The saithe's habitat is in the North Atlantic Ocean, from the Barent Sea to the Biscaya Bay, and around Iceland and Greenland, and from the Hudson Bay to the coasts of North Carolina, USA.  In Icelandic waters it is more common in the warmer seas off the southwest and south coasts than of the north coast.

It is found from the surface to the ocean floor, down to 450 m, but most commonly at 200 m.  Its ideal temperatures lie between 4°C and 12°C.  It migrates in great schools too feed.  Tagging has confirmed the great migration distances of this species.  Its feeding habits depend on its size.  The fries feed on worms and crustreceans, while the larger fish  feed on capelin, sand eel, other fishes and krill.  The saithe fries feed other fishes and birds, and the larger fishes sharks and toothed whales.

During the first year the saithe grows fast.  At the age of 4-5 months it is 5-6 cm long and seven months later 10-25 cm.  Two years old it measures 28-42 cm and heads for deeper waters.  It reaches puberty 4-7 years old.  It is believed, that can reach the age of 30 years.