Polluted stormwater runs over hard surfaces like parking lots and streets, carrying a chemical cocktail directly into Seattle’s urban salmon streams. 6PPD-quinone, a tire chemical derivative, is acutely toxic to coho salmon. These fish die of Urban Runoff Mortality Syndrome (URMS) within hours of encountering 6PPD-quinone in toxic stormwater.

Puget Soundkeeper volunteers document fish experiencing URMS, characterized by gasping, circling, and thrashing at the water’s surface. Volunteers also document female coho salmon that die of URMS before they can spawn.

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Salmon Survey Background

During the salmon run each fall, coho salmon enter the Duwamish River from Elliott Bay, and then swim up Longfellow Creek to spawn. Historically, Longfellow Creek contained populations of coho, chum, and Chinook salmon, cutthroat trout, and steelhead trout. The creek was an Indigenous fishery dating back to the 14th century.

Today, Longfellow Creek, like many urban creeks, suffers from habitat and water quality degradation. Various federal and state agencies conducted surveys on coho (Oncorhynchus kisutch), Chinook (O. tshawytscha) and chum (O. keta) salmon that use Longfellow Creek as spawning habitat in order to gauge the effectiveness of stream restoration projects. During these surveys they noticed coho salmon uniquely suffered from exposure to urban stormwater runoff, a disease now referred to as Urban Runoff Mortality Syndrome (URMS).

Fish deaths caused by toxic stormwater is of particular concern as regional efforts are underway to restore endangered salmonoid species and Southern Resident Killer Whales.

Efforts to survey fish mortality in Longfellow Creek, and specifically coho females that died before being able to spawn began in 1999. When public funding was no longer available to continue these survey efforts, Puget Soundkeeper trained community volunteers to collect salmon run data and continue to monitor trends in spawning success and salmon survival. Puget Soundkeeper began monitoring the salmon trends in 2015 and continues in October every year.