Atlantic cod

The Atlantic cod (Gadus morhua) is a benthopelagic fish of the family Gadidae, widely consumed by humans. It is also commercially known as cod or codling.[2][n 1] Dry cod may be prepared as unsalted stockfish,[3][9][n 2] as cured salt cod or clipfish.[n 3]

In the western Atlantic Ocean, cod has a distribution north of Cape Hatteras, North Carolina, and around both coasts of Greenland and the Labrador Sea; in the eastern Atlantic, it is found from the Bay of Biscay north to the Arctic Ocean, including the Baltic Sea, the North Sea, Sea of the Hebrides,[13] areas around Iceland and the Barents Sea.

The largest individual on record was 1.8 m (6 ft) long and weighed 96 kg (211 lb), but usually the cod is between 61 cm (24 in) and 1.2 m (4 ft) long and weighs up to 40 kg (88 lb). There is generally no difference in weight or size between sexes of Atlantic Cod.[14][15]

Atlantic cod can live for 25 years, and usually attain sexual maturity between ages two and four,[16] although cod in the northeast Arctic can take as long as eight years to mature fully.[17] Colouring is brown or green, with spots on the dorsal side, shading to silver ventrally. A stripe along its lateral line (used to detect vibrations)[18] is clearly visible. Its habitat ranges from the shoreline down to the continental shelf.

Several cod stocks collapsed in the 1990s (declined by >95% of maximum historical biomass) and have failed to fully recover even with the cessation of fishing.[19] This absence of the apex predator has led to a trophic cascade in many areas.[19] Many other cod stocks remain at risk. The Atlantic cod is labelled vulnerable on the IUCN Red List of Threatened Species.[1]

Atlantic cod
Atlantic cod
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Gadiformes
Family: Gadidae
Genus: Gadus
Species:
G. morhua
Binomial name
Gadus morhua
Gadus morhua-Atlantic cod
Distribution of Atlantic cod
Synonyms
  • Asellus major
  • Gadus callarias Linnaeus, 1758
  • Gadus vertagus Walbaum, 1792
  • Gadus heteroglossus Walbaum, 1792
  • Gadus ruber Lacepède, 1803
  • Gadus arenosus Mitchill, 1815
  • Gadus rupestris Mitchill, 1815
  • Morhua vulgaris Fleming, 1828
  • Morhua punctatus Fleming, 1828
  • Gadus nanus Faber, 1829
  • Morrhua americana Storer, 1839

Lifecycle

Gravid female cod

Gravid female in captivity

Juveniles on a wreck in the North Sea

Gadus morhua (head)

Atlantic cod juvenile

Gadus morhua Cod-2b-Atlanterhavsparken-Norway

Adult

Adult cod form spawning aggregations from late winter to spring.[20][21] Females release their eggs in batches,[22] and males compete to fertilize them.[23][24][25] Fertilized eggs drift with ocean currents and develop into larvae ("fry"). Age of maturation varies between cod stocks, from ages two to four in the west Atlantic,[26] but as late as eight years in the northeast Arctic.[17] Cod can live for 13 years or more.[27]

Taxonomy

The Atlantic cod is one of three cod species in the genus Gadus along with Pacific cod and Greenland cod. A variety of fish species are colloquially known as cod, but they are not all classified within the Gadus, though some are in the Atlantic cod family, Gadidae.

Behaviour

Shoaling

Shoaling Atlantic cod on a wreck in the North Sea

Atlantic cod are a shoaling species and move in large, size-structured aggregations. Larger fish act as scouts and lead the shoal's direction, particularly during post spawning migrations inshore for feeding. Cod actively feed during migration and changes in shoal structure occur when food is encountered. Shoals are generally thought to be relatively leaderless, with all fish having equal status and an equal distribution of resources and benefits.[28] However, some studies suggest that leading fish gain certain feeding benefits. One study of a migrating Atlantic cod shoal showed significant variability in feeding habits based on size and position in the shoal. Larger scouts consumed a more variable, higher quantity of food, while trailing fish had less variable diets and consumed less food. Fish distribution throughout the shoal seems to be dictated by fish size, and ultimately, the smaller lagging fish likely benefit from shoaling because they are more successful in feeding in the shoal than they would be if migrating individually, due to social facilitation.[29]

