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Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00444

    Genetic structure and origin of non-native, free-living Atlantic salmon Salmo salar along a latitudinal gradient in Chile, South America

    Rodrigo Marín-Nahuelpi, José M. Yáñez, Selim S. Musleh, Diego Cañas-Rojas, Juan Carlos Quintanilla, Sergio Contreras-Lynch, Gonzalo Gajardo, Maritza Sepúlveda, Chris Harrod, Daniel Gomez-Uchida*

    *Corresponding author:

    ABSTRACT: Limited stocking efforts to introduce Atlantic salmon Salmo salar into Chilean rivers and streams were unsuccessful during the 20th century. Following the arrival of the aquaculture industry during the 1980s, escaped Atlantic salmon may pose ecological risks to native populations through predation, competition, and transmission of pathogens or parasites. However, whether commercial aquaculture strains represent the likely source of free-living Atlantic salmon in marine and freshwater environments is unclear. We used 272 single nucleotide polymorphisms to characterize free-living Atlantic salmon (n = 80) captured from 12 marine and freshwater locations from southern Chile. These were compared with 8 reference collections, 6 known commercial strains, and 2 wild populations of Atlantic salmon. We evaluated genetic structure among free-living Atlantic salmon and assessed individual ancestry and origin by assigning mixture samples to reference collections. We found evidence for genetic structure (K = 3; number of clusters) among free-living salmon unexplained by geography, environment, or life stage, but consistent with the number of clusters among commercial aquaculture strains. Most free-living Atlantic salmon had a close ancestry with farmed Norwegian strains, the most widely used by the industry, pointing to recent aquaculture escapes as their origin. Yet, recent establishment of self-sustaining populations weakly differentiated from aquaculture broodstock cannot be ruled out. We propose increasing monitoring efforts of free-living Atlantic salmon in remote sites, as well as in watersheds located in densely stocked aquaculture areas.