Overview
- The peer-reviewed study in Current Biology, published Monday, found salmon exposed to benzoylecgonine swam up to 1.9 times farther per week and dispersed about 12.3 km more than unexposed fish.
- Researchers tracked 105 hatchery-reared smolts for eight weeks in Sweden’s Lake Vättern using acoustic tags and slow-release implants calibrated to pollutant levels found below urban sewage outlets.
- The cocaine metabolite benzoylecgonine altered movement more than cocaine itself, challenging risk assessments that focus on the parent drug rather than breakdown products.
- Scientists warn that longer, wider-ranging swims can raise energy costs and change predator encounters and feeding, which could shift population patterns and food webs if confirmed in follow-up studies.
- The team urges stronger monitoring and wastewater treatment for drug residues that are now common in rivers and lakes, and notes the experiment signals no risk to people because exposures were low and fish were juveniles.