Cod

Cod(pl.: cod) is thecommon namefor thedemersal fishgenusGadus, belonging to thefamilyGadidae.Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genusGadusis commonly not called cod (Alaska pollock,Gadus chalcogrammus).
The two most common species of cod are theAtlantic cod(Gadus morhua), which lives in the colder waters and deeper sea regions throughout theNorth Atlantic, and thePacific cod(Gadus macrocephalus), which is found in both eastern and western regions of the northernPacific.Gadus morhuawas named byLinnaeusin1758. (However,G. morhua callarias, a low-salinity, nonmigratoryracerestricted to parts of the Baltic, was originally described asGadus callariasby Linnaeus.)
Cod as foodis popular in several parts of the world. It has a mild flavour and a dense, flaky,white flesh. Cod livers are processed to makecod liver oil, a common source ofvitamin A,vitamin D,vitamin E, andomega-3 fatty acids(EPAandDHA). Young Atlantic cod orhaddockprepared in strips for cooking is calledscrod. In the United Kingdom,Atlantic codis one of the most common ingredients infish and chips, along withhaddockandplaice.
At various times in the past, taxonomists included many species in  the genusGadus. Most of these are now either classified in other genera, or have been recognized as forms of one of three species. All these species have a number ofcommon names, most of them ending with the word "cod", whereas other species, as closely related, have other common names (such aspollockandhaddock).  However, many other, unrelated species also have common names ending with cod. The usage often changes with different localities and at different times.
Three species in the genusGadusare currently called cod:
The fourth species of genus Gadus,Gadus chalcogrammus, is commonly calledAlaska pollockorwalleye pollock. But there are also less widespread alternative trade names highlighting the fish's belonging to the cod genus, likesnow codorbigeye cod.
Codforms part of thecommon nameof many other fish no longer classified in the genusGadus. Many are members of the familyGadidae; others are members of three related families within the orderGadiformeswhose names include the word "cod": themorid cods,Moridae(100 or so species); the eel cods,Muraenolepididae(four species); and theEucla cod,Euclichthyidae(one species). The tadpole cod family (Ranicipitidae) has now been placed in Gadidae.
Some fish have common names derived from "cod", such ascodling,codlet, ortomcod. ("Codling" is also used as a name for a young cod.)
Some fish commonly known as cod are unrelated toGadus. Part of this name confusion is market-driven. Severely shrunken Atlantic cod stocks have led to the marketing of cod replacements usingculinary namesof the form "xcod", according to culinary rather than phyletic similarity. The common names for the following species have become well established; note that all inhabit theSouthern Hemisphere.
Fish of theorderPerciformesthat are commonly called "cod" include:
Almost allcoral cod,reef codorrock codare also in orderPerciformes. Most are better known asgroupers, and belong to the familySerranidae. Others belong to theNototheniidae. Two exceptions are theAustralasianred rock cod, which belongs to a different order (see below), and the fish known simply as the rock cod and assoft codin New Zealand,Lotella rhacina, which as noted above actually is related to the true cod (it is a morid cod).
From the orderScorpaeniformes:
The tadpole cod family,Ranicipitidae, and theEucla codfamily,Euclichthyidae, were formerly classified in the orderOphidiiformes, but are now grouped with theGadiformes.
Some fish that do not have "cod" in their names are sometimes sold as cod. Haddock and whiting belong to the same family, the Gadidae, as cod.
Cods of the genusGadushave three roundeddorsaland twoanal fins. Thepelvic finsare small, with the first ray extended, and are set under thegillcover (i.e. the throat region), in front of thepectoral fins.The upper jaw extends over the lower jaw, which has a well-developedchin barbel. The eyes are medium-sized, approximately the same as the length of the chin barbel. Cod have a distinct whitelateral linerunning from the gill slit above the pectoral fin, to the base of thecaudalor tail fin. The back tends to be a greenish to sandy brown, and shows extensive mottling, especially towards the lighter sides and white belly. Dark brown colouration of the back and sides is not uncommon, especially for individuals that have resided in rocky inshore regions.
TheAtlantic codcan change colour at certain water depths. It has two distinct colour phases: gray-green and reddish brown. Its average weight is 5–12 kilograms (11–26 pounds), but specimens weighing up to 100 kg (220 lb) have been recorded. Pacific cod are smaller than Atlantic codand are darker in colour.
Atlantic cod(Gadus morhua) live in the colder waters and deeper sea regions throughout the North Atlantic.Pacific cod(Gadus macrocephalus) is found in both eastern and western regions of thePacific.
