LAKE VATTERN — Wild Atlantic salmon exposed to cocaine and its metabolite benzoylecgonine swam 1.9 times farther per week than unexposed fish, according to joint research released Monday by scientists at Australia's Griffith University and the Swedish University of Agricultural Sciences. The study examined how the substances affect the movements of wild fish in their natural habitats.

Researchers took 105 wild Atlantic salmon in Sweden's Lake Vattern, exposed them to cocaine and benzoylecgonine, and tracked their movements. Salmon exposed to benzoylecgonine swam 7.6 miles farther per week than unexposed salmon.

"Any unnatural change in animal behavior is a concern," said Marcus Michelangeli, a report co-author at Griffith University's Australian Rivers Institute. "We're finding higher and higher concentrations of not just illicit drugs but all types of pharmaceuticals in our waterways."

"Our study shows that drugs are not only a societal issue, but also a concrete environmental challenge," said Michael Bertram, an associate professor at the Swedish University of Agricultural Sciences. "The idea of cocaine affecting fish might seem surprising, but the reality is that wildlife is already being exposed to a wide range of human-derived drugs every day. The unusual part is not the experiment, it's what's already happening in our waterways."

An estimated 25 million people used cocaine in 2023, according to the U.N., which also reports that cocaine is increasingly found in waterways. A study released last month found that sharks in the Bahamas are consuming caffeine, painkillers, and cocaine. In 2024, scientists reported that sharks in waters off Brazil tested positive for cocaine and benzoylecgonine.