Stormwater runoff from highways has been found to contain one or more toxic compounds that can bring on sudden death in coho and possibly other salmon as well.
Researchers from NOAA’s Northwest Fisheries Science Center first noticed the problem in Seattle’s Longfellow Creek, which gets a high volume of stormwater when it rains. Returning adult coho were dying in the stream before they could spawn.
The problem was confirmed last fall at Grover’s Creek Hatchery in North Kitsap, where coho were placed into tanks containing highway runoff. Even after days of rain, the runoff was deadly, causing the fish to become disoriented and die within hours. This was not a disease process but a severe physiological disruption of the salmon’s metabolism.
On Monday, I reported on these dramatic new findings made by Nat Scholz and his colleagues at NOAA. Since then, the story was picked up by the Associated Press and has appeared in dozens of publications and news digests across the country.
I won’t go into detail about the study here, because most of what I know is the story. See Kitsap Sun, Jan. 21. Toward the end, I describe some actions that Kitsap County officials are taking to keep highway dirt and debris from getting into local streams, even before the deadly compounds are identified.
I’ll continue to follow this story as scientists try to narrow down the list of possible toxic compounds that are causing the problem. The next step will be to take clues from tissues removed from the dying salmon at Grover’s Creek Hatchery.
Naturally, these new findings raise many questions about how the unknown chemicals affect the fish so rapidly and where these compounds come from. Could it be from automobile tires or exhaust, or could it be something in the road material itself? Are certain chemicals acting synergistically to heighten the problem? Answering these questions could make a significant difference for urban streams and possibly for rural streams as well.
Personally, I can’t help wondering about the salmon that survive. It’s not easy to find a coho stream where highway runoff does not contribute something to the flow. If these compounds can kill a fish in concentrations found in stormwater, what are they doing to fish exposed to lower concentrations? Are the salmon that survive as successful in finding a mate and conducting their spawning rituals as salmon not exposed at all?
I’m not sure where this line of research will lead, but the early implications appear to be quite serious. On an optimistic note, if the compounds can be identified, Washington state has a reputation for reducing or eliminating toxic chemicals at the source.