Toward the Genetic Basis of Age at Maturity in Chinook Salmon (Oncorhynchus tshawytscha)

Chinook salmon (Oncorhynchus tshawytscha) exhibit tremendous life history diversity, among which is variation in the age at sexual maturity.  Fish that achieve maturation at a later age attain a greater body size and are generally more competitive and fecund spawners than smaller and younger fish, though fish which delay maturation trade-off higher reproductive success with lower survival.   Although non-heritable environmental factors contribute to variation in age at maturity, there is also support for a substantial heritable genetic component underlying this trait in Chinook salmon.  However, the number and distribution of associated genetic loci underlying this trait are unknown.  To detect genetic regions associated with the variation in age at maturity we present here an experiment to perform a genome-wide association analysis of thousands of RAD-tag SNP markers distributed throughout the genome in two populations of natural and hatchery origin Chinook salmon from the Wenatchee River (n=523) and Johnson Creek (n=384), both tributaries of the Columbia River.  In order to determine the relative genetic position and distribution of associated loci, we align RAD-tag loci in this study against those from two Chinook salmon linkage maps.  Understanding the genetic basis to age at maturity will assist in shaping the age class distributions of populations to meet conservation and management goals for Pacific salmon.