An analysis of variables influencing the migration of juvenile salmonids in the Columbia River basin
migration, juvenile, salmonids, Columbia River, chinook, salmon, steelhead, travel time, models, smolt, Snake River, hydroelectric
Journal or Book Title
North American Journal of Fisheries Management
The amount of tie that it takes juvenile Chinook salmon (Oncorhynchus tshawytscha)and steelhead (O. mykiss) to migrate (travel time) at different river flows through index reaches inthe Snake and Columbia rivers was analyzed with bivariate- and multiple-regression models.Smolt travel time estimates for yearling Chinook salmon and steelhead in the Snake River (USA), steelhead in the middle Columbia River, and subyearling Chinook salmon in the lower ColumbiaRiver were inversely related to average river flows. In the multiple-regression analyses, additionalpredictor variables that were related either to flow or to smoltification were used. These predicatorvariables were calculated over the same time period as the travel time estimates. Flow-relatedvariables were referenced to a key hydroelectric site within each index reach, and includedaverage river flow, minimum river flow, and absolute change in river flow. The smoltificationrelatedvariables provided indirect indices of smoltification. They included water temperature, dateof entry into an index reach, Chinook salmon race, and travel time prior to entry into an indexreach. The final models included those predictor variables explaining significant variation in smolttravel time. The variables in the final multiple-regression models explained 74% and 39% of thevariation in the travel time for yearling Chinook salmon within the Snake and middle Columbiariver index reaches, respectively; 90% and 62% for steelhead within the Snake and middleColumbia reaches; and 65% for subyearling Chinook salmon in the lower Columbia reach.Average river flow made the largest contribution to explaining variations in smolt travel time in themajority of the multiple-regression models. Additional variation in smolt travel time could beexplained by including other flow- and smoltification-related variables in the models.