Grenadiers, Hakes, Cods, and Relatives: Gadiformes
GRENADIERS, HAKES, CODS, AND RELATIVES: GadiformesATLANTIC COD (Gadus morhua): SPECIES ACCOUNTS
HADDOCK (Melanogrammus aeglefinus): SPECIES ACCOUNTS
Some fishes in the group that includes grenadiers, hakes, cods, and their relatives have three separate dorsal (DOOR-suhl) fins and two separate anal fins. The dorsal fin is the fin along the midline of the back. The anal (AY-nuhl) fin is the fin along the midline of the belly. Other fishes in this group have two dorsal fins. The front one is small and may have a long spine. The rear dorsal fin in these fishes is quite long, extending from just behind the first dorsal fin all the way to the tail. Some fishes in this group have two anal fins. Others have one long anal fin that extends almost the length of the body. Still others have one small anal fin. Other fishes in this group have long bodies that get thinner toward the tail and have a long thin tail rather than a tail fin. Some fishes in this group have a large chin barbel (BAR-buhl), or a feeler used for the senses of taste, touch, and smell. Cods that live in open water are small, about 6 inches (15 centimeters) long. Bottom-dwelling fishes in this group have a well-developed swim bladder, which is an internal sac that fishes use to control their position in the water. The open-water species do not have a swim bladder.
Grenadiers, hakes, cods, and their relatives live all over the world.
Grenadiers, hakes, cods, and their relatives live in the open ocean at all depths, the deepest-occurring species living deeper than 3,000 feet (900 meters). Fishes in this group also live in estuaries (EHS-chew-air-eez), or the areas where rivers meet the sea, sometimes in eel grass beds; in shallow waters near the coast; on bottoms consisting of rock, sand, mud, gravel, or broken shells; and on the bottoms of rivers and lakes. Some fishes in this group migrate (MY-grayt) or travel from one habitat to another to spawn, or reproduce, and then continue to change habitats as they change life stages. A fish may move from an estuary, across the continental shelf, to the upper part of the continental slope, and from the surface to the bottom.
Bottom-dwelling grenadiers, hakes, cods, and their relatives use their chin barbels to find bottom-dwelling prey, or animals hunted and killed for food. Open-water species eat krill, which are tiny crustaceans (krus-TAY-shuns). Crustaceans are water-dwelling animals that have jointed legs and a hard shell but no backbone. Some of the fishes in this group eat other fishes such as Atlantic herring.
BEHAVIOR AND REPRODUCTION
Many grenadiers, hakes, cods, and their relatives travel with the changes of seasons to reproduce or to find important prey. Some of these fishes stop feeding during spawning season. Most grenadiers, hakes, cods, and their relatives release masses of eggs into the open water, and the eggs are fertilized (FUR-teh-lyzed), or penetrated by sperm to start development, outside the body.
COD IN HISTORY
The Vikings crossed the Atlantic Ocean in pursuit of cod. In medieval times the Basques, people from an area between Spain and France, turned cod into a commercial product. Cape Cod, Massachusetts, was named in honor of the cod in 1602. Cod have been the cause of wars between countries from American colonial times to a twentieth-century conflict between Iceland and Great Britain. Newfoundland, Canada, was settled by Irish and English natives in the early eighteenth century, largely because of opportunities for cod fishing. Throughout most of the nineteenth century, cod fishing was the most important source of employment and income for people in eastern Canada.
GRENADIERS, HAKES, CODS, THEIR RELATIVES, AND PEOPLE
Some grenadiers, hakes, cods, and their relatives are among the world's most important food fishes.
In 1992 cod nearly became extinct in waters off eastern Canada, and cod fishing was banned. This ban removed the main source of employment and income for thousands of fishermen from hundreds of small fishing communities and devastated the Canadian economy. The effects have been compared to the Great Depression of the 1930s in the United States.
The World Conservation Union (IUCN) lists one species of grenadiers, hakes, cods, and relatives as Critically Endangered, or facing extremely high risk of extinction in the wild in the near future, and two as Vulnerable, or facing high risk of extinction in the wild.
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 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. ∎
Physical characteristics: Haddock have three separate dorsal fins and two separate anal fins. They also have a small chin barbel. The pelvic fins sometimes have one long ray. The lateral (LAT-uhr-uhl) line is dark. The lateral line is a series of pores and tiny tubes along each side of a fish's body and is used for sensing vibrations. Haddock have a large dark blotch over the pectoral fin on each side. The pectoral (PECK-ter-uhl) fins are the front pair and correspond to the front legs of four-footed animals.
Geographic range: Haddock live in the northern part of the Atlantic Ocean from off the coast of Virginia to the Barents Sea, which is north of Norway and Russia.
Habitat: Haddock live near the bottom of cool water 148–443 feet (45–135 meters) deep. They prefer bottoms of rock, sand, gravel, or broken shells. Haddock shift habitat depending on their life stage. The young live in shallower water in bank and shoal areas. Larger adults live in deeper water.
Diet: Haddock eat crabs, sea urchins, worms, and clams. They rarely eat other fish.
Behavior and reproduction: Adult haddock do not undertake long travels to reproduce. Spawning occurs between January and June, peaking in late March and early April. Depending on size, females produce 850,000 to three million eggs each year.
Haddock and people: Haddock is an extremely important food fish.
Conservation status: The IUCN lists haddock as Vulnerable or facing a high risk of extinction in the wild. ∎
FOR MORE INFORMATION
Kurlansky, M. Cod: A Biography of the Fish That Changed the World. New York: Walker, 1997.
Schultz, Ken. Ken Schultz's Field Guide to Saltwater Fish. New York: Wiley, 2004.
"Atlantic Cod." Fisheries and Oceans Canada. http://www.dfo-mpo.gc.ca/zone/underwater_sous-marin/atlantic/acod_e.htm (accessed on October 7, 2004).
"Cod War." All Science Fair Projects. http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Cod_War (accessed on October 7, 2004).
"Empty Oceans, Empty Nets." PBS. http://www.pbs.org/emptyoceans/cod (accessed on October 7, 2004).