But Accola sees salmon. The Washington Sea Grant fellow knows what to look for after spending four months snorkeling this waterway with the University of Washington’s Seawall Project research group, in its effort to enhance and monitor salmon habitat along the newly renovated Elliott Bay Seawall .

Her colleagues are still snorkeling, but in recent months, Accola has been kayaking along the same section. At least once a week, about six hours at a time, at all times of day — sometimes with an intern, often alone — she paddles and collects data on how many salmon use the seawall corridor and the behavior they exhibit when they do. The way she’s doing this — with a hydroacoustic sonar camera mounted on the bottom of the kayak — is novel, and giving her access into a world few get to experience: the cultures of salmon, and Seattle’s harbor, at night.

“We know virtually nothing about [salmons’] nighttime behavior along the seawall,” says Jeff Cordell , a principal research scientist at UW who advises Accola.

Salmon depend on light for both navigation and feeding: Not understanding how these activities play out along the waterfront is a huge hole in our knowledge of how built environments impact the animals that lived there first.

Kerry Accola, a UW graduate student, tracks salmon with a hydro-acoustic camera, located under her kayak, along the Elliot Bay Seawall on June 14, 2019. (Photo by Dorothy Edwards/Crosscut)

What Accola is learning about these behaviors in response to the seawall could influence the management of seawalls in places that nearshore fish have been impacted by urbanization.

Accola developed a love of freshwater ecosystems in her native Wisconsin, and pursued a fishery biology career. When family brought her to Seattle a few years ago, she observed the new seawall construction and realized a latent curiosity in marine fish. She reached out to Cordell and began classes at UW’s School of Aquatic and Fishery Sciences (SAFS) program.

“I knew … that this was something exciting, a large-scale seawall modification project to benefit juvenile salmon,” she says. “I tried to think of ways to study them that would be able to give a complete picture of their migration behaviors along the waterfront.”

Accola first thought of tagging the fish, but the sheer number of salmon to tag would require significant effort and expense. There’s also the matter of “tag burden,” or tags that sometimes can irritate fish. She and Cordell settled on a hydroacoustic camera called the Dual-Frequency Identification Sonar 300m (DIDSON 300m). She spent last spring learning to use the technology, while snorkeling to get better at recognizing juvenile fish.

The 0.7-mile corridor is a critical juncture for juvenile salmon exiting their spawning grounds in the Superfund-designated Duwamish River and swimming toward the sea, where they spend most of their adult lives; but because of the structures that make up the Port of Seattle and the original seawall, built in 1936, Elliott Bay has effectively been boobytrapped.

“They school between the piers because the piers constrain them — they all jam up, waiting for low tide to go around, or go through all together,” Accola says. The new corridor is intended to expedite their journey.

Juvenile salmon are hardwired to stay close to shore in brightly lit water as they spend their adolescence fueling up on shallow-living invertebrates and getting big enough to head to sea. But the seawall, which stabilizes the ground beneath downtown Seattle and protects important underground utilities from briny saltwater, removed those shallow nearshore feeding grounds.

Seven species of salmon, including the federally endangered chinook (the orca food of choice) , travel through that corridor. And while researchers don’t know how many fish use the corridor each year, or the extent to which the seawall impacted their survival rates, they do know it didn’t help: The salmon that did swim through rarely swam beneath the piers, and didn’t have great feeding opportunities along the seawall.

Between 2013 and 2017, as the southern section of the seawall was being replaced, Cordell’s team decorated the wall with salmon-friendly enhancements. These include things like textured walls to encourage vegetative growth that attracts shrimplike invertebrates ; “marine mattresses” — deceptively named mesh bags filled with rocks — which artificially elevate the seafloor to house invertebrates closer to sunlight and make fish feel more comfortable feeding there; and light-penetrating glass sidewalks overhanging the corridor, to boost plant growth and help salmon navigate and hunt.

“[The idea is to create] better feeding opportunities, but also just a safer environment,” she says. “If [salmon] can stay close to nearshore in shallow water, where there are fewer predators, and don’t have to go around piers or wait for a really low tide [to continue], they can feed the whole way, instead of only feeding sporadically in between piers.”

The salmon enhancements made up only 2% of the overall seawall budget, but represent the largest-ever ecological engineering project in an urban marine setting. Researchers, including Accola, are contributing to a 10-year monitoring program studying the enhancements’ effectiveness in adjusting vegetation, invertebrate and salmon populations, while curious international engineers from as far as New Zealand follow along.