Hakes Grenadiers Cods and Relatives: Gadiformes

Physical characteristics: Atlantic cod have three separate dorsal fins and two separate anal fins. They also have chin barbels. The pelvic fins sometimes have one long ray. Pelvic fins are the rear pair and correspond to the rear legs of four-footed animals. Atlantic cod are usually about 2 feet (60 centimeters) long and weigh about 10 pounds (4.5 kilograms), although they can reach a length of 4 feet (120 centimeters) and a weight of 60 pounds (27 kilograms). The record is 6 feet (1.8 meters), 209 pounds (95 kilograms). These fish are brownish to greenish gray on the upper sides and paler toward the belly. The body is covered with spots.

Geographic range: Atlantic cod live in the northern part of the Atlantic Ocean from Hudson Bay in Canada south to the coast of the Carolinas in the United States to the Barents Sea, which is north of Norway and Russia.

Habitat: The habitat of Atlantic cod changes with the life stages. The fertilized eggs drift in open water. Larvae (LAR-vee) also live in Atlantic cod is an extremely important food fish for humans. The annual catch is tens of thousands of tons. (Illustration by Emily Damstra. Reproduced by permission.) open water and drift slowly away from spawning areas as they develop. Larvae are animals in an early stage and must change form before becoming adults. The young sink to the bottom when they are about 2 inches (5 centimeters) long and settle on pebble and gravel deposits. After settlement, young fish live in habitats such as eel grass in protected coastal waters, where they avoid being eaten by older cod and other predators. One- and two-year-old fish join the adults. Adult cod travel into shallower waters during summer and deeper waters with rock, pebble, sand, or gravel bottoms for the winter.

Diet: The diet of Atlantic cod changes with life stage. Cod are greedy eaters and eat any plant or meat available. Adult Atlantic cod feed at dawn and dusk, but young fish feed almost continuously. Larvae feed on plankton, which are microscopic plants and animals drifting in water. Young Atlantic cod feed on invertebrates, or animals without a backbone, especially small crustaceans. Older fish feed on invertebrates and fishes, including young cod.

Behavior and reproduction: Huge schools of Atlantic cod leave their wintering areas in deep, oceanic waters and follow tongues of deep, relatively warm, oceanic waters across the continental shelf to summer feeding areas nearer to the coast. Spawning occurs in dense groups as the fish begin their travels. As it moves toward shore, the huge mass of cod encounters groups of important prey animals such as shrimp and breaks up to feed. The mass is led by the largest fish, or scouts, and the smallest bring up the rear. After reaching nearshore waters, the fish turn and move northward along the coast in late summer, then eventually return to their deep-water wintering areas.

Atlantic cod produce more eggs than almost any other fish. A female weighing 11 pounds (5 kilograms) can produce 2.5 million eggs. These fish start reproducing when they are about two years old and 15 inches (38 centimeters) long. Reproduction peaks in winter and spring but continues sporadically throughout the year. Eggs and larvae live in open water, and young Atlantic cod begin moving to the bottom when they are between 1 and 2 inches (2.5 and 6.0 centimeters) long.

Atlantic cod and people: Atlantic cod is an extremely important food fish. The annual catch is tens of thousands of tons.

Conservation status: The IUCN lists Atlantic cod as Vulnerable or facing a high risk of extinction in the wild. ∎