Efforts to restore a population of native Lahontan cutthroat trout in McDermitt Creek in southeast Oregon suffered a setback earlier this month when biologists discovered a reproducing population of non-native brook and rainbow trout in the river.

According to Shannon Hurn, ODFW fish biologists in Hines, biologists were aware that some non-native trout had been illegally re-introduced into the creek but didn’t realize the extent of the of the population until they tried to remove it.

“We had hoped to be able to remove most of the non-native trout in order to set the stage for continued reintroduction of native Lahontan cutthroat trout,” Hurn said. “However, we were surprised by the number and size of the brook and rainbow trout that we found.”

Even more concerning, Hurn added, was the presence of at least two age classes of non-native trout, indicating the fish had been in the river long enough to have reproduced.

The discovery casts some doubt on the agency’s eight-year effort to restore native Lahontan cutthroat trout to this remote watershed in southeast Oregon, where native fish have been pushed out by brown and brook trout or genetically comprised by hybridizing with rainbow trout.

Hurn said she suspects the non-native fish may have been illegally introduced by anglers frustrated with the slow pace of reintroduction efforts. Between 2006 and 2009 biologists methodically treated the creek with rotenone, a plant-based fish toxicant, in order to remove non-native trout, and in 2012 the watershed was closed to all fishing after the Holloway fire in order to protect any remaining Lahontans.

“Obviously we need to do a better job of communicating with the angling community,” Hurn said. “If we can successfully re-establish a Lahontan trout fishery if could mean huge 20-inch Lahontan trout instead of 10 to 12-inch brooks and rainbows.”

Biologists will conduct blood, genetic and scale tests on the rainbow and brook trout they removed from the creek to try to find out how old the fish are and whether they are from a hatchery stock. It is a felony in Oregon to transport and release live fish without a permit.

In the meantime, biologists will take some time to re-evaluate their fish restoration plan for McDermitt Creek.

“In the short-term, we’re going to focus on the Lahontan cutthroat trout populations in the upper tributaries,” Hurn said. “They’re our strongholds and we want to make sure they stay strong.”

Image courtesy Oregon Department of Natural Resources

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