Arctogadus glacialis

Arctogadus glacialis, known also with ambiguous common names Arctic cod[1][2] and polar cod,[1][3] is an Arctic species of fish in the cod family Gadidae, related to the true cod (genus Gadus). Arctogadus glacialis is found in icy water. They grow to about 30 cm long, and are favorite food of narwhals and other arctic whales.

Arctogadus glacialis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Gadiformes
Family: Gadidae
Genus: Arctogadus
Dryagin, 1932
Species:
A. glacialis
Binomial name
Arctogadus glacialis
Synonyms

Arctogadus borisovi Dryagin, 1932
Gadus glacialis W. K. H. Peters, 1872
Phocaegadus megalops Jensen, 1948

Common names and taxonomy

The common names "Arctic cod" and "polar cod" can refer to either Arctogadus glacialis or Boreogadus saida, and "Arctic cod" may also refer to Eleginus nawaga.[4]

Another Arctic gadid, the East Siberian cod (Arctogadus borisovi), was until recently considered the closest relative of A. glacialis. It has, however, been found not to be distinct from A. glacialis, and should be included in this species. According to this result, Arctogadus is a monotypic genus. However, Arctogadus is a close relative of Boreogadus, and should perhaps be included in that genus.[5]

Appearance

Arctic cod is completely white in appearance and has been cited to grow up to 32.5 cm (12.8 in) in total length. It has been distinguished from other cod species by its lack of the chin barbel. Populations of Arctic cod previously referred to the East Siberian cod however do have a chin barbel and grow up to 50–60 cm length.[5][6]

Distribution

The Arctic cod is widely distributed in the western part of the Arctic basin and the northwest and northeast coasts of Greenland. Its range is between 85° and 72°N latitude. Arctic cod can be found at depths of up to 1000 m, and frequently under ice.

Fish earlier attributed to the East Siberian cod are found off the western half of the Canadian coast and the coasts of Siberia and also off the northern and southern coasts of Greenland. The fish lives close to the sea floor at depths of 15 to 40 m, but it sometimes enters estuaries, and may also be found under pack ice.

The species is of minor commercial value.

Diet

A. glacialis in an ice-free area off northeastern Greenland were found to feed almost exclusively on pelagic prey (primarily copepods, amphipods, and mysids).[7]

References

  1. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2012). "Arctogadus glacialis" in FishBase. April 2012 version.
  2. ^ Gadiform fishes of the World (Order Gadiformes) An annotated and illustrated catalogue of Cods, Hakes, Grenadiers and other gadiform fishes known to date. FAO Fisheries Synopsis No. 125, Volume 10. 1990.
  3. ^ Polar Cod University of Guelph.
  4. ^ Froese, R.; D. Pauly., eds. (2013). "FishBase. World Wide Web electronic publication. www.fishbase.org, version (10/2013)". Retrieved 28 November 2013.
  5. ^ a b Jordan, AD; Møller, PR; Nielsen, JG (2003). "Revision of the Arctic cod genus Arctogadus". Journal of Fish Biology. 62: 1339–1352. CiteSeerX 10.1.1.1.3927. doi:10.1007/s00300-001-0348-5.
  6. ^ Toothed cod, Arctogadus borisovi Canada's Polar Life Portal, University of Guelph (2002)
  7. ^ Süfke, Lis; Piepenburg, Dieter; von Dorrien, Christian F. (1998). "Body size, sex ratio and diet composition of Arctogadus glacialis (Peters, 1874) (Pisces: Gadidae) in the Northeast Water Polynya (Greenland)". Polar Biology. 20: 357–363. doi:10.1007/s003000050314.
Beaufort Sea

The Beaufort Sea (French: Mer de Beaufort) is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, and west of Canada's Arctic islands. The sea is named after Sir Francis Beaufort, a hydrographer. The Mackenzie River, the longest in Canada, empties into the Canadian part of the Beaufort Sea west of Tuktoyaktuk, which is one of the few permanent settlements on the sea shores.

