: cod) is the common name for the demersal fish genus Gadus, belonging to the family Gadidae.

In the United Kingdom, Atlantic cod is one of the most common ingredients in fish and chips, along with haddock and plaice.

[13] Cod forms part of the common name of many other fish no longer classified in the genus Gadus.

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.

Off the Norwegian and New England coasts and on the Grand Banks of Newfoundland, cod congregate at certain seasons in water of 30–70 m (100–200 ft; 20–40 fathoms) depth.

This planktonic phase lasts some ten weeks, enabling the young cod to increase its body weight by 40-fold, and growing to about 2 cm (3⁄4 in).

[46] Many studies that analyze the stomach contents of these fish indicate that cod is the top predator, preying on the herring and sprat.

For example, the cod worm, Lernaeocera branchialis, starts life as a copepod-like larva, a small free-swimming crustacean.

There the larva clings to the gills while it metamorphoses into a plump sinusoidal wormlike body with a coiled mass of egg strings at the rear.

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.

[54] 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.

[55] 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 [56][57] 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.

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 Basques played an important role in the cod trade, and allegedly found the Canadian fishing banks before Columbus' discovery of America.

By the end of the 14th century, the Hanseatic League dominated trade operations and sea transport, with Bergen as the most important port.

[65] 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 French.

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 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 Honourable John Crosbie, Canadian Federal Minister of Fisheries and Oceans, declared a two-year moratorium on the Northern Cod fishery,[68] 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.

[70] The fisheries had long shaped the lives and communities on Canada's Atlantic eastern coast for the preceding five centuries.

Nearly 40,000 workers and harvesters in the provinces of Newfoundland and Labrador applied for the federal relief program TAGS (the Atlantic Groundfish Strategy).

[68] 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.

[72] The moratorium, initially lasting for only two years,[70] 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.

"[70] Factors which had been implicated as contributing to the collapse include: overfishing; government mismanagement; the disregard of scientific uncertainty;[70] warming habitat waters; declining reproduction; and plain human ignorance.