Salmon and seals at Capitol Lake
New technology aims to help salmon returning to south Puget Sound
Every fall at Capitol Lake in Olympia, the salmon return.
At the tail end of a long journey from the ocean to the far southern end of Puget Sound, Chinook salmon congregate at a fish ladder climbing into the lake. And every year, crowds gather at a bridge crossing Fifth Avenue in downtown Olympia, observing the salmon as they work up the courage to make the leap into the fish ladder.
But there’s another type of observer that likes to come watch the salmon here: harbor seals.
Seals love fish ladders like these because they’re chokepoints for migrating salmon — engineered to allow salmon to move over them, but still an obstacle to migration, in this case one of the final obstacles salmon face on their long journey back to the mouth of the Deschutes River. The salmon can make for an all-you-can-eat buffet for seals in the right place at the right time.
But this year, something’s different. This year, hanging from underneath the bridge, a red tether runs to a set of underwater speakers, emitting a sound at irregular intervals meant to keep these smart — but skittish — seals at bay.
The speaker is part of a relatively new system known as GenusWave Targeted Acoustic Startle Technology (TAST), designed to deter seals. For the past several years, the research nonprofit Oceans Initiative — under a contract with the Washington Department of Fish and Wildlife (WDFW) — has been researching the effectiveness of this technology at locations like the Ballard Locks in Seattle and Whatcom Creek in Bellingham, gauging whether the technology could be a useful tool for wildlife and fishery managers working to conserve threatened salmon runs in Puget Sound.
Positive results
Laura Bogaard, a research biologist with Oceans Initiative, said that preliminary results indicate that when the device is active, it can keep seals at about a 50-meter distance from the speaker location.
“We don’t necessarily see a change in the total number of seals at places like the [Ballard] Locks, but we do see that spatial redistribution pretty prominently in all the places we’ve had it deployed,” Bogaard said.
Katie Wold, a biological technician with Oceans Initiative who was monitoring the device on a sunny September Saturday in Olympia, agreed. She noted that although the device doesn’t stop seals from preying on salmon altogether, so far it has been effective at keeping the animals away from the base of the fish ladder where salmon are gathering.
Observers like Wold record the number of pinnipeds, like seals, spotted both while the device is turned on and when it’s inactive. They also observe the number of predation events, when a seal actually catches an adult salmon.
Developed at the University of St. Andrews in Scotland, the technology is tuned to deter pinnipeds with minimal impacts to fish that may be swimming nearby, and the salmon entering Capitol Lake seem to ignore the bursts of static-like sound that can be heard occasionally over the sounds of passing traffic.
Many passersby stopped to talk to Wold, asking questions about the project with some expressing their support for the work to help salmon and exploring this novel approach to predator management.
WDFW researchers and others are looking closely at exactly how predation may be impacting salmon runs in Puget Sound and elsewhere in Washington, since the passage of the Marine Mammal Protection Act in 1972 helped seal and sea lion populations bounce back along the West Coast. Bogaard noted that although the technology won’t completely eliminate predation, it could be one more tool in the toolkit for managers trying to find a balance between two protected species.
“It has the potential to be a much less harmful and invasive tactic compared to other deterrents,” Bogaard said. “It looks like this will be a useful tool to give these salmon a bit more room to get where they’re going.”
