title: Assessing risks of invasion through gamete performance: farm Atlantic salmon sperm and eggs show equivalence in function, fertility, compatibility and competitiveness to wild Atlantic salmon.
abstract: Adaptations at the gamete level (a) evolve quickly, (b) appear sensitive to inbreeding and outbreeding and (c) have important influences on potential to reproduce. We apply this understanding to problems posed by escaped farm salmon and measure their potential to reproduce in the wild. Farm Atlantic salmon (Salmo salar) are a threat to biodiversity, because they escape in large numbers and can introgress, dilute or disrupt locally adapted wild gene pools. Experiments at the whole fish level have found farm reproductive potential to be significant, but inferior compared to wild adults, especially for males. Here, we assess reproductive performance at the gamete level through detailed in vitro comparisons of the form, function, fertility, compatibility and competitiveness of farm versus wild Atlantic salmon sperm and eggs, in conditions mimicking the natural gametic microenvironment, using fish raised under similar environmental conditions. Despite selective domestication and reduced genetic diversity, we find functional equivalence in all farm fish gamete traits compared with their wild ancestral strain. Our results identify a clear threat of farm salmon reproduction with wild fish and therefore encourage further consideration of using triploid farm strains with optimized traits for aquaculture and fish welfare, as triploid fish remain reproductively sterile following escape.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park Norwich, UK.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Yeates
authors.affiliation: Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology Trondheim, Norway ; Norwegian Institute for Nature Research Trondheim, Norway.
authors.forename: Sigurd
authors.initials: S
authors.lastname: Einum
authors.affiliation: Norwegian Institute for Nature Research Trondheim, Norway ; Department of Ocean Sciences, Memorial University of Newfoundland Newfoundland, Canada.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Fleming
authors.affiliation: Academic Department of Reproductive and Developmental Medicine, University of Sheffield Sheffield, UK.
authors.forename: William V
authors.initials: WV
authors.lastname: Holt
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park Norwich, UK.
authors.forename: Matthew Jg
authors.initials: MJ
authors.lastname: Gage
keywords: aquaculture; fertilization; gamete; salmon; sperm competition