Not all lineages are equally invasive: genetic origin and life-history in Atlantic salmon and brown trout acclimated to the Southern Hemisphere

Salmonids are fish from the Northern Hemisphere which have been introduced and acclimated to many regions in the Southern Hemisphere for commercial (aquaculture) and recreational (sport fishing) purposes. In some cases a species like brown trout Salmo trutta rapidly spread across the host ecosystem and became invasive, threatening local fauna, and even outcompeting other exotic fish. We have analyzed life-history traits in combination with genetic variation of Atlantic salmon and brown trout adapted to the lake systems of the Argentinean Patagonia (South America). We have identified two main characteristics that conferred invasive capacity to those exotic species: undomesticated status and lifelong growth. Stocks originated from wild populations adapted better than long-term domestic lineages, and their geographic origin seems to be less important for adaptation to exotic environments. We propose that considering these characteristics in future planning of commercial aquaculture projects by selecting non-invasive lineages will minimise the impact of accidental escapes.