The Use of Traits-Based Assessment to Estimate Effects of Hydropower Projects on Fish Populations

Safe downstream passage of fish at hydropower projects affects not only migratory species, but also resident fish by altering biomass, biodiversity, and gene flow. Thus, it is important to maximize turbine-passage and reservoir-passage survival of a wide range of riverine fish. Advanced (fish-friendly) turbines show promise for reducing downstream passage mortality, but data on their beneficial effects are limited to only a few species, mainly salmon and trout. For thousands of untested species and sizes of fish, the particular causes of downstream passage losses and the benefits of advanced turbine designs remain unknown.

It is not possible to measure the downstream passage survival of every species of fish for every hydroelectric project or turbine design. We are exploring the use of a Traits-Based Assessment (TBA) approach to group species based on their environmental, biological, behavioral, and life history characteristics. TBA allows us to identify species most susceptible to turbine passage, identify species sharing similar sensitivities to turbine passage stressors, and consider population sustainability in the event of downstream passage losses. The approach is transferable to fish communities from different biogeographic regions. TBA could be used to identify representative fish species for testing, assess impacts of new hydropower development, and develop mitigation measures.