Overview
- Researchers tracked 105 juvenile Atlantic salmon in Sweden’s Lake Vättern for eight weeks using implants that released cocaine, its metabolite benzoylecgonine, or no drug.
- Benzoylecgonine exposure led fish to travel up to nearly twice as far each week and to range about 20 miles from the release site compared with roughly 12 miles for controls.
- The metabolite produced stronger and more consistent behavioral changes than cocaine itself, pointing to breakdown products as key drivers of impact.
- People excrete benzoylecgonine into wastewater, and many treatment plants do not fully remove it, so it often occurs in higher levels than the parent drug in rivers and lakes.
- Scientists urge expanded monitoring and better wastewater treatment, noting the study measured behavior with implanted slow‑release doses and did not test survival or reproduction.