Psychoactive Drugs Alter Fish Behaviour

Published on: 

E-Separation Solutions

Concerns have been raised throughout the scientific community about the potential effects of pharmaceuticals on the environment.

Concerns have been raised throughout the scientific community about the potential effects of pharmaceuticals on the environment. Drugs are designed to be highly stable and also to be released from the body. Consequently, many pharmaceutical compounds survive wastewater treatment and are released into the aquatic environment.

Liquid chromatography–mass spectrometry (LC–MS) was used to identify the concentrations of psychoactive drugs in water and fish from the River Fyris (Uppusula, Sweden) Scientists from Umeå University, Sweden, published the findings in Science earlier this year.1

One class of pharmaceuticals commonly prescribed globally for the treatment of anxiety are benzodiazepines, including Oxazepam. Scientists performed LC–MS to discover the presence of Oxazepam in the River Fyris at concentrations reported to be similar to those in other American and European waters. The source of the drugs was thought to be an upstream wastewater treatment plant that released treated effluent into the river.

Samples were taken from the treated effluent, the river and also from the wild European Perch (Perca fluviatilis) that reside in the River Fyris. According to the results, the concentration of Oxazepam was six times higher in the muscle tissues of fish samples compared to the concentration in water samples, which indicates bioaccumulation of Oxazepam in the food chain.

Oxazepam acts on GABA receptors in the human brain, but these are also found throughout the animal kingdom. Therefore the investigators hypothesized that the drugs could have a behavioural impact on the resident perch, even though the concentrations of the drug in the water samples were relatively low.

Juvenile perch were exposed to either an environmentally relevant or high concentration of Oxazepam in the laboratory. Exposure to the lower concentration reported to be environmentally relevant resulted in a “personality” change within the fish. The fish became bolder, more active and displayed reduced sociality. In addition, an increase in the food consumption of the fish was observed. The data suggests that Oxazepam increases the predation of the fish, which, as in any ecosystem, could have a far-reaching impact.


The effects of the Oxazepam on the behaviour and feeding efficiency of perch is alarming and potentially ecosystem-changing according to Tomas Brodin, lead author of the study. He added that the concentrations of Oxazepam found to have effects were lower than found in other waters in Europe, for example France.

However, although a clear impact on the aquatic ecosystem, Brodin told LCGC: “At this point there are no reasons to reduce consumption of perch as human food as you would have to eat 4000 kg of perch to get equivalent amounts of Oxazepam that can be found in one prescribed pill.”

The indirect effects on the aquatic ecosystem are a possible cause for concern with the potential to increase the frequencies of algal blooms, reduce fish stocks and other unanticipated effects, according to Brodin.


1. T. Brodin et al, Science 339, 814 (2013).