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Fish Could Be Getting High and Horny off our Wastewater Drugs

Scientists are worried that all those drugs pumped through our sewers might be having a strange effect on the fish.
Gavin Butler
Melbourne, AU
Goldfish on black background
A goldfish. Image via Shutterstock

Between all the stashes that get flushed down the toilet, all the bricks of coke that get lost at sea, and the collective piss of everybody who’s ever taken a pill, the world’s waterways are laced with second-hand substances. The accumulation of these substances from sewage, runoff, and wastewater is resulting in what has been described as a “drug soup”. And that soup is having all kinds of effects on the fish.

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Earlier this year, a study published by research scientists at the University of Naples found that trace concentrations of cocaine in certain river systems were causing eels to behave in a “hyperactive” manner. In 2015, a researcher from the University of Wisconsin-Milwaukee found that certain types of diabetes medication were causing certain species of freshwater fish to display intersex properties. And now, studies by Monash University have found that water laced with Prozac could have the unintended consequence of making fish super horny.

Ph.D. candidate Michael Bertram investigated the effects of fluoxetine, the active ingredient in Prozac, on certain species of aquatic wildlife. Specifically, he dosed a number of male mosquitofish with both low and high concentrations of the psychiatric drug.

“These tests revealed, for the first time, that exposure to fluoxetine at levels consistent with those reported in the environment can disrupt both male reproductive behaviour and sperm production in fish,” Michael wrote in an article for Science Trends. “Specifically, in one-on-one mating trials, males in the high-fluoxetine treatment performed more frequent copulatory behaviour towards females than did males in the unexposed treatment.”

There’s something about fluoxetine, it seems, that gets these fish feeling hot under the collar and sends their sperm count into overdrive. Researchers observed that males who were dosed up on the drug spent more time chasing females than those in clean water conditions. As a result, Michael speculates that the fish in the wild who are high on Prozac are probably getting more action than their sober peers.

“Given that males in the high-fluoxetine exposure treatment performed increased copulatory behaviour towards females and were also found to have increased sperm counts, this would suggest that, in nature, males inhabiting contaminated habitats may be more successful at securing fertilisations,” he said.

It’s not all good news for the sex-obsessed mosquitofish, though. Speaking to IFLScience, Martin explained that the males might actually become so insatiable as to render themselves vulnerable to predators, and possibly even start eating less. He’s also kind of worried about what this might mean for females.

It's been reported that male mosquitofish are notorious for their sexual proclivities, forcing prospective partners to expend large amounts of energy just to avoid them. Add a bit of libido-boosting Prozac to that equation, and researchers have real concerns about the lengths females will have to go to just to keep the thirsty males at bay.