Mature Gadus morhua
grow to approximately 120 cm in length, weighing around 12 kg, however larger fish have been recorded. Age of maturity varies regionally but is usually between one and fifteen years. Colour is variable depending on habitat but most are spotted with white bellies. Atlantic cod are commonly found on sandy bottoms and are often mottled brown in appearance. This is a heavy and powerful fish with three dorsal and two anal fins, all slightly rounded, and either a square or rounded tail fin. The upper jaw overhangs the lower and the long chin barbel is equal to the eye in diameter. A prominent curved, white (or very pale) lateral line makes this species easy to identify. Mainly demersal, although pelagic under certain conditions.Atlantic cod is one of the UKs most popular commercial species and as a result has been fished extensively in UK waters. They can often be found in large, dense shoals, making them an easy target for fishermen. Extensive over fishing has resulted in this once prolific species becoming commercially rare.
Atlantic cod are productive breeders. Spawning occurs between February and April when 3 to 6 million buoyant eggs are released, often forming great swarms that can be transported miles by ocean currents before hatching after 12 days. The larval stage of this species is also planktonic and will be carried by currents for up to 2 months before settling on the seabed where the Atlantic cod spend most of their life (Dipper, 2001).
Young Gadus morhua
feed mainly on copeopods but become increasingly dependant on fish as they age, eating the likes of herring, capelin, haddock and even other cod (Dipper, 2001; Wheeler, 1969).
Sub-species Gadus morhua morhua is the most common, and is found from both the western and eastern north Atlantic. Gadus morhua callarias is a low salinity non-migratory race found in the Baltic, and Gadus morhua marisalba occurs in the White Sea.