Domestication-Admixed Atlantic Salmon (Salmo salar) Establish a Productive Population in the Wild

Widespread aquaculture escapes have led to domestication-admixture in many wild Atlantic salmon populations, widely regarded as a threat to their evolutionary trajectory and persistence amid historically low population numbers. Although decades of research document reduced fitness of domesticated-admixed offspring in the wild, productivity measurements of domestication-admixed or feral salmon populations are lacking. Over a 10-year period, we document colonisation of a river by highly (average 37%) domestication-admixed salmon using up- and downstream traps, genomic data and genetic identification of over 4000 spawners and smolts. Colonisers were identified as strays originating from admixed neighbouring rivers. The resulting population now displays freshwater and marine productivity within ranges observed in wild populations. Our data therefore demonstrate that domestication-admixed individuals can rapidly establish populations in the wild, likely facilitated in this case by an absence of local competition. Furthermore, high levels of domestication admixture do not preclude a productive population trajectory.