The Atlantic halibut (''Hippoglossus hippoglossus'') 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 ...

of the family Pleuronectidae. They are

demersal fish Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes (the demersal zone).Walrond Carl . "Coastal fish - Fish of the open sea floor"Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 They oc ...

living on or near sand, gravel or clay bottoms at depths of between . The halibut is among the largest

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

(bony) fish in the world, and is a

threatened species A threatened species is any species (including animals, plants and fungi) which is vulnerable to extinction in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensatio ...

owing to a slow rate of growth and

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 ...

. Halibut are strong swimmers and are able to migrate long distances. Halibut size is not age-specific, but rather tends to follow a cycle related to halibut (and therefore food) abundance. The native habitat of the Atlantic halibut is the temperate and arctic waters of the 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 ...

, from

Labrador Labrador () is a geographic and cultural region within the Canadian province of Newfoundland and Labrador. It is the primarily continental portion of the province and constitutes 71% of the province's area but is home to only 6% of its populatio ...

and

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

, the

Barents Sea The Barents Sea ( , also ; , ; ) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territorial waters.World Wildlife Fund, 2008. It was known earlier among Russi ...

and as far south as the

Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...

and

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

. It is the largest flatfish in the world, reaching lengths of up to and weights of . Its lifespan can reach 50 years. Age can be estimated by counting the rings laid down inside the otolith – a bony structure found inside the inner ear of the fish.

Description

The Atlantic halibut is a right-eyed flounder. It is flattened sideways and habitually lies on the left side of its body with both eyes migrating to the right side of its head during development. When the larvae are born, they start in the upright position like most other fish, having one eye on each side of the head. Once the larvae reach one inch in length, the left eye moves over the snout to the right side of the head. At the same time, the coloring on the left side begins to fade to white while the upper side of the fish is a uniformly dark chocolate, olive or slate color, and can be almost black. The end of the caudal fin is concave. Young fish are paler with more mottled coloration.Atlantic halibut
Gulf of Maine Research Institute: ''Fishery Bulletin'' (February, 2006) Male adults average about but can range to upwards of , rarely reaching . Females can get as large as .

Biology

Atlantic Halibut have a relatively slow growth rate and late onset of sexual maturity, with males attaining maturity at seven to eight years old, females at 10 to 11 years, and individuals averagely live around 25 to 30 years old. The oldest to have been caught was 50 years old. The Atlantic Halibut is a batch spawner where females lay anywhere from a few thousand to four million eggs (depending on the size and age of the fish, older females tend to lay only two million in one spawning period). Spawning occurs between December and April near the bottom of the ocean between . The egg size is around 3.0–3.8 mm and the larvae at time of hatching is 6.5 mm. Growth weight is dependent on the density, competition, and availability of food.

Habitat

This marine fish usually lives on the ocean floor at depths between , but it occasionally comes closer to the surface. The larvae are

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

, drifting relatively helplessly, but at around 4 cm, they migrate to the bottom. Young between the ages of two and four years live close to the shore, moving into deeper waters as they grow older.

Geographic distribution

Found in both the eastern and western portions of the North Atlantic. In the western Atlantic, found from southwestern Greenland and Labrador, Canada to Virginia in the USA. They are found in the eastern Atlantic around Iceland, the United Kingdom, Ireland and northern Europe to Russia. A map of the Atlantic Halibut's geographic distribution can be found on the Official Website of Massachusetts Division of Marine Fisheries. This demersal fish is found ranging from the latitude and longitude coordinates: 79°N - 36°N, 77°W - 55°E.

Role in ecosystem

The Atlantic halibut occupies a relatively high

trophic level The trophic level of an organism is the position it occupies in a food web. Within a food web, a food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the ...

in the

food chain A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...

Diet

The diet of the Atlantic halibut consists mainly of other fish, e.g.,

cod Cod (: cod) is the common name for the demersal fish genus ''Gadus'', belonging to the family (biology), family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gad ...

haddock The haddock (''Melanogrammus aeglefinus'') is a saltwater ray-finned fish from the Family (biology), family Gadidae, the true cods. It is the only species in the Monotypy, monotypic genus ''Melanogrammus''. It is found in the North Atlantic Oce ...

herring Herring are various species of forage fish, belonging to the Order (biology), order Clupeiformes. Herring often move in large Shoaling and schooling, schools around fishing banks and near the coast, found particularly in shallow, temperate wate ...

, pogge, sand eels and capelin, but it will also eat

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s, large

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s and other

benthos Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.seals, and are a

staple food A staple food, food staple, or simply staple, is a food that is eaten often and in such quantities that it constitutes a dominant portion of a standard diet for an individual or a population group, supplying a large fraction of energy needs an ...

of the Greenland shark. Killer whales are also natural predators of the halibut. Humans also consume halibut.

Commercial fishing of wild Atlantic halibut

The wild Atlantic halibut was formerly a very important food fish, but because of its slow rate of population growth, it is unable to recover quickly from overfishing, and the fishery has largely collapsed. Consequently, wild fish labelled as "halibut" are usually one of the other large flatfishes, including Pacific halibut, ''Hippoglossus stenolepis''. The most popular way to catch the Atlantic halibut is to use circle hooks that are baited with herring or other similar fish, fished from the bottom with cannonball weights of up to 36 ounces on a slider. The survival rate of caught and released halibut is 95 percent owing to the lack of having a swim bladder and not severely suffering from changes in water pressure (as long as the captured halibut is in excellent condition).

Farming

Because of its popularity as a food fish, Atlantic halibut has attracted investment in

fish farming Fish farming or pisciculture involves commercial breeding of fish, most often for food, in fish tanks or artificial enclosures such as fish ponds. It is a particular type of aquaculture, which is the controlled cultivation and harvesting of ...

. As of 2006, five countries—Canada, Norway, the UK, Iceland and Chile—were engaged in some form of Atlantic halibut

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. Nelu ...

production.

Conservation status

In 1996, the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

rated it as

Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

and placed it on its Red List. The Atlantic halibut is a US National Marine Fisheries Service Species of Concern, one of those species about which the U.S. Government's

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with Weather forecasting, forecasting weather, monitoring oceanic and atmospheric conditions, Hydrography, charting the seas, ...

has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S.

Endangered Species Act The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...

(ESA). The American Fisheries Society has classified the species as "Vulnerable". In 2010, Greenpeace International added the Atlantic halibut to its seafood red list of "fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."Greenpeace International Seafood Red list
The Atlantic halibut has been on the endangered species list since 1996 because of overfishing. It became commercially important during the 19th century because of the great demand for its meat and halibut being one of the largest flatfishes and essentially easy to capture.

References

External links

Video of larval Atlantic halibut reared in a tank and feeding on Artemia
{{Authority control

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 ...

Fish of the North Sea Fish of the North Atlantic Fauna of Atlantic Canada Fauna of the British Isles