Biologists applied a chemical piscicide to Kelly Warm Spring last week to kill invasive fish crowding the Grand Teton National Park waterway after decades of illegal dumping.

The fish-killing agent, rotenone, has been used by wildlife managers for decades to manage invasive fish populations. It is also widely used by farmers as a pesticide. Concerns have been raised over the years about the toxicity of rotenone for people who come into contact with it, but experts maintain that its use as a piscicide does not put people at risk.

On Aug. 21 park fisheries biologists and biologists from the Wyoming Game and Fish Department applied both a liquid and powder form to the spring, dripping it into the water from the tank on the back of a small paddle boat and manually spreading the powder form into the nooks and crannies on the edges of the spring.

Before the treatment, non-native cichlids, tilapia, swordtail and goldfish made up over 95 percent of the fish in the warm springs near Kelly.

The treatment made a difference.

“We’ve seen a dramatic shift in the abundance of goldfish especially,” said Chad Whaley, the aquatic invasive species coordinator for Grand Teton National Park.

Invasive fish species can outcompete native fish for food and introduce diseases. Proliferation of invasive species coupled with climatic changes can spell doom for native fish, spurring park managers to step up efforts to restore native species.

Rotenone is a naturally occurring product found in certain members of the pea family in South America and Southeast Asia.

The main human health concern is the link between rotenone and Parkinson’s Disease. In laboratory studies, researchers have induced Parkinson’s-like symptoms by injecting rotenone into the bloodstream of rats in order to study potential treatments for the disease.

A 2011 study by researchers at the University of California, San Francisco, found a strong correlation between occupational exposure, consistent exposure to professionals using the chemical over an extended period of time, and the risk of developing Parkinson’s Disease.

In 2012 the American Fisheries Society published a paper reviewing the research on the links between rotenone and Parkinson’s after concerns about its use as a piscicide kept surfacing.

The report found that the human health risk of rotenone as a piscicide was negligible.

People can come into contact with rotenone by inhaling it, swallowing it or getting it on their skin. Biologists wear coveralls or waders, rubber gloves and a face mask when applying the chemical.

No one is drinking the spring water or eating the fish, and the chemical properties of rotenone prevent it from passing easily through human skin, so the biggest risk to people comes from inhaling it.

The liquid form of rotenone is not volatile, so inhaling it in that form is unlikely. In its powder form, it can become airborne, but biologists applying the powder form wore masks covering their nose and mouth to prevent particles from being inhaled, Whaley said.

Dave Gustine, the park’s chief of fish and wildlife, said he was confident in the safety of the rotenone treatment.

“We’ve done our homework,” Gustine said.

When treating a waterway, rotenone treatments are often followed by a second treatment with a chemical to neutralize rotenone’s effects.

At Kelly Warm Spring, the fisheries biologists were able to manipulate the headgates along Ditch Creek to direct the affected water to spill into the Kelly Hayfields, preventing the contamination from affecting waterways farther downstream and removing the need to apply a second neutralizing chemical.

Whaley deemed last week’s project a partial success.

Goldfish are the invaders most likely to violate other waterways in the park because they can survive in a wide range of water temperatures. So he’s glad to see a reduced number of them in the spring, Whaley said.

They didn’t manage to kill all the invasive fish though, Whaley said.

Biologists are looking into options to eliminate the remaining fish, but the biggest help would be if people would stop dumping their aquarium rejects in Kelly Warm Spring, he said. It is illegal to release non-native fish, or wildlife of any kind, into a national park.

Rotenone breaks down quickly in the environment, so it is no longer affecting the water, but there are still dead fish in the waterway, so they’re keeping the area closed to protect public safety, Whaley said.

Have aquarium fish, but need to get rid of them? Try a pet store, like Pets Place Plus, instead of the wild. The shop on Martin Lane keeps a bulletin board devoted to adoption notices, Brenda Sherwin, a Pets Place Plus sales associate, told the News&Guide.

Contact Frederica Kolwey at intern@jhnewsandguide.com.

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