Cod, Atlantic

Gadus morhua

phylum: Chordata

class: Osteichthyes

order: Gadiformes

family: Gadidae

status: Vulnerable, IUCN

range: Oceanic: Atlantic Ocean, northeast and northwest

Description and biology

The Atlantic cod (sometimes called the North Sea cod) has been one of the world's major food fishes for centuries and is especially popular among Europeans and Americans. Tens of thousands of tons of this fish are caught every year, and thousands of people earn their living in the cod market. Atlantic cod are large fish: an average adult is over 4 feet (1.3 meters) long and weighs about 60 pounds (27 kilograms). Exceptionally large cod have been known to grow to about 6 feet (1.8 meters) and 210 pounds (95 kilograms). The Atlantic cod ranges from a dark greenish-gray to orange-brown in color. The upper body has spots across it, and there is a white line running from side to side. The fish has a stout body, a large head, and long barbel (a fleshy whisker) on its chin. Its fins—three dorsal (rear) fins and two anal fins—are all rounded in shape. Its belly is white.

The Atlantic cod is omnivorous (eats animals and plants). It generally feeds at dawn and at dusk. Young cod feed at the bottom of the ocean floor on small crustaceans, like shrimp or amphipods. Adults eat a great variety of mollusks, crabs, lobsters, and fish. Although cod do not form large schools for traveling, they do form small groups when they are hunting for food.

Cod travel long distances to their spawning grounds (the places where they produce their eggs) each year. Spawning generally takes place in the winter. The older a female cod becomes, the more eggs she will produce—a younger female may produce 3 million eggs, while an older female may produce 9 million eggs, in a season. Cod reach sexual maturity between the ages of 2 and 4 and they may live to be about 20 years old.

Habitat and current distribution

Cod live in a variety of habitats near shore and in the ocean depths. They are called "groundfish," because they stay near the bottom of the ocean much of the time. They generally prefer depths of about 200 to 360 feet (61 to 109 meters) in the summer and 295 to 440 feet (90 to 134 meters) in the winter. Their maximum depth is about 660 feet (200 meters). They prefer cool waters.

Atlantic cod occur on both sides of the North Atlantic Ocean. In the western North Atlantic, it occurs from Greenland in the north down to North Carolina in the south. In the eastern North Atlantic, it occurs from Iceland in the north down to the Norwegian Sea, to the Barents Sea and Spitsbergen (both north of Norway), and southward to the Baltic Sea and Bay of Biscay (on west coast of France). It is widespread all around the coasts of Britain and Ireland. In the waters off the United States, cod are managed as two commercial and recreational stocks: the Gulf of Maine and the Georges Bank (off the coast of Massachusetts) stocks.

DID YOU KNOW?

Since the late 1980s, many ocean fish populations have seriously declined. Some of the species threatened by overfishing besides Atlantic cod are: swordfish, black sea bass, red snappers, and some sharks. The populations are threatened by loss of habitat, pollution, and fishing practices that are not sustainable—that is, they allow fishers to take so many fish that the remaining population is unable to reproduce fast enough to make up for the ones taken.

Though the prospects for many of the endangered fish have seemed bleak, there is at least one case in which government-enforced fishing restrictions have successfully corrected the problem. The swordfish (Xiphias gladius) has experienced a dramatic recovery. In 1999, it was determined that the population had dropped to one-third of what it would have been without fishing. To continue existing fishing practices meant certain extinction for swordfish. A plan was enacted that limited fishing quotas to 10,160 tons (10,000 metric tons) per year. In addition, the United States closed 132,670 square miles (343,610 square kilometers) of swordfish habitat waters to longline fishing, in which the fishing line can be a couple of miles long and has baited hooks placed at intervals along its length. Remarkably, within just three years, the swordfish population has risen to about 94 percent of the number that scientists believe will assure the survival of the species if controls on commercial fishing are kept in place. Not all species have been so successful.

History and conservation measures

For centuries, abundant cod populations provided tons of food as well as reliable employment in cod fishery to thousands of fishermen in Europe, Greenland and Newfoundland, Canada, and the United States. Then, in the late 1980s, the cod fishery in most of the western Atlantic collapsed due to overfishing. The Atlantic cod population was in such decline that by 1992 moratoriums (enforced prohibitions) on cod fishing were in place throughout the northwestern part of its range. Even with the moratoriums, the stock in many places of the western sector has never recovered. The cod in the areas around Greenland and Newfoundland have experienced a 97 percent decline in population. Plans are in place to create protected areas for cod off the coast of New England. Canada's once-thriving cod industry has collapsed, and in April 2003, the Canadian government listed the Atlantic cod as an endangered species. The northeastern Atlantic cod population was later to experience the decline, but the fishing industry in Europe began to collapse in the early 2000s. In 2001 the stock was at such a low point that a large part of the North Sea was closed to cod fishing.

Overfishing is certainly responsible for the huge decline in the cod population, but the failure to recover stems from other very serious problems. Destruction of ocean habitat is one area of concern. A fishing technique known as "bottom trawling," in which fishers scour the ocean floor for fish, removes the cod's food sources and also eliminates places for young cod to hide along the ocean floor, so that they become easy prey for other fish. Pollution and climate changes are also likely causes of the population decline. Some species of seals, which are natural predators of the cod, are being blamed for the cod population's failure to recover.

Scientists do not understand what is causing some of the deaths and illnesses among cod. Many fish appear to be starving to death; they are found in very frail condition with emaciated bodies. Others appear to have developed a different body shape, perhaps to adapt to difficult conditions. In April 2003, hundreds of tons of Atlantic cod froze to death in the seas off eastern Newfoundland, and the incident remains unexplained. Scientists have also noted a mysterious lack of older fish in the cod population.

Since Canada imposed a moratorium on cod fishing in 1992, some populations of cod are beginning to recover, while others continue to decline. There are numerous recovery plans in the United States and in the other affected countries. On May 6, 2003, the European Commission met to launch a revised recovery plan for cod (Europe had already limited fishing in a temporary emergency plan). The cod catch in the seas off Europe is to be strictly controlled for a period of 10 years, with quotas set so that each year there will be 30 percent more adult cod than the year before.