Will Overdosing on Copper Make You More Susceptible to Predation?
Source: Tasha Eichenseher, National Geographic
Only if you are a young coho salmon, or similar aquatic species.
A new study published in the latest edition of Ecological Applications reports that small amounts of copper in water can deaden a salmon’s sense of smell, which normally alerts the fish to the presence of predators.
When olfactory systems are fully functional, the fish will detect a compound called Schreckstoff—German for “scary stuff.” Schreckstoff wafts from nearby fish that have been attacked and it cues yet-unharmed fish to stay still and on guard.
Previous studies had already established that copper affects a fish’s sense of smell, and that a dulled sense of smell changes a fish’s behavior.
But Washington State University (WSU) postdoctoral research associate Jenifer McIntyre and her colleagues put two and two together. They exposed juvenile coho salmon to copper and pitted them against cutthroat trout, a common coho predator.
Watch this video of what happens when coho salmon—some that are exposed to copper and others that aren’t—are warned of an approaching predator (10 micrograms/L = 10 parts per billion).
Just a minute amount of copper—five parts per billion—in a four-foot-diameter and approximately 12-inch deep tank was enough to kill a coho’s nasal sensory system. The fish kept swimming and were attacked within eight seconds. (You can think of five parts per billion as five drops of water among a billion drops of water.) Copper-free fish remained quiet and weren’t discovered by predators for at least an average of 30 seconds.
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