Comment: Surprising salmonid response to water diversion at four run-of-river hydroelectric projects in British Columbia

Abstract

Although the authors have completed an ambitious long-term field experiment involving the effects of water diversion on fish and invertebrates inhabiting steep mountain stream ecosystems, certain aspects of their study design and their interpretations create doubt and skepticism. Additional information is required on how the authors addressed challenging aspects of the research environment and how the sample sites were configured. A substantial decrease in water velocity during the treatment phase may have impacted capture probability. The authors downplay challenges of electrofishing in streams with extremely low conductivity. The authors do not discuss the potential effects of the dams at the boundary between the control and treatment sites, which may include entrainment and migration obstruction. The authors identify opportunities to extrapolate their findings to other systems but have not sufficiently characterized the environment and limiting factors within their study sites to facilitate extrapolation to different ecosystems. Additional work is required to explain how the alterations in this environment contributed to the increase in fish biomass that was observed.