Cod

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Gadidae
Atlantic cod, Gadus morhua
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Order:
Gadiformes
Family:
Gadidae
Genera

See text for genera and species.

This article is about the fish. For other uses, see Cod (disambiguation).

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). Also the cod fish can change colors at certain depths of the water. The Atlantic cod has two distinct color phases, gray-green and reddish brown. Its average weight is 10 to 25 lb (4.5—11.3 kg), but specimens weighing up to 200 lb (90 kg) have been recorded. Young Atlantic cod or haddock prepared in strips for cooking is called scrod. Cods 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 N of Oregon. The tomcod resembles a young Atlantic cod with long, tapering ventral fins. It rarely exceeds 15 in. (37.5 cm) in length and lives close to shore. There is also a Pacific tomcod. The pollock, also called coalfish or green cod, is a plump olive-green cod found in cool waters of the Atlantic. Pollacks have forked tails and pale lateral lines and grow to 3 ft (90 cm) and 30 lb (13.6 kg). Some grow to 6 feet in length.

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, where it is considered a treasure of the nation's cuisine. It is an important link in the food chain.

Species in genus Gadus

Cod caught by a fisherman

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 recognised as simply forms of one of three species. Modern taxonomy, therefore, recognises only three species in this genus:

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.

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 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.

Cod postage stamp, Newfoundland

Species within the order Gadiformes that are commonly called cod include:

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

File:Fisher with cod.jpg
Norwegian fisher with cod

Fish of the order Perciformes that are commonly called "cod" include:

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:

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.

Identification

Classic codfish 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 (ie 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 of 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 200m in specific spawning grounds at water temperatures of between 4-6oC. 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 8cm in the first six months, 14 to 18cm by the end of their first year, and some 25 to 35cm by the end of the second. This rate of growth tends to be less in individuals occupying northerly grounds. Cod reach maturity at about 50cm in length at about 3 to 4 years of age.

Habitat

Varied, although often favouring rough ground especially inshore. Demersal in depths of between 20 to 200m (80m Av.), although not uncommon to depths of 600m. Gregarious and forms schools, although shoaling tends to be a feature of the spawning season.

Food

Adult cod are active hunters, feeding on sandeels, whiting, haddock, small cod, and squid, crabs, mussels, worms, mackerel, and molluscs supplementing their diets. While young cod eat the same they may not eat food sources that are too large.

Range

Throughout most of the UK waters, although generally seen as a winter fish in the south.

Cod trade

Stockfish

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.[1] 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.

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.[2] 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.[3]

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 triangular 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.

Trivia

A Norwegian "king cod" commonly used for weather forecast in the old days.
  • The Norwegian municipalities Vikna and Vågan have cods in their coats-of-arms.
  • A "Sacred Cod" hangs in the Massachusetts House of Representatives.
  • In Sweden, a person who solicit prostitutes is known as a "torsk", meaning cod in Swedish.
  • Cod is the fish used in McDonald's Filet-O-Fish.
  • Every now and then cod with deformed skull is found, the skull has a top or crown giving it the name "king cod" or kongetorsk in Norwegian. This rare fish was earlier considered to have the ability of forecasting the weather and in Norway it was commonly used. A woollen thread was used to hang the fish in the ceiling and the fish nose will point in different directions depending on the weather to come the few next days. Actually it was not the fish, but rather the thread giving reason for the movement. By absorbing humidity from the air, the twisted thread served as a primitive hygrometer, turning the fish to slightly different positions depending on air humidity.

References

  • Clover, Charles (2004). The End of the Line: How Overfishing Is Changing the World and What We Eat. London: Ebury Press. ISBN 0-09-189780-7.
  • Kurlansky, Mark (1997). Cod: A Biography of the Fish That Changed the World. New York: Walker. ISBN 0-8027-1326-2.
  1. ^ James Barrett, Roelf Beukens, Ian Simpson, Patrick Ashmore, Sandra Poaps and Jacqui Huntley (2000). "What Was the Viking Age and When did it Happen? A View from Orkney". Norwegian Archaeological Review. 33(1).{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ G. Rolfsen (1966). "Norwegian fisheries Research". FiskDir. Skr. Ser. HavUnders. 14(1): 36.
  3. ^ A. Holt-Jensen (1985). "Norway and sea the shifting importance of marine resources through Norwegian history". GeoJournal. 10(4).

See also

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