Anxiety drugs change the behavior of humans—and a new study suggests they change the behavior of salmon, too. Researchers in Sweden set out to study how medication that leeches into waterways might affect fish, explains NPR. They implanted two drugs in various amounts in about 280 farm-raised salmon: clobazam, often used to treat anxiety, and the pain medication tramadol. When the fish were released, those with higher amounts of clobazam seemed to take more risks, which translated into more successful migrations to the sea, reports DW.
"On the face of it, it sounds like giving drugs to fish is beneficial," says biologist Jack Brand of the Swedish University of Agricultural Sciences, lead author of the study in Science. "But any departure from natural behavior is likely to have potential broad and negative consequences for the population." In the case of the salmon, the fish on clobazam might have been less fearful of passing through large dams with dangerous blades, the researchers speculate. On average, the fish passed through such sites two to three times faster than their undoped cousins.
"Maybe the bolder fish are spending less time trying to decide if they're going to go through the scary turbines or not," says biologist Olivia Simmons of the Norwegian Institute for Nature Research, who was not involved in the study. The tramadol didn't seem to affect the fish one way or the other. What worries researchers is how the clobazam might affect the salmon when they reach the sea—will they be less social, and thus more vulnerable, as has happened in lab experiments? If so, that could ultimately lower survival rates. (More discoveries stories.)
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