Small amounts of estrogen can have a huge impact on freshwater fish’s ability to reproduce.
Photo by FormosanFish

Study finds that birth control in Canada’s lakes affects fish fertility

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A new study has found that unless we improve Canada’s wastewater treatment facilities, our ecosystems could face devastating consequences such as male fish growing eggs, female fish no longer able to reproduce, and the extinction of some types of freshwater species.

Researchers at the University of New Brunswick and the IISD Experimental Lakes Area discovered that when small amounts of estrogen – a common hormone in birth control pills – is introduced into waterways, it interferes with the fathead minnow’s ability to reproduce, creating a domino effect among other fish populations. In the real world, birth control pills enter our lakes and rivers via our municipal water treatment facilities.

The team of researchers, lead by Karen Kidd of the University of New Brunswick, added small amounts of estrogen into an artificial freshwater lake at the IISD Experimental Lakes Area research facility over many years. The team immediately noticed a decline in the fathead minnow population.

“The crash in the population was very evident and very dramatic and very rapid and related directly to the estrogen addition,” Kidd told the Canadian Press.

The male population was disturbed as well.

“Right away, the male fish started to respond to the estrogen exposure by producing egg yolk proteins and shortly after that, they started to develop eggs.”

Once the fathead minnow’s population began to tumble, it created a chain reaction among other species. The minnow’s main predator, the lake trout, began dying off, while the insects the minnow’s feasted on felt a surge in numbers.

Kidd and her team first began the study in the late 1990s, after a group of British researchers discovered that estrogen levels can cause male fish to develop eggs.

And although Kidd’s research was completed in a supervised, artificial body of water, real-life examples that mimic the study’s findings are present in Canada. Alarming levels of synthetic estrogen and other chemicals were detected in two waterways in southern Alberta – the Red Deer and Oldman rivers – causing the feminization of male minnows.

There is hope for our minnows, however. Kidd found that once the estrogen was eliminated from the water, the fish population recovered to its original numbers.

“It’s evidence that removing these chemicals from our effluents will have downstream benefits for the fish population.”