Variation in Age and Size at Maturation in Salmonids: Causes and Consequences.

Age and size at sexual maturity in Salmonid fishes (and fishes in general) are phenotypically plastic quantitative traits that are strongly correlated with growth rate.  Variability in age and size at maturity within and among anadromous salmonid populations presents major challenges for conserving natural populations, managing fisheries and harvest rates, forecasting adult run-size and return rates, and developing scientifically-defensible spawning protocols in hatcheries.   Age and size at maturity are influenced by numerous factors including genotype, emergence timing, nutrition quality, freshwater and marine growth, sexual selection, natural selection in the freshwater and marine environments, size-selective fisheries, and other factors.  In particular, hatchery spawning practices and rearing environments that promote high growth rates can have substantial effects on life history diversity and mean size and age at maturity. Thus, resource managers tasked with regulating the abundance of hatchery and wild salmonids in fisheries and natural habitats require a thorough, “state of the art” scientific understanding of the genetic, environmental, and anthropogenic mechanisms that affect age and size at maturity.  This symposium will bring together physiologists, ecologists, geneticists, population dynamics biologists, and other experts to describe the current state of scientific understanding regarding the mechanisms influencing age and size at sexual maturity of salmonid fishes with an emphasis on management implications.