Predation

Young Atlantic cod avoid larger cod and pouting (Trisopterus luscus) and crabs on a wreck in the southern North Sea

Atlantic cod are apex predators in the Baltic and adults are generally free from the concerns of predation.[30] Juvenile cod, however, may serve as prey for adult cod, which sometimes practice cannibalism. Juvenile cod make substrate decisions based on risk of predation. Substrates refer to different feeding and swimming environments. Without apparent risk of predation, juvenile cod demonstrated a preference for finer-grained substrates such as sand and gravel-pebble. However, in the presence of a predator, they preferred to seek safety in the space available between stones of a cobble substrate. Selection of cobble significantly reduces the risk of predation. Without access to cobble, the juvenile cod simply tries to escape a predator by fleeing.

Additionally, juvenile Atlantic cod vary their behaviour according to the foraging behaviour of predators. In the vicinity of a passive predator, cod behaviour changes very little. The juveniles prefer finer-grained substrates and otherwise avoid the safer kelp, steering clear of the predator. In contrast, in the presence of an actively foraging predator, juveniles are highly avoidant and hide in cobble or in kelp if cobble is unavailable.[31]

As apex predators, heavy fishing of cod in the 1990s and the collapse of American and Canadian cod stocks resulted in trophic cascades. Overfishing cod removed a significant predatory pressure on other Atlantic fish and crustacean species. Population-limiting effects on several species including American lobsters, crabs, and shrimp from cod predation have decreased significantly, and the abundance of these species and their increasing range serve as evidence of the Atlantic cod's role as a major predator rather than prey.[30]

Cod are cannibals and are eaten at various life stages by various other fishes, seals and whales.[32]

Swimming

Atlantic cod have been recorded to swim at speeds of a minimum of 2–5 cm/s (0.79–1.97 in/s) and a maximum of 21–54 cm/s (8.3–21.3 in/s) with a mean swimming speed of 9–17 cm/s (3.5–6.7 in/s). In one hour, cod have been recorded to cover a mean range of 99 to 226 m2 (1,070 to 2,430 sq ft). Swimming speed was higher during the day than at night. This is reflected in the fact that cod more actively search for food during the day. Cod likely modify their activity pattern according to the length of daylight, thus activity varies with time of year.[33]

Response to changing temperatures

Swimming and physiological behaviours change in response to fluctuations in water temperature. Respirometry experiments show that heart rates of Atlantic cod change drastically with changes in temperature of only a few degrees. A rise in water temperature causes marked increases in cod swimming activity. Cod typically avoid new temperature conditions, and the temperatures can dictate where they are distributed in water. They prefer to be deeper, in colder water layers during the day, and in shallower, warmer water layers at night. These fine-tuned behavioural changes to water temperature are driven by an effort to maintain homeostasis to preserve energy. This is demonstrated by the fact that a decrease of only 2.5 °C (5 °F) caused a highly costly increase in metabolic rate of 15 to 30%.[34]

Feeding and diet

Stomach sampling studies have discovered that small Atlantic cod feed primarily on crustaceans, while large Atlantic cod feed primarily on fish.[35] In certain regions, the main food source is decapods with fish as a complementary food item in the diet.[36] Wild Atlantic cod throughout the North Sea depend, to a large extent, on commercial fish species also used in fisheries, such as Atlantic mackerel, haddock, whiting, Atlantic herring, European plaice, and common sole, making fishery manipulation of cod significantly easier.[35] Ultimately, food selection by cod is affected by the food item size relative to their own size. However, providing for size, cod do exhibit food preference and are not simply driven by availability.[35]

Atlantic cod practice some cannibalism. In the southern North Sea, 1–2% (by weight) of stomach contents for cod larger than 10 cm (3.9 in) consisted of juvenile cod. In the northern North Sea, cannibalism was higher, at 10%.[35] Other reports of cannibalism have estimated as high as 56% of the diet consists of juvenile cod.[37]

Reproduction

Gadus morhua (High Arctic, Canada)
Atlantic cod in a High Arctic Lake in Canada. These cod resemble those of past Atlantic catches. Measuring 120–130 cm (47–53 in) long and weighing between 20 and 26 kg (44 and 57 lb), it is easy to see that today's 41–51 cm (16–20 in) commercially caught cod are less than half this size.

