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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 one species that belongs to genus Gadus is commonly not called cod (Alaska pollock, Gadus chalcogrammus).
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), which is found in both eastern and western regions of the northern Pacific Ocean. Gadus morhua was named by Carl Linnaeus in 1758. (However, G. morhua callarias, a low-salinity, nonmigratory Subspecies restricted to parts of the Baltic, was originally described as Gadus callarias by Linnaeus.)
Cod as food is popular in several parts of the world. It has a mild flavour and a dense, flaky, white flesh. Cod livers are processed to make cod liver oil, a common 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.
The fourth species of genus Gadus, Gadus chalcogrammus, is commonly called Alaska pollock or walleye pollock. But there are also less widespread alternative trade names highlighting the fish's belonging to the cod genus, like snow codAlaska Seafood Marketing Institute: Whitefish Buyers Guide. (Memento of the original as of 26 September 2006 in the Internet Archive).SeafoodSource.com (23 January 2014): Alaska pollock .Doré, Ian (1991): The New Fresh Seafood Buyer’s Guide: A manual for distributors, restaurants, and retailers , p. 126. or bigeye cod.
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| Arctic cod | Arctogadus glacialis (Peters, 1872) | 32.5 cm | cm | kg | years | 3.8 | Not assessed | |||
| East Siberian cod | Arctogadus borisovi (Dryagin, 1932) | 55.6 cm | cm | 1.5 kg | years | 3.9 | Not assessed | |||
| Eucla cod | Euclichthys polynemus (McCulloch, 1926) | 35.0 cm | 22.5 cm | kg | years | 3.6 | Not assessed | |||
| Common ling | Molva molva (Carl Linnaeus, 1758) | 200 cm | 106 cm | 45.0 kg | 25 years | 4.3 | Molva molva (Carl Linnaeus, 1758) FAO, Species Fact Sheet. Retrieved April 2012. | Not assessed | ||
| Pelagic cod | Melanonus gracilis (Günther, 1878) | 18.7 cm | cm | kg | years | 3.5 | Not assessed | |||
| Polar cod | Boreogadus saida (Lepechin, 1774) | 40.0 cm | 25.0 cm | kg | 7 years | 3.1 | Boreogadus saida (Lepechin, 1774) FAO, Species Fact Sheet. Retrieved April 2012. | Not assessed | ||
| Poor cod | Trisopterus minutus (Linnaeus, 1758) | 40.0 cm | 20.0 cm | kg | 5 years | 3.8 | Not assessed | |||
| Rock cod | Lotella rhacina (Forster, 1801) | 50.0 cm | cm | kg | years | 3.5 | Not assessed | |||
| Saffron cod | Eleginus gracilis (Tilesius, 1810) | 55.0 cm | cm | 1.3 kg | 15 years | 4.1 | Eleginus gracilis (Tilesius, 1810) FAO, Species Fact Sheet. Retrieved April 2012. | Not assessed | ||
| Small-headed cod | Lepidion microcephalus (Cowper, 1956) | 48.0 cm | cm | kg | years | 3.5 | Not assessed | |||
| Tadpole cod | Guttigadus globosus (Paulin, 1986) | 18.1 cm | cm | kg | 3.5 years | Not assessed |
Some fish have common names derived from "cod", such as Morids, codlet, or tomcod. ("Codling" is also used as a name for a young cod.)
The Atlantic cod can change colour at certain water depths. It has two distinct colour phases: gray-green and reddish brown. Its average weight is , but specimens weighing up to have been recorded. Pacific cod are smaller than Atlantic cod and are darker in colour.
Atlantic cod could be further divided into several Fish stocks, including the Norway, North Sea, Baltic Sea, Faroe Islands, Iceland, East Greenland, West Greenland, Newfoundland, and Labrador stocks. There seems to be little interchange between the stocks, although migrations to their individual breeding grounds may involve distances of or more. For instance, eastern Baltic cod shows specific reproductive adaptations to low salinity compared to Western Baltic and Atlantic cod.
