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

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 throug hout early (November-December) and late (February-March) winter, river and sea age distributions were estimated from 2350 scale samples obtained in th e early and late winter during four consecutive fishing periods 1991/1992-1 994/1995. The origin of recaptures of salmon tagged as smelts in different European countries were also compared between early and late winter. The fi sh were classified as being of wild or fish farm origin from scale characte ristics. and farmed salmon were excluded from the analyses. Age composition s in samples from the four fishing periods showed consistent patterns. The average smelt age (+/-S.E.) was significantly lower in the early than in th e 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 Eu ropean countries tend to smelt at an earlier age and produce more one sea-w inter salmon than in northern Europe, we suggest that a significant proport ion of the salmon caught in the Faroes area during early winter originate f rom southern European countries and that fish from northern regions appear to be more abundant in the late winter period. Recaptures in the Faroese fi shery during early and late winter of salmon tagged as smelts in different countries support this. (C) 2001 Elsevier Science B.V. All rights reserved.