Cod Fishes

The cods belong to the family Gadidae, which has three subfamilies, the Lotinae, the Phycinae, and the Gadinae. As Figure 2 shows, the cods have elongate bodies with large heads and mouths. They have well-formed caudal fins and may have two or three dorsal fins as well as one or two anal fins. They are normally dark and colored brown to gray. The cods produce free-floating eggs that do not contain oil globules. There are approximately 55 species of cods belonging to 21 genera. They are primarily marine and inhabit the cooler waters, near the bottom of northern seas. Most migrate inshore during the summer and move to deeper waters in the fall and winter. There are exceptions such as the burbot (Lota lota), which is a freshwater fish, and landlocked populations of the Atlantic tomcod (Microgadus tomcod). Furthermore, there are species that

reside in southern seas. The 7 species discussed here were selected on the basis of their commercial importance as food fishes.

Atlantic Cod

The Atlantic cod (Gadus morhua) is one of the most important food fishes of the world. It is Canada's most important commercial species in terms of net value. Atlantic cod is caught commercially in a many ways, including trawl gear, seine, and gill nets, hand lines and jiggers. In 1984, the 463,100 tons of Atlantic cod landed in Canada was valued at $168.6 million. The Atlantic cod is also caught for sport with hook and line. The Atlantic cod cheek is a delicacy, served in the finest restaurants. By-products of the cod include fish meal, cod liver oil, and glue. Between these two extremes, the Atlantic cod is present in almost every food niche. It is sold fresh, frozen, smoked, salted, and canned. Fish and chips and fish sticks are prime market products for the cod.

The Atlantic cod is distributed throughout the cooler northern waters of the Atlantic Ocean. On the eastern shore, the Atlantic cod is found from Iceland, south to the Baltic Sea and to the Bay of Biscay. On the western side of the Atlantic, it is found in the North Atlantic from Greenland and southern Baffin Island, to Cape Hatteras, N.C. The majority of the populations are found on the continental shelf.

The Atlantic cod can be found spawning during most months of the year, from February to December, throughout their extensive range. The northern populations spawn earlier. As an example, spawning in the Grand Bank, which is one of the major fishing grounds for the Atlantic cod, begins in April, peaks in May, and ends in June. Spawning takes place in the open ocean at varying depths. While some may spawn at depths less than 110 m, other Atlantic cod populations will spawn deeper than 182 m. Both eggs and milt are broadcast into the water. Fecundity is high and increases with age. Although a fish 51 cm in length may produce 200,000 eggs, a female 140 cm may produce 12 million eggs. Like the haddock, the eggs are about 1.5 mm in diameter, spherical, transparent, and bouyant. They rise and float freely under the surface during incubation. As for all fish eggs, incubation time depends on temperature. Due to the colder waters that characterize their environment, the eggs take from 40 to 60 days to hatch (—1.5 to 1°C). The newly hatched young are about 3-6 mm long and remain pelagic until a length of about 25-30 mm. They then descend to the bottom to feed and mature to adult sizes. The average adult caught by the commercial fishery is about 5-6 yr old, 50-60 cm long, and about 1-2 kg. They can live to be over 20 yr old and the largest recorded animal was 95.9 kg.

Pacific Cod

The Pacific cod (Gadus macrocephalus) is known as the common or gray cod. Like its counterpart on the Atlantic Coast, it is the most important trawl-caught bottom fish in western Canada. This trawl catch increased to a peak of about 9.1 million kg in 1966. It decreased after that to about 2.3 million kg in 1970. The Pacific cod is sold fresh and frozen. The flesh is filleted, and products such as fish sticks or fillet blocks are made for the domestic and export markets.

The Pacific cod is similar in appearance to the Atlantic cod. In general, it may be more slender and may have a longer barbel under the lower jaw that equals or exceeds the diameter of the eye. The Pacific cod is found on both sides of the Pacific Ocean. Its distribution extends from Santa Monica, Calif, north to Alaska and around into the Okhotsk and Japan seas. It is also found off Korea and in the Yellow Sea to Port Arthur.

The Pacific cod may be found in shallow waters in the spring but migrates into deep water in the fall. They spawn in the winter months. Spawning females range from 40 to 60 cm in length and are two to three years old when they spawn the first time. A 60-cm female may produce about 1.2 million eggs, which measure about 1 mm in diameter. The eggs and milt are broadcast into open waters and the fertilized eggs may float near the surface, depending on the salinity. In the cold northern waters, the eggs may take four weeks to hatch at 2°C. The incubation time is reduced to about 8 days at about 10°C. At 5°C, the yolk sac is absorbed in about 10 days. The young will grow to about 2050 cm in one year and to about 45-75 cm in about two years.

