A wild salmon fed cocaine swims twice as long as a sober salmon

It could be cocaine contamination Affect behavior fish– Changing, for example, the Atlantic way salmon They move through their environment, causing them to swim farther and disperse over a wider area.

So found a recent study conducted by a research team coordinated by Griffith University, the Swedish University of Agricultural Sciences, the Zoological Society of London, and the Max Planck Institute for Animal Behavior and Research. published In the journal Current Biology. The results provide the first evidence that the effects of cocaine contamination on fish behavior occur not only under laboratory conditions but also in the wild, where animals are exposed to more complex environmental conditions.

Cocaine and its metabolites have been detected with increasing frequency in rivers and lakes around the world, entering waterways primarily through wastewater treatment systems. Although previous research has shown that cocaine contamination can affect animal behavior, this evidence has been limited to laboratory conditions. A 2024 study by the Oswaldo Cruz Institute in Brazil showed that even sharks are exposed to cocaine, but little is known about its effects on animals in the wild.

To understand more about this topic, the authors of the new study surgically implanted small devices that slowly release chemicals in 105 juvenile Atlantic salmon in Lake Vättern in Sweden. They were then divided into three groups: a control group, which was not exposed to the substances; A group exposed to cocaine. One group was exposed to benzoylecgonine, the main metabolite of cocaine that is commonly detected in wastewater. The researchers also attached small tags to the fish so they could monitor their movements over a period of two months. From subsequent analyses, the team found that, compared to the control group, fish exposed to benzoylecgonine swam up to 1.9 times farther, and dispersed at the end of the experiment about 20 miles from the release point.

“The location of fish determines what they eat, what they eat, and how the population is structured,” said co-author Marcus Michael Angeli. “If pollution is changing these patterns, it is likely to affect ecosystems in ways that we are only now beginning to understand.”

In addition to showing how cocaine contamination changed the way salmon use space in a natural ecosystem, the new study found that the most pronounced effect was observed not so much in the group exposed to cocaine itself, but in the group exposed to its metabolite. This finding has implications for monitoring, as metabolites are often more common in waterways and current risk assessments generally focus on the main compound, which may lead to neglect of important biological effects.

“The idea that cocaine might have effects on fish may seem surprising, but the reality is that wildlife are already exposed to a wide range of man-made drugs on a daily basis,” Michelangeli said. The next step for researchers will be to be able to determine how widespread these effects are, identify which species are most at risk, and test whether changes in behavior translate into changes in survival and reproduction.

This story originally appeared on Wired Italy It was translated from Spanish.