The sea, characterized by severe climate, is frozen over most of the year. Historically, only a narrow pass up to 100 km (62 mi) opened in August–September near its shores, but recently due to climate change in the Arctic the ice-free area in late summer has greatly enlarged. Claims that the seacoast was populated about 30,000 years ago have been largely discredited (see below); present population density is very low. The sea contains significant resources of petroleum and natural gas under its shelf, such as the Amauligak field. They were discovered in the period between the 1950s and 1980s, and their exploration became the major human activity in the area since the 1980s. The traditional occupations of fishery and whale and seal hunting are practiced only locally, and have no commercial significance. As a result, the sea hosts one of the largest colonies of beluga whales, and there is no sign of overfishing. To prevent overfishing in its waters, the US adopted precautionary commercial fisheries management plan in August 2009. In April 2011 the Canadian government signed a memorandum of understanding with the Inuvialuit as a first step in developing a larger ocean management plan. The Canadian government announced in October 2014 that no new commercial fisheries in the Beaufort Sea will be considered until research has shown sustainable stocks that would be made available to Inuvialuit first.The Canadian government has set a new block of the Beaufort Sea off the Parry Peninsula in the Amundsen as a Marine Protected Area (MPA). The protected area is set to protect species and habits for the Inuvialuit community.

Boreogadus saida

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

B. saida has a slender body, a deeply forked tail, a projecting mouth, and a small whisker on its chin. It is plainly coloured with brownish spots and a silvery body. It grows to a length of 40 cm (16 in). This species is found further north than any other fish (beyond 84°N) with a distribution spanning the Arctic seas off northern Russia, Alaska, Canada, and Greenland.

This fish is most commonly found at the water's surface, but is also known to travel at depths greater than 900 m. The polar cod is known to frequent river mouths. It is a hardy fish that survives best at temperatures of 0–4 °C, but may tolerate colder temperatures owing to the presence of antifreeze protein compounds in its blood. They group in large schools in ice-free waters.

B. saida feeds on plankton and krill. It is in turn the primary food source for narwhals, belugas, ringed seals, and seabirds. They are fished commercially in Russia.

Cod

Cod is the common name for the demersal fish genus Gadus, belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and some species suggested to belong to genus Gadus are not called cod (the Alaska pollock).

The two most common species of cod are the Atlantic cod (Gadus morhua), which lives in the colder waters and deeper sea regions throughout the North Atlantic, and the Pacific cod (Gadus macrocephalus), found in both eastern and western regions of the northern Pacific. Gadus morhua was named by Linnaeus in 1758. (However, G. morhua callarias, a low-salinity, nonmigratory race restricted to parts of the Baltic, was originally described as Gadus callarias by Linnaeus.)

Cod is popular as a food with a mild flavour and a dense, flaky, white flesh. Cod livers are processed to make cod liver oil, an important source of vitamin A, vitamin D, vitamin E, and omega-3 fatty acids (EPA and DHA). Young Atlantic cod or haddock prepared in strips for cooking is called scrod. In the United Kingdom, Atlantic cod is one of the most common ingredients in fish and chips, along with haddock and plaice.

East Siberian cod

The East Siberian cod (Arctogadus borisovi) also known as the toothed cod, is an Arctic fish closely similar to the Arctic cod Arctogadus glacialis and also related to true cods (genus Gadus). It has been differentiated in appearance from the Arctic cod by having pronounced chin barbel. Their sides and back are dark olive and the belly are light grey with dark spots. They may grow up to 60 cm.Fishes attributed to East Siberian cod are found off the western half of the Canadian coast and the coasts of Siberia and also off northern and southern coasts of Greenland. The fish prefers living close to the sea floor at depths of 15 to 40 m, but it sometimes enters estuaries. They may also be found under pack ice. They are of little economic value.Newer research, based on both morphological and mitochondrial DNA data, has however concluded that the East Siberian cod is not a distinct species from the Arctic cod, but the genus Arctogadus comprises just a single species i.e. the Arctic cod Arctogadus glacialis.

Frozen Planet

Frozen Planet is a 2011 British nature documentary series, co-produced by the BBC and The Open University. It was filmed by the BBC Natural History Unit. The production team, which includes executive producer Alastair Fothergill and series producer Vanessa Berlowitz, were previously responsible for the award-winning series The Blue Planet (2001) and Planet Earth (2006), and Frozen Planet is billed as a sequel of sorts. David Attenborough returns as narrator. It is distributed under licence by the BBC in other countries, Discovery Channel for North America, ZDF for Germany, Antena 3 for Spain and Skai TV for Greece.The seven-part series focuses on life and the environment in both the Arctic and Antarctic. The production team were keen to film a comprehensive record of the natural history of the polar regions because climate change is affecting landforms such as glaciers, ice shelves, and the extent of sea ice. The film was met with critical acclaim and holds a Metacritic score of 90/100.Whilst the series was broadcast in full in the UK, the BBC chose to make the series' seventh episode, which focuses on climate change, optional for syndication in order to aid sales of the show in countries where the issue is politically sensitive. The US Discovery Channel originally announced that they would air only the first six episodes of the show, but they later added the seventh episode to their schedule.In 2012, the US broadcast won four Emmy Awards, including Outstanding Nonfiction Series. A sequel titled Frozen Planet II is currently announced and planned to air in 2021.

