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Aquaculture Environment Interactions

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AEI 14:243-262 (2022)  -  DOI:

Fitness consequences of hybridization between wild Newfoundland and farmed European and North American Atlantic salmon

Shahinur S. Islam1,*, Brendan F. Wringe2, Corinne M. Conway1, Ian R. Bradbury1,3, Ian A. Fleming1

1Department of Ocean Sciences, Ocean Sciences Centre, Memorial University of Newfoundland, St John’s, NL A1C 5S7, Canada
2Salmon Section, Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, NS B2Y 4A2, Canada
3Salmonids Section, Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, 80 East White Hills Road, St John’s, NL A1C 5X, Canada
*Corresponding author:

ABSTRACT: Selection due to multi-generational domestication and genetically distinct origins raises concerns about potential fitness consequences of hybridization between farmed and wild Atlantic salmon. In Newfoundland (NF), Canada, the aquaculture industry uses the North American (NA) Saint John River strain, though site-specific permission has been granted to farm a European origin (EO) strain. We used complementary experiments to investigate differences in (1) dominance status and (2) growth and survival in allopatry (NF wild fish) versus sympatry (NF wild fish with NA/EO farmed individuals and related F1 hybrids) in contrasting tank and semi-natural stream environments. NA farmed salmon were more dominant than NF wild individuals, with hybrids being intermediate in expression and not differing from wild fish. EO farmed salmon also tended to dominate NF wild individuals, but not significantly. Competition with farmed fish and hybrids did not affect the growth of wild fish in sympatry versus allopatry in the tank environment. However, that was not the case in one instance in the stream environment where wild fish in sympatry with NA farmed fish and hybrids outgrew those in allopatry. Within sympatric treatments, both EO and NA farmed salmon outgrew wild individuals in the tank environment, but not always in the stream environment (exception: NA farmed). Hybrids tended to display intermediate growth performance relative to farmed and wild fish in both environments. Survival did not differ among cross types in either environment. These findings suggest that irrespective of distinct origins, both EO and NA farmed salmon displayed greater dominance and growth than NF wild salmon in the tank environment. However, in the stream environment, competition imposed by NA farmed fish and related hybrids on wild fish appeared less than that imposed by the EO strain and related hybrids, as evident in growth performance. Findings thus provide valuable insight into the effects of hybridization and, consequently, fitness-related trait differences among divergent EO and NA farmed, NF wild, and F1 hybrid populations of importance for the conservation and management of Atlantic salmon.

KEY WORDS: Hybridization · Dominance · Growth · Survival · Farmed-wild salmon interaction · Salmo salar

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Cite this article as: Islam SS, Wringe BF, Conway CM, Bradbury IR, Fleming IA (2022) Fitness consequences of hybridization between wild Newfoundland and farmed European and North American Atlantic salmon. Aquacult Environ Interact 14:243-262.

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