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Posted 3/26/2018

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By Tom Conning, Public Affairs Office


PORTLAND, Ore. – The U.S. Army Corps of Engineers has two ways to pass fish above dams: fish ladders and a method called trap and haul. Many times, the type of fish passage selected depends on the height of the dam, but there could be other factors involved. Taller dams, also known as high-head dams, tend to rely on the trap and haul method.

Fish Ladder:
Fish ladders allow adult fish to migrate upstream of a barrier on their own. These ladders are at each of our mainstem Columbia River hydro-projects. Fish ladders often have weirs with overflow sections and orifices to give fish options for swimming over or through the weirs. These are important aspects of our fish passage facilities as they allow fish to travel at all times.

Trap and Haul:
Trap and Haul is used for both upstream (generally adults) and downstream (generally juveniles) migrating fish. This method requires a crew to operate a fish trap, sort the collected fish, move those fish to a truck and then haul them to a final release location. The Corps uses trap and haul for lamprey at the Columbia River Dam projects and at the adult fish facilities in the Willamette River and Rogue River basins. Trap and haul does not allow fish to move at their discretion but on a schedule set by the trap operators.

Transport is not the whole answer to long-term fish population restoration, but it is one tool in our toolbox. There is a time and place for transport, and as we incorporate new technologies like spillway weirs (to help fish migrate downstream of dams), we’re reconfiguring the project to accommodate them. We also are building new juvenile facilities and incorporating flexibility into our systems so we can operate the dams to maximize adult fish returns.

Learn more about our new fish weir at Foster Dam here: www.nwp.usace.army.mil/news/article/Article/1379478/

Learn more about our fish program here: www.nwp.usace.army.mil/Missions/Environmental-Stewardship/Fish/.