A genetic evaluation of mating system and determinants of individual reproductive success in Atlantic salmon (Salmo salar L.)

The primary objective of this study was to use highly polymorphic microsatellite loci to estimate individual reproductive success in Atlantic salmon based on the number of surviving juveniles (young of the year) at the population level under natural conditions. We inferred reproductive strategies adopted by both sexes by applying a maximum likelihood method to determine parent-offspring genotype relationships. A high degree of variance in individual reproductive success for both males and females was revealed. The high number of mates used by both sexes is not concordant with previous behavioral studies proposing that females are mainly monogamous in this species. We found little evidence supporting the prediction from previous reports of a positive relationship between individual size and realized reproductive success for either males or females. For both sexes, however, there was a significant correlation between the number of mates and the number of offspring. These results indicate that this species' mating system is more flexible than previously thought and suggest that factors such as potential genetic benefits or environmental uncertainty may also be driving the evolution and the plasticity of mating systems in Atlantic salmon.