Innovative project hopes to guide salmon, steelhead to survival at Hood Canal Bridge

||| FROM LUCAS HALL for LONG LIVE THE KINGS |||

Port Gamble, WA – On April 10, the Hood Canal Bridge Assessment Team will deploy a $1.6 million fish guidance structure at the Hood Canal Bridge to help threatened salmon and steelhead pass one of the deadliest migration barriers in Washington.

This is the first test of a long-awaited strategy to reduce the high number of young steelhead – up to 50% – that die at the bridge each year. The floating wedge-shaped structure, called a fillet, was the top near-term recommendation of the Hood Canal Bridge Assessment Team in their 2020 report analyzing the causes of high steelhead mortality at the bridge. It was built with state-appropriated funding by contractors Global Diving and Salvage, with design and engineering by Kleinschmidt Associates and Art Anderson Associates, fabrication at Pacific Netting Products in Kingston, and transportation by Boyer Logistics. The massive structure measures more than 20 feet high and 85 feet long and will sit in the water to fill in the 90-degree corner at the southeast end of the bridge.

Research by the National Oceanic and Atmospheric Administration (NOAA) and the Port Gamble S’Klallam Tribe indicates that migrating juvenile steelhead and salmon tend to get disoriented in these corners, making them easy targets for predators. With the fillet in place, researchers hope to see fish finding their way past the corner and around the bridge more quickly.

Representatives from the Assessment Team, including Port Gamble S’Klallam Tribe, NOAA, the Washington State Departments of Fish and Wildlife (WDFW) and Transportation (WSDOT), the Hood Canal Coordinating Council, and project coordinator Long Live the Kings look forward to watching this major milestone, which comes after more than a decade of collaborative effort.

As in previous years, NOAA has tagged juvenile steelhead with acoustic transmitters and placed underwater receivers around the bridge to track their movements. The Port Gamble S’Klallam Tribe is using underwater video and acoustic imaging to monitor fish and harbor seals during the test period. The fillet will be installed and removed in one-week windows during the peak of steelhead migration, between April 10 and May 14, allowing the research team to compare their behavior and survival with and without it.

The discovery that the Hood Canal Bridge poses a deadly barrier for steelhead emerged from research first published by NOAA’s Northwest Fisheries Science Center in 2013, which found that tracked steelhead smolts were slowed down at the bridge and faced unusually high mortality there. In response, the Assessment Team conducted a comprehensive assessment of the bridge’s impact on salmon and steelhead and concluded that the bridge’s design was inadvertently blocking salmon migration and creating a predator hotspot.

The bridge rests on floating concrete pontoons that extend 15 feet under the water’s surface, blocking more than 80% of the canal width. As the fish attempt to find a way past this underwater wall, they become easy prey for harbor seals. A NOAA study published in 2022 found that approximately half of juvenile steelhead that made it to the Hood Canal Bridge died nearby, most likely eaten by seals.

Hood Canal steelhead are threatened under the Endangered Species Act, along with Hood Canal Chinook and chum populations. Research by the Port Gamble S’Klallam Tribe indicates that Chinook and chum may also be affected by the bridge. Steelhead and Chinook remain at a fraction of their historic numbers despite significant investments in habitat restoration and watershed-based recovery actions, impacting Tribal and recreational fisheries, local economies and cultural traditions, and the health of the surrounding ecosystem. 

“Addressing this one mortality hotspot could meaningfully restore productivity for imperiled salmon and steelhead in Hood Canal and is relatively simple compared to other more controversial salmon recovery actions that involve compromise,” says Megan Moore, NOAA. “Facilitating fish passage and eventual replacement of the Hood Canal Bridge benefits salmon and the entire ecosystem, including people.”

The fillet, which is installed at water level by a tugboat and partially submerged, is not expected to impact traffic or be visible to cars on the bridge. If the data collected this year show that it improves steelhead survival, the project partners hope to pursue funding for additional fillets to cover the other corners on the bridge. In the long run, those involved in this study agree that a new bridge design will be needed to meet the needs of Hood Canal’s salmon, steelhead, and people. “As we learn how our built environment impacts salmon, steelhead and other natural assets that define our amazing region, we are called to find safe ways to reverse the damage,” said Long Live the Kings Executive Director, Jacques White. “Our hats are off to all the partners and funders that played key roles in this creative and remarkable effort to help juvenile steelhead safely past the Hood Canal Bridge. This story is about different groups coming together to solve problems for our fish, and the current and future generations of people who care about them.”