Stormwater runoff in Puget Sound is killing fish.

Following a four-year stormwater study, scientists from the National Oceanic and Atmospheric Administration (NOAA), Washington State University, U.S. Fish and Wildlife Service, and the University of Washington, with support from the Suquamish Tribe, are investigating what is in that runoff.

“We know the cause of pre-spawning mortality is stormwater, and we know using state-recommended bioretention systems such as stormwater filtering systems work to prevent pollutants from getting in the streams,” said Julann Spromberg, a research toxicologist with NOAA. “Now we’re looking at the chemistry makeup of the stormwater to figure out what exactly in the water is killing the fish.”

Over a five-week period this fall, scientists exposed 45 coho from the tribe’s Grovers Creek Hatchery to stormwater collected from streets around Puget Sound. Blood, organ and tissue samples were taken from each fish.

Researchers from the University of Washington, a new partner in the project, will test the samples and profile the specific chemicals found in both the fish and stormwater.
The team also is looking at how chum salmon fare.

“We know coho are affected after a few hours of exposure to stormwater and wanted to see if chum were affected too,” Spromberg said. “We exposed the chum to stormwater for the same length of time and found they were not as sensitive as the coho.”

The team has added a new tool to the diagnostic arsenal: blood chemistry.

So far, many blood chemistry parameters of coho salmon are affected by urban road runoff. The blood of chum is not affected the same way by stormwater.