Atlantic cod reproduce during a 1- to 2-month spawning season annually. Males and females aggregate in spawning schools and each spawning season yields an average of 8.3 egg batches. Females release gametes in a ventral mount, and males then fertilize the released eggs. Evidence suggests male sound production and other sexually selected characteristics allow female cod to actively choose a spawning partner. Males also exhibit aggressive interactions for access to females.[38] Based on behavioral observations of cod, that cod mating systems resemble those of lekking species, which is characterized by males aggregating and establishing dominance hierarchies, at which point females may visit and choose a spawning partner based on status and sexual characteristics.[37]

Cod males experience reproductive hierarchies based on size. Larger cod males are ultimately more successful in mating and produce the largest proportion of offspring in a population. However, cod males do experience high levels of sperm competition. In 75% of examined spawning in one study, sperm from multiple males contributed to offspring. As a result of high competition and unpredictable paternity, males may engage in varied mating strategies and may invest in courtship or may simply ejaculate with other spawning couples. Spawning success also varies according to male size relative to female size. Males that are significantly smaller than females demonstrate significantly lower success rates relative to males that are larger than females.[39]

Parasites

Atlantic cod act as intermediate, paratenic, or definitive hosts to a large number of parasite species: 107 taxa listed by Hemmingsen and MacKenzie (2001)[40] and seven new records by Perdiguero-Alonso et al. (2008).[40] The predominant groups of cod parasites in the northeast Atlantic were trematodes (19 species) and nematodes (13 species), including larval anisakids, which comprised 58.2% of the total number of individuals.[40] Parasites of Atlantic cod include copepods, digeneans, monogeneans, acanthocephalans, cestodes, nematodes, myxozoans, and protozoans.[40]

Fisheries

Total harvest of Atlantic cod 1950-2012
Capture of Northeast and Northwest Atlantic cod 1950–2012, (FAO)

Northwest Atlantic cod

The Northwest Atlantic cod has been regarded as heavily overfished throughout its range, resulting in a crash in the fishery in the United States and Canada during the early 1990s.

Newfoundland's northern cod fishery can be traced back to the 16th century. On average, about 300,000 t (300,000 long tons; 330,000 short tons) of cod were landed annually until the 1960s, when advances in technology enabled factory trawlers to take larger catches. By 1968, landings for the fish peaked at 800,000 t (790,000 long tons; 880,000 short tons) before a gradual decline set in. With the reopening of the limited cod fisheries in 2006, nearly 2,700 t (2,700 long tons; 3,000 short tons) of cod were hauled in. In 2007, offshore cod stocks were estimated at 1% of what they were in 1977.[41]

Technologies that contributed to the collapse of Atlantic cod include engine-powered vessels and frozen food compartments aboard ships. Engine-powered vessels had larger nets, greater range, and better navigation. The capacity to catch fish became limitless. In addition, sonar technology gave an edge to detecting and catching fish. Sonar was originally developed during World War II to locate enemy submarines, but was later applied to locating schools of fish. These new technologies, as well as bottom trawlers that destroyed entire ecosystems, contributed to the collapse of Atlantic cod. They were vastly different from old techniques used, such as hand lines and long lines.[42]

The fishery has only recently begun to recover, and may never fully recover because of a possibly stable change in the food chain. Atlantic cod was a top-tier predator, along with haddock, flounder and hake, feeding upon smaller prey, such as herring, capelin, shrimp, and snow crab.[19] With the large predatory fish removed, their prey have had population explosions and have become the top predators, affecting the survival rates of cod eggs and fry.

