The Greenland halibut or Greenland turbot (''Reinhardtius hippoglossoides'') belongs to the family

Pleuronectidae Pleuronectidae, also known as righteye flounders, are a family of flounders. They are called "righteye flounders" because most species lie on the sea bottom on their left sides, with both eyes on their right sides. The Paralichthyidae are the o ...

(the right-eye flounders), and is the only species of the genus ''Reinhardtius''. It is a predatory fish that mostly ranges at depths between , and is found in the cold northern

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

, northern

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

, and

Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...

Oceans. It has a variety of other English vernacular names, including black halibut, blue halibut, lesser halibut, and Newfoundland turbot; while both Newfoundland turbot and Greenland turbot are in common use in North America (sometimes even without the location, just "turbot"), these names are typically not used in Europe, where they can cause easy confusion with the true

turbot The turbot ( ) ''Scophthalmus maximus'' is a relatively large species of flatfish in the family Scophthalmidae. It is a demersal fish native to marine or brackish waters of the Northeast Atlantic, Baltic Sea and the Mediterranean Sea. It is a ...

(''Scophthalmus maximus''). The Greenland halibut is fished commercially across its range with disputes over the fishing rights for this species in the Atlantic Ocean off Canada resulting in the

Turbot War The Turbot War (; ) was an international fishing dispute and bloodless war, bloodless conflict between Canada and Spain (with the European Union) and their respective supporters. On 9 March 1995, Canadian officials from the Canadian Coast Guar ...

of the mid-1990s (a "war" without any injuries or casualties). The Greenland halibut is a

flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish Order (biology), suborder Pleuronectoidei, also called the Heterosomata. In many species, both eyes lie on one side of the head, one or the other migrating through or around ...

, and the left eye has migrated during the fish's development so that it is on the right side of the head. However, in this fish, it has not moved as far as in bottom-dwelling flatfish and the fish can probably see forwards. The Greenland halibut can swim in a vertical position and both sides of its body are a speckled brown colour, but the left side is rather paler than the right. The Hellefisk Fjord in Greenland is named after this fish, ''hellefisk'' being the Danish name for Greenland halibut.

Description

Its morphology with the left eye positioned on the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

ridge of the forehead gives it an appearance of a

cyclops In Greek mythology and later Roman mythology, the Cyclopes ( ; , ''Kýklōpes'', "Circle-eyes" or "Round-eyes"; singular Cyclops ; , ''Kýklōps'') are giant one-eyed creatures. Three groups of Cyclopes can be distinguished. In Hesiod's ''Th ...

when looking straight at it. The central position of the left eye in the Greenland halibut probably gives it a much wider range of

peripheral vision Peripheral vision, or ''indirect vision'', is vision as it occurs outside the point of fixation, i.e. away from the center of gaze or, when viewed at large angles, in (or out of) the "corner of one's eye". The vast majority of the area in the ...

in comparison to other flatfish, where the eye has migrated completely. Its body shape is elongated and compressed dorsoventrally and muscles on both sides are equally developed. Both sides are pigmented, but the left blind side is slightly lighter in color than the right side. The maximum length is about and the maximum weight is about , the normal length is and they usually weigh .

Distribution and habitat

The Greenland halibut is a cold-water species found at depths from near the surface to , but mainly between . It is mainly found in waters with temperatures from , but has also been observed at subzero temperatures down to . It has a circumpolar distribution in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

and is found in both the North Atlantic and the North Pacific Oceans. In the North Pacific, it ranges from the

Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, it ...

near

Honshu , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...

northwards to the

Chukchi Sea The Chukchi Sea (, ), sometimes referred to as the Chuuk Sea, Chukotsk Sea or the Sea of Chukotsk, is a marginal sea of the Arctic Ocean. It is bounded on the west by the Long Strait, off Wrangel Island, and in the east by Point Barrow, Alaska, ...

, east through the

Aleutian Islands The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...

, and south as far as northern

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

in Mexico. In the North Atlantic, it occurs from the British Isles to northern Norway, Faroe Islands, Iceland, and eastern Greenland in the east and from

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

to northwestern Greenland in the west.

