands and Crozet Islands in the South Indian Ocean. Scientific oversight is provided by the National Museum of Natural History. Six companies based in Reunion Island are authorized to fish there. The Kerguelen fishery was MSC-certified in 2013 (recertified in 2018), and the Crozet fishery was certified in 2017.

The Falkland Islands, a British Overseas Territory, also has a toothfish fishery. It was MSC-certified in 2014. The Falklands are not in the CCAMLR Convention Area, but their fishing rules follow CCAMLR guidelines. A single longline vessel catches the total allowed amount of toothfish.

Over 50% of all legally caught toothfish is certified by the MSC as coming from sustainable and well-managed fisheries.

The Chilean toothfish fishery is divided into two groups. The "artisanal fleet" uses small boats north of 47°S within Chile's EEZ. Six vessels in the "industrial fleet" fish south of 47°S within Chile's EEZ and on the high seas. The total allowed catch for the industrial fleet is set yearly by the Chilean government based on scientific studies. Artisanal fleet catches have varied between 2,091 tonnes and 1,558 tonnes annually since 2006.

Argentina's toothfish fishery is managed by the Argentine Federal Fisheries Council, following advice from the National Fisheries Research Institute. Five vessels catch the total allowed amount of toothfish.

The Prince Edward and Marion Islands toothfish fishery is managed by Branch Fisheries, part of South Africa's Ministry of Agriculture, Forestry, and Fisheries. South Africa supports all CCAMLR conservation rules. Two vessels from two fishing companies or cooperatives catch the total allowed amount, which has increased slowly as fish stocks recover from overfishing in the late 1990s.

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