Humans aren't alone in a battle with illicit drugs, which have penetrated waterways worldwide via wastewater and other means. European eels are feeling the effects, and probably other animals, too, say researchers at Italy's University of Naples Federico II. After previously finding cocaine in eel flesh, the team investigated how the drug affects the swimmers, known to travel 3,700 miles across the Atlantic Ocean to spawn in the Sargasso Sea, near the Bahamas. It certainly wasn't beneficial: Farm-raised eels confined for 50 days in a lab tank with roughly the same low-level amount of cocaine found in some rivers, about 20 nanograms per liter, appeared hyperactive and swam faster than their sober counterparts, reports New Scientist. Dissection revealed more: skeletal muscle damage that remained even after the eels spent 10 days in clean water.
Researchers predict migration difficulties as a result. "In addition to sufficient energy reserves, the eel needs a healthy skeletal muscle and an efficient aerobic metabolism, in order to complete successfully its migration," they write in Science of the Total Environment. Study author Anna Capaldo offers more at National Geographic, explaining cocaine's effect on cortisol and dopamine levels could impair reproduction and prevent an eel from reaching sexual maturity. It's more bad news for the eels already critically endangered by habitat loss, pollution, and over-fishing, per Smithsonian. But humans should be concerned, too: "Since the skeletal muscle is the edible part of the eel," those with a taste for European river eels could be ingesting cocaine, though probably not enough to be dangerous, researchers say. (There might also be cocaine in your fingerprint.)