Seasonal differences in the origin of Atlantic salmon ( Salmo salar L.) in the Norwegian Sea based on estimates from age structures and tag recaptures

Abstract

To test if the population structure of Atlantic salmon ( Salmo salar L.) at the feeding areas in the Norwegian Sea north of the Faroes is stable throughout early (November–December) and late (February–March) winter, river and sea age distributions were estimated from 2350 scale samples obtained in the early and late winter during four consecutive fishing periods 1991/1992–1994/1995. The origin of recaptures of salmon tagged as smolts in different European countries were also compared between early and late winter. The fish were classified as being of wild or fish farm origin from scale characteristics, and farmed salmon were excluded from the analyses. Age compositions in samples from the four fishing periods showed consistent patterns. The average smolt age (±S.E.) was significantly lower in the early than in the late winter (2.5±0.04 and 2.7±0.03, range 1–5) as was average sea age (1.9±0.03 and 2.2±0.02, range 1–6). As salmon from southern European countries tend to smolt at an earlier age and produce more one sea-winter salmon than in northern Europe, we suggest that a significant proportion of the salmon caught in the Faroes area during early winter originate from southern European countries and that fish from northern regions appear to be more abundant in the late winter period. Recaptures in the Faroese fishery during early and late winter of salmon tagged as smolts in different countries support this.