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Fish are becoming increasingly HORNY because of massive quantities of unnatural chemicals in the water, according to a study.

Prozac, used as an antidepressant in humans, is making fish hellbent on reproduction, researchers from Monash University found.

Animals that were given the drug in a tank in a lab spent more time chasing females than those that weren't.

Scientist Michael Bertram dosed male mosquitofish in an aquarium with high and low quantities of fluoxetine, the active ingredient in Prozac.

The fish given higher doses showed "more frequent copulatory behaviour" and spent more time pursuing females, he described.

Mr Bertram wrote in Science Trends : "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."

(Image: Getty Images)

The study adds: "A significant positive correlation was detected in control fish between activity levels in the maze and time spent pursuing females in the reproductive assay."

Fluoxetine makes its way into the ecosystem because our water treatment systems cannot filter it out, along with many other pharmaceutical drugs making their way into the environment.

Mr Bertram said: "Fluoxetine can cause a wide range of adverse effects in aquatic species, including disrupting development and reproduction and altering morphological and physiological traits."

(Image: Getty Images/iStockphoto)

He added it can also influence behaviour in animals, just like it can when administered as an antidepressant to humans.

It was previously reported how cocaine contamination in rivers was making wildlife behave in an hyperactive manner.

Two years ago scientists were racing to discover how fish in Seattle, US had tested positive for 81 different drugs, including coke .

And a study in 2014 found drugs, including insulin, were entering the water supply and causing fish to become intersex.

A piece of research for the Society of Environmental Toxicology and Chemistry said: "It has been suggested that the prevalence of intersex fish in certain watersheds may be the result of... a cocktail of potential and known endocrine disruptors."