The Atlantic cod, Gadus morhua, is a well-known demersal food fish belonging to the family Gadidae. It is also commercially known as cod, codling or haberdine.
In the western Atlantic Ocean cod has a distribution north of Cape Hatteras, North Carolina, and round both coasts of Greenland; in the eastern Atlantic it is found from the Bay of Biscay north to the Arctic Ocean, including the Baltic Sea, the North Sea, areas around Iceland and the Barents Sea.
It can grow to 2 meters in length and weigh up to 96 kilograms (210 lb). It can live for 25 years and sexual maturity is generally attained between ages 2 to 4, but can be as late as 8 years in the northeast Arctic. Colouring is brown to green with spots on the dorsal side, shading to silver ventrally. A lateral line is clearly visible. Its habitat ranges from the shoreline down to the continental shelf.
Several cod stocks collapsed in the 1990s (declined by >95% of maximum historical biomass) and have failed to recover even with the cessation of fishing. This absence of the apex predator has led to a trophic cascade in many areas. Many other cod stocks remain at risk. The "Atlantic Cod" is labelled VU (vulnerable) on the IUCN Red List of Threatened Species.

The northwest Atlantic cod has been regarded as heavily overfished throughout its range, resulting in a crash in the fishery in the United States and Canada during the early 1990s.
Newfoundland's northern cod fishery can be traced back to the 16th century. "On average, about 300,000 tonnes of cod was landed annually until the 1960s, when advances in technology enabled factory trawlers to take larger catches. By 1968, landings for the fish peaked at 800,000 tonnes before a gradual decline set in. With the reopening of the limited cod fisheries last year (2006), nearly 2,700 tonnes of cod were hauled in. Today (2007), it's estimated that offshore cod stocks are at one per cent of what they were in 1977".
Technologies that contributed to the collapse of Atlantic Cod include engine power vessels and frozen food compartments aboard ships. Engine power vessels had larger nets, larger engines, and better navigation. The capacity to catch fish became limitless. In addition, sonar technology gave an edge to catching and detecting fish. Sonar was originally developed during WWII to locate enemy submarines, but was later applied to locating schools of fish. These new technologies, as well as bottom-trawlers that destroyed entire ecosystems, contributed to the collapse of Atlantic Cod. They were vastly different from old techniques used, such as hand lines and long lines.
The fishery has yet to recover, and may not recover at all because of a possibly stable change in the food chain. Atlantic cod was a top-tier predator, along with haddock, flounder and hake, feeding upon smaller prey such as herring, capelin, shrimp and snow crab. With the large predatory fish removed, their prey has had a population explosion and have become the top predators, affecting the survival rates of cod eggs and fry.