AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00468

ABSTRACT: Farming of Atlantic salmon Salmo salar has resulted in highly domesticated individuals, with notable genetic and phenotypic differences relative to their wild counterparts. Understanding how interbreeding with aquaculture escapees affects wild often at-risk populations is increasingly essential to conservation efforts. Here, we used an experimental release of wild, farm, and reciprocal F₁ hybrid fry at 3 sites in the Garnish River in Newfoundland, Canada, to evaluate family and cross-specific patterns of recapture/survival, size, sex ratio, and precocial male maturation over a 28 mo period. Trends in cross type recapture changed over the study period, with the highest recapture at 3 mo in parr with wild mothers, contrasting with that between 15 and 28 m where aquaculture offspring had overall the highest rates of recapture. Size trends among crosses and sites remained consistent over the study duration, with pure farm and wild-mother hybrids consistently being larger than wild individuals and one site displaying elevated sizes in all crosses. Rates of parr maturation differed by sex and cross type, and the family-based analysis indicated family representation and size also remained consistent through time. These results indicate that there is a difference in vital rates such as survival and precocial maturation between farm and wild Atlantic salmon during the freshwater early life history period and this can change significantly over time. As such, an improved understanding of genetic and ecological interactions which takes this ontogenetic variation into account is likely essential to fully understand how hybridization and introgression with farm escapes are affecting wild populations.