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AEI
Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00370

    Escape history and proportion of farmed Atlantic salmon Salmo salar on the coast and in an adjacent salmon fjord in Norway

    Tonje Aronsen*, Eva M. Ulvan, Tor F. Næsje, Peder Fiske

    *Corresponding author:

    ABSTRACT: To gain more knowledge about escaped farmed salmon Salmo salar L. in the wild, we investigated the proportion of escapees, body length at escape, proportion escaped as smolts/post-smolts (£300 mm) and number of winters in the wild (winter zones in the growth pattern in the scale samples) after escape in catches on the coast and in an adjacent fjord in the years 2013─2017. The mean proportion of escapees was higher on the coast (26%) than in the fjord (4%), and escapees caught on the coast had a slightly larger mean body length at escape (607 mm) than in the fjord (557 mm). However, the mean proportion escaped as smolts/post-smolts did not differ between the coast (8%) and the fjord (11%). There were also no differences in the mean proportion of farmed salmon with 1 or more winter zones after escape (50% on the coast and 56% in the fjord). The proportions of escapees with 1, 2, 3 or 4 winter zones after escape were 28, 20, 2 and 0.4% and 30, 21 and 4% in catches on the coast and in the fjord, respectively. This study found that the proportion of escapees was considerably higher in coastal waters than in the nearby fjord. Escapees consisted of farmed salmon from several escape events over several years, and approximately 50% of the escapees had one or more winter zones after escape. Thus, escaped farmed salmon may pose a threath to wild salmon populations for several years after the escape event.