The Genetic Architecture of Juvenile Migration in Rainbow Trout

Much is known of the behavior, ecology and physiology of smoltification and marine migration within the salmonid fishes, but little is understood of the underlying genetic architecture. In this study we utilize experimental F2 out-crossed populations derived from “migratory” and “resident” rainbow trout (Oncorhynchus mykiss) to identify the underlying genetic architecture of migration in this species. Utilizing quantitative genetic approaches, including a heritability analysis of growth and morphological traits, and a quantitative trait locus (QTL) analysis, including SNP markers derived from RAD tag sequencing, and a suite of phenotypic traits (including morphological and physiological traits that differ between the life-histories during the smoltification process) we have found several QTL, their genetic positions, and their relative contribution to the migratory life history. Furthermore, when comparing the QTL that were isolated in this cross, with those isolated in a similar study between clonal line crosses of migratory and resident rainbow trout from Idaho and California respectively, we find both similar genetic regions and different genetic regions associated with similar traits of the smoltification process. QTL that are shared between the crosses are candidate for major genetic control regions to the migratory life history, while those that differ could be evidence of parallel evolution. Finding QTL associated with the migratory life history will allow us to investigate the role of candidate genes in the smoltification process, and their ultimate role in this complex life history.