Atlantic cod under a shipwreck
Atlantic cod are demersal fish—they prefer sea bottoms with coarse sediments.[43]

In the winter of 2011–2012, the cod fishery succeeded in convincing NOAA to postpone for one year the planned 82% reduction in catch limits. Instead, the limit was reduced by 22%. The fishery brought in $15.8 million in 2010, coming second behind Georges Bank haddock among the region's 20 regulated bottom-dwelling groundfish. Data released in 2011 indicated that even closing the fishery would not allow populations to rebound by 2014 to levels required under federal law. Restrictions on cod effectively limit fishing on other groundfish species with which the cod swim, such as flounder and haddock.[44]

Cod populations or stocks can differ significantly both in appearance and biology. For instance, the cod stocks of the Baltic Sea are adapted to low-salinity water. Organisations such as the Northwest Atlantic Fishery Organization (NAFO) and ICES divide the cod into management units or stocks; however, these units are not always biologically distinguishable stocks. Some major stocks/management units on the Canadian/US shelf are the Southern Labrador-Eastern Newfoundland stock (NAFO divisions 2J3KL), the Northern Gulf of St. Lawrence stock (NAFO divisions 3Pn4RS), the Northern Scotian Shelf stock (NAFO divisions 4VsW), which all lie in Canadian waters, and the Georges Bank and Gulf of Maine stocks in United States waters. In the European Atlantic, the numerous separate stocks are on the shelves of Iceland, the coast of Norway, the Barents Sea, the Faroe Islands, off western Scotland, the North Sea, the Irish Sea, the Celtic Sea, and the Baltic Sea.

Northeast Atlantic cod

NEAcodBiomass
Estimated biomass of the Northeast Arctic cod stock for the period 1946–2012, in million tons: Light blue bars represent the immature fraction of the stock, while the darker blue bars represent the spawning biomass.[45]

The Northeast Atlantic has the world's largest population of cod. By far, the largest part of this population is the Northeast Arctic cod, as it is labelled by the ICES, or the Arcto-Norwegian cod stock, also referred to as skrei, a Norwegian name meaning something like "the wanderer", distinguishing it from coastal cod. The Northeast Arctic cod is found in the Barents Sea area. This stock spawns in March and April along the Norwegian coast, about 40% around the Lofoten archipelago. Newly hatched larvae drift northwards with the coastal current while feeding on larval copepods. By summer, the young cod reach the Barents Sea, where they stay for the rest of their lives, until their spawning migration. As the cod grow, they feed on krill and other small crustaceans and fish. Adult cod primarily feed on fish such as capelin and herring. The northeast Arctic cod also show cannibalistic behaviour. Estimated stock size was 2,260,000 t (2,220,000 long tons; 2,490,000 short tons) in 2008.

The North Sea cod stock is primarily fished by European Union member states and Norway. In 1999, the catch was divided among Denmark (31%), Scotland (25%), the rest of the United Kingdom (12%), the Netherlands (10%), Belgium, Germany and Norway (17%). In the 1970s, the annual catch rose to between 200,000 and 300,000 t (200,000 and 300,000 long tons; 220,000 and 330,000 short tons). Due to concerns about overfishing, catch quotas were repeatedly reduced in the 1980s and 1990s. In 2003, ICES stated a high risk existed of stock collapse if then current exploitation levels continued, and recommended a moratorium on catching Atlantic cod in the North Sea during 2004. However, agriculture and fisheries ministers from the Council of the European Union endorsed the EU/Norway Agreement and set the total allowable catch at 27,300 t (26,900 long tons; 30,100 short tons).[46] Seafood sustainability guides, such as the Monterey Bay Aquarium's Seafood Watch, often recommend environmentally conscious customers not purchase Atlantic cod.

