Fish Radio

Road runoff  kills cohos, harms fish senses, easy fix

October 23, 2015                     Runoff logo

This is Fish Radio. I’m Laine Welch … An easy fix protects fish from road runoff toxins. I’ll tell you more after this —

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Rain water runoff from urban roadways is so toxic to coho salmon, it can kill them in as little as 2½ hours. Scientists have long suspected that the mixture of oil, heavy metals and grime that washes off highways is toxic to coho salmon, and now it’s been proven.  To do so, researchers at the Northwest Fisheries Science Center in Seattle tested the real thing:    runoff from a highway downspout near Montlake.  When 60 adult coho were exposed to the toxic brew in the lab, some died within hours, all within a day.

The study, published this month in the Journal of Applied Ecology,  highlights how little is known about which chemicals and combinations are toxic to fish in a watery mix of oil and gas, chemicals from tires or brake linings and other automotive byproducts.

An earlier study at Oregon State University proved that copper runoff from vehicle brake pads and exhaust affects the senses of juvenile salmon. Copper levels as low as just two parts per billion impaired the small salmon’s sense of smell, which helps them avoid predators. Study co-author Jason Sandahl says at higher levels, that avoidance ability was almost nonexistent.

  In the environment that has some serious implications. If there are predators around and the fish are not able to response to these danger signals in the water, I guess they would be the next snack for these larger predators in the water.

Fluctuations due to storm run-offs  can increase copper levels in waterways,  Sandahl says to more than 60 parts per billion.

  In the Northwest, copper from brake pads, for example from the summer months can accumulate on the roadsides for several months, and in the fall when we have our first rainstorms,  that accumulated copper can run into the streams. Those short, tense pulses of copper I think are the most concerning.

But there is an easy fix to protecting the fish.  The coho scientists found that simply  filtering the road runoff through 55 gallon drums packed with layers of gravel, soil and compost did the trick.

Washington State regulations now strongly encourage creation of grassy valleys and other ‘green’  alternatives to drains and pipes, that let road runoff percolate through the ground, as it did before   areas were paved over.

Washington State University is leading a campaign to install 12,000 rain gardens in the Seattle/Puget Sound Region by next year.

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Fish Radio is also brought to you by Ocean Beauty Seafoods – who salutes and says thanks to the men and women fishing across Alaska for their hard work and dedication. ( In Kodiak, I’m Laine Welch.