Spatial and temporal distribution of post-smolts of Atlantic salmon (Salmo salar L.) in the Norwegian Sea and adjacent areas

Knowledge of the migrations and geographic distribution of post-smolts of Atlantic salmon (Salmo salar L.) in oceanic waters is sparse. Surface trawl surveys were carried out by the Institute of Marine Research, Bergen, Norway, in the Norwegian Sea and adjacent areas in 1990–1998. Sampling was carired out south of 62°N in May–June, in the Norwegian Sea north of 62°N in July–August and in the Barents Sea in August–September. In a total of 955 surface trawl hauls, 535 post-smolts were caught. The highest incidences of post-smolts were in the slope current west of the British Isles, where the highest catch per unit of effort (c.p.u.e.) value was recorded between northern Scotland and the Faroes in June 1997. The lowest c.p.u.e. was observed in August/September 1998 in the Barents Sea, where no post-smolts were caught. The post-smolts appear to follow the main surface currents northwards into the Norwegian Sea where they spread in a fan-like distribution over an area covering most of the international waters between the exclusive economic zone (EEZ) of Norway, the Faroes and Iceland up to about 73–75°N. This pattern appeared to be stable between these years with the exception of 1997, when almost no post-smolts were caught in the northernmost areas, although catches in the south were similar to or higher than in the previous years. The geographical distribution of post-smolts of Atlantic salmon is associated with the warmer, saline Atlantic water.