Candidate Genetic Markers Associated with Anadromy in Oncorhynchus mykiss of the Klickitat River

Both environmental and genetic factors influence anadromy in rainbow trout Oncorhynchus mykiss, but the genetic mechanisms that contribute to migratory selection are not well understood. In this study, we used a limited genome scan approach to identify candidate geneticmarkers associated with anadromy in 10 populations of O. mykiss from the Klickitat River, Washington. From an initial panel of 96 single-nucleotide polymorphism (SNP) markers, we identified 3 SNPs that were significantly associated with anadromy after accounting for underlying population structure and selective environmental conditions. Univariate logistic regression of allele frequencies and residency/anadromy were also significant, and thus three SNPs were considered candidate markers associated with anadromy (Omy_IL6-320, Omy-LDHB-2_i6, and Omy-ndk-152). A multivariate logistic model was developed from the allele frequencies of these three markers to predict the potential for anadromy in natural populations. This model was applied to eight additional populations of O. mykiss to evaluate its utility. The results of this study indicate that these markers are strong candidates for association with anadromy in O. mykiss in the Klickitat River, but further testing is needed to evaluate this association across more of this species' range. Common-garden experiments may also help clarify the association of these candidate markers with the smoltification phenotypes of individual fish.