Cod
2008/9 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and Fish
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 Atlantic cod, Gadus morhua
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Species in genus Gadus
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Cod is the common name for the genus Gadus of fish, belonging to the family Gadidae, and is also used in the common name of a variety of other fishes. Cod is a popular food fish with a mild flavor, low fat content and a dense white flesh that flakes easily. Cod livers are processed to make cod liver oil, an important source of Vitamin A, Vitamin D and omega-3 fatty acids ( EPA and DHA). Larger cod caught during spawning are sometimes called skrei. Young Atlantic cod or haddock prepared in strips for cooking is called scrod.
The Atlantic cod, which can change color at certain water depths, has two distinct colour phases: gray-green and reddish brown. Its average weight is 5 kg to 12 kg (10 lb to 25 lb), but specimens weighing up to 100 kg (200 lb) have been recorded. 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 midocean, a very small number of which survive.
The Pacific cod is found north of Oregon.
The tomcod resembles a young Atlantic cod with long, tapering ventral fins. It rarely exceeds 15 inches (37.5 cm) in length and lives close to shore. The pollock, and coalfish are related species found in cool waters of the Atlantic. Pollock have forked tails and pale lateral lines and grow to 1 m (3 ft) and 15 kg (30 lb). Some grow to 2 m (6 feet) in length.
Cod is moist and flaky when cooked and is white in colour. In the United Kingdom, Atlantic cod is one of the most common kinds of fish to be found in fish and chips, along with haddock and plaice. It is also well known for being largely consumed in Portugal and the Basque Country, where it is considered a treasure of the nation's cuisine.
Cod are currently at risk from overfishing.
Species in genus Gadus
At various times in the past, a very considerable number of species have been classified in this genus. However the great majority of them are now either classified in other genera, or have been recognized as simply forms of one of three species. Modern taxonomy, therefore, recognizes only three species in this genus:
- Atlantic cod, Gadus morhua
- Pacific cod, Gadus macrocephalus
- Greenland cod, Gadus ogac
All these species have a profusion of common names, most of them including the word "cod". Many common names have been used of more than one species, in different places or at different times.
Related species called cod
Cod forms part of the common name of many other fish no longer classified in the genus Gadus. Many of these are members of the family Gadidae, and several were formerly classified in genus Gadus; others are members of three related families within the order Gadiformes whose names include the word "cod": the morid cods, Moridae (100 or so species); the eel cods, Muraenolepididae (4 species); and the Eucla cod, Euclichthyidae (1 species). The tadpole cod family ( Ranicipitidae) has now been absorbed within Gadidae.
Species within the order Gadiformes that are commonly called cod include:
- Arctic cod Arctogadus glacialis
- East Siberian cod Arctogadus borisovi
- Eucla cod Euclichthys polynemus
- Pelagic cod Melanonus gracilis
- Polar cod Boreogadus saida
- Poor cod Trisopterus minutus
- Rock cod Lotella rhacina
- Saffron cod Eleginus gracilis
- Small-headed cod Lepidion microcephalus
- Tadpole cod Guttigadus globosus
Some other related fish have common names derived from "cod", such as codling, codlet or tomcod. ("Codling" is also used as a name for a young cod.)
Unrelated species called cod
However there are also fish commonly known as cod that are quite unrelated to the genus Gadus. Part of this confusion of names is market-driven. Since the decline in cod stocks has made the Atlantic cod harder to catch, cod replacements are marketed under names of the form "x cod", and culinary rather than phyletic similarity has governed the emergence of these names. A very large number of fish have thus been named as some kind of cod at some time. The following species, however, seem to have well established common names including the word "cod"; note that all are Southern Hemisphere species.
Perciformes
Fish of the order Perciformes that are commonly called "cod" include:
- Blue cod Parapercis colias
- Eastern freshwater cod Maccullochella ikei
- Mary River cod Maccullochella peelii mariensis
- Murray cod Maccullochella peelii peelii
- Sleepy cod Oxyeleotris lineolatus
- Trout cod Maccullochella macquariensis
- The cod icefish family, Nototheniidae, including:
- Antarctic cod Dissostichus mawsoni
- Black cod Paranotothenia microlepidota
- Maori cod Paranotothenia magellanica
Rock cod, reef cod, and coral cod
Almost all the fish known as coral cod, reef cod or rock cod are also in order Perciformes. Most are better known as groupers, and belong to the family Serranidae. Others belong to the Nototheniidiae. Two exceptions are the Australasian red rock cod, which belongs to a different order (see below), and the fish known simply as the rock cod also by soft cod in New Zealand, Lotella rhacina, which as noted above actually is related to the true cod (it is a morid cod).
