New policy planned for poisoning Montana streams

BOZEMAN — Officials with Montana Fish, Wildlife and Parks are working on a new policy for poisoning streams to kill nonnative fish in the wake of a poisoning attempt last year that went farther downstream and killed more fish than expected.

"We made a mistake and we learned from that mistake, and we're putting additional safeguards in place," fisheries biologist Travis Horton told the Bozeman Daily Chronicle.

The streams will be poisoned with a naturally produced chemical called rotenone. They will then be restocked with native westslope cutthroat trout.

Biologists in the region say nonnative fish — such as brook and rainbow trout — and hybridization have reduced the range of westslope cutthroats to about 5 percent of its historically occupied habitat.

Officials said the new policy should be in place by August when the agency plans to poison some streams.

"There are trade-offs to doing this kind of work, but when talking about saving a sort of keystone species like cutthroat trout in the Yellowstone ecosystem, those kinds of things are worth it," said Todd Koel, a fisheries biologist for Yellowstone National Park. "The alternative isn't acceptable because if the fish aren't restored, then over time we'll lose them. That's kind of the bottom line."

He said rotenone also kills insects, but those populations recover quickly.

Last August, biologists planned to poison several sections of Cherry Creek. They usually use potassium permanganate to break down the rotenone at the end of the stream section being poisoned.

Biologists at Cherry Creek decided not to do that because the section being poisoned was followed by another section immediately downstream that was also slated to be poisoned.

The rotenone ended up going through both sections and moving farther downstream, killing between 1,000 and 1,500 trout in a section of river not included in the plan. Biologists said that section has yet to recover.

"It's from these accidents that we learn and make these adjustments," said Pat Clancey, a fisheries biologist with FWP who oversaw the Cherry Creek treatment. "As far as the use of (poison) to achieve what we're trying to achieve for native fish, it's a necessary tool."