Fish Behavior Influenced By Dissolved Prescription Medication In Water, Study Finds

Published on February 17th, 2013 | by

February 17th, 2013 by

Trace amounts of commonly prescribed prescription medications are present in nearly all of the freshwater supplies now used for drinking water by humans. Even after being treated in wastewater treatment plants these pharmaceuticals remain in the water, indeed much of what is released into the natural environment is from these facilities themselves. In recent years, concerns have been raised by a variety of different researchers from different medical fields about how these drugs may be affecting the general population, and possibly animals.


And now, a new study from Umea University in Sweden, has found that fish found living in waters tainted with low levels of the anti-anxiety drug, Oxazepam, radically change in behavior as a result. They become less ‘concerned’, less wary of predators, more aggressive at feeding, and ceasing their schooling behavior.

Specifically, the researchers compared three separate groups of wild European perch. One was in ‘clean’ water, one in waters contaminated with low levels of Oxazepam, and one in waters with 500 times the level of Oxazepam typically found in modern waterways. The ones exposed, even to the low levels, all significantly changed in behavior.

It’s hard to predict what these changes mean in the fish’s natural habitat and associated ecosystems. Does the decreased schooling behavior and increased risk taking make them more vulnerable to predation? And of course, there is the possibility that the changes induced by the drug may take away some of the fish’s own plasticity and variety of behavior. Leaving the fish with less of an ability to change behavior in response to their environment, just as many behavior altering drugs do to people.

Oxazepam is a very widely prescribed drug, used to “treat anxiety” in people. The drug is now commonly found in low levels in many of the waterways of the world. Previous research has found that many commonly prescribed drugs can have profound mental and physiological effects on many species of fish, completely altering their behavior, and in some species even their biological sex.

The enormous scale of the situation likely precludes any in-depth understanding of the changes that are occurring as a result of the massive release of prescription drugs, among other chemicals, into the wider environment. It’s been noted in recent years that many species of wild animals have been becoming more indifferent towards humans, avoiding them less. Typically this has been assumed to be a result of expanding human developments, deforestation, and the loss of the animal’s natural environment. But perhaps there is considerably more to it? Why wouldn’t behavior altering drugs, that are now present in many of the world’s ‘natural’ waterways, have an effect on animal behavior?

Source: Reuters

Image Credits: Perch via Wikimedia Commons

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