April 24, 2026 — The world’s waterways are becoming increasingly contaminated with pharmaceuticals and illegal drugs—and the pollutants are seeping into marine animals. Cocaine, specifically, has been found in sharks, shrimp, mussels and eels, but exactly how these human-derived contaminants might be affecting wildlife has remained mysterious.
Now, new research offers a first look at how cocaine can alter the behavior of fish in the wild. Young Atlantic salmon exposed to cocaine’s primary metabolite—the compound created when human bodies break down the drug, which gets excreted into wastewater—swam farther than their sober peers in a Swedish lake, researchers report in a study published April 20 in the journal Current Biology.
The findings affirm the need to “carefully understand and manage all of the diverse chemicals society uses that can end up in our waterways,” Mark Servos, an ecotoxicologist at the University of Waterloo in Canada who was not involved with the research, tells Science’s Erik Stokstad.
The scientists behind the new study visited an Atlantic salmon hatchery in southern Sweden, where they outfitted 105 two-year-old, captive-raised fish with tracking tags and slow-release capsule implants. In one-third of the group, the implants gradually released cocaine into the creatures’ bodies. In another third, the devices released cocaine’s main metabolite, benzoylecgonine. In the final third—the control group—the implants provided no chemical related to the drug.