Hydropower

Improving Passage for Fish

Upper Columbia spring Chinook salmon and steelhead trout pass through seven to nine dams on their way to and from the ocean, depending on where they were born. Improvements to hydropower dams and their operation have ensured that most fish pass through successfully and standards for passage survival are met.

Although much progress has been made to better understand and improve survival in the Columbia River, some uncertainties and opportunities for improvement remain. Columbia River dam operators have used flexible spill operations in 2019 to increase survival of young fish as they migrated downstream. This practice increases flows through spillways instead of electrical turbines during important times for young fish movement. It is too early to tell what effect those changes have had on survival rates.

Fish cannot travel above Chief Joseph Dam, cutting off 40 percent of historic habitat in the Columbia River. Efforts are underway to reintroduce migrating fish into this blocked habitat.

For more about hydropower in this region, see the Hydropower Background Summary.

Danger to Adults from Sea Lions and Seals

Adult salmon also face increased predation as they enter freshwater to return to spawning grounds. In the past decade, increasing numbers of sea lions below Bonneville Dam have been killing more salmon. Studies indicate that 22 percent of the salmon returning to the Columbia River early in the spring, including Methow spring Chinook, are being eaten by sea lions, the largest amount of predation in recent years. Of intermediate arriving populations, including Entiat and Wenatchee spring Chinook, 11 percent also are being eaten by sea lions. Sea lions are being hazed and removed at the Bonneville Dam to reduce predation pressure on adult salmon and steelhead.

Dangers to Young Fish from Predators

During their complex life cycles, salmon occupy numerous habitats and face challenges during each of them. During their downstream migration from freshwater to the ocean, salmon and steelhead smolts from the upper Columbia River migrate more than five hundred miles and pass seven to nine dams and reservoirs. In recent years, birds have eaten young migrating fish in such large numbers that they are identified as a factor limiting recovery of imperiled salmon populations. Upper Columbia River steelhead appear particularly susceptible to predation by Caspian terns, double-crested cormorants, and gulls. Birds have caused more than 50 percent of the smolt deaths, making them the largest killer of these young migrating fish.