Cocaine in the Water Nearly Doubled How Far Wild Salmon Swam
Juvenile Atlantic salmon have tight energy budgets. Every kilometer they swim is fuel they're not storing for winter, not putting into immune function, not banking for the migration ahead. They don't have margin to waste.
Cocaine doesn't know that.
A study published in Current Biology in April 2026 tracked 105 wild salmon smolts in Sweden's Lake Vättern over eight weeks. Fish implanted with benzoylecgonine, cocaine's primary metabolite, and the form most commonly found in waterways, swam nearly twice as far per week as the control group and dispersed 12 kilometers farther from their release point. The cocaine group showed a similar pattern, but weaker. The metabolite hit harder than the drug itself, which the researchers weren't expecting. That detail matters because environmental monitoring typically measures cocaine, not what the body turns it into after consumption.
Both compounds enter waterways through wastewater that treatment plants aren't designed to remove. Cocaine is now one of the most detected illicit drugs in aquatic environments worldwide. The fish aren't choosing this.
What the extra distance costs them in energy, in habitat quality, and in predator exposure, is still being mapped. But for a smolt trying to survive its first year, burning fuel on unplanned kilometers is not a recoverable loss.
Read the full story at Science.org
Hot Take: The fish aren't on drugs. The water is. That distinction is doing a lot of work for a lot of industries that would prefer we not think too hard about what comes out the other end of a treatment plant.
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