Cocaine and its derivatives entering waterways are changing the behaviour of juvenile Atlantic salmon, causing them to swim farther and disperse more widely, according to a new study published in the journal Cell Press.
Researchers from Griffith University in Australia tracked over a hundred juvenile salmon over eight weeks in Lake Vättern, Sweden. Fish exposed to benzoylecgonine, the main cocaine derivative found in wastewater, swam about twice as far per week and dispersed up to 12.3 kilometres farther across the lake compared to unexposed fish.
“Where fish go determines what they eat, what eats them, and how populations are structured,” said study author Marcus Michelangeli. “If pollution is changing these patterns, it has the potential to affect ecosystems in ways we are only beginning to understand.”
This is the first study to demonstrate such effects on fish behaviour in the wild, as previous research was limited to laboratory settings. The contaminants enter waterways through wastewater systems not designed to fully remove them.
Researchers note that the study does not indicate any risk to people consuming fish, as the salmon studied were juveniles below legal-catch size. “The idea of cocaine affecting fish might seem surprising, but the reality is that wildlife is already being exposed to a wide range of human-derived drugs every day,” Dr Michelangeli said.
Further studies are planned to assess how these altered movement patterns affect survival and reproduction, and to identify which species are most at risk.
