There is another issue associated with dams and fish, and that is permitting enough flow to maintain downstream habitats. In Northern California, there's been a fight going on for years over how much water can be drawn off for agriculture, and how much must be allowed to flow downstream to maintain the proper habitat for several different species.
If water is drawn off for agricultural (or other) uses, is it still available to generate power?
Is maintenance of downstream habitats consistent with the generation of electricity from dams?