NMFS will take comments on the studies until Oct. 29, and after that the papers will influence both the 1999 BiOp and the way the Columbia River power system will operate in the coming years. The studies look at passage of both juveniles and adults past the dams, the relationship of survival to flow and time, transportation of juveniles around Snake River dams and predation.
Survival is highest through spillbays, followed by mechanical screen bypass and turbines.
Spill survival is 98 percent to 100 percent, except at The Dalles Dam, where, since 1997, it's ranged from 76 percent to 99 percent. Screen bypass works without much harm to fish. Although stress in a fish can rise while traveling through bypass facilities, stress levels generally return to normal within several hours. But, during that time, it could contribute to a limited ability to respond to some in-river conditions, such as predators. Other findings are that scaling could be a problem when debris is present and high temperature at McNary kills fish.