Cocaine Metabolite Makes Salmon Swim Faster, Farther in Swedish Lake Study

A study published April 20 in Current Biology reveals that juvenile Atlantic salmon exposed to benzoylecgonine—cocaine's primary metabolite—swam up to twice as far per week and traveled up to 20 miles from the release site in Lake Vättern, Sweden, compared to 12 miles for unexposed fish. Researchers from Griffith University and the Swedish University of Agricultural Sciences tagged 105 salmon with slow-release implants containing cocaine, benzoylecgonine, or a placebo, then tracked them for eight weeks. The metabolite had a stronger effect than cocaine itself. The findings highlight the environmental risk of pharmaceuticals and illicit drugs in waterways, as wastewater treatment plants often fail to remove these compounds. Ecotoxicologist Mark Servos of the University of Waterloo and NOAA toxicologist James Meador emphasize the need to assess such contaminants' impact on fish behavior and survival. The study did not examine long-term effects on reproduction or survival, but altered behavior could waste energy or expose fish to new predators. Atlantic salmon already face threats from habitat loss and climate change.