About Dams & Fish

Dams provide electricity, flood control, recreation and transportation as well as water for domestic and agricultural use. However, dams also change the way rivers function, and may interfere with the life cycles of salmon, steelhead, and other animals. They are barriers to juvenile salmon migrating to the ocean, and an obstacle as adult fish return to their natal streams to spawn.

Dams affect the way water moves down a river, by changing the amount and timing of flow, as well as its temperature and chemical characteristics. And because dams transform the upstream habitat from a river into a lake, they change the amount and location of available habitat and significantly alter the salmon’s interaction with predators and competitors.

For salmon to thrive, it is important to provide safe, swift passage for juveniles traveling to the ocean and for adults migrating back to their spawning grounds. There are many types of passage infrastructure in use at and around dams, depending on factors such a dam’s age, size, location and purpose. Sometimes passage facilities are added many years after a dam is built. These are the most common types of fish passage. 

Adult Upstream Passage

Fish Ladders

Trap and Haul