cod, member of the large family Gadidae, comprising commercially important food fishes. The cods include the hake and the haddock, all found in the N Atlantic and Pacific. The cod was extremely important to the economic and social growth of New England; it has been used as a Massachusetts state emblem. Today the cod stocks have been greatly depleted off the coast of New England and Newfoundland owing to overfishing, and restrictions on the catch have had to be imposed. The European Union has also restricted cod fishing in the North Sea, but it is unclear if the restrictions will be sufficient to preserve cod populations. All cods are bottom-feeders with soft fins; the large ventral fins are located under or in front of the pectorals rather than behind them as in other fishes.

The Atlantic cod has two distinct color phases, gray-green and reddish brown. Its average weight is 10 to 25 lb (4.5-11.3 kg), but specimens weighing up to 200 lb (90 kg) have been recorded. Young Atlantic cod or haddock prepared in strips for cooking is called scrod. Cods feed on mollusks, crabs, starfish, worms, squid, and small fish. Some migrate south in winter to spawn. A large female lays up to five million eggs in midocean, a very small number of which survive. The Pacific cod is found N of Oregon. The tomcod resembles a young Atlantic cod with long, tapering ventral fins. It rarely exceeds 15 in. (37.5 cm) in length and lives close to shore. There is also a Pacific tomcod. The pollack, also called coalfish or green cod, is a plump olive-green cod found in cool waters of the Atlantic. Pollacks have forked tails and pale lateral lines and grow to 3 ft (90 cm) and 30 lb (13.6 kg).

The haddock is the most important food fish of Atlantic waters; most of the large annual catch is marketed frozen. It is also found in colder European waters. Haddocks are also bottom-feeders but are found in deeper water (up to 100 fathoms). They are smaller than cods, reaching 30 lb (13.6 kg) and a length of 3 ft (90 cm), and have black lateral lines and dark side patches. Finnan haddie is lightly smoked haddock. The burbot is the only freshwater cod, found deep in northern streams and lakes. It has a single barbel on its chin. A similar burbot is found in Europe and Asia. Lings and hakes, closely related to the cod, are fishes of commercial importance found in warmer waters. More slender than the cod, they are strong swimmers, preying on crustaceans and small fish.

Cods are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Gadiformes, family Gadidae.