Topic: Atlantic cod - North Sea, Skagerrak and the Eastern English Channel

"Southern" cod is found in the southern North Sea and the eastern English Channel. "Viking" cod is found in northeastern North Sea and Skagerrak, where juveniles recruit into the main sub-population. "Northwestern" cod is found along the western parts of the North Sea and the Scottish coast, and is suspected to form a wider population unit with cod west of Scotland.

Spawning takes place from January to the end of May, starting earliest in the south. The main spawning season is January–February in southern North Sea, February–March in the central region and March in the northernmost parts of the North Sea. The eggs hatch after two to three weeks. In June, the young-of-the-year are between 20 and 80 mm long. The main nursery areas are found along the Danish coast up to Skagerrak. Juveniles are also commonly found around Shetland.

The first winter the juveniles grow up to 13–27 cm. Some mature as early as two years old and as small as 25 cm, but most will mature between the age of 3 and 4 and at an average size of 50 cm. Six years old can already weigh as high as 10 kgs.

North Sea cod grows and mature much earlier than the northern population of Barents Sea cod, and also has a shorter lifespan.
 
Cod diet changes with age and maturity stage. Young juveniles eat mainly crustacean prey, but as they grow in size fish become a gradually more important part of their diet. Cod lives mainly close to the bottom where it commonly feeds on sand eel, herring, and Norway pout, but they can also swim higher in the water column to feed on shoals of pelagic fish. Cod is also prone to cannibalism and fish up to three years old can be eaten by older individuals.