Scorpaeniformes
From the order Scorpaeniformes:
- Ling cod Ophiodon elongatus
- Red rock cod Scorpaena papillosa
Ophidiiformes
The tadpole cod family, Ranicipitidae, and the Eucla cod family, Euclichthyidae, were formerly classified in the order Ophidiiformes, but are now grouped with the Gadiformes.
Species marketed as cod
Some fish that do not have "cod" in their names are sometimes sold as cod. Haddock and whiting belong in the same family, the Gadidae, as cod.
- Haddock Melanogrammus aeglefinus
- Whiting Merlangius merlangus
Identification
Classic cod shape, with three rounded dorsal and two anal fins. The pelvic fins are small with the first ray extended, and are set under the gill cover (i.e. the throat region), in front of the pectorals. The upper jaw extends over the lower jaw, which has a well developed chin barbel. Medium sized eyes, approximately the same as the length of the chin barbel. It has a distinct white lateral line running from the gill slit above the pectoral fin, to the base of the caudal or tail fin. The back tends to be a greenish to sandy brown, and showing extensive mottling especially towards the lighter sides and white belly. Dark brown colouration of the back and sides is not uncommon especially for individuals who have resided in rocky inshore regions.
Breeding
The cod population comprises a number of reasonably distinct stocks over its range. These include the Arcto-Norwegian, North Sea, Faroe, Iceland, East Greenland, West Greenland, Newfoundland, and Labrador stocks. There would seem to be little interchange between the stocks, although migrations to their individual breeding grounds may involve distances of 200 miles or more. Spawning occurs between January to April (March and April are the peak months), at a depth of 200 m in specific spawning grounds at water temperatures of between 4-6 °C. Around the UK, the major ones are associated with the Middle to Southern North Sea, the start of the Bristol Channel (north of Newquay), the Irish Channel (both east and west of the Isle of Man), around Stornoway, and east of Helmsdale.
Pre-spawning courtship involves fin displays, and male grunting, which leads to pairing. The male is inverted underneath the female, whilst the pair swim in circles during the spawning process. The eggs are planktonic and hatch between 8 to 23 days with the larva being some 4mm in length. This planktonic phase lasts some ten weeks, during which the young cod will increase it's body weight by 40 times, and be about 2cm in length. The young cod move to the seabed and their diet changes to small benthic crustaceans, such as isopods and small crabs. They increase in size to 8 cm (3 inches) in the first six months, 14 cm to 18 cm (6 to 7 inches) by the end of their first year, and some 25 cm to 35 cm (10 to 14 inches) by the end of the second. This rate of growth tends to be less in individuals occupying northerly grounds. Cod reach maturity at about 50 cm (20 inches) in length at about 3 to 4 years of age.
Biome
Varied, although often favouring rough ground especially inshore. Demersal in depths of between 20 m to 200 m, 80 m on average (70 to 700 feet, 270 feet on average), although not uncommon to depths of 600 m (2000 feet). Gregarious and forms schools, although shoaling tends to be a feature of the spawning season.
Predation
Adult cod are active hunters, feeding on sand eels, whiting, haddock, small cod, squid, crabs, lobsters, mussels, worms, mackerel, and molluscs, supplementing their diets. Young cod eat the same but avoid larger prey.
Range
Gadus morhua cod are found in the colder waters and deeper sea regions throughout the Northern Atlantic. The Gadus macrocephalus is found in both eastern and western regions of the Pacific.
Cod trade
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| fin fish |
| anchovy |
| beluga sturgeon |
| catfish |
| cod |
| atlantic cod |
| eel |
| eel history |
| halibut |
| herring |
| mackerel |
| pollock |
| sillaginids |
| salmon |
| sardine |
| sole |
| sturgeon |
| white sturgeon |
| tilapia |
| toothfish |
| tuna |
| turbot |
| whitebait |
| more... |
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| fishing industry |
| fisheries |
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| I N D E X |
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Cod has been an important economic commodity in an international market since the Viking period (around 800 AD). Norwegians used dried cod during their travels and soon a dried cod market developed in southern Europe. This market has lasted for more than 1000 years, passing through periods of Black Death, wars and other crises and still is an important Norwegian fish trade. The Portuguese since the 15th century have been fishing cod in the North Atlantic and clipfish is widely eaten and appreciated in Portugal. The Basques also played an important role in the cod trade and are claimed to have found the Canadian fishing banks before the Colombus' discovery of America. The North American east coast developed in part due to the vast amount of cod, and many cities in the New England area spawned near cod fishing grounds.
