Evaluating Dam Water Release Strategies for Migrating Adult Salmon Using Computational Fluid Dynamic Modeling and Biotelemetry

Abstract

AbstractHydrodynamics in dam tailraces can influence the swimming behavior and survival of fish, and yet there have been few studies that have linked the movement patterns of fish to encountered flow patterns. In this study, we examined the flow field downstream of Seton Dam in British Columbia, Canada using acoustic Doppler current profilers (ADCPs), and computational fluid dynamic (CFD) modeling of two dam water release scenarios to understand their impacts on the swim speed and behavior of upriver‐migrating adult sockeye salmon (Oncorhynchus nerka). Forty‐five sockeye salmon were tagged with acoustic transmitters and tracked to understand their movement patterns, swim speed, residence time in the dam tailrace, and postdam passage survival. The water release scenarios produced contrasting tailrace hydrodynamics and altered the behavior of migrating sockeye salmon. Tagged fish avoided areas of high velocity (>2.4 m/s or four body lengths/s, twice their critical swim speed), high Reynolds shear stress (>21 Pa), and high turbulence kinetic energy (>0.12 m2 s−2) in the dam tailrace. Excessive use of anaerobic metabolism, together with high water shear stress adjacent to and downstream of the fishway entrance, were thought to be the main cause for low postdam passage survival of sockeye salmon. Additional dam water release strategies were assessed with the CFD model to target releases that improve the migration conditions for sockeye salmon. Our study highlights the importance of pairing hydraulic and ecological information to better understand and improve the migration conditions for wild fish.