Overview
- The peer-reviewed study, published Monday in Current Biology, found juvenile Atlantic salmon exposed to benzoylecgonine swam up to 1.9 times farther per week and spread as much as 12.3 kilometers beyond unexposed fish.
- Researchers implanted 105 hatchery-reared fish with slow-release capsules and acoustic tags, released them into Sweden’s Lake Vättern, and tracked their movements for eight weeks across three groups: control, cocaine, and benzoylecgonine.
- The metabolite benzoylecgonine changed movement more than cocaine itself, underscoring a blind spot because most risk assessments target the parent drug rather than its longer-lived byproducts.
- Movement changes intensified over time as drug-exposed fish failed to settle near the release site like controls, indicating a lasting shift in how they use space in a natural ecosystem.
- Scientists warn altered movement could drain energy, change feeding and raise predator exposure, yet they note no sign of risk to people eating fish and urge monitoring of metabolites that enter waterways through wastewater plants not designed to remove them.