The stock of Northeast Arctic cod was more than four million tons following World War II, but declined to a historic minimum of 740,000 t (730,000 long tons; 820,000 short tons) in 1983. The catch reached a historic maximum of 1,343,000 t (1,322,000 long tons; 1,480,000 short tons) in 1956, and bottomed out at 212,000 t (209,000 long tons; 234,000 short tons) in 1990. Since 2000, the spawning stock has increased quite quickly, helped by low fishing pressure. The total catch in 2012 was 754,131 t (742,221 long tons; 831,287 short tons), the major fishers being Norway and Russia.[47]

Human consumption

Torskfilé (Gadus morhua) - Ystad-2017
Atlantic cod as food

See also

Notes

  1. ^ During the Middle Ages, Middle English used many, many forms of mulvel, milvel, melvel, and milwell to refer to fresh, large cod[3] and morhwell to refer to smaller ones.[4] Fresh cod was also known as the common cod,[5][6] the Scotch cod,[7] and as the green fish or greenfish.[8] "Greenfish", however, now more often refers to other fish. Similarly, "codling" may refer to various morids.
  2. ^ In South Africa, however, "stockfish" refers to the local hake (Merluccius capensis).
  3. ^ Former names for salted cod include cured cod,[10] ling,[10][11][12] and haberdine.[2][12] Freshly-salted cod was known as green cod, white cod, corefish,[10] coursfish,[9] and green fish or greenfish.[8] "Green cod" may also refer to the saithe (Pollachius virens), pollack (P. pollachius), or uncommonly to the lingcod (O. elongatus).[8] "Ling" now more often refers to other fish, particularly the common ling (Molva molva).[11]

References

This article incorporates CC BY-2.0 text from the reference.[40]

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  2. ^ a b Atlantic Cod Archived 2009-12-25 at the Wayback Machine. Seafood Portal.
  3. ^ a b Oxford English Dictionary, 3rd ed. "milwell, n." Oxford University Press (Oxford), 2002.
  4. ^ Oxford English Dictionary, 3rd ed. "morhwell, n." Oxford University Press (Oxford), 2002.
  5. ^ Richardson, John (1836), "93. Gadus Morrhua. (Auct.) Common Cod-fish", Fauna Boreali-Americana; or the Zoology of the Northern Parts of British America: Containing Descriptions of the Objects of Natural History Collected on the Late Northern Land Expeditions under Command of Captain Sir John Franklin, R.N., Vol. III: The Fish, London: Richard Bentley, pp. 242–245.
  6. ^ Grant, Francis William (1836), "Parish of Banff (Presbytery of Fordyce, Synod of Aberdeen.)", The New Statistical Account of Scotland, Vol. XI, Edinburgh: William Blackwood & Sons, p. 12.
  7. ^ Riley, Henry Thomas, ed. (1860), "Glossary of Mediæval Latin", Munimenta Gildallæ Londoniensis: Liber Albus, Liber Custumarum, et Liber Horn, Vol. II, Part II., containing Liber Custumarum, with extracts from the Cottonian MS Claudius, D. II., London: Eyre & Spottiswoode for Her Majesty's Stationery Office, p. 816.
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  25. ^ D. Bekkevold; M. M. Hansen & V. Loeschcke (2002). "Male reproductive competition in spawning aggregations of cod". Molecular Ecology. 11 (1): 91–102. doi:10.1046/j.0962-1083.2001.01424.x. PMID 11903907.
  26. ^ O'Brien, L., J. Burnett, and R. K. Mayo. (1993) Maturation of Nineteen Species of Finfish off the Northeast Coast of the United States, 1985–1990. NOAA Tech. Report. NMFS 113, 66 p.
  27. ^ ICES (2007), Arctic Fisheries Working Group Report, Section 03, International Council for the Exploration of the Sea Archived 2011-06-12 at the Wayback Machine (accessed 2008/12/11)
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  32. ^ Coad Brian W. (1995), Encyclopedia of Canadian Fishes, p. 52
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  39. ^ Bekkevold, D; Hansen, M M; Loeschcke, V (1 January 2002). "Male reproductive competition in spawning aggregations of cod (Gadus morhua, L.)". Molecular Ecology. 11 (1): 91–102. doi:10.1046/j.0962-1083.2001.01424.x. PMID 11903907.
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External links

Alaska pollock

The Alaska pollock or walleye pollock (Gadus chalcogrammus) is a marine fish species of the cod family Gadidae. It is a semipelagic schooling fish widely distributed in the North Pacific with largest concentrations found in the eastern Bering Sea.While belonging to the same family as the Atlantic pollock, the Alaska pollock is not a member of the same genus, Pollachius. Alaska pollock was long put in its own genus, Theragra and classified as Theragra chalcogramma, but more recent research has shown it is rather closely related to the Atlantic cod and should be moved back to genus Gadus, in which it was originally described. Furthermore, Norwegian pollock (Theragra finnmarchica), a rare fish of Norwegian waters, is likely the same species as the Alaska pollock.

