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Tests at Hood Canal Bridge prompt new tactics for steelhead survival; engineering study to follow
Summary
Scientists and managers reported that fish guidance structures reduced eddies but did not yet cut delay times at the Hood Canal Bridge, while acoustic deterrent devices significantly reduced seal presence in the immediate test zone. A community needs study and bridge conceptual designs are planned to explore longer-term solutions.
Shara Ainsley of Long Live the Kings presented results from phase‑2 tests at the Hood Canal Bridge and outlined near‑term and conceptual next steps.
Key findings: Ainsley said the tested fish‑guidance structures reduced eddy formation at the bridge corners but did not deliver the expected improvement in fish passage and delay time. In contrast, acoustic startle devices—underwater sound units tested to discourage seals—reduced seal presence in the device hearing zone by an estimated 60–80% and reduced the time seals spent in that area by about 30%.
What the tests mean: Ainsley framed the bridge problem as twofold: reducing the time fish spend delayed at the bridge and reducing predator (seal) concentrations that increase mortality. She told the board that while interim devices show promise for reducing predators, solving delays will likely require a longer‑term engineering and community planning process.
Next steps: The group has completed a community needs survey (more than 6,600 responses reported for the broader bridge conversation) and will produce a conceptual engineering report in October, followed by a layperson summary for public review next March. Funding to support conceptual design work is being sought from state and federal sources.
Why it matters: The Hood Canal Bridge is located on a migration route for ESA-listed steelhead and salmon; work on passage and predator mitigation has cascading benefits for regional recovery investments in restoration projects upstream.
