As its name implies, the Atlantic salmon is native to the continents bordering the Atlantic Ocean in the Northern Hemisphere. There, it is a highly prized sports fish renowned for its large size and fighting abilities. Although early settlers in New Zealand were eager to establish Atlantic salmon populations here, most introductions were not successful and feral stocks are confined to the upper Waiau River catchment where it is considered to be close to extinction. Breeding stocks of Atlantic salmon are maintained at the Otago Fish and Game Council hatchery in Wanaka.
Atlantic salmon closely resemble brown trout, but are a more slender, elongate fish. The caudal peduncle is also longer; if the anal fin is folded up against the body, it does not reach the base of the caudal fin. Atlantic salmon have dark backs, fading to a silvery colour below the lateral line. The back and sides are covered in small, darker spots but these generally do not extend below the lateral line. There are no spots on the tail.
In their native waters, adult Atlantic salmon live in the sea and migrate to their freshwater spawning grounds in winter. Unlike the Pacific salmon species, Atlantic salmon can spawn more than once. In New Zealand most adults reside in lakes and migrate upstream for spawning. Spawning here also occurs in winter.