Atlantic cod occupy varied habitats, favouring rough ground, especially inshore, and are demersal in depths between , on average, although not uncommonly to depths of . Off the Norwegian and New England coasts and on the Grand Banks of Newfoundland, cod congregate at certain seasons in water of depth. Cod are gregarious and form schools, although shoaling tends to be a feature of the spawning season.
Prespawning courtship involves fin displays and male grunting, which leads to pairing. The male inverts himself beneath the female, and the pair swim in circles while spawning. The eggs are planktonic and hatch between eight and 23 days, with larva reaching in length. This planktonic phase lasts some ten weeks, enabling the young cod to increase its body weight by 40-fold, and growing to about . The young cod then move to the seabed and change their diet to small benthic crustaceans, such as isopods and small crabs. They increase in size to in the first six months, by the end of their first year, and to by the end of the second. Growth tends to be less at higher latitudes. Cod reach maturity at about at about 3 to 4 years of age. Changes in growth rate over decades of particular stocks have been reported, current eastern Baltic cod shows the lowest growth observed since 1955.
In the Baltic Sea the most important prey species are Atlantic herring and sprat. Many studies that analyze the stomach contents of these fish indicate that cod is the top predator, preying on the herring and sprat. Sprat form particularly high concentrations in the Bornholm Basin in the southern Baltic Sea. Although cod feed primarily on adult sprat, sprat tend to prey on the cod eggs and larvae.
Cod and related species are plagued by parasites. For example, the cod worm, Lernaeocera branchialis, starts life as a copepod-like larva, a small free-swimming crustacean. The first host used by the larva is a flatfish or lumpsucker, which it captures with grasping hooks at the front of its body. It penetrates the fish with a thin , which it uses to suck the fish's blood. The nourished larvae then mate on the fish. The female larva, with her now fertilized eggs, then finds a cod, or a cod-like fish such as a haddock or whiting. There the larva clings to the while it metamorphoses into a plump sinusoidal wormlike body with a coiled mass of egg strings at the rear. The front part of the worm's body penetrates the body of the cod until it enters the rear bulb of the host's heart. There, firmly rooted in the cod's circulatory system, the front part of the parasite develops like the branches of a tree, reaching into the main artery. In this way, the worm extracts nutrients from the cod's blood, remaining safely tucked beneath the cod's gill cover until it releases a new generation of offspring into the water.
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's soft liver can be tinned (canned) and eaten.
Apart from the long history, cod differ from most fish because the fishing grounds are far from population centres. 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 and salted cod (clipfish or 'klippfisk' in Norwegian) has also been exported. By the end of the 14th century, the Hanseatic League dominated trade operations and sea transport, with Bergen as the most important port.
William Pitt the Elder, criticizing the Treaty of Paris in Parliament, claimed cod was "British gold"; and that it was folly to restore Newfoundland fishing rights to the France.
In the 17th and 18th centuries in the New World, especially in Massachusetts and Newfoundland, cod became a major commodity, creating trade networks and cross-cultural exchanges. In 1733, Britain tried to gain control over trade between New England and the British Caribbean by imposing the Molasses Act, which they believed would eliminate the trade by making it unprofitable. The cod trade grew instead, because the "French were eager to work with the New Englanders in a lucrative contraband arrangement". In addition to increasing trade, the New England settlers organized into a "codfish aristocracy". The colonists rose up against Britain's "tariff on an import".
In the 20th century, Iceland re-emerged as a fishing power and entered the Cod Wars. In the late 20th and early 21st centuries, fishing off the European and American coasts severely depleted stocks and become a major political issue. The necessity of restricting catches to allow stocks to recover upset the fishing industry and politicians who are reluctant to hurt employment.
The near-complete destruction of the Atlantic northwest cod biomass off the shores devastated coastal communities, which had been overexploiting the same cod population for decades. The fishermen along the Atlantic northwest had employed modern fishing technologies, including the ecologically-devastating practice of trawling, especially in the years leading up to the 1990s, in the misguided belief that fishing stocks are perpetually plentiful and unable to be depleted. After this assumption was empirically and abruptly shown to be incorrect, to the dismay of government officials and rural workers, some 19,000 fishermen and cod processing plant workers in Newfoundland lost their employment. Nearly 40,000 workers and harvesters in the provinces of Newfoundland and Labrador applied for the federal relief program TAGS (the Atlantic Groundfish Strategy). Abandoned and rusting fishing boats still litter the coasts of Newfoundland and the Canadian northwest to this day.
