TRAVELERS ALONG HOOD Canal Bridge in recent days likely have spotted commercial fishing vessels netting migrating chum returning to the Hoodsport Hatchery and/or streams south of the bridge.
Besides avoiding the commercial nets, migrating salmon and steelhead find great difficulty in getting past the bridge, a bottleneck that turns into a buffet, attracting predators such as harbor seals, sea lions and sea birds.
Endangered Species Act-listed Hood Canal steelhead are particularly impacted at the bridge, delayed by its design, as 50 percent of canal steelhead end up dying at the bridge, according to Long Live the Kings, a fish recovery group that holds the Survive the Sound, an online game that uses real fish migration data, to track how fish survive in Puget Sound.
Long Live the Kings’ recent assessment of the bridge is available at tinyurl.com/PDN-BridgePlan and includes a number of engineering recommendations to improve fish passage.
Steelhead ride high in the top 3 feet of the water column, leading them directly into the Hood Canal Bridge’s 36 floating concrete pontoons, which extend 15 feet below the water’s surface.
Embedded transmitters show some steelhead figure out the puzzle and dive deeper to get past the obstacle. Others swim along 1.2 miles of the bridge’s 1.4-mile span, trying to find an exit, but encounter more pontoon resistance when they reach the center draw span or the west and east ends of the bridge.
“Observers noted that when fish swimming along the edge of the bridge encountered a 90-degree turn, they often turned around and moved down the bridge in the direction they came, resulting in a circular swimming pattern,” Long Live the Kings’ report said.
Some studies and designs are underway for projects expected to reduce fish mortality at the bridge. Recommendations include installing flexible or solid corner fillet (pronounced fill-it) structures in front of pontoon corners to reduce back eddies caused by 90-degree angles. This would create smoother water flow around the fillets and ensure juvenile salmon and steelhead would have a more linear path as they navigate past the bridge.
Eddy-reduction structures such as a bullnose, a vertical half-pipe and fillet installed on the last pontoon in the open channel at each end of the bridge, could help reduce the tidal turbulence at the corner of the pontoons, especially during outgoing tides, when most steelies are migrating.
More and longer center draw span openings, particularly during peak ebb tides when steelhead are migrating, also are a possibility, as is changing bridge lighting so more light falls on the bridge’s roadway and less on the water.
Between $2.5 million and $4 million would be required to fund the construction of attachments for the bridge and begin monitoring efforts by 2022.
A hefty price, for certain, and would surely add to the price tag of preexisting efforts to save chinook, chum and steelhead runs that are all listed as threatened in Hood Canal under the Endangered Species Act.
Sports reporter Michael Carman can be contacted at 360-406-0674 or [email protected].