Fish Behavior in Relation to Passage through Hydropower Turbines: A Review

We evaluated the literature on fish behavior as it relates to passage of fish near or through hydropower turbines. Our goal was to foster compatibility of engineered systems with the normal behavior patterns of fish species and life stages such that passage into turbines and injury in passage are minimized. In particular, we focused on aspects of fish behavior that could be used for computational fluid dynamics (CFD) modeling of fish trajectories through turbine systems. Salmon smolts approaching dams are generally surface oriented and follow flow. They can be diverted from turbines by spills or bypasses, with varying degrees of effectiveness. Smolts typically become disoriented in dam forebays. Those smolts drawn into turbine intakes orient vertically to the ceilings but are horizontally distributed more evenly, except as they are affected by intake-specific turbulence and vortices. Smolts often enter intakes while oriented with their heads upstream, but they may change orientation in the flow fields of the intake. Nonsalmonids most often enter intakes from the vicinities of shorelines, and they do so episodically, which suggests accidental capture of schools (often of juveniles or in cold water) and little behavioral control during turbine passage. Models of fish trajectories should not assume neutral buoyancy throughout the time period during which a fish passes through a turbine, largely because of pressure effects on swim bladders and the resulting compensatory behavior. Fish use their lateral line system to sense obstacles and to change their orientation, but this sensory-response system may not be effective in the rapid passage times and complex pressure regimes of turbine systems. The effects of preexisting stress levels on fish performance in turbine passage (especially as they affect trajectories) are not known but may be important. There are practical limits of observation and measurement of fish and flows in the proximity of turbines that may inhibit the development of much information that is germane to developing a more fish-friendly turbine. We provide recommendations for CFD modelers of fish passage and for additional research.