Brand, J.A., Michelangeli, M., Shry, S.J., Moore, E.R., Bose, A.P.H., Cerveny, D., Martin, J.M., Hellström, G., McCallum, E.S., Holmgren, A., Thoré, E.S.J., Fick, J., Brodin, T., Bertram, M.G. 2025. Pharmaceutical pollution influences river-to-sea migration in Atlantic salmon (Salmo salar). Science 388, 217–222. https://doi.org/10.1126/science.adp7174 | PDF
ABSTRACT
Despite the growing threat of pharmaceutical pollution, we lack an understanding of whether and how such pollutants influence animal behavior in the wild. Using laboratory- and field-based experiments across multiple years in Atlantic salmon (Salmo salar; n = 730), we show that the globally detected anxiolytic pollutant clobazam accumulates in the brain of exposed fish and influences river-to-sea migration success. Clobazam exposure increased the speed with which fish passed through two hydropower dams along their migration route, resulting in more clobazam-exposed fish reaching the sea compared with controls. We argue that such effects may arise from altered shoaling behavior in fish exposed to clobazam. Drug-induced behavioral changes are expected to have wide-ranging consequences for the ecology and evolution of wild populations.
