Cheney Free Press -

By Paul Delaney
Staff Reporter 

Rotenone treatment not so scary



Crews of professional applicators use an airboat to disperse rotenone in a treatment effort. Airboats are used in shallow areas while traditional power boats are used for deeper parts of lakes. 

Editor's note: This is part two of a series started in last week's issue.

Mention the use of rotenone treatments to help create a healthier fishery and it can make some people panic.

But it should not be thought of as such a scary word, Department of Fish and Wildlife district fish biologist Randy Osborne said.

The planned treatment of West Medical Lake in the fall to rid it of an invasive goldfish population will use rotenone for the first time since 2009. Rotenone has been used successfully for over 80 years. It is not harmful to mammals.

The product used is totally organic. It comes from a ground up tree root from South America. Enzymes break rotenone down into harmless components after it does its duty.

Tribes in this part of the world use the product in a crude form, Osborne explained. "They will take the tree root and smash it with a rock against a rock." They then take it and slap the water to get the product into it.

"They are out there almost naked, chest-deep in water, see one of these fish come up and throw it up on the bank," Osborne said. "This drill has been done for hundreds and hundreds of years."

Nobody had been harmed, other than smashing a finger pulverizing the root, he said.

Because of false information, the permit to treat a lake or stream has become quite restricted, Osborne said.

"For years and years, we used to let people gather these fish and take them home," Osborne said, with never a report of a related illness. But this is no longer the case.

The dead fish are left in the lake and when they decompose it starts the food cycle again. The lake is left fish-free over the winter, waiting for spring before it is restocked.

Treatment is done after the season closes so there is no real conflict with user groups. Typically, the month before it is treated the lake is opened to unlimited harvest.

"People can go in and catch as many trout as they want," Osborne said.

The reason for needing to treat the lake in the first place is likely the innocent release of the goldfish. But people who do that do not know the harm, or cost of fixing the problem once it gets out of control.

The cost of just the treatment is approximately $150,000, Osborne said. It's a price tag that an offender could bear if they were identified.

Long-term, on an 11-year cycle with 2019 being the starting point, stocking fish for that period with catchables would cost over $1.8 million - in West Medical Lake alone.

"If we rehab, and this includes the cost of the rehab, and stocking for the next 11 years with fry, it would cost about $253,000," Osborne said. "That's a huge difference," he added. By following opening day in April that plant will be in the 11-inch range.

And it will pay back with a shot in the arm to the local economy.

"What we like to do is produce a seamless fishery," Osborne said. It will be initially restocked with as many catchable fish as possible for the following spring.

The restocking continues in the spring with a release of the fry, which by the following spring, are catchables. That process continues each year to keep the cycle in place.

"That's when you get a nice size range of fish," Osborne said.

On average, there will be 35,000 of what are called "angler trips" each season, Osborne said. A 2011 survey, the most recent available, showed that each of those visits has a dollar value of $31 each. Added up it is nearly $1.1 million spent in the local economy.

Paul Delaney can be reached at


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