Apart from the long history this particular trade also differs from most other trade of fish by the location of the fishing grounds, far from large populations and without any domestic market. The large cod fisheries along the coast of North Norway (and in particular close to the Lofoten islands) have been developed almost uniquely for export, depending on sea transport of stockfish over large distances. Since the introduction of salt, dried salt cod ('klippfisk' in Norwegian) has also been exported. The trade operations and the sea transport were by the end of the 14th century taken over by the Hanseatic League, Bergen being the most important port of trade.
William Pitt the Elder, criticizing the Treaty of Paris in Parliament, claimed that cod was "British gold"; and that it was folly to restore Newfoundland fishing rights to the French.
In the 17th and 18th centuries, the New World, especially in Massachusetts and Newfoundland, cod became a major commodity, forming trade networks and cross-cultural exchanges. In the 20th century, Iceland re-emerged as a fishing power and entered the Cod Wars to gain control over the north Atlantic seas. In the late 20th and early 21st centuries, cod fishing off the coast of Europe and America severely depleted cod stocks there which has since become a major political issue as the necessity of restricting catches to allow fish populations to recover has run up against opposition from the fishing industry and politicians reluctant to approve any measures that will result in job losses. The 2006 Northwest Atlantic cod quota is set at 23,000 tons representing half the available stocks, while it is set to 473,000 tons for the Northeast Atlantic cod.
The Pacific Cod is currently enjoying a strong global demand. The 2006 TAC for the Gulf of Alaska and Berning Sea Aleutian Island was set at 260,000,000 kg (574 million pounds).
Endangered Species Controversies in Canada and Europe
Following collapse of the Canadian cod stock in the early 1990's, the Canadian Department of Fisheries and Oceans (DFO) issued in 1992 a ban on Northern cod fishing, which caused great economic hardship in the east coast Canadian province of Newfoundland and Labrador. In 1995, in a controversial move, Brian Tobin the Canadian Federal Minister of Fisheries and Oceans, reopened the hunt on the harp seal, which prey on cod, stating: "There is only one major player still fishing the cod. His name is harp and his second name is seal." In 1998, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), the body that develops Canada's national list of species submitted a report that listed the Atlantic cod as a species of "special concern", though not an endangered species. Dr.Kim Bell, who drafted the report for COSEWIC, subsequently stated that the original report in fact had advised endangered status but that this advice had been suppressed under political pressure by the DFO. The ban on cod fishing was partly lifted in 1997 by the DFO, though according to the International Council for the Exploration of the Sea the recovery of the Canadian cod stock had been quite poor . In general, depleted populations of cod and other gadids do not appear to recover easily when fishing pressure is reduced or stopped . In 2003, COSEWIC did place the Newfoundland and Labrador population of Atlantic cod on the list of endangered species and Fisheries Minister Robert Thibault announced an indefinite closure of the cod fishery in the Gulf of St. Lawrence and off the northeast coast of Newfoundland. In 2005 the WWF-Canada accused both foreign and Canadian fishing vessels of deliberate, large-scale violations of the restrictions on cod fishing on the Grand Banks, in the form of bycatch and of poor enforcement of the restrictions by NAFO, an intergovernmental organization with a mandate to provide scientific advice and management of fisheries in the northwestern part of the Atlantic Ocean.
In 2000, cod was placed on the list of endangered species by the World Wide Fund for Nature (WWF), an international non-governmental organization for the conservation, research and restoration of the natural environment, formerly named the World Wildlife Fund. The WWF issued a report stating that global cod catch had suffered a 70 per cent drop over the last 30 years, and that if this trend continued, the world’s cod stocks would disappear in 15 years. The endangered species claim by the WWF was disputed by Åsmund Bjordal, director of the Norwegian Institute of Marine Research who stated that in view of the health of the Barents Sea cod population, cod should not be placed on an endangered species list. Cod is among Norway's most important fishery export items and the Barents Sea is the most important cod fishery of Norway. In a 2004 report , the WWF agreed that the Barents Sea cod fishery appeared to be healthy but that that may not last due to illegal fishing, industrial development, and high fishing quota.
According to Seafood Watch, cod is currently on the list of fish that American consumers, who are sustainability minded, should avoid.