Atlantic Cod

(Gadus morhua)

Atlantic Cod

Distribution

Atlantic cod occur on both sides of the North Atlantic. In the eastern North Atlantic, cod stocks are distributed from Iceland to the Norwegian Sea, to the Barents Sea and Spitsbergen, and southward to the Baltic Sea and Bay of Biscay. In the western North Atlantic, their geographic range is from Greenland and southern Baffin Island, along the continental slope off Labrador, Newfoundland, the Gulf of St Lawrence, the Grand Bank and Scotian Shelf, Bay of Fundy-Gulf of Maine, and southward to Cape Hatteras, North Carolina (lat 3510' N). Throughout the range of distribution, there are many different and identifiable cod stocks, each with its own set of characteristics.

Habitat

Atlantic cod inhabit cool-temperate to subarctic waters from inshore regions to the edge of the continental shelf. Although cod are adapted for bottom feeding, they can be found at any depth between the surface waters and the sea bed. Their preferred temperature range is from -0.5 to 10 degrees Celsius, although this can vary with time of year, geographic location, and size of fish.Cod have also been reported making incursions into waters outside their preferred range in order to feed on capelin or other prey, or during periods of migration.

Atlantic cod tend to move in schools and, in some areas at least, they move offshore in winter and onshore in summer. They can travel great distances during their migrations, possibly the greatest recorded distance travelled by a tagged cod being from the central North Sea, to the Grand Bank off the Canadian coast, a distance of over 3228 km.

Food

As fry, cod feed on a variety of small creatures such as copepods, amphipods, and barnacle larvae. Juveniles and young adults continue to eat crustaceans such as euphausiids, mysids, shrimps, small lobsters, spider crabs, and hermit crabs. As they reach adulthood, fish, such as capelin, herring and sand lance, becomes the predominant food.

Atlantic cod can attain great size - up to and over 100 cm - under favorable conditions. Size at age, and maximum size depend on a variety of environmental conditions. In recent times, large cod have become more and more scarce.

Antifreeze Production - Antifreeze Glycoprotein

To date, the only populations of Atlantic cod to be examined for antifreeze production are those found off the east coast of Canada. Adult cod produce antifreeze glycoproteins in response to sub-zero water temperatures, with photoperiod playing only a minor role in control of production.

Reference

Fletcher,G.L., M.J.King, and M.H.Kao. 1987. Low temperature regulation of antifreeze glycopeptide levels in Atlantic cod (Gadus morhua). Canadian Journal of Zoology: 65, 227-233.

Greenland Cod

(Gadus ogac)

Greenland Cod

Distribution

Also known as the rock cod, ogac, uvac, and pilot, the Greenland cod occurs from Alaska, along the Arctic coast of Canada, round to Greenland, and southward into Hudson Bay, Ungava Bay and the Hudson Strait, along the Labrador coast to Newfoundland, through the Strait of Belle Isle and into the Gulf of St Lawrence, and further south to Bras d'Or Lake and Cape Breton, NS.

Habitat

Greenland cod inhabit cold temperate to arctic waters, usually in inshore regions in the northern part of the range. Along the Labrador coast, this species is the most common type of codfish to be found in harbours and fjords, occurring less commonly in offshore waters.

Food

In Greenland waters, the Greenland cod eats mainly fishes, especially capelin, Arctic cod, smaller Greenland cod, and Greenland halibut. Among the invertebrates, amphipods, shrimps, crabs, molluscs, and polychaete worms are commonly eaten. Gadus ogac is similar in appearance to the Atlantic cod, but is generally smaller and rounder, and with somewhat different (darker) colouration both externally and internally.

Antifreeze Production - Antifreeze Glycoprotein

The seasonal cycle of antifreeze production in Gadus ogac has yet to be documented. However, it seems likely that antifreeze is produced during the winter months in response to environmental stimuli and is lost from the plasma and other extracellular fluids during the warmer summer months (as is the case with the Atlantic cod, Gadus morhua).

References

Van Voorhies, W.V., J.A.Raymond, and A.L.DeVries. 1978. Glycoproteins as biological antifreeze agents in the cod, Gadus ogac (Richardson). Physiological Zoology. 51: 347-353.

O'Grady,S.M., J.D.Schrag, J.A.Raymond, and A.L.DeVries. 1982. Comparison of antifreeze glycopeptides from Arctic and Antarctic fishes. Journal of Experimental Zoology. 224: 177-185.


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