A Swedish study recently revealed that the residues of psychopharmaceuticals that are used to treat anxiety in humans lowered the mortality rate of perch.

Some headlines on this topic seem to be suggesting that this means pollutants may be beneficial to fish.  While within the narrow scope of the study this is true, In our view, that is a terrifying interpretation.  Taking one result ( that perch live longer) and suggesting that is a good thing is a very short-sighted interpretation.  Further into the stories is the acknowledgement that this little fact doesn’t mean that putting these pollutants into the water is a good thing.  Umeå University in Sweden has performed considerable research on the effects that pharmaceutical drug residue produces on the behavior of fish. One study published in 2013 showed that remnants of oxazepam, a drug used for anxiety, resulted in braver and more curious activity among normally timid fish. Fish exposed to the drug examined their surroundings more freely than normally.  A more recent study added that exposing fish between three and six days old to oxazepam for 24 hours reduced the mortality rate of juvenile fish, when compared with the control group.  It may be that the bolder fish gather more nutrition.  Yet the controlled lab result reveals very little about the overall effects of drug residue on natural populations.  Of course, in the wild, what is being called ‘anxiety’ in the fish is an inherited awareness of the risks of predators.  While the study doesn’t show this, it’s likely that the bolder fish would more quickly succumb to predators.  And of course isolating one result doesn’t tell us much.  If more perch survived a little longer, likely their prey would increase too.  But perhaps not.  Perhaps as a result of this unnatural impact, an imbalance would result.  The study was published by Environmental Research Letters.  They do charge for access to articles.