Back Bay, New Brunswick

Back Bay is an unincorporated settlement in New Brunswick, Canada on the shore of a bay of the same name in the Bay of Fundy.

Integrated multi-trophic aquaculture at the site includes Atlantic cod, saccharina latissima (sugar kelp), alaria esculenta (winged kelp), blue mussels, and Atlantic salmon, produced in a collaborative project by the University of New Brunswick and Fisheries and Oceans Canada, and Cooke Aquaculture.In 1866 Back Bay was a fishing and farming community, with a population of about 30 resident families. The population had grown by 1871 to approximately 200 people. And in 1898 Back Bay was a port of entry with one post office, two stores, two churches and a population of 300.It is the site of the Back Bay Elementary School.

Caligus curtus

Caligus curtus is a sea louse species and a parasite of the Atlantic cod.

Canadian Atlantic Cod

Canadian Atlantic Cod or Gadus morhua, are cold water fish, which weigh 2 to 3 kg in the wild [6]. Atlantic Cod were originally found in the Atlantic Ocean, along the borders of both Canada and England and all the way down to the southern United States. Heavy fishing in these areas, in the late 1800s and early 1900s led to a massive decline in Cod population.[7] Today, they are grown in onshore temperature controlled, seawater tanks as eggs and eventually taken to sea cages when more developed.[2] The majority of these artificial environments found in Canada, are located in British Columbia, New Brunswick and as well as Newfoundland and Labrador. It takes about 6 months for the fish to hatch followed by a 2 to 3-year period for them to reach their maximize selling size, therefore taking an average of 3 years for a fish to reach market which is 3 to 5 kg.[2] According to Fisheries and Oceans Canada (2014) in 2013 1 kg of Cod was being sold for on average $7.12 fish.[4] Overall, Atlantic Cod are a relatively recent farmed fish, however are gaining popularity due to price, nutrition and feed to growth ratio.

Capelin

The capelin or caplin (Mallotus villosus) is a small forage fish of the smelt family found in the North Atlantic, North Pacific, and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat a great deal of krill and other crustaceans. Among others, whales, seals, Atlantic cod, Atlantic mackerel, squid, and seabirds prey on capelin, in particular during the spawning season of the capelin while it migrates southwards. Capelin spawn on sand and gravel bottoms or sandy beaches at the age of 2–6 years, and have an extremely high mortality rate on the beaches after spawning, for males close to 100%.

Males reach 20 cm (8 in) in length, while females are up to 25.2 cm (10 in) long. They are olive-colored dorsally, shading to silver on sides. Males have a translucent ridge on both sides of their bodies. The ventral aspects of the males iridesce reddish at the time of spawn.

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.

Cod fisheries

Cod fisheries are fisheries for cod. Cod is the common name for fish of the genus Gadus, belonging to the family Gadidae, and this article is confined to the three species that belong to this genus: the Atlantic cod, the Pacific cod and the Greenland cod.

Cod are demersal fish found in huge schools confined to temperate waters in the northern hemisphere. Atlantic cod are found in the colder waters and deeper sea regions throughout the Northern Atlantic. The Pacific cod is found in both eastern and western regions of the Pacific. Atlantic cod can grow to 2 metres (6.6 ft) in length. Its average weight is 5 to 12 kilograms (11 to 26 lb), but specimens weighing up to 100 kilograms (220 lb) have been recorded. Pacific cod are smaller, and may grow up to 49 centimetres (19 in) and weigh up to 15 kilograms (33 lb). Cod feed on mollusks, crabs, starfish, worms, squid, and small fish. Some migrate south in winter to spawn. A large female lays up to five million eggs in mid-ocean, a very small number of which survive.

