Overview
- Researchers in Sweden tracked 105 farm‑reared Atlantic salmon in Lake Vättern with acoustic tags after implanting slow‑release doses of cocaine, its metabolite benzoylecgonine, or nothing.
- Fish exposed to benzoylecgonine moved up to about 60% farther than controls, covering nearly 14 kilometers more per week, and cocaine also increased distance by roughly 5 kilometers over two weeks.
- Treated fish ventured into parts of the lake with more large predators, a shift that could raise energy demand and predation risk for young salmon.
- The team warned that small behavioral changes at low doses may alter habitat use, while outside experts cautioned that implants may not match natural exposure through gills, skin, and diet.
- Wastewater systems often miss such drug residues, and benzoylecgonine lasts longer than cocaine, prompting calls to include persistent byproducts in environmental risk assessments.