The fishery minister, John Crosbie, after delivering a speech on the day before the declaration of the moratorium, or July 1, 1992, was publicly heckled and verbally harassed by disgruntled locals at a fishing village. The moratorium, initially lasting for only two years, was indefinitely extended after it became evident that cod populations had not recovered at all but, instead, had continued to spiral downward in both size and numbers, due to the damage caused by decades of horrible fishing practices, and the fact that the moratorium had permitted exceptions for food fisheries for "personal consumption" purposes to this very day. Some 12,000 tons of Northwest cod are still being caught every year along the Newfoundland coast by local fishermen.
The collapse of the four-million ton biomass, which had persevered through several previous marine extinctions over tens of millions of years, in a timespan of no more than 20 years, is oft-cited by researchers as one of the most visible examples of the phenomenon of the "Tragedy of the Commons." Factors which had been implicated as contributing to the collapse include: overfishing; government mismanagement; the disregard of scientific uncertainty; warming habitat waters; declining reproduction; and plain human ignorance. The Northern Cod biomass has been recovering slowly since the imposition of the moratorium. However, as of 2021, the growth of the cod population has been stagnant since 2017, and some scientists argue that the population will not rebound unless the Fisheries Department of Canada lower its yearly quota to 5,000 tons.
Fisheries
The 2006 northwest Atlantic cod quota is 23,000 tons, representing half the available stocks, while the northeast Atlantic quota is 473,000 tons. Pacific cod is currently enjoying strong global demand. The 2006 total allowable catch (TAC) for the Gulf of Alaska and Aleutian Islands was 260,000 tons.
Aquaculture
Farming of Atlantic cod has received a significant amount of interest due to the overall trend of increasing cod prices alongside reduced wild catches. The State of World Fisheries and Aquaculture 2010 . fao.org. . However, progress in creating large scale farming of cod has been slow, mainly due to bottlenecks in the larval production stage, where survival and growth are often unpredictable. It has been suggested that this bottleneck may be overcome by ensuring cod larvae are fed diets with similar nutritional content as the copepods they feed on in the wild Recent examples have shown that increasing dietary levels of minerals such as selenium, iodine and zinc may improve survival and/or biomarkers for health in aquaculture reared cod larvae.
As food
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).
History
Cod has been an important economic commodity in international markets since the Viking period (around 800 AD). Norway travelled with dried cod and soon a dried cod market developed in southern Europe. This market has lasted for more than 1,000 years, enduring the Black Death, wars and other crises, and is still an important Norwegian fish trade. The Portuguese began fishing cod in the 15th century. Clipfish is widely enjoyed in Portugal. The Basques played an important role in the cod trade, and allegedly found the Canadian fishing banks before Columbus' discovery of America.
The North American east coast developed in part due to the vast cod stocks. Many cities in the New England area are located near cod fishing grounds. The fish was so important to the history and development of Massachusetts, the state's House of Representatives hung a wood carving of a codfish, known as the Sacred Cod of Massachusetts, in its chambers.
Collapse of the Atlantic northwest cod fishery
On July 2, 1992, the Honourable John Crosbie, Canadian Federal Minister of Fisheries and Oceans, declared a two-year moratorium on the Northern Cod fishery, a designated fishing region off the coast of Newfoundland, after data showed that the total cod biomass had suffered a collapse to less than 1% of its normal value.Hamilton and Butler, 1. The minister championed the measure as a temporary solution, allowing the cod population time to recover. The fisheries had long shaped the lives and communities on Canada's Atlantic eastern coast for the preceding five centuries. Societies which are dependent on fishing have a strong mutual relationship with them: the act of fishing changes the ecosystems' balance, which forces the fishery and, in turn, the fishing societies to adapt to new ecological conditions.
See also
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