Escaped farmed Atlantic salmon represent a well-documented and ongoing threat to wild conspecific populations. In Norway, the world-leading producer of farmed salmon, annual monitoring of straying and genetic introgression by farmed escapees in wild salmon rivers has been carried out since the late 1980s. In this study, we applied molecular and statistical methods routinely used in the Norwegian monitoring program to investigate the magnitude of escaped farmed salmon and genetic introgression in salmon rivers on the west coast of Sweden, where suspected escapees have been observed. Our results confirm that escaped farmed salmon stray, successfully spawn, and produce offspring at levels similar to those observed in neighboring Norway.
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