An individual-based model (IBM) was developed to explore juvenile Chinook salmon (Oncorhynchus tshawytscha) migration patterns in the Columbia River estuary. The model used outputs from the hydrodynamic model SELFE as a virtual environment. There were several submodels, including a movement model that simulated Lagrangian transport and active swimming and a bioenergetics model that computed growth. A predation model was also developed to explore potential impacts of avian predators on survival. Migration was simulated for yearling and subyearling Chinook salmon, and swimming behaviors were developed based on assumptions regarding habitat usage. Yearling Chinook salmon behaviors optimized efficient migration, while subyearling Chinook salmon behaviors prioritized growth. Passive drift and random walk behaviors for both life-history types served as null models to compare the more sophisticated behaviors against.