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 roughly 12 kilometers beyond unexposed fish.
- Researchers tracked 105 hatchery-raised smolts in Sweden’s Lake Vättern for eight weeks using slow-release implants and acoustic telemetry across three groups: control, cocaine, and the cocaine metabolite benzoylecgonine.
- The metabolite disrupted movement more than cocaine itself, raising red flags for risk assessments that focus on the parent drug and may miss effects from more persistent breakdown products.
- Scientists warn that extra swimming and wider dispersal could drain energy, push fish into poor habitats, change predator and prey encounters, and alter population links across a lake or river system.
- The team notes limits to the work because implants and hatchery fish do not perfectly mirror natural exposure, and they report no food-safety risk to people since levels reflect polluted waters and the fish were undersized, with follow-up studies now planned to test mechanisms and long-term effects.