Gadimyxa arctica

Gadimyxa arctica is a species of parasitic myxozoan. Together with G. atlantica and G. sphaerica, they infect Gadus morhua and Arctogadus glacialis by developing coelozoically in bisporic plasmodia in their urinary systems. These 3 species' spores exhibit two morphological forms: wide and subspherical, being both types bilaterally symmetrical along the suture line. The wide spores have a mean width ranging from 7.5-10μm, respectively, while the subspherical ones range from 5.3-8μm in mean width. The subspherical forms of Gadimyxa are similar to Ortholinea, differing in the development of the spores and in the arrangement of the polar capsules.

Gadimyxa atlantica

Gadimyxa atlantica is a species of parasitic myxozoan. Together with G. arctica and G. sphaerica, they infect Gadus morhua and Arctogadus glacialis by developing coelozoically in bisporic plasmodia in their urinary systems. These 3 species' spores exhibit two morphological forms: wide and subspherical, being both types bilaterally symmetrical along the suture line. The wide spores have a mean width ranging from 7.5-10μm, respectively, while the subspherical ones range from 5.3-8μm in mean width. The subspherical forms of Gadimyxa are similar to Ortholinea, differing in the development of the spores and in the arrangement of the polar capsules. Polychaetes Spirorbisspecies act as invertebrate hosts of G. atlantica.

Gadimyxa sphaerica

Gadimyxa sphaerica is a species of parasitic myxozoan. Together with G. arctica and G. atlantica, they infect Gadus morhua and Arctogadus glacialis by developing coelozoically in bisporic plasmodia in their urinary systems. These 3 species' spores exhibit two morphological forms: wide and subspherical, being both types bilaterally symmetrical along the suture line. The wide spores have a mean width ranging from 7.5-10μm, respectively, while the subspherical ones range from 5.3-8μm in mean width. The subspherical forms of Gadimyxa are similar to Ortholinea, differing in the development of the spores and in the arrangement of the polar capsules.

Narwhal

The narwhal (Monodon monoceros), or narwhale, is a medium-sized toothed whale that possesses a large "tusk" from a protruding canine tooth. It lives year-round in the Arctic waters around Greenland, Canada, and Russia. It is one of two living species of whale in the Monodontidae family, along with the beluga whale. The narwhal males are distinguished by a long, straight, helical tusk, which is an elongated upper left canine. The narwhal was one of many species described by Carl Linnaeus in his publication Systema Naturae in 1758.

Like the beluga, narwhals are medium-sized whales. For both sexes, excluding the male's tusk, the total body size can range from 3.95 to 5.5 m (13 to 18 ft); the males are slightly larger than the females. The average weight of an adult narwhal is 800 to 1,600 kg (1,760 to 3,530 lb). At around 11 to 13 years old, the males become sexually mature; females become sexually mature at about 5 to 8 years old. Narwhals do not have a dorsal fin, and their neck vertebrae are jointed like those of most other mammals, not fused as in dolphins and most whales.

Found primarily in Canadian Arctic and Greenlandic and Russian waters, the narwhal is a uniquely specialized Arctic predator. In winter, it feeds on benthic prey, mostly flatfish, under dense pack ice. During the summer, narwhals eat mostly Arctic cod and Greenland halibut, with other fish such as polar cod making up the remainder of their diet. Each year, they migrate from bays into the ocean as summer comes. In the winter, the male narwhals occasionally dive up to 1,500 m (4,920 ft) in depth, with dives lasting up to 25 minutes. Narwhals, like most toothed whales, communicate with "clicks", "whistles", and "knocks".

Narwhals can live up to 50 years. They are often killed by suffocation when the sea ice freezes over. Other causes of death, specifically among young whales, are starvation and predation by orcas. As previous estimates of the world narwhal population were below 50,000, narwhals are categorized by the International Union for Conservation of Nature (IUCN) as Nearly Threatened. More recent estimates list higher populations (upwards of 170,000), thus lowering the status to Least Concern. Narwhals have been harvested for hundreds of years by Inuit people in northern Canada and Greenland for meat and ivory, and a regulated subsistence hunt continues.

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