FY25 Port Gamble S’Klallam Tribe - Hood Canal Bridge Fish Passage Mitigation Evaluation

This project aims to test and evaluate practical mitigation measures identified in the 2020 Hood Canal Bridge Ecosystem Impact Assessment – Phase 1 Report to reduce the negative ecological impacts associated with the Hood Canal Bridge. The bridge has been shown to act as a migration barrier for juvenile salmonids, including ESA-listed Puget Sound steelhead, Puget Sound Chinook Salmon, and Hood Canal summer-run Chum Salmon. Acoustic telemetry studies conducted by NOAA in 2017 and 2018 demonstrated that approximately 50% of steelhead smolts tagged in these studies did not survive past the Hood Canal Bridge, highlighting the need for targeted mitigation efforts. The Tribe will employ hydroacoustic monitoring to evaluate pinniped behavioral responses to the deterrent signal. The goal is to develop a semi-autonomous detection and monitoring tool capable of identifying reductions in device effectiveness—such as predator habituation—and to inform adaptive management strategies. Data collected by PGST will provide valuable insights into predator-prey interactions and behavioral dynamics near the bridge, enhancing the scientific basis for mitigation planning.

Ultimately, this project will support the development of effective, non-lethal tools to reduce predator impacts and improve salmon survival rates during outmigration through Hood Canal—contributing to the long-term recovery and resilience of Puget Sound salmon populations.