Federally protected Chinook salmon were among the dead fish found this summer in Lake Washington under Sound Transit’s new light rail tracks, according to interviews with fishery managers and photos of the suspected fish die-off.
The investigations now underway below I-90 focus on how underwater anode cables, which carry a low-level electrical current, could have killed fish — and how many of which species perished.
Sound Transit last week disclosed that about 2,000 fish died, mostly nonnative species but also some salmon. Agency CEO Dow Constantine’s brief announcement also said the agency has sent divers and has pulled some cables off the lake bed since it was first notified of the dead fish on Aug. 3 as a result of discoveries by amateur divers.
The discovery of threatened salmon, protected under the federal Endangered Species Act, among the fish killed has unsettled those who have fought to rebuild or save struggling salmon in the Lake Washington watershed.
“It hurts us to know that our salmon are getting killed,” said Jaison Elkins, the chair of the Muckleshoot Indian Tribe Fisheries Commission.
The National Oceanic and Atmospheric Administration Fisheries West Coast Region confirmed that salmonids were affected, but said in a statement the agency is awaiting further details, such as the number and species of fish involved. “In the meantime,” the statement said, “we appreciate that Sound Transit continues to assess and address the problem to prevent further impacts on fish.”
Scientists with the Muckleshoot Indian Tribe, in an August meeting with Sound Transit and the state Department of Transportation, reviewed images from the die-off that included Chinook salmon, said Mike Mahovlich, assistant director of Muckleshoot Fisheries. While the images were blurry, Mahovlich said it appeared sockeye were killed as well.
In mid-2025, two amateur divers exploring underwater ruins from a 1990 bridge collapse saw carcasses on the silty lake floor, near the Seattle shore, and made more trips last fall. They say they explored the Mercer Island side this July, and immediately found dead fish beneath eastbound I-90.
Threatened Cedar River Chinook salmon have not been harvested for more than three decades to allow them to recover. Lake Washington sockeye nearly went extinct and Muckleshoot and state Department of Fish and Wildlife officials have kept the run on life support by trucking them around the lake to a hatchery.
“It’s a never ending battle.” Elkins said, reached by phone from his fishing boat on Elliott Bay Monday evening. “It’s pinnipeds. It’s pollution. It’s water temperature. It’s barriers. Now it’s these electric cables.”
The cables are designed to transmit low-level current into the water that counteracts effects of any stray current from electrified train operations. Stray current, left unchecked, can potentially cause long-term corrosion to steel rebar inside pontoons that support the bridge, or to I-90s anchor cables.
Below the surface
Travis Eiler and Shahein Moussavi say they first saw a dead-fish pile in August 2025 offshore from Seattle, a short distance south of the eastbound I-90 bridge, about 65 feet deep.
For a few years, the divers had been exploring lost pontoons, concrete and metal anchors, and other objects, but that was their first time at this specific site. The pile was about 4 feet in diameter and 2 ½ feet high.
Moussavi, the Seattle chapter president of the nonprofit Global Underwater Explorers (GUE), said in an interview Tuesday that he originally thought the fish, which looked fresh, might be part of some scientific study.
They returned there in the fall and took photos, but didn’t make a concerted effort to inform wildlife agencies yet.
They say they explored the Mercer Island side this July, encountering dead fish beneath eastbound I-90, at depths of 60 feet to 180 feet.
They found “nine to 12 different piles” of fish, took photographs, and each sat next to a hanging anode cable that rested upon the lake bottom, said Moussavi. “It was the same thing, anode assemblies had crashed into the ground,” he said. Those piles were along a swath from south of the bridges, to the waters next to light rail tracks.
They weren’t fearful of being electrocuted and followed at least one anode cable from floor to surface. “We’re in dry suits, rubber gloves, we’re pretty well insulated, but no we don’t go grabbing onto them,” said Eiler, the group’s local vice president.
This time, they contacted Washington Conservation Action, then Long Live the Kings, and wound up exchanging messages this summer with environmental, tribal and transportation agencies, Moussavi said.
The Washington State Department of Transportation says it notified Sound Transit on Aug. 3, immediately after WSDOT was notified by the state Fish and Wildlife, which was contacted July 31 by Long Live the Kings, according to WSDOT communications director Ryan Overton. The amateur divers examined the area again Aug. 9.
