Fish Ladders
The most common way for adult fish to get past a dam is to use a fish ladder, a water-filled structure that allows fish to pass up and over in a series of steps. Migrating salmon are attracted to current at the base of an extended concrete stairway. The fish swim or jump from step to step. Depending on the height of the dam, the fish ladder may have many switchbacks with turning pools.
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Trap and Haul
At dams and places where it is not practical to install a fish ladder, a trap and haul operation can be used to move adult fish upstream. Migrating salmon are attracted to flow at the base of a fish ladder. They climb the ladder to a loading system where they wait in pools or tanks before transfer into specialized tankers or barges. These vehicles release the salmon into the river on the other side of the dam. All trap and haul facilities are different. The diagram below gives an example of an operation using specialized tanker trucks.
For more information about the use of trap and haul and other fish passage solutions, see our online FAQ—California Fish Passage: Frequently Asked Questions.
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More Information
Veteran intern Antonio Jones at an oyster farm in Drayton Harbor, Washington, checking traps for European Invasive Green Crab. Credit: Northwest Straits Commission
The Klamath River mouth. Credit: Thomas Dunklin
Aerial view of restored floodplain habitat and agricultural property near Sacramento, California.
Chinook salmon jump in frothy white water. Credit: Laura Mahoney/USFWS