The name "cod" is affixed to a whole gaggle of unrelated fishes---and seafood dishes. Over 20 species belong to Family Gadidae, the true cods and haddocks, among them the well-known Atlantic, Pacific and Greenland cod, and haddock itself, all of which are found in North American waters. Codfish are ray-finned fish with one to three dorsal fins, small scales and often benthic tendencies; some have prominent chin barbels.
The Atlantic cod has long supported an active commercial fishery in the North Atlantic Ocean---so active, indeed, that its vitality is threatened in many areas. This species, largest of its family, prowls nearshore waters to the continental shelf in search of mollusks, smaller fish and other prey. Exceptional specimens may span 6 feet and weigh over 200 pounds, although the average size is much less.
The Pacific cod, which shares many characteristics with its larger Atlantic brethren, inhabits the North Pacific. This schooling species hunts fish, crustaceans, octopi and other invertebrates in benthic habitats along the continental shelf, and is harvested commercially.
This more solitary, broad-headed species inhabits deep coastal waters of the Arctic and North Atlantic oceans, feeding on fish, crustaceans, cephalopods and other fare. Like the Atlantic and Pacific species, the Greenland cod has suffered prominently from overfishing.
Haddock is another codfish of notable commercial importance. Preferring deeper waters and smooth seafloor substrate, haddock range on both sides of the North Atlantic; certain populations are migratory.