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 microsate llite loci to estimate individual reproductive success in Atlantic salmon b ased on the number of surviving juveniles (young of the year) at the popula tion level under natural conditions. We inferred reproductive strategies ad opted by both sexes by applying a maximum likelihood method to determine pa rent-offspring genotype relationships. A high degree of variance in individ ual reproductive success for both males and females was revealed. The high number of mates used by both sexes is not concordant with previous behavior al 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 su ccess for either males or females. For both sexes, however, there was a sig nificant correlation between the number of mates and the number of offsprin g. 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 an d the plasticity of mating systems in Atlantic salmon.