Based on the amateur divers’ pictures, some anode strings “may be resting on the lake bed and spaced closer together than intended,” Tony Raben, Sound Transit’s executive project director, wrote in an email to other parties.
Sound Transit arranged for commercial divers to take their own look and made several trips starting Aug. 10.
A Fish and Wildlife expert said some “carcasses not covered with silt include yellow perch, sculpin, smallmouth bass, and an unknown salmonid (possibly a small cutthroat trout); so the wires appear to be affecting pretty much whatever type of fish gets close to them,” according to an email excerpt provided by Moussavi.
Fish and Wildlife on Aug. 7 issued a permit for Sound Transit to perform “corrective maintenance” of the anode strings. The project description stated, “anode strings have become displaced and are currently coiled on the lake bed rather than suspended in their intended configuration.”
Eiler said he and his son revisited the spot near Seattle a week ago, where they found the anode cable no longer touching the lake bed, and no more fish pile.
That account jibes with reports from Sound Transit that it relocated 32 anode cables in August..
The explorers’ group will continue to monitor and photograph these sites in concert with the nonprofit Project Baseline.
“I think we demonstrated the value of our unique community of hobbyists,” Moussavi said of their discovery.
Sound Transit said it’s examining whether electric current harmed the fish, or perhaps caused a chemical reaction with lake sediment.
Struggling salmon
Lake Washington is today dominated by warm-water-loving invasive predator fish, said Mahovlich, of Muckleshoot fisheries. But native fish are in the lake and struggling to recover.
One dead salmon here is bad news, Mahovlich said.
It’s unclear how many salmon have died near the bridge, or the exact cause of death. Mahovlich says he identified at least two Chinook salmon carcasses in images provided by Sound Transit.
Adult salmon trying to return to spawn in the Cedar River are stressed by the time they reach the bridge. Lake Washington salmon face an army of seals and sea lions as they navigate the Ballard Locks. They endure hot and at times lethal water temperatures.
After encountering the threat at the bridge, they could continue to swim, weakened and stressed, before dying elsewhere in the lake, Mahovlich said.
From the counts at the Ballard Locks, adult salmon go missing before making it back to a hatchery or their spawning grounds each year, he said. Fisheries managers over the past 15 years have seen about 69% of the Chinook and about 41% of the sockeye making it from the locks to spawning grounds or hatcheries, Mahovlich said. Juvenile salmon heading to the ocean in spring also face threats and their carcasses would likely be eaten by predators before they could be seen and counted, Mahovlich said.
Sound Transit has been taking this seriously, Mahovlich said, holding meetings to share information with tribal nations and other agencies since the dead fish were discovered. Fish and Wildlife said it is monitoring reports for impacts on species of conservation concern and coordinating with state and regional agencies.
The Lake Washington basin was once a pillar of Muckleshoot salmon harvests. “Now it’s nothing,” Mahovlich said, as he helped biologists sample freshly caught coho along the Duwamish River Tuesday morning.
“That’s what we do in these urban concrete jungles of watersheds,” Mahovlich said, “we fix one thing and find another problem.”
“We’re here for the fish,” he continued. “If you’re harming them, you’ve got to be accountable. That’s the bottom line.”
Next steps
WSDOT still hasn’t given its final signoff to accept the cathodic protection system, but did give “interim acceptance” March 25, three days before the first trains carried the public.
“The fish issue will need to be resolved prior to the system being transferred to WSDOT,” according to a statement from Overton, the agency spokesperson.
The state owns the bridge, and at the $1 billion rail project’s inception required Sound Transit to design light rail so I-90 can last another 70 years serving motor vehicles and trains.
Sound Transit Board Chair Dave Somers — a former fisheries biologist turned Snohomish County Executive — has asked for more-frequent updates on how the problem is being solved, his chief of staff Julie Moore said.
Sound Transit says divers are out this week inspecting the 32 anode cables that were moved in August. Sampling and testing of fish carcasses are planned this week.
The agency might change its I-90 protections, by attaching the anode lines to bridge anchor cables, which reduces the amount of current necessary to protect the bridge,” transit spokesperson Rachelle Cunningham said.
Isabella Breda:206-652-6536 or ibreda@seattletimes.com: Isabella Breda is a reporter with The Seattle Times' Climate Lab.
Mike Lindblom:206-515-5631 or mlindblom@seattletimes.com: Mike Lindblom is a transportation reporter at The Seattle Times.
