In Sweden, Atlantic salmon are being exposed to cocaine for research purposes, causing them to exhibit altered behavior. Erin McCallum, an associate professor of aquatic ecology at the Swedish University of Agricultural Sciences, explained that this study aimed to investigate the effects of cocaine, a substance found in waterways globally, on fish behavior. The research, recently published in Current Biology, revealed that juvenile Atlantic salmon in Lake Vättern, Sweden, showed increased swimming activity after ingesting cocaine or its metabolite, benzoylecgonine.
According to McCallum, the fish exposed to benzoylecgonine swam nearly double the distance per week compared to their sober counterparts, covering over 12 kilometers more across the lake. The study involved using slow-release chemical implants to administer the substances to the salmon and monitoring their movements over an eight-week period. Mark Servos, a biology professor at the University of Waterloo, commended the innovative approach of studying the effects of drugs on wild fish outside of controlled laboratory conditions.
McCallum emphasized that traces of illicit drugs and pharmaceuticals, including cocaine, often end up in waterways due to incomplete filtration at wastewater treatment plants. This phenomenon is not limited to Sweden, as a previous study reported the presence of cocaine and other drugs in water bodies worldwide. Notably, wild sharks off the coast of Rio de Janeiro were found to have traces of cocaine in their muscles and liver, indicating the widespread contamination of aquatic environments.
While the impact of these substances on human health is minimal, McCallum highlighted the potential risks to fish populations, particularly concerning their reproductive abilities. Servos underscored the need for further research to understand the long-term implications of drug exposure on aquatic ecosystems. He also mentioned the challenges associated with upgrading wastewater treatment facilities to mitigate drug pollution, emphasizing the importance of balancing environmental risks with economic considerations in decision-making processes.
The study in Sweden underscores the necessity of investigating not only the direct presence of drugs in water but also the metabolites generated by these substances, which may have significant effects on wildlife. McCallum stressed the importance of expanding research efforts to include the study of drug metabolites and their impacts on the environment to better assess the overall effects of pollution on wildlife.