Origin and life history of Atlantic salmon (<i>Salmo salar</i>) near their northernmost oceanic limit

Abstract

138 Atlantic salmon (Salmo salar) captured in the Advent Fjord off Svalbard were genetically assigned to two main clusters of European salmon. Two-thirds were assigned to salmon rivers in Finnmark (the northernmost county in Norway) and the rest to salmon rivers further south in Norway. The genetic assignment was based on genetic profiles from 60 Norwegian rivers. The two clusters correspond to two larger genetic groupings: the Barents–White seas and Atlantic groupings. Thus, we cannot rule out other populations from these groupings as sources of Atlantic salmon at Svalbard. Svalbard salmon assigned to the two genetic groupings differed in ecological and phenological traits, with highest smolt age and lowest postsmolt growth in the Finnmark salmon cluster. High smolt ages in both groups, however, suggest a northern origin of most individuals in the sample. Although Atlantic salmon have sporadically been observed in the Arctic Ocean at earlier times, the high abundance outlined here seems to be a recent phenomenon, suggesting a northward penetration caused by climate change.