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Sirois, Pascal

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Département de biologie, Faculté des sciences et de génie, Université Laval
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  • Publication
    Accès libre
    The role of ecotype‐environment interactions in intraspecific trophic niche partitioning subsequent to stocking
    (Ecological Society of America, 2019-01-24) Sirois, Pascal; Morissette, Olivier; Wilson, Chris Carroll; Bernatchez, Louis; Laporte, Martin
    Worldwide, stocking of fish represents a valuable tool for conservation andmaintenance of species exploited by recreational fishing. Releases of hatchery-reared fish aremore and more recognized to have numerous demographic, ecological, and genetic impacts onwild populations. However, consequences on intraspecific trophic relationships have rarelybeen investigated. In this study, we assessed the impacts of supplementation stocking andresulting introgressive hybridization on the trophic niches occupied by stocked, local, andhybrid lake trout (Salvelinus namaycush) within populations of piscivorous and planktivorousecotypes stocked from a wild piscivorous source population. We compared trophic niches usingstable isotope analysis (d13C andd15N) and trophic position among the three genetic origins.Putative genetic effects were tested with phenotype–genotype association of“life history”ecological traits (body size, growth rate, condition index, and trophic niche) and genotypes(RADseq SNP markers) using redundant discriminant analysis (RDA). Results showed thatsympatry resulting from the stocking of contrasting ecotypes is a risk factor for niche parti-tioning. Planktivorous populations are more susceptible to niche partitioning, by competitiveexclusion of the local fish from a littoral niche to an alternative pelagic/profundal niche.Observed niche partitioning is probably a manifestation of competitive interactions betweenecotypes. Our results emphasize that ecotypic variation should be considered for more efficientmanagement and conservation practices and in order to mitigate negative impact ofsupplementation stocking.
  • Publication
    Accès libre
    Supplementation stocking of lake trout (salvelinus namaycush) in small boreal lakes : ecotypes influence on growth and condition
    (Plos, 2018-07-12) Sirois, Pascal; Morissette, Olivier; Lester, Nigel Paul; Bernatchez, Louis; Wilson, Chris Carroll
    Supplementation stocking is a commonly used management tool to sustain exploited fish populations. Possible negative consequences of supplementation on local stocks are a concern for the conservation of wild fish populations. However, the direct impacts of supplementation on life history traits of local populations have rarely been investigated. In addition, intraspecific hybridization between contrasting ecotypes (planktivorous and piscivorous) has been seldom considered in supplementation plans. Here, we combined genetic (genotype-by-sequencing analysis) and life history traits to document the effects of supplementation on maximum length, growth rates, body condition and genetic admixture in stocked populations of two Lake Trout ecotypes from small boreal lakes in Quebec and Ontario, Canada. In both ecotypes, the length of stocked individuals was greater than local individuals and, in planktivorous-stocked populations, most stocked fish exhibited a planktivorous-like growth while 20% of fish exhibited piscivorous-like growth. The body condition index was positively related to the proportion of local genetic background, but this pattern was only observed in stocked planktivorous populations. We conclude that interactions and hybridization between contrasting ecotypes is a risk that could result in deleterious impacts and possible outbreeding depression. We discuss the implications of these findings for supplementation stocking.