April 11, 2025 — It has to be stressful: an obstacle course of giant dams, rushing rapids and hungry predators.
That’s what juvenile salmon can face when they migrate out to the salty sea from the freshwater rivers and streams where they hatched. But it turns out that a very specific kind of pollution might be giving some fish an edge, at least on part of the journey.
According to a new study published on Thursday in the journal Science, young salmon exposed to anti-anxiety drugs in the water made it past dams faster. But ecologists are doubtful that it means a survival advantage.
Pharmaceutical pollution is rampant. Nearly 1,000 drugs and their byproducts have been detected in the world’s waterways, including in surprising places like Antarctica. They enter the environment as direct pollution from drug producers, from people flushing unused medications, and from human and animal waste.
Scientists have been studying the effects of these drugs on wildlife for years, but there is still much to learn about how animals respond to the “cocktail of different pharmaceuticals” they’re exposed to, said Michael G. Bertram, a behavioral ecologist at the Swedish University of Agricultural Sciences and a leader of the new study.