Simulated juvenile Chinook salmon movement and growth in the Yankee Fork of the Salmon River, Idaho: model input parameters and results

The growth potential and movement propensity of juvenile Chinook salmon (Oncorhynchus tshawytscha) was simulated across 16 representative reaches in the Yankee Fork of the Salmon River (YFSR), Idaho. For growth potential, we used the Aquatic Trophic Productivity model, which incorporates dynamics of the food web members and the stream-riparian conditions at each reach. Environmental conditions at each reach were taken from previously collected data under the Columbia Habitat Monitoring Program, student thesis, and the Shoshone-Bannock Tribes. Summarized model inputs from these data sources for the ATP are provided. Next, movement and growth patterns of individual juvenile salmon that could move among these reaches by tracking shifting patterns of growth potential across the riverscape was examined using an individual-based model. We then used the two models to examine juvenile salmon responses to current and historical conditions, as well as planned restoration actions in the basin, including restoration of floodplains habitats by adding side channel habitat and salmon carcass additions. Specifically, scenarios include 1) Baseline - growth of juvenile fish that are restricted to their natal reach, 2) Current - current conditions of the YFSR where juvenile fish can move among reaches, 3) Side channel - where a theoretical side channel is added to each reach, 4) Carcass - addition of 25 adult Chinook salmon and 50 adult steelhead (O. mykiss) carcasses at each reach, 5) Carcass.SC - scenario 3 and 4 combined, and 6) Historical - return of theoretical spawning adult Chinook salmon and steelhead and connected side channels. Inputs for model simulations and results for all scenarios are provided.