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Aquaculture Environment Interactions

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AEI 12:45-59 (2020)  -  DOI:

Model-based evaluation of the genetic impacts of farm-escaped Atlantic salmon on wild populations

Ian R. Bradbury1,*, Steve Duffy1, Sarah J. Lehnert1, Ragnar Jóhannsson2, Jon Hlodver Fridriksson2, Marco Castellani3, Ingrid Burgetz4, Emma Sylvester1, Amber Messmer1, Kara Layton1, Nicholas Kelly1, J. Brian Dempson1, Ian A. Fleming5

1Science Branch, Fisheries and Oceans Canada, 80 East White Hills Rd., St. John’s, NL A1C 5X1, Canada
2Marine and Freshwater Research Institute, Skulagata 4, 101 Reykjavik, Iceland
3Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK
4Fisheries and Oceans Canada, 200 Kent Street Ottawa, ON K1A 0E6, Canada
5Department of Ocean Sciences, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
*Corresponding author:

ABSTRACT: Genetic interactions (i.e. hybridization) between wild and escaped Atlantic salmon Salmo salar from aquaculture operations have been widely documented, yet the ability to incorporate predictions of risk into aquaculture siting advice has been limited. Here we demonstrate a model-based approach to assessing these potential genetic interactions using a salmon aquaculture expansion scenario in southern Newfoundland as an example. We use an eco-genetic individual-based Atlantic salmon model (IBSEM) parameterized for southern Newfoundland populations, with regional environmental data and field-based estimates of survival, to explore how the proportion of escapees relative to the size of wild populations could potentially influence genetic and demographic changes in wild populations. Our simulations suggest that both demographic decline and genetic change are predicted when the percentage of escapees in a river relative to wild population size is equal to or exceeds 10% annually. The occurrence of escapees in southern Newfoundland rivers under a proposed expansion scenario was predicted using river and site locations and models of dispersal for early and late escapees. Model predictions of escapee dispersal suggest that under the proposed expansion scenario, the number of escapees is expected to increase by 49% and the highest escapee concentrations will shift westward, consistent with the location of proposed expansion (20 rivers total >10% escapees, max 24%). Our results identify susceptible rivers and potential impacts predicted under the proposed aquaculture expansion scenario and illustrate how model-based predictions of both escapee dispersal and genetic impacts can be used to inform both aquaculture management decisions and wild salmon conservation.

KEY WORDS: Hybridization · Atlantic salmon · Aquaculture · Management · Newfoundland

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Cite this article as: Bradbury IR, Duffy S, Lehnert SJ, Jóhannsson R and others (2020) Model-based evaluation of the genetic impacts of farm-escaped Atlantic salmon on wild populations. Aquacult Environ Interact 12:45-59.

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