Haddock

The haddock (Melanogrammus aeglefinus) is a commercially valuable food fish of the cod family. Haddock are caught commercially with the otter trawl. They are sold as a fresh, frozen, smoked, and canned product. The major stocks are presently recovering from the overexploitation of the 1960s.

Like the other cods, the haddock is rather dark in color. The color fades from the purplish gray on the dorsal surface, laterally to a light pink below the lateral line, and eventually to a white on the ventral surface. There is a characteristic black blotch on the lateral side posterior to the head and just dorsal to the pectoral fins.

The haddock is found on both sides of the Atlantic. On the eastern side of the North Atlantic, it is distributed from Iceland south to the English Channel. It is found in the White, Kara, Norwegian, and North seas. On the western side of the Atlantic, the haddock is found from southwestern Greenland, south along the east coast of Canada and the United States to about Cape Cod. They migrate between the shallower (30-37 m) warm waters of the banks during the summer and the deeper (55-125 m) waters in the winter.

The haddock spawns in waters up to 90 m in depth, primarily on the Grand, Emerald, Browns, and Georges banks. They spawn between January and May, depending on location. The spawning adults are between 3 and 5 yr old. While many features of the reproductive process in the haddock are characteristic of the cods, observations of aquarium specimens suggest that the reproductive behavior of the male fish is complex, involving color changes, sound production, and courtship displays. The spawning female measures between 40 and 60 cm long and may produce between 230,000 and 1.77 million eggs, respectively.

The eggs resemble that of the Atlantic cod. Like the other cods, the eggs and milt are broadcast into the open waters. After fertilization, the eggs float to the surface and float freely until they hatch. In the cooler waters of the North Atlantic, incubation may take between one (10°C) and four (2°C) weeks. The newly hatched alevins are about 4 mm long and grow to young larvae of about 25 mm before they resemble the adult in body form. They start to descend to deeper waters between 40 and 50 mm. Although the average 5-yr-old haddock may measure about 50 cm in length, the fish can live to be over 15 yr in age and an individual 112 cm long and 16.8 kg has been recorded.

Pollock

The pollock (Pollachius virens) is also known by other names such as Boston bluefish, coalfish, and green cod. The flesh, which is of a darker color than the cods and haddock, has a richer flavor than its relatives. The adult weighs about 2-5 kg and is fished commercially as an important food fish. The pollock is caught commercially in a number of ways, including trawling, longline, hand line, weirs, and traps. It is sold in fresh, frozen, and smoked forms. It is also fished for sport in the shallower waters with artificial lures.

Like the haddock, the pollock are distributed throughout the North Atlantic. On the east side, they are found from Iceland, south to the Bay of Biscay. On the west side of the Atlantic, the pollock are found from southwestern Greenland to Cape Hatteras, N.C.

At maturity, the male and female are about 3 yr old and are about 50 cm long; although records show that they can live up to 14 yr, weight 70 kg, and measure over 100 cm. The pollock shares much of the reproductive features of other cod fishes. They produce about 225,000 eggs each; the eggs are about 1 mm in diameter, spherical, bouyant, and remain pelagic until hatching. Eggs and milt are released into the open waters at a depth of about 100-200 m. Unlike other cod fishes, the pollock spends more time swimming throughout the water column as opposed to being a primarily bottom fish. Its preferred depth is about 110-180 m. Like the cod fishes, however, the pollock migrates toward shore and shallow waters in the summer and offshore to deeper waters in the winter.

Walleye Pollock

The walleye pollock (Theragra chalcogramma) has come to be one of the most important commercial fisheries in the world. It has been described as the most productive single-species fishery in the world. While it once had a limited market for human consumption due to its soft flesh, it is fished intensively today for the roe, frozen fish block and fillets, and processed fish flesh markets. Surimi, a processed minced fish flesh product, is also one of the prime products from the flesh of walleye pollock. These fishery products that derive from the walleye pollock are taken by separate fisheries, although trawling and seining are the common methods of catch. The surimi fishery consists of large factory trawlers or large factory ships with fleets of smaller catcher vessels; walleye pollock of all sizes are taken from the bottom and midwater depths. The freezer fishery consists of large factory trawlers and smaller independent fisherman that harvest walleye pollock off the bottom, along with other species such as turbot and the Pacific cod. The spawning adults are caught for the roe fishery from the midwaters.

