A fish called Wayne – or is it Wanda? | VailDaily.com
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A fish called Wayne – or is it Wanda?

Matt Terrell
Vail CO, Colorado
Preston Utley/Vail DailyYoung brown trout are particularly sensitive to hormones in treated water, which could alter their gender and make Gore Creek's female trout population higher than the male population.
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VAIL – Every time you flush a toilet, you could be assisting a confused young trout with an unwanted sex change, says a researcher from the University of Colorado.

Alan Vajda has set up a tiny, solar-powered lab in the parking lot of Vail’s wastewater treatment plant on Gore Creek. He’s pumping water from the creek into several tanks in his trailer, where schools of young brown trout await a bloody dissection and probing of their sexual organs. Vajda is trying to find out how treated wastewater in Vail is affecting fish development and reproduction.

He’s concerned that small amounts of hormones and other chemicals – from urine, feces, birth control, antibiotics, soap and the wide range of drugs we send down our drains – could be changing the sex of fish and harming the ecosystem.

Estrogen, the main female sex hormone, is the big culprit here. While most treatment plants remove 90 percent to 95 percent of chemicals and hormones from wastewater before it heads back to a river, trace amounts of estrogen are enough to alter the sex of a fish.

“Sex determination is dependent on hormones, and hormones from the outside could override the ones inside a fish,” Vajda said.

The consequence of too much estrogen in the water? The Waynes become Wandas, and women rule the river.

The food web

Women had indeed taken over Boulder Creek on the Front Range.

Vajda compared groups of fish there from above a wastewater treatment plant to groups of fish downstream. The difference was huge – the ratio of female to male fish shifted from 1-to-1 upstream to 5-to-1 downstream.

“It was consistent with their exposure to estrogens,” Vajda said.

A major sex shift like that can have profound consequences, the biggest being what Vajda calls a “total population failure,” which basically means no more babies.

“It can affect other components of the food web – the prey below the fish and the predators above them,” Vajda said.

This phenomenon is not exclusive to Colorado – it’s been reported in lakes and rivers all around the United States.

Sensitive trout

Vail’s situation is quite a bit different from the experiment in Boulder Creek.

For one, there’s not as much wastewater. In Gore Creek, anywhere from less than 5 percent to 20 percent of the stream is made up of treated wastewater, which is far less than Boulder Creek and other metro areas, which can be made up of 50 percent to 70 percent treated wastewater.

“In heavy population areas, effluent (treated wastewater) can dominate stream flows,” Vajda said. “In Vail, though, it’s more proportionate to the stream.”

Vail also has more sophisticated treatment methods and a smaller population, which could make a difference, Vajda said.

The bad news is that trout – the main fish in our rivers – are more sensitive to estrogen than other fish, like the minnows studied in Boulder Creek.

“It takes lower doses of estrogen to have a sex reversal in trout,” Vajda said.

So Vail may not put as much wastewater back into Gore Creek, but it could still be enough to change some fish, he said.

It’s too early to discuss results from the Gore Creek experiment, but they should be ready by June, Vajda said.


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