Using Hydroacoustic Data to Model the Entrainment Process and Population Response for Kokanee In Revelstoke Reservoir

For kokanee populations in reservoirs, mobile acoustic surveys play a key role in stock assessment while fixed arrays can be used to estimate entrainment losses through the dam.  In order to apply this data in a management decision process, both types of acoustic data need to be integrated into a management model that estimates the impacts of alternative management policies on a performance measure, such as kokanee population density.   In Revelstoke Reservoir, we model the details of the entrainment process using fixed-array, split-beam acoustic data to document velocity fields and fish behavioural in the immediate vicinity of one of the penstocks. Fixed arrays often do not sample the entire volume of entrained flow and entrainment rate must be estimated by using a behavioural response model to velocity fields.  We use this behavioural response model document the importance of diurnal variation in behaviour and turbine startup/shutdown in determining entrainment rates.  Unlike salmon smolts, where downstream migration behaviour may enhance entrainment, kokanee are a pelagic species that avoid littoral areas and may therefore exhibit behavioural avoidance of the dam face independent of the presence of intake flow.  At this larger scale, we fit a behavioural model to spatially explicit kokanee density data from mobile acoustic surveys.  This model incorporates passive advection with the water mass and passive diffusion toward areas of low fish density to estimate a parameter that represents active behavioural avoidance of shorelines and the dam.  Finally, we integrate both behavioural models into a population model that estimates performance measures (kokanee density and age structure, angler effort) under alternative mitigation or compensation regimes.