Toxic Runoff Is Killing Coho Salmon, But A Simple Solution Can Save Them

Posted: Oct 10 2015, 6:37pm CDT | by , in News | Latest Science News


Toxic Runoff Is Killing Coho Salmon, But a Simple Solution Can Save Them
Courtesy of NOAA

Urban stormwater which contains runoff from highways and traffic is causing death of the iconic Coho Salmon at a very high rate.

Highway and traffic runoff is devastating for Coho Salmon. New research suggests that the toxic runoff is causing premature deaths of the fish at a high rate of around 50%.

Coho Salmon is a fish species with exceptional economic and cultural significance and it is commonly found in the freshwater streams of Western North America. The recent study has found a fatal connection between the polluted urban stormwater (that falls into freshwater streams) and the killing of Coho Salmon.

According to the study, Coho Salmon cannot withstand the stormwater which comes from urban areas and contains harmful, toxic runoff. The stormwater is causing mortality syndrome in fish and increasing their deaths. Luckily, scientists have found an inexpensive and reliable solution for their survival and their deaths can be reduced by soil infiltration, a conventional green stormwater infrastructure technology.

“Our goal with this research is to find practical and inexpensive ways to improve water quality. The salmon are telling us if they work." Julann Spromberg, a research scientist at NOAA Fisheries' Northwest Fisheries Science Center in Seattle, said.

Scientists extensively studied the impact of urban stormwater on Coho Salmon and chosen the area of Puget Sound in Washington, where they found many adult Coho die prematurely every year before they can spawn. 

To prevent this already endangered species from becoming extinct, researchers believe it is necessary to incorporate pollution prevention methods such as green stormwater infrastructure, which filters out all the pollutants from the stormwater.

To find out how effective the method is, researchers tested it on Coho Salmon. They put a fish in the water which was filtered through a soil column containing layers of gravel, sand, compost and bark and others in a tank which had unfiltered water collected from a highway in Seattle. 

The fish exposed to the filtered water survived while the other which was put in the actual stormwater started to die. The demonstration indicates how effective this simple strategy turned out if utilized properly and to the maximal extent.

"If we can incorporate clean water design strategies into future growth, as some transportation projects are already doing, wild salmon might have a chance.” Nat Scholz, manager of the Ecotoxicology Program at the NWSFC in Seattle and a co-author of the study said. 

“It's remarkable that we could take runoff that killed all of the adult coho in less than 24 hours - sometimes less than four hours - and render it non-toxic, even after putting several storms worth of water through the same soil mixture."

The full study can be read here.

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Hira Bashir covers daily affairs around the world.




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