Over millennia, native salmonids in North America have developed a complex strategy where important life events, such as spawning, coincide with specific river conditions, like flow and temperature. As river systems are modified by development and climate change, the current adaptations of native salmonids may not be compatible with future altered river flow and temperature, directly impacting their survival. USDA Forest Service scientists at the agency's Pacific Northwest Research Station and colleagues developed a new tool to assess the adaptability of salmonids to changing river conditions: the ichthyograph. Combining long-term records of river flow, water temperature, and upstream fish movement, the ichthyograph offers new insight into the ability of salmonids to survive in a range of future river conditions. Scientists used the ichthyograph method to assess endangered Coho salmon (Oncorhynchus kisutch) populations in rivers across Washington and Oregon under various possible future river conditions. In some rivers, future river conditions may be within the current behavioral adaptations of Coho salmon. In other rivers, future conditions may fall outside the ability of Coho salmon to adapt, suggesting potential negative impacts to their migration and survival. The ichthyograph is being used by fisheries biologists with the U.S. Army Corps of Engineers and National Oceanic and Atmospheric Administration fisheries to inform interpretation of river flows needed to support multiple salmonid life stages.