Hood Canal Bridge Impact Assessment

This project provided resources for the Port Gamble Tribe to participate in the Hood Canal bridge impact assessment. Project contributions supported: 1) conducting data analysis of past acoustic data in conjunction NOAA to determine best placement and timing of an acoustic arrays to track fish movement; 2) placement and operation of acoustic arrays; 3) conducting additional acoustic surveys, surface and subsurface video and camera imagery and visual observations of predation activity during peak outmigration time periods; 4) Performed video surveys under the bridge to investigate a secondary hypothesis that the underside of the bridge and anchor cables are creating a significant artificial reef habitat that may be creating a localized ecosystem that attracts predators by creating habitat for other small fish and whether or not juvenile salmonids are being attracted as well to high densities of feed and therefore delaying their transition past the bridge enough to elevate their exposure to predation at the site.

This project will support the Port Gamble S’Klallam tribe’s (PGST) Hood Canal Bridge Impact Assessment. The Hood Canal Bridge is an important regional transportation asset. It carries traffic across the northern outlet of Hood Canal, drastically shortening the trip between the Olympic and Kitsap peninsulas and in turn supporting tourism and other economic activities. As a 1.5-mile long floating bridge, its pontoons span much of the width of Hood Canal and extend 12 feet underwater. Because of its location, all salmon and steelhead must pass the Hood Canal Bridge on their migration to and from the Pacific Ocean. Recent studies indicate the bridge is a barrier to fish passage. Slower migration times and higher mortality rates suggest the bridge is impeding migration and increasing predation. Recent research also shows that the bridge may disrupt water circulation. Fjords depend upon strong surface flows to be replenished with healthy, oxygenated water. The bridge could therefore be contributing to low dissolved oxygen levels and fish kills, and exacerbate effects of ocean acidification—which is more prevalent in Hood Canal than anywhere else in Puget Sound—and climate change. We will work in partnership with NOAA, Long Live the Kings, Hood Canal Coordinating Council, WDFW, Battelle’s Pacific Northwest Laboratories and others.