Modelling the linkages between flow management and salmon recruitment in rivers

We developed a simulation model to predict instream flow effects on smolt production for fall chinook salmon (Oncorhynchus tshawytscha) in regulated rivers. The principal purpose of this model is to serve as a management tool to evaluate effects on salmon of instream releases from upstream reservoirs. The dramatic decline in chinook salmon in California rivers suggests a need for such a tool. We developed an individual-based and spatially explicit model to simulate the influences of riverine habitat on each lifestage leading to successful outmigration of chinook salmon. Model predictions of development, growth and survival showed good agreement with four years of field data collected on the Tuolumne River, California. Our analysis of parameter sensitivities identified flow-related redd mortality and temperature-related juvenile mortality as limitations on smolt production.