Introgression of non-native mitochondrial haplotypes from farmed to wild Atlantic salmon

Farmed salmon escape and interbreed with wild Atlantic salmon on a large scale. We studied introgression of mitochondrial haplotypes from farmed Atlantic salmon originating from the Eastern Atlantic phylogenetic group to wild salmon of the Barents-White Sea (BWS) phylogenetic group. We find that farmed genetic introgression introduced novel, non-native haplotypes into the BWS phylogenetic group. The mitochondrial genome has important functional effects and is inherited as a haploid from the mother. Hence, the observed introgression across natural genetic barriers is expected to cause long-lasting functional maladaptation of the hybrids in the maternal line. As the use of farmed Atlantic salmon from non-native phylogenetic groups is widespread in aquaculture, the impact on wild Atlantic salmon may be more severe than previously recognized. Our results highlight the ecological risks of releasing non-native wild and domesticated animals.

Automated summary

Farmed Atlantic salmon escape and hybridize with wild Atlantic salmon, introducing non-native haplotypes into the wild population. This genetic introgression can cause functional maladaptation in the hybrids, particularly in the mitochondrial genome inherited from the mother. As the use of farmed salmon from different phylogenetic groups is widespread in aquaculture, the impact on wild salmon may be more severe than previously recognized. This study highlights the ecological risks of releasing non-native domesticated animals into the wild.