Pattern and variability in the breeding system of Atlantic salmon (Salmo salar), with comparisons to other salmonids

The breeding system of Atlantic salmon (Salmo salar) is shaped both by natu ral selection for offspring production and by sexual selection for access t o mating opportunities. These evolutionary forces operate with differing in tensities in the two sexes to shape their breeding behaviour and tactics. F emale breeding success is largely dependent on egg production, access to br eeding territories, and nest quality and survival. By contrast, male breedi ng success is largely determined by access to ovipositing females. As such, the breeding system of Atlantic salmon is similar to that of other members of the subfamily Salmoninae. However, early male maturity, a common patter n within the Salmoninae, reaches its greatest expression in both terms of f requency and magnitude of the mature male size difference in Atlantic salmo n. Despite generalities, spawning populations of Atlantic salmon are not st atic, as they exhibit spatial and temporal variability in demography (e.g., spawner density, sex ratio, age at maturity, and body size). Events, both natural and anthropogenic (e.g., exploitation, habitat alteration, and clim atic changes), affect this variability and ultimately shape the breeding sy stem.