Annual numbers of Atlantic salmon (Salmo salar) and anadromous brown sea trout (S. trutta) leaping at the Pots of Gartness, Loch Lomond, Scotland

Abstract

The Atlantic salmon (Salmo salar) and anadromous brown sea trout (S. trutta), present in the North Atlantic and many rivers both in Europe and North America that run into this ocean, undergo seasonal migrations moving between rivers and the sea (Sutterby & Greenhalgh, 2005;Freyhof, 2011). Young Scottish salmon hatch as alevins in streams and rivers from where they develop into parr and, as smolts, move out to the Norwegian Sea or North Atlantic west of Greenland to feed and grow before returning to fresh water to mate and spawn; Scottish sea trout perform similar life cycles, although they feed mostly in the coastal marine areas relatively close to the shore. Furthermore, Atlantic salmon are iteroparous, in that adults can return to salt water after spawning, and repeat the breeding cycle in later years, with some fish attaining a significant age and large size.