Behavioral ecology can contribute valuable insights to aquatic conservation, but typically occurs at spatial scales too small to be relevant (e.g., microhabitats or aquaria). Landscape ecology can also offer insights, but typically occurs at very large spatial scales (e.g., watersheds to regions) and often glosses over mechanisms of statistical patterns. We describe a process for merging behavioral and landscape ecology in the South Fork John Day River in eastern Oregon. Using remotely-sensed geomorphic and stream temperature criteria, we identified river sections for monitoring fish distribution and behavior. Video observations of fish aggression and feeding indicated that two species in particular—steelhead-rainbow trout (Oncorhynchus mykiss) and juvenile Chinook salmon (O. tshawytscha)—experienced significant intra- and interspecific interference competition; and raised the question of whether competition for food was limiting salmonid growth. A subsequent, manipulative field experiment revealed (via invertebrate drift abundance and instantaneous growth rates) that food was indeed a limiting factor, fish movement among pools and potentially out of tributaries was affected by food availability, and fish behavior was influenced by both habitat quality and density of competitors. These findings provide contextual knowledge about mechanisms driving observed species distributions and therefore have direct implications for research, monitoring, and restoration programs.