Swedish toxicologist Jack Brand loaded Atlantic salmon with slow‑release capsules of cocaine and its metabolite benzoylecgonine to mimic polluted waterways. After tagging the two‑year‑old fish, his team released them into Lake Vättern, a popular recreational fishery. Tracking over eight weeks showed the drugged salmon swimming faster and covering greater distances than untreated controls. These findings raise questions for fisheries managers.

The metabolite‑treated group outperformed even the cocaine cohort, traveling roughly 7.6 miles farther from the release point and nearly doubling weekly range. Co‑author Tomas Brodin warned that risk assessments focusing solely on cocaine may miss broader ecological impacts of breakdown products. Prior studies have found pharmaceuticals such as Prozac and Advil in North American salmon, raising concerns about cumulative stressors.

Environmental toxicologists argue any physiological or behavioral shift in fish signals adverse effects, as increased activity forces higher energy expenditure and may raise predation risk. With wastewater treatment plants handling roughly 34 billion gallons daily in the U.S., removing trace drug residues poses costly infrastructure challenges. The study underscores that illicit‑drug pollution is an emerging vector of ecological disruption and public safety concerns.