An international team of researchers has found that cocaine-related pollution in natural waters can significantly alter how Atlantic salmon move and use space.
The study provides the first field evidence that drug contaminants can affect fish behavior outside laboratory conditions. The research was published in the journal Current Biology.
Study design and tracking methods
Scientists from Griffith University, the Swedish University of Agricultural Sciences, the Zoological Society of London, and the Max Planck Institute of Animal Behavior led the study. They examined how exposure to drug residues influences fish behavior in a large natural ecosystem.
The team studied 105 juvenile Atlantic salmon in Lake Vättern, Sweden. Researchers divided the fish into three groups: a control group, a group exposed to cocaine, and a group exposed to benzoylecgonine, the primary breakdown product of cocaine commonly found in wastewater.
They used slow-release chemical implants to deliver controlled exposure and tracked the fish over eight weeks using acoustic telemetry.
Metabolite shows stronger effects
The results showed clear changes in movement. Fish exposed to benzoylecgonine traveled up to 1.9 times farther per week than unexposed fish. They also dispersed across a much wider area, moving up to 12.3 kilometers (7.6 miles) farther across the lake. These effects became stronger over time, suggesting that continued exposure can gradually alter how fish use space in complex natural environments.
A new study finds cocaine pollution is altering how Atlantic salmon move in the wild. Fish exposed to wastewater contaminants traveled farther and spread wider across a natural lake. Researchers warn drug residues in waterways may disrupt ecosystems more than understood. pic.twitter.com/KUogAiMWJt
— Tom Marvolo Riddle (@tom_riddle2025) April 20, 2026
Researchers found that benzoylecgonine had a stronger impact than cocaine itself. This finding is important because environmental risk assessments often focus on the original drug rather than its metabolites.
However, these breakdown products are more commonly detected in rivers and lakes. Scientists say this approach may overlook key biological effects in aquatic life.
Why movement matters for ecosystems
Co-author Marcus Michelangeli said the findings highlight the importance of animal movement in ecosystems. He explained that where fish travel shapes what they eat, which predators they encounter, and how populations are structured. Changes in these patterns could affect entire food webs.
Pollution pathways and global concern
The study also underscores growing concern over drug contamination in waterways. Cocaine and its metabolites are increasingly detected in rivers and lakes worldwide. These substances typically enter the environment through wastewater systems that are not designed to fully remove complex chemical compounds.
No risk to consumers
Researchers emphasized that the findings do not indicate any risk to people who consume fish. The exposure levels reflect those already found in polluted waters, the compounds break down over time, and the fish studied were juveniles below legal catch size.
The team plans to investigate how widespread these effects are and which species are most at risk. Future work will also examine whether altered movement patterns influence survival and reproduction, offering deeper insight into the long-term ecological impact of emerging pollutants.
See all the latest news from Greece and the world at Greekreporter.com. Contact our newsroom to report an update or send your story, photos and videos. Follow GR on Google News and subscribe here to our daily email!
