An Overview of Experimental Efforts to Understand the Mechanisms of Fish Injury and Mortality Caused by Hydropower Turbine Blade Strike

Injury and mortality of fish during downstream passage through hydropower turbines is one of the most significant concerns with regards to hydropower impacts on fish. Downstream turbine passage has the potential to be detrimental to fish due to a complex suite of stressors that are experienced as fish pass through a turbine, which can lead to injury and/or mortality. These stressors include rapid pressure changes, shear forces, mechanical strike from turbine runners, and collisions with turbine housing (Pracheil et al. 2016a). Hydropower owners/operators are frequently ordered to mitigate this threat through various means, such as installing racks or bypass systems that exclude fish from turbines or temporarily suspending generation by spilling water instead of routing it through turbines during periods of fish migration. These measures typically result in increased construction and operation costs or lost generation revenue (Schramm et al. 2016).