The walleye pollock has a typical codlike appearance with three, well-separated dorsal fins and very small or no barbels projecting from the lower jaw. It usually has an olive green to brown color on its back with irregular blotches or mottled appearance. It is lighter on its ventral surface and has silvery sides.

The walleye pollock is distributed from central California, north through the Bering Sea, around to Asian waters to the southern reaches of the Sea of Japan. It has a wide distribution vertically in the water column. It has been found from the surface to depths below 380 m.

Walleye pollock begin to mature sexually at about 2-3 yr of age, when they measure about 25 cm. By the time they are 5-6 yr old and 45 cm, more than 90% are mature. The fecundity of a 50-cm female is between about 200,000 and 220,000 eggs. Estimates of fecundity range from about 100,000 to 1 million eggs for females between 30 and 70 cm in length, and 225 to 2,000 g, respectively. While spawning occurs during one season of the year, the female will spawn a number of times within that season. The eggs develop and mature in batches over time to allow multiple spawnings. Spawnings takes place mostly between March and April. The eggs measure about 1.4 mm in diameter and float freely in the water, once they are spawned. They are found mostly in the upper 20 m of the water column. Hatching may take place between 14 (5°C) and 24 (2°C) days. The hatched young measure about 4 mm in length and resemble tadpoles, with characteristic markings. They are born with yolk sacs, which are absorbed by the time they attain about 7 mm in length. At 22 mm and about 50 days after hatching, they have all the adult fin rays and are considered juveniles. Adults can live to 15 yr, although most are between 1 and 7 yr of age.

Hake

The red hake (Urophycis chuss) and the white hake (U. tenuis) are often considered as good food fishes. The white hake grows to a larger size and is distributed over a broader range than the red hake. Characteristics of the white hake are presented here. Similar in size to other cod fishes, the hake is distinguished by the smaller head, large eyes, long dorsal and anal fins and the numerous barbels on the ventral side of the chin. They have a reddish brown color on their back, which fades to lighter shades on the side and white on the belly. The lateral line is pale. While some hake fisheries exist, this species is mostly taken incidental to other fisheries.

The hake live on mud bottoms, 200-1,000 m in depth. They are distributed on the continental slopes in the North Atlantic from Iceland south to North Carolina. Some have strayed as far south as Florida in deep water. Like the other cod fishes, they move to deeper waters in the fall and winter.

The average size of an adult at maturity is between 60 and 70 cm, although specimens over 100 cm have been re corded. Spawning takes place at different times depending on the location, although most takes place in the winter and early spring. Fecundity is high relative to other cods. A 70-cm-long female may produce about 4 million eggs, and one 90 cm long may produce 15 million eggs. The eggs, therefore, are smaller than those of the other cod fishes and measure about 0.75 mm in diameter. The eggs, which are transparent and bouyant, float about the sea until the young alevins, about 2 mm long, hatch. The young grow up to about 80 cm as pelagic fish, after which they migrate to deeper waters to feed and grow to maturity.

Whiting

The name whiting can refer to any one of three species of fish. It was a name originally given to the walleye pollock (Theragra chalcogramma) (1). The Pacific tomcod (Micro-gadus proximus) is also commonly called the whiting. While the Pacific tomcod is highly regarded as a tasty food fish, it is not abundant enough for a commercial fishery. The blue whiting (Micromesistius poutassou) on the other hand is fished in Europe for food. The blue whiting is rather rare in North America.

The blue whiting is normally found in the northeast Atlantic, off the coast of Greenland and off southern Iceland. It may also be found off Europe between Norway, south to western Mediterranean. Records of the blue whiting in North American range from Sable Island, south to Woods Hole, Mass. The blue whiting is a deep-water fish, caught by otter trawls at depths beyond 183 m off the continental slope during the spring or early summer. The scarce data on the reproductive features of this fish suggest that they resemble, verly closely, reproduction in other species of the Gadidae. It has been suggested that spawning occurs between mid March to mid May (2). Spawning probably occurs in deep waters, deeper than 1,000 m, and the eggs are about 1-1.3 mm in diameter. The few specimens inspected from the northwest Atlantic suggest that the blue whiting is smaller than other Gadids, measuring less than 40 cm.

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