Salmon are swimming faster due to painkillers and other drugs dumped into water: study
Wild salmon are swimming quicker due to painkillers and other drugs dumped in rivers and the sea, reveals new research.
Traces of a sleeping pill shortened the time it took for juvenile salmon to navigate through two hydropower dams along their regular migration route that usually slow up the journey, say scientists.
Levels of clobazam — a medication often prescribed for sleep disorders — also increased the river-to-sea migration success of juvenile salmon in the wild, according to the findings of the largest study of its kind.
An international team of international researchers, led by the Swedish University of Agricultural Sciences investigated how pharmaceutical pollution affects the behavior and migration of endangered Atlantic salmon.
They warned that their findings, published in the journal Science, may seem beneficial, but any change to the natural behavior and ecology of a species is likely to have wider negative consequences.
Dr. Marcus Michelangeli, of Griffith University’s Australian Rivers Institute, emphasized the increasing threat of pharmaceutical pollution to wildlife and ecosystems worldwide.
He said: “Pharmaceutical pollutants are an emerging global issue, with over 900 different substances having now been detected in waterways around the world.
“Of particular concern are psychoactive substances like antidepressants and pain medications, which can significantly interfere with wildlife brain function and behavior.
Michelangeli noted that the study’s “real-world” focus sets it apart from previous research.
He said: “Most previous studies examining the effects of pharmaceutical pollutants on wildlife have been conducted under controlled laboratory conditions, which don’t fully capture the complexities of natural environments.
“This study is unique because it investigates the effects of these contaminants on wildlife directly in the field, allowing us to better understand how exposure impacts wildlife behaviour and migration in a natural context.
“While the increased migration success in salmon exposed to clobazam might seem like a beneficial effect, it is important to realise that any change to the natural behavior and ecology of a species is expected to have broader negative consequences both for that species and the surrounding wildlife community.”
The researchers used innovative slow-release pharmaceutical implants and animal-tracking transmitters to monitor how exposure to clobazam and the opioid painkiller tramadol affected the behavior and migration of juvenile Atlantic salmon in Sweden’s River Dal as they migrated to the Baltic Sea.
A follow-up lab experiment also found that clobazam altered shoaling behavior, indicating that the observed migration changes in the wild may result from drug-induced shifts in social dynamics and risk-taking behavior.
But Michelangeli says that predicting the full extent of the impacts remains “challenging.”
He said: “When you consider realistic exposure scenarios where entire ecosystems are exposed -encompassing multiple species and a diversity of contaminants — the potential consequences become even more complex.”
While recent declines in Atlantic salmon numbers are primarily attributed to overfishing, habitat loss, and fragmentation — leading to their “endangered” status — the research team said their findings highlights how pharmaceutical pollution could also influence key life events in migratory fish.
Michelangeli says that many pharmaceuticals persist in the environment due to poor biodegradability and insufficient wastewater treatment.
But he added: “Advanced wastewater treatment methods are becoming more effective at reducing pharmaceutical contamination, and there is promising potential in green chemistry approaches.
“By designing drugs that break down more rapidly or become less harmful after use, we can significantly mitigate the environmental impact of pharmaceutical pollution in the future.”