Cod has been an important economic commodity in international markets since the Viking period (around A.D. 800). Cod are popular as a food fish with a mild flavour, low fat content and a dense white flesh. When cooked, cod is moist and flaky. Cod livers are processed to make cod liver oil. Cod are currently at risk from overfishing.

Collapse of the Atlantic northwest cod fishery

In 1992 the Canadian Federal Minister of Fisheries and Oceans, John Crosbie, declared a moratorium on the Northern Cod fishery, which for the preceding 500 years had largely shaped the lives and communities of Canada's eastern coast. Fishing societies interplay with the resources which they depend on: fisheries transform the ecosystem, which pushes the fishery and society to adapt. In the summer of 1992, when the Northern Cod biomass fell to 1% of earlier levels, Canada's federal government saw that this relationship had been pushed to the breaking point, and declared a moratorium, ending the region's 500-year run with the Northern Cod.

Observations on the reduced number and size of cod, and concerns of fishermen and marine biologists was offered, but generally ignored in favour of the uncertain science and harmful federal policies of Canada's Department of Fisheries and Oceans until the undeniable complete collapse of the fishery. According to any reasonable analysis, the collapse was first due to massive overfishing. Second, the dependence for maintenance of the fishery itself on the nutrient cycle that was being disrupted by removal of megatons of biomass from a closed system resulted in the starvation of the residual fish. Academics have highlighted these following four contributing factors in the eventual collapse of the cod fishery.

Cusk (fish)

The cusk or tusk (Brosme brosme) is a North Atlantic cod-like fish in the ling family Lotidae. It is the only species in the genus Brosme. Other common names include brismak, brosmius, torsk and moonfish.

Francisella piscicida

Francisella piscicida is a bacterium present in Atlantic cod. It is a serious disease present in Norwegian cod farming.

Gadiformes

Gadiformes are an order of ray-finned fish, also called the Anacanthini, that includes the cod and its allies. Many major food fish are in this order. They are found in marine waters throughout the world and the vast majority of the species are found in temperate or colder regions (tropical species are typically deep-water). A few species may enter estuaries but only one, the burbot (Lota lota), is a freshwater fish.

Common characteristics include the positioning of the pelvic fins (if present), below or in front of the pectoral fins. Gadiformes are physoclists, which means their gas bladders do not have a pneumatic duct. The fins are spineless. Gadiform fish range in size from the codlets, which may be as small as 7 cm (2.8 in) in adult length, to the Atlantic cod, Gadus morhua, which reaches up to 2 m (6.6 ft).

Gadus

Gadus is a genus of demersal fish in the family Gadidae, commonly known as cod, although there are additional cod species in other genera. The best known member of the genus is the Atlantic cod.

Until recently, three species in the genus were recognized. Modern taxonomy also includes a fourth one, the Alaska pollock (Gadus (=Theragra) chalcogrammus), which is not separate from the Norway pollock. Furthermore, Greenland cod (G. ogac) is no longer considered a distinct species but rather a subspecies of Pacific cod (G. macrocephalus).

Grand Banks of Newfoundland

The Grand Banks of Newfoundland are a group of underwater plateaus south-east of Newfoundland on the North American continental shelf. These areas are relatively shallow, ranging from 15 to 91 metres (50 to 300 ft) in depth. The cold Labrador Current mixes with the warm waters of the Gulf Stream here, often causing extreme foggy conditions.

The mixing of these waters and the shape of the ocean bottom lifts nutrients to the surface. These conditions helped to create one of the richest fishing grounds in the world. Fish species include Atlantic cod, swordfish, haddock and capelin; shellfish include scallop and lobster. The area also supports large colonies of seabirds such as northern gannets, shear waters and sea ducks and various sea mammals such as seals, dolphins and whales.

Overfishing in the late 20th century caused the collapse of several species, particularly cod, leading to the closure of the Canadian Grand Banks fishery in 1993.

