Impacts of Dams on River Taxa

As part of a large collaborative project with Sarah Kupferberg (UC-Berkeley, Questa), Amy Lind (US Forest Service), Alessandro Catenazzi (UC-Berkeley), and many others, we have been estimating the impact of altered river hydrology for the California-listed Foothill yellow-legged frog (Rana boylii).

The spatial distribution of large hydroelectric and retention dams in California overlaps to a large degree with R. boylii breeding and rearing areas, and altered hydrology imposed by dams is considered to be a key driver of R. boylii declines. The majority of hydroelectric dams are now going through a re-licensing process, and for the first time in over 60 years, will be subject to modern environmental review. Foothill yellow-legged frogs represent one of only a handful of species that carry legislative protections that must be considered during this review process, yet there is little ecological data available to evaluate the specific aspects of dam operations that contribute to this species endangerment. The backbone of this project lies in Kupferberg’s long-term (20 year) population survey for R. boylii in the South Fork Eel river (Mendocino Co., CA), one of the last large river systems in California without large dams. We compliment this population study in the absence of hydrologic modification with a range of short-term experiments to estimate growth and survival consequences under different hydrologic and ecological conditions imposed by dams (flow, algal availability, temperature, predators, etc.), and demographic modeling to ‘up-scale’ these short-term studies and evaluate the potential population-scale effects for R. boylii vulnerability to extinction. The aim is to provide a rigorous scientific assessment of the current status of R. boylii populations, and reduce the impact of dams through changes to dam operations under new licenses.

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