Army Corps of Engineers assist juvenile salmon at Ballard Locks

It is getting to that time of year again when Ballard Locks will be filled with salmon of all shapes and sizes. To prepare for the new season the Army Corps of Engineers is reinstalling four smolt flumes in spillway gates four and five this week.

What is a smolt flume and why do they need to be reinstalled? A smolt flume (see image below) provides a passageway for juvenile salmon and steelhead (smolt) to cross through the Locks and into Puget Sound. The flumes are reinstalled each spring in two spillway gates to help the fish on their journey from fresh to salt water.

“They’re sort of like slides, smolt slides, to give them a quick ride out of the system and get them out to sea,” Valentine told KUOW reporter Ann Dornfield.


According to the Army Corps of Engineers, “the flumes have significantly reduced harm and eased passage for smolt through the Locks to Puget Sound.”

The flumes also contain electronic passive integrated transponder (PIT) tag readers that count fish and provide more information about how fish pass through the locks. “This system provides in-formation about smolt survival and migration,” reports the Army Corps of Engineers.

According to the Army Corps of Engineers, the passage of fish through Ballard Locks is key to salmon survival in the Lake Washington watershed as the Locks are the only route for fish to travel to the Puget Sound.

Studies back in the 90s revelaed that young salmon had a difficult time passing through the Locks from Lake Washington to Puget Sound. The reports showed that salmon were often dragged into the filling culverts for the large locks, where some were injured or killed. Other salmon had issues getting over the spillway near the fish ladder.

Since then, because of the importance of Ballard Locks in the fish passage from Lake Washington into Puget Sound, an ongoing cooperative was founded to make improvements to allow fish to pass with ease.

This cooperative continues today between the U.S. Fish and Wildlife Service, National Marine Fisheries Service, Washington State Department of Fish and Wildlife, Muckleshoot Indian Tribe, City of Seattle, King County and Water Resource Inventory Area 8, and the Seattle District of the U.S. Army Corps of Engineers.

The work of the cooperative over the years has resulted in many successful salmon seasons for the Lake Washington watershed. Valentine reported to KUOW that approximately 200,000 sockeye salmon returned back through the Locks last year.

The fish ladder at Ballard Locks is set to open in time for Memorial Day weekend. To learn more about Ballard Locks and the salmon ladder click here.

Photo courtesy of KUOW. Photo credit – Ann Dornfield.

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