Some 16 million salmon and steelhead once returned to the Columbia River Basin each fall, but impediments like the Bonneville Dam near Portland, Ore., decimated their numbers. Costly recovery efforts and courtroom battles brought only marginal improvements, and populations were largely supported by hatchery stock. In 2006, court-mandated spillovers -- running less water through turbines and spilling more over dams -- were introduced to help wild runs recover ("Columbia Basin (Political) Science," HCN, 4/13/09).
On Sept. 24, the number of spawning chinook salmon passing the Bonneville Dam reached the 1 million mark for the first time since 1938. Dam proponents point to safer turbines and improved habitat, but many biologists credit the increased spillovers. A new river management plan, however, may allow dam operators to cut back on future spillovers. At the same time, the record-breaking fish numbers have emboldened calls to remove chinook from the endangered species list.