ODFW killing fish to fight invasion at North Twin Lake

It was an unusual sight on North Twin Lake on Tuesday morning: fishing boats carrying people in hazmat suits.

Crews with the Oregon Department of Fish and Wildlife continued a several-day project to treat the lake with toxins in an effort to rid the water of brown bull catfish.

“We have a powder form and a liquid form, and we have boats out here with pumps to distribute the product evenly, so we have a lethal concentration in the lake,” said Bend Assistant District Fish Biologist Erik Moberly.

ODFW is dumping more than 32,000 pounds of poison into the lake to combat the fish that were illegally planted in North Twin about 20 years ago. The toxin, called Rotenone, is derived from a South American root, and was brought to North Twin from Peru.

The project costs about $300,000. The majority of the funding is provided by grants distributed by ODFW’s Fish Restoration and Enhancement program. The group gets its money from a charge applied to angling licenses.

“If you look on the shoreline, you see a lot of smaller bullhead, which tells me there’s a whole lot of bullhead in the lake,” Moberly said, estimating there’s hundreds of thousands of the species in the water.

Moberly said the catfish crowd out the desired species for the lake: the rainbow trout. He said 95 percent of the fish in the lake are catfish.

“It’s