Top recommendation for helping to reduce steelhead smolt deaths at the Hood Canal Bridge in the short term?
No, not that kind!
Rather, attaching a flexible screen known as a corner fillet structure to four 90-degree sections of the crossing where the young fish otherwise end up circling and circling, becoming easy prey for harbor seals.
It and several other ideas came out of a new assessment by Long Live The Kings, which has long been studying the perils that young fish face trying to swim past the Highway 104 saltwater crossing between the Kitsap and Olympic Peninsulas.
It’s a baffling bottleneck for Endangered Species Act-listed steelhead in particular, delaying them for a day or two on average, with 50 percent dying there, LLTK reports. Their Survive the Sound game annually illustrates that and other fish issues to thousands of Pugetropolites.
The fish migrate in the top 3 feet of the water column which takes them smack dab straight into the bridge’s floating concrete pontoons, which extend 15 feet under the surface.
Those that don’t figure out they need to dive down have to swim along the 1.4-mile span until they find an opening, but when they get to the middle drawspan or the west or east ends they come upon pontoons that jut out from the bridge and get concentrated there.
“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,” LLTK reports.
The idea with installing a fillet – in the engineering world it’s actually pronounced fill-it – during the relatively brief migration period is to turn that 90-degree corner into a 45-degree onramp to getting around the bridge and out of the canal.
The report was put together by a team that includes federal, tribal, state and other representatives. Ultimately they recommend redesigning the bridge so it’s fish-passage friendly, but that’s expensive.
Meanwhile, with harbor seals in Puget Sound still protected by the federal marine mammal act, tribal and state biologists have also been surveying their populations with an eye on determining “optimal” levels that allow ESA-listed salmon and steelhead to better recover.
Back at the Hood Canal Bridge, cost estimates for the corner fillet structures range from $120,000 to $342,000 apiece and depend on how deep they’re made to extend, either 8 or 15 feet.
Another idea from LLTK is to install bullnoses – strong plastic bumpers – on the open-water side of the 90-degree pontoons to deflect current eddies that form on strong outgoing tides and act as another baffler for the fish, turning them around at what otherwise would be their exit to the upper canal.
Those could run from $62,000 to $158,000.
Depending on how many fillets and bullnoses are installed, design, materials and implementation costs range from $432,000 to $1.172 million, according to LLTK.
The organization also wants to study whether keeping the bridge’s center drawspan open longer during the spring migration and ebb tides improves steelhead survival.
“The openings could be scheduled so that motorists would know when the bridge would be closed to traffic. Openings of one hour during the strongest ebb tides are likely to provide sufficient information about fish passing through. While not considered a long-term solution, experimentation could provide information useful for future changes in the bridge structure that ultimately address this migration barrier,” LLTK states.
And they suggest rejiggering overhead lighting so more of it falls on the bridge and less on the water, where it possibly attracts prey and then young fish.
Besides steelhead, listed Chinook and chum also have trouble getting past the bridge.
LLTK says now that the first phase of the assessment is done, they’re doing some design work ahead of the long 2021 legislative session.
“If we’re able to secure much sought after funding by next spring, we’ll have short-term solutions intended to reduce fish mortality in the water as soon as 2022,” reads a statement from Iris Kemp, a senior project manager. “In the long-run, we hope to work with our partners to replace the bridge with a fish-friendly design that is better for people and fish.”