Greenland cod

The Greenland cod (Gadus ogac), commonly known also as ogac, is a species of ray-finned fish in the cod family, Gadidae. Genetic analysis has shown that it may be the same species as the Pacific cod (Gadus macrocephalus). It is a bottom-dwelling fish and is found on the continental shelf in the Arctic Ocean and northwestern Atlantic Ocean, its range extending from Alaska to West Greenland, then southwards along the Canadian coast to the Gulf of St. Lawrence and Cape Breton Island. It is a commercially harvested food fish, but landings have been greatly reduced in recent years.

History of Canada (1992–present)

The history of Canada (1992–present) refers to the period immediately following the end of the Cold War, until present.

List of diseases and parasites in cod

Cod and related species in the family Gadidae are susceptible to a variety of diseases and parasites.

List of fish and chip restaurants

This is a list of notable fish and chip restaurants which are renowned for, or whose main dish is, fish and chips. Fish and chips is a hot dish of English origin, consisting of battered fish, commonly Atlantic cod or haddock and deep-fried chips. It is a common take-away food. A common side dish is mushy peas.

A fish and chip shop, colloquially known as a 'chippy' in the UK and 'chipper' in Ireland, is an outlet that predominantly sells the English dish of fish and chips. It is usually a takeaway operation, although some have limited seating facilities.

M74 syndrome

The M74 syndrome is a reproduction disorder of salmon (Salmo salar) feeding in the Baltic Sea. M74 manifests as offspring mortality during the yolk-sac fry phase. Before dying, the yolk-sac fry display typical symptoms.Thiamine (vitamin B1) deficiency in eggs is the immediate cause of M74 mortality. The deficiency can be prevented by thiamine treatments. For the first time Bulgarian research team opines that with M74 syndrome are affected also male gametes and worsened parameters of the spermograme. The use of Bulgarian semen protective media 49282, 49283 and 49397 for trout sperm fertility improving was proposed.The thiamine deficiency syndrome M74 is related to the fat and thiamine content of prey fish. The diet of Baltic salmon leads to thiamine deficiency in eggs and consequently to the mortality of yolk-sac fry: The main prey species of the Baltic salmon are sprat (Sprattus sprattus) and herring (Clupea harangus membras). Average fat content is greater in sprat than in herring. The fat content is highest and the thiamine concentration is lowest in the youngest sprat. The need for thiamine depends on the amount of fat in the diet. Thiamine deficiency in eggs results from an unbalanced diet abundant in fatty prey fish, such as young sprat, from which the supply of thiamine is insufficient in proportion to the supply of energy and unsaturated fatty acids for salmon.Relationships between fish stock changes in the Baltic Sea and the M74 syndrome: The M74 syndrome is connected to a weak Atlantic cod (Gadus morhua) stock and strong year classes of sprat in the Baltic Sea. Since the collapse, heavy fishing mortality as well as predation on cod eggs by sprat and food competition between sprat and young-of-the-year cod has inhibited cod recovery. Coincidentally with the decline in the cod stock since 1982, and following the consequent reduction in predation pressure, the sprat stock increased rapidly, and salmon therefore had more food. Salmon grew faster, resulting also in a high CF.

Whitefish (fisheries term)

Whitefish or white fish is a fisheries term for several species of demersal fish with fins, particularly Atlantic cod (Gadus morhua), whiting (Merluccius bilinearis), haddock (Melanogrammus aeglefinus), hake (Urophycis), pollock (Pollachius), and others. Whitefish (Coregonidae) is also the name of several species of Atlantic freshwater fish.

Whitefish live on or near the seafloor, and can be contrasted with the oily or pelagic fish which live in the water column away from the seafloor. Unlike oily fish, whitefish contain oils only in their liver, rather than in their gut, and can therefore be gutted as soon as they are caught, on board the ship. Whitefish have dry and white flesh.

Whitefish can be divided into benthopelagic fish (round fish which live near the sea bed, such as cod and coley) and benthic fish (which live on the sea bed, such as flatfish like plaice).

Whitefish is sometimes eaten straight but is often used reconstituted for fishsticks, gefilte fish, lutefisk, surimi (imitation crabmeat), etc. For centuries it was preserved by drying as stockfish and clipfish and traded as a world commodity. It is commonly used as the fish in the classic British dish of fish and chips.

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