Atlantic cod could be further divided into severalstocks, including theArcto-Norwegian,North Sea,Baltic Sea,Faroe,Iceland,East Greenland,West Greenland,Newfoundland, andLabradorstocks. There seems to be little interchange between the stocks, although migrations to their individual breeding grounds may involve distances of 300 kilometres (190 statute miles; 160 nautical miles) 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 aredemersalin depths between 6 and 60 metres (20 and 200 feet; 3 and 30 fathoms), 80 m (260 ft; 44 fathoms) on average, although not uncommonly to depths of 600 m (2,000 ft; 330 fathoms). Off the Norwegian and New England coasts and on theGrand Banks of Newfoundland, cod congregate at certain seasons in water of 30–70 m (100–200 ft; 20–40 fathoms) depth. Cod are gregarious and form schools, althoughshoalingtends to be a feature of the spawning season.
Spawning of northeastern Atlantic cod occurs between January and April (March and April are the peak months), at a depth of 200 metres (660 ft) in specific spawning grounds at water temperatures between 4 and 6 °C (39 and 43 °F). Around the UK, the major spawning grounds are in the middle to southern North Sea, the start of theBristol Channel(north ofNewquay), theIrish Channel(both east and west of theIsle of Man), aroundStornoway, and east ofHelmsdale.
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 reaching4 millimetres (5⁄32inch) in length. This planktonic phase lasts some ten weeks, enabling the young cod to increase its body weight by 40-fold, and growing to about2 cm (3⁄4in). The young cod then move to the seabed and change their diet to smallbenthiccrustaceans, such asisopodsand small crabs. They increase in size to 8 cm (3 in) in the first six months,14–18 cm (5+1⁄2–7 in) by the end of their first year, and to 25–35 cm (10–14 in) by the end of the second. Growth tends to be less at higher latitudes. Cod reach maturity at about 50 cm (20 in) 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.
Adult cod are active hunters, feeding onsand eels,whiting,haddock, small cod,squid,crabs,lobsters,mussels,worms,mackerel, andmolluscs.
In the Baltic Sea the most important prey species areherringandsprat.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 theBornholmBasin 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, thecod worm,Lernaeocera branchialis, starts life as acopepod-like larva, a small free-swimming crustacean. The first host used by the larva is aflatfishorlumpsucker, which it captures with grasping hooks at the front of its body. It penetrates the fish with a thinfilament, 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 ahaddockorwhiting. There the larva clings to thegillswhile 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'sheart. 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 mainartery. 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.
The 2006 northwest Atlantic codquotais 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 2006total allowable catch(TAC) for theGulf of AlaskaandAleutian Islandswas 260,000 tons.
Farming of Atlantic cod has received a significant amount of interest due to the overall trend of increasing cod prices alongside reduced wild catches.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 wildRecent 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.
Cod is popular as afoodwith a mild flavour and a dense, flakywhite flesh. Cod livers are processed to makecod liver oil, an important source ofvitamin A,vitamin D,vitamin Eandomega-3 fatty acids(EPAandDHA).
Young Atlantic cod orhaddockprepared in strips for cooking is calledscrod. In theUnited Kingdom,Atlantic codis one of the most common ingredients infish and chips, along withhaddockandplaice. Cod's soft liver can be tinned (canned) and eaten.
Cod has been an important economic commodity ininternational marketssince theVikingperiod (around 800 AD).Norwegianstravelled withdried codand soon a dried cod market developed in southernEurope. This market has lasted for more than 1,000 years, enduring theBlack Death, wars and other crises, and is still an important Norwegian fish trade.ThePortuguesebegan fishing cod in the 15th century.Clipfishis widely enjoyed in Portugal. TheBasquesplayed an important role in the cod trade, and allegedly found theCanadian fishing banksbeforeColumbus' 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 ofMassachusetts, the state's House of Representatives hung a wood carving of a codfish, known as theSacred Cod of Massachusetts, in its chambers.
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 ofNorth Norway(and in particular close to theLofotenislands) have been developed almost uniquely forexport, depending on sea transport ofstockfishover 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, theHanseatic Leaguedominated trade operations and sea transport, withBergenas the most important port.
William Pitt the Elder, criticizing theTreaty of ParisinParliament, claimed cod was "British gold"; and that it was folly to restoreNewfoundlandfishing rights to theFrench.
In the 17th and 18th centuries in the New World, especially inMassachusettsand 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 BritishCaribbeanby imposing theMolasses 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,Icelandre-emerged as a fishing power and entered theCod 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.
On July 2, 1992, the HonourableJohn Crosbie, CanadianFederal Minister of Fisheries and Oceans, declared a two-yearmoratoriumon the Northern Cod fishery,a designated fishing region off the coast ofNewfoundland, after data showed that the total cod biomass had suffered a collapse to less than 1% of its normal value.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.
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 oftrawling, 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.The powerful economic engine of rural Newfoundland coughed, wheezed, and died. 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.