Abstract
Partial migration describes a population that includes both resident and migratory individuals. For steelhead (Oncorhynchus mykiss), variation in the relative costs and benefits of an ocean migration can have consequences for the decision to migrate and its effect on individual lifetime fitness. Understanding the factors that influence migratory decisions, and how they may shift in the face of global change, is important for conserving these threatened species. The objectives of this study were to determine biotic and abiotic factors influencing juvenile O. mykiss life-history decisions in a partially migratory population, as well as how migration barriers alter these migratory behaviors and influence population connectivity. Using a combination of movement, genetic, and maternal origin analysis, our results illustrate the temporal and spatial variability of O. mykiss migratory behaviors in a degraded and fragmented watershed.