Probabilistic maturation reaction norms of sockeye salmon spawning populations of Bristol Bay, Alaska
Humans can influence life history traits of domesticated and wild animals through selective processes. Fishing is often deliberately size-selective for economic and biological reasons. Size-selective fishing mortality has been associated with directional selection and changes in life history traits such as age and size at maturity. Norms of reaction show the ranges of potential phenotypes, such as different ages and sizes at maturation, that a given genotype could develop if an individual is exposed to different environmental conditions. Selection, due to many causes, may act on age and size at maturation and cause the reaction norm of an individual or population to change in position or shape. Maturation reaction norms may help to disentangle phenotypic plasticity associated with different growth and mortality conditions from genetic effects that influence maturation as a result of reaction norm evolution. Thus, they may reveal changes in maturation schedules associated with size-selective fishing. Bristol Bay, Alaska has some of the most diverse and abundant sockeye salmon (Oncorhynchus nerka) populations in the world. A large commercial gillnet fishery has exerted strong, size-selective fishing pressure on these salmon since 1884. I will use data from 1946-present to calculate probabilistic maturation reaction norms (PMRNs) for length and age at maturation of locally adapted sockeye spawning populations of the Wood River system of Bristol Bay. While PMRNs have been developed for a number of fish species who spawn multiple times, little work has been done understanding reaction norms for semelparous species, such as Pacific salmon, who spawn only once before dying. With these PMRNs, in the future I can understand changes in these life history traits over time and will evaluate if this fishery selection has the potential to cause life history evolution.