One way to get rid of those pesky pikeminnows in Cultus
Unfortunately it might also be the cause of the Salmon disappearing
Estrogen making fish too female to reproduce
Population in previously clean water needed two years to recover, fish scientist reports
Tom Spears
CanWest News Service
Tuesday, May 22, 2007
Estrogen that goes down Canadian toilets -- some naturally from women, some from the Pill -- is enough to make entire fish species too feminine to reproduce, a seven-year Canadian study shows.
Fish scientist Karen Kidd dripped small amounts of estrogen into a clean lake in northwestern Ontario over several years, just as if urine with the female hormone were running in via sewage from a nearby municipality.
This constant hormone bath made male minnows produce eggs in unnatural, part-female sex organs.
And even after she stopped adding estrogen and the water turned clean again, the minnows almost completely disappeared for several years.
Even small concentrations of estrogen can decimate wild fish populations, the University of New Brunswick biology professor concludes, even at levels found in some Canadian waters. She wouldn't name individual rivers.
While the minnows were prone to fast extinction because of their short lifespan (about two years), she says bigger fish such as trout or pike might also be hurt if exposed for long enough.
The first dramatic news of "feminized" fish came from British rivers in the 1990s where male fish near sewage plants were producing eggs and carrying reproductive organs that were partly female.
"A lot of follow-up studies showed it was the natural estrogens that women excrete and then the synthetic estrogens in birth control pills that were the main causes of feminization in male fish," Kidd said.
"The Pill is one of the most heavily prescribed pharmaceuticals in the world. There are over a million women on it in Canada."
She chose an unpolluted lake with healthy fish to learn what damage estrogen would cause.
Male minnows in water with estrogen just stopped looking male. Where they should have distinct colours and bumps at spawning time, they didn't have any visible sign of maleness.
"And then when you opened them up, their testes were much smaller than they should have been" -- about one-third the normal size. By the third year of adding estrogen to the lake, the testes had ovary-type tissue, and were producing eggs -- a condition called "intersex."
It's exactly what scientists had seen in the wild. The achievement is in reproducing this effect in a previously clean lake, proving that estrogen is the cause.
Meanwhile, the female fish produced eggs too slowly.
The Kidd team found these effects early, but continued the study for several years to see what would happen. And the whole minnow population crashed.
The last estrogen went into the lake in 2003. Since then, bacteria and sunlight have broken down the estrogen and the water quickly returned to normal. The minnow population, however, took a further two years to recover.
And in the real world, no one stops adding estrogen after a couple of years of study. "That's the issue for our waterways. There's a constant input of these kinds of chemicals into our rivers and lakes," she said. "Certainly we're more concerned about the systems [rivers] that are still getting untreated sewage.
The seven-year study was funded by Fisheries and Oceans Canada, where Kidd worked during most of it, and the American Chemistry Council. It's published today in the Proceedings of the National Academy of Sciences.
© The Vancouver Sun 2007
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