Copper in water makes salmon vulnerable

PUYALLUP, Wash., July 10 (UPI) -- Copper pollution in water can affect salmon, interfering with their sense of smell that normally warns of a predator's presence, a U.S. researcher says.

Jenifer McIntyre at Washington State University found tiny amounts of copper from brake linings and mining operations finding its way into waterways affects the fishes' sense of smell so much they can't detect a compound in water that ordinarily alerts them to be still and wary.

"A copper-exposed fish is not getting the information it needs to make good decisions," McIntyre said in a release Tuesday.

McIntyre put juvenile coho salmon exposed to varying amounts of copper in tanks with cutthroat trout, a common predator.

McIntyre explained salmon are attuned to smell a substance called Schreckstoff, German for "scary stuff," released when a fish is physically damaged, thereby alerting nearby fish to the predator's presence.

In her experiments, 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, kept swimming, and were attacked in about five seconds.

"It's very simply and obviously because predators can see them more easily," McIntyre said. "They're not in lockdown mode."

The copper had no effect on the behavior of the predators, she found.