PUYALLUP, Wash.Minute amounts of copper from brake linings and mining operations can affect salmon to where they are easily eaten by predators, says a Washington State University researcher. Jenifer McIntyre found the metal affects salmon's sense of smell so much that they won't detect a compound that ordinarily alerts them to be still and wary.
"A copper-exposed fish is not getting the information it needs to make good decisions," says McIntyre, a postdoctoral research associate in WSU's Puyallup Research and Extension Center. Her research, conducted for a University of Washington doctorate with colleagues at UW and the National Oceanic and Atmospheric Administration, appears in the latest issue of the journal Ecological Applications.
Earlier research showed that copper impacts a salmon's sense of smell. Other research showed that when a salmon's sense of smell is affected, its behavior changes.
McIntyre put the two together, exposing juvenile coho salmon to varying amounts of copper and placing them in tanks with cutthroat trout, a common predator. The results were striking.
Salmon are attuned to smell a substance called Schreckstoff. German for "scary stuff," it is released when a fish is physically damaged, alerting nearby fish to the predator's presence.
In her experiments, conducted in a four-foot-diameter tank, fish that weren't exposed to copper would freeze in the presence of Schreckstoff, making it harder for motion-sensitive predators to detect them. On average, half a minute would go by before they were attacked.
But salmon in water with just five parts of copper per billion failed to detect the Schreckstoff and kept swimming. They were attacked in about five seconds.
"It's very simply and obviously because predators can see them more easily," says McIntyre. "They're not in lockdown mode."
The unwary exposed fish were also more likely to be killed in the attack, being captured 30 per
|Contact: Jenifer McIntyre|
Washington State University