Coho salmon face fatal levels of pollution in 40 percent of their range in the Puget Sound Basin, chiefly because of stormwater runoff, says a study published in the journal Ecological Applications.
Stormwater-derived pollution ultimately accounts for 10-20 of Coho salmon deaths before spawning. “Every time it rains, a witch’s brew of pollutants from every impervious surface — roofs, parking lots, roads and more — sluices into storm drains,”explains The Seattle Times. “Most of it passes untreated into Puget Sound.”
Females, full of eggs and ready to spawn, become disoriented in the polluted waters, swim to the surface and die within a few hours. The researchers, including scientists at NOAA’s Northwest Fisheries Science Center in Seattle and the U.S. Fish and Wildlife Service, mapped problem areas in the region in the hopes that urban planners and officials can address the problem. Millions of dollars have been spent on urban stream restoration, but those efforts are undermined when toxic runoff still seeps in.