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A team of engineers and biologists from the U.S. Department of Energy’s HydroPASSAGE project assembled 99 biological response models for exposure to blade strike, fluid shear, and rapid decompression to determine what fish may experience as they travel downstream through turbines and other hydropower structures. The models evaluated 31 different species of fish, including American shad, Chinook salmon, and American eel.

• Considerable variation in susceptibility from one species to another has been reported for exposure to blade strike, fluid shear, and rapid decompression.

Egg and larval fish drifting downstream are likely to encounter river infrastructure leading to mortality. Elevated fluid shear is one likely cause. To confirm this and determine tolerable strain rates resulting from fluid shear, egg and larvae of three Australian species were exposed to a high-velocity, submerged jet in a laboratory flume. Mortality was modelled over a broad range of strain rates, allowing critical thresholds to be estimated.

Use of surrogacy remains a useful method for prioritizing research on representatives of at-risk groups of fishes, yet quantifiable evidence in support of its use is generally not available. Blade strike impact represents one of the most traumatic stressors experienced by fish during non-volitional movements through hydropower turbines. Here, we use data generated from laboratory trials on blade strike impact experiments to directly test use of surrogacy for salmonid and clupeid fishes.

One-way connectivity maintained by fish passing through hydropower turbines in fragmented rivers can be important to population dynamics, but can also introduce a new and significant source of mortality. Sources of mortality during turbine passage can come from several sources including blade strike, shear forces, cavitation, or pressure decreases and parsing the contributions of these individual forces is important for advancing and deploying turbines that minimize these impacts to fishes.

American eel are likely to encounter and pass through hydropower turbines, particularly during the downstream spawning migration, where exposure to stressors can potentially lead to injuries and mortality. Previous research has recovered dead eels downstream of hydropower facilities and, for some fish, injuries were easily attributed to blade strike; however, others showed no external signs of injury suggesting that other stressors, such as rapid decompression may be a potential source of mortality.