Biology

As a species of

, it is presumed that this fish would be primarily associated with the seabed, however, tagging information shows that they spend time both close to the seabed and with frequent excursions into the water column, presumably for feeding. These movements up into the water column explain why it is often caught pelagically. It has been speculated that when in the water column they will swim in a vertical position, but data from data storage tags do not support this hypothesis. Greenland halibut are opportunistic predators and consume a variety of prey from demersal and pelagic habitats. Generally, individuals less than 20 cm in length feed upon small crustaceans, such as

amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

. As they grow, their diet shifts and they begin to feed upon

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

s and fish, and individuals greater than 60 cm are primarily piscivorous. Their diet also varies spatially, reflecting the availability of different prey items in different areas. In the north-east Arctic,

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

and fish, such as

Atlantic herring Atlantic herring (''Clupea harengus'') is a herring in the family Clupeidae. It is one of the most abundant fish species in the world. Atlantic herrings can be found on both sides of the northern Atlantic Ocean, congregating in large schools. ...

, capelin and

Atlantic cod The Atlantic cod (: cod; ''Gadus morhua'') is a fish of the family Gadidae, widely consumed by humans. It is also commercially known as '' cod'' or ''codling''. In the

Beaufort Sea The Beaufort Sea ( ; ) is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, Yukon, and Alaska, and west of the Canadian Arctic Archipelago. The sea is named after Sir Francis Beaufort, a Hydrography, hydrographer. T ...

and eastern Canada,

polar cod ''Boreogadus saida'', known as the polar cod or as the Arctic cod, is a fish of the cod Family (biology), family Gadidae, related to the true cod (genus ''Gadus''). Another fish species for which both the common names Arctic cod and polar cod a ...

and Gelatinous Snailfish are important prey items while in the shrimp grounds of west Greenland, shrimp and

redfish Redfish is a common name for several species of fish. It is most commonly applied to certain deep-sea rockfish in the genus ''Sebastes'', red drum from the genus ''Sciaenops'' or the reef dwelling snappers in the genus ''Lutjanus''. It is also app ...

are the primary prey. They are known to feed on significant quantities of offal discarded from fishing vessels. Greenland halibut spawn from January–March. During spawning, Greenland halibut will perform spawning rises where they will rise up through the water column from deep water to depths of around 200–350 m where they will release their eggs and sperm before descending back to deeper water. Females will release one batch of eggs each year thereafter while the males will spawn with multiple females over the course of the spawning season. The eggs and larvae remain suspended in the water column throughout development and complete their

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

on attaining a length of Greenland halibut have an unusual form of gonad development in comparison with many other fish species. They will develop two groups of

oocyte An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ger ...

s concurrently, one group will be spawned in the current spawning cycle, the other will be spawned in the next spawning cycle. The reason for this is due to the large eggs (2.5-3.0 mm in diameter) and in the cold water which they inhabit, it takes more than one year for oocytes to complete vitellogenesis. If they were to develop one group of oocytes at a time, they would be able to spawn only every two years.

Fishing and conservation

Greenland halibut are fished commercially by several countries, including Russia, Norway, Iceland, Germany, Spain, Greenland and Canada, and are caught using a variety of gear, including bottom trawls, longline and

gillnets Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

. Reported landings have been around 50–140 thousand metric tonnes per year since 1960. Fishing is the most important industry in Greenland, and Greenland halibut is the second-most important species (after

northern prawn ''Pandalus borealis'' is a species of caridean shrimp found in cold parts of the northern Atlantic Ocean, Atlantic and northern Pacific Oceans, although the latter population now often is regarded as a separate species, ''P. eous''. The Food ...

), meaning that any changes can have a significant effect on the country's overall economy, as well as the local economy as most inshore fisheries involve small-scale, small-boat fishers. Similarly, the fishery for Greenland halibut is very important to some

First Nations First nations are indigenous settlers or bands. First Nations, first nations, or first peoples may also refer to: Indigenous groups *List of Indigenous peoples *First Nations in Canada, Indigenous peoples of Canada who are neither Inuit nor Mé ...

and

Inuit Inuit (singular: Inuk) are a group of culturally and historically similar Indigenous peoples traditionally inhabiting the Arctic and Subarctic regions of North America and Russia, including Greenland, Labrador, Quebec, Nunavut, the Northwe ...

communities in Canada. The species is not threatened overall, and it can be locally abundant, but it is

near threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...

. Until the 1970s, the species declined due to overfishing, but since the 1980s, an overall slight increase has been seen, although some local populations have further declined. The primary threat is

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

. Secondary threats are related to their deep-water spawning grounds. Some are in areas with oil and gas extraction. Other spawning grounds are in deep, near-shore regions where the ecosystem relies on nutrients from meltwater from

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

s, but these are gradually disappearing. In 2010, Greenpeace International added the Greenland halibut to its seafood red list because some fishing for the Greenland halibut is by bottom trawl, which can cause significant environmental damage, and some populations appear to be overfished. In coastal regions and some offshore regions, fishing for Greenland halibut mainly is done by deep-sea long line fishing (out of reach of seabirds and too cold for sea turtles, issues for this fishing type elsewhere in shallower and warmer waters) and stationary bottom

gillnet Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

s, which does not cause the same damage as bottom trawling. In 2017, the

Marine Stewardship Council The Marine Stewardship Council (MSC) is a non-profit organisation which aims to set standards for sustainable fishing. Fisheries that wish to demonstrate they are well-managed and sustainable compared to the MSC's standards are assessed by a tea ...

certified that the fishery for Greenland halibut was sustainable. Because Canada and Greenland share the offshore populations in the

Davis Strait The Davis Strait (Danish language, Danish: ''Davisstrædet'') is a southern arm of the Arctic Ocean that lies north of the Labrador Sea. It lies between mid-western Greenland and Baffin Island in Nunavut, Canada. To the north is Baffin Bay. The ...

–

Baffin Bay Baffin Bay (Inuktitut: ''Saknirutiak Imanga''; ; ; ), located between Baffin Island and the west coast of Greenland, is defined by the International Hydrographic Organization as a marginal sea of the Arctic Ocean. It is sometimes considered a s ...

region in between them, the two have shared the fishing quota and follow the same guidelines in this region. Offshore populations in this region are healthy, stable and well-managed, but in more coastal areas some populations have fallen due to overfishing, although they do get a regular input of young fish from the stable offshore populations. Deals on fishing quotas for offshore fishing for Greenland halibut and other species have also been reached between Greenland, the Faroe Islands, Norway, and Russia. Among well-monitored populations, the ones in the East Greenland–Iceland region (i.e., Greenland Sea, Denmark Strait and nearby) experienced the greatest decline since the 1970s. In 2019, the parties agreed on a reduction of fishing for Greenland halibut in the Greenland Sea region, following recommendations by biologists. In some inshore waters of Greenland, fishing quotas for Greenland halibut have been temporarily raised several times, contrary to recommendations by fisheries biologists, and leading to recommendations of a clearer separation of decisions on quotas and the Greenlandic Government (decisions not fully left to Greenland's Fisheries Commission). A smaller fishery for the species also exists in the

Gulf of Alaska The Gulf of Alaska ( Tlingit: ''Yéil T'ooch’'') is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the ...

(where relatively uncommon) and the

Bering Sea The Bering Sea ( , ; rus, Бе́рингово мо́ре, r=Béringovo móre, p=ˈbʲerʲɪnɡəvə ˈmorʲe) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasse ...

region (where more common), and these populations are not overfished. The oil-rich, soft meat is regarded as good, but inferior to that of the

Atlantic halibut The Atlantic halibut (''Hippoglossus hippoglossus'') is a flatfish of the family Pleuronectidae. They are demersal fish living on or near sand, gravel or clay bottoms at depths of between . The halibut is among the largest Teleostei, teleost (bon ...

and European

. Traditionally, it was salted, but today it is mostly smoked or frozen, and the primary market is in East Asia, where it is regarded as a delicacy. However, because of the thick skin, high fat content, and low meat yield, as much as one-third of the fish can be lost in production. In Greenland, the remains are often used as food for the

sled dog A sled dog is a dog trained and used to pull a land vehicle in Dog harness, harness, most commonly a Dog sled, sled over snow. Sled dogs have been used in the Arctic for at least 8,000 years and, along with watercraft, were the only transpor ...

s ( Greenland dogs).

References

External links

* * {{Authority control

Greenland halibut The Greenland halibut or Greenland turbot (''Reinhardtius hippoglossoides'') belongs to the family Pleuronectidae (the right-eye flounders), and is the monotypic, only species of the genus ''Reinhardtius''. It is a predatory fish that mostly rang ...

Fish of Greenland Commercial fish Fish of the Arctic Ocean Fish of the North Atlantic

Taxa named by Johann Julius Walbaum Taxobox binomials not recognized by IUCN