New Study Reveals That Atlantic Salmon Are Jacked Up on Pharmaceutical Drugs

In a new study published earlier this month, researchers from Griffith University have uncovered some surprising effects that pharmaceutical pollution might be having on juvenile Atlantic salmon as they navigate their regular migration routes. The study focused on the effects two common pharma drugs, that are ending up in our waterways, had on migrating salmon and what it could mean for them over the course of their lives.

The unfortunate reality of the world we live in, is that beyond human dependence on these drugs, pharmaceuticals, from painkillers to anti-anxiety medications, are increasingly detected in rivers and streams worldwide due to our consumption of them and shoddy wastewater treatment methods. While much research has focused on their lethal effects, less is known about how low, environmentally relevant concentrations alter animal behavior. This recent study, led by Dr. Jack A. Brand and his colleagues tackle that gap by examining how clobazam (used for sleep disorders) and tramadol (an opioid painkiller) influence salmon migration—a journey essential for their survival and reproduction.

Aptly titled “Pharmaceutical pollution influences river-to-sea migration in Atlantic salmon,” the study tracked salmon as they traversed from Sweden’s River Dal out to the Baltic Sea. But unlike lab-based experiments, the team conducted their research in the natural setting of the River Dal in order to enhance the study’s ecological relevance. Juvenile salmon were fitted with slow-release pharmaceutical implants to mimic real-world exposure levels and equipped with tiny tracking devices to monitor their movements. This innovative approach allowed researchers to observe how the drugs affected the fish’s ability to navigate the challenging transition from freshwater to the sea.

What researchers found was slightly unexpected. In the case of clobazam, the study found that the presence of the drug in the migrating fish actually increased the migration success of juvenile salmon. The belief here is that the drug actually seemed to reduce anxiety-like behaviors or boost metabolic efficiency, enabling the fish to move more effectively through the river. 

“It’s a counterintuitive result,” notes the study, “as we often assume pollutants harm wildlife.” 

On the other hand, tramadol seemed to show no significant effect on migration success at the tested concentrations. This is notable, as tramadol is another widespread pollutant, and its neutrality in this context raises questions about how different drugs interact with wildlife in unique ways.

While clobazam’s role in boosting migration success is intriguing, it’s not necessarily good news. Altered behavior could disrupt ecological balance or mask subtler harms, like reduced reproductive fitness. The researchers caution that their study is simply a snapshot and the real-world picture is likely more complex.

“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 study went on to say.

Here’s the thing: Atlantic salmon are a keystone species that supports ecosystems and fisheries across the Northern Hemisphere. Their migrational patterns are a high-stakes endeavor that leave only a fraction of juveniles surviving to adulthood and any factor that alters this process could ripple through populations and the broader environment. 

The study highlights the complexity of pharmaceutical pollution, showing that effects aren’t always straightforward or immediately harmful. 

“This is one of the first studies to demonstrate that low-level drug exposure can change wildlife behavior in the wild,” the authors write.

Beyond salmon, the findings raise broader concerns about our aquatic ecosystems around the world. Rivers and other waterways often contain cocktails of pharmaceuticals, and what seemingly benefits one species may very well harm another. 

So while there might be some underlying positive results from jacking up our fisheries with pharmaceuticals, this study also (rightfully) calls for improved wastewater treatment to reduce drug pollution and more investigations into how these compounds will ultimately affect the biodiversity of our fisheries.

For now, the journey of the Atlantic salmon serves as a reminder that even small traces of our daily lives can leave big ripples in the wild. 

It’s something we all ought to remain mindful of.