Source: Daniel Beekman, Seattle Times, June 4 2019
The primary goal in Seattle is to boost the region’s culturally iconic chinook salmon, which are listed under the U.S. Endangered Species Act and which southern resident orcas rely on. Not every urban port in the world has chinook, but all have marine creatures under threat.
“This project has really hit the radar screen internationally,” said Jeff Cordell, the principal UW research scientist studying the seawall. “I’ve traveled to Australia to talk about it. We’ve had people visit from South Korea.”
Seattle has wreaked havoc with its shoreline as the city has grown, replacing a natural, sloping beach with seawalls, dumping pollutants into the water and anchoring colossal ships in Elliott Bay. Salmon have never completely abandoned the downtown waterfront, however, and early research indicates the new seawall is easing their passage.
The more they eat and grow as they migrate from the Duwamish River and other waterways to the open Puget Sound and beyond, the better chance they have to survive at sea and return to mate. The UW team saw an estimated 10,000 juvenile salmon of various species on a single day of surveying last May and as many as 300 chinook on another day the same month.
“We’re lucky. We haven’t decimated them to quite the point where they’re no longer here at all,” UW research scientist Jason Toft said. “So now we’re just trying to make little improvements for them.”
Every year, juvenile salmon leave the streams where they hatch and head to the ocean. They hug the shore, where they can munch on small invertebrates and avoid predators. They’re “visual feeders” that need light to forage.
hen the old seawall was in place, “We’d see them between the piers in the sunlight and then they’d school around the edges of the piers but not go underneath,” Toft said. “They’d hit the shadows, then circle back around.”
The UW researchers, who surveyed certain waterfront areas before the new seawall was built, returned with their snorkels to the same areas last spring and summer. They were hoping to see salmon interacting with the habitat improvements. But they didn’t know quite what to expect.
“I remember the first time I saw a juvenile salmon below a pier, under those glass blocks,” Toft said. “I had a handheld camera, so I took a video. There were some chum salmon swimming and feeding like you’d see them do in a more natural setting. That was super cool.”
In January, the researchers completed their Year 1 report, based on snorkel surveys last March through October. Pink and chum salmon and shiner perch were the fish they saw most along the new seawall, with the salmon mostly present in April and May. They also saw some chinook.
More salmon showed up between than under the piers. But more were present under the piers than previously, clustered in the shallow, illuminated areas created by the new sidewalk and the rock beds.
Though not yet quantified in a report, that change “indicates that a proportion of the juvenile salmon along the seawall are using the corridor under the piers lit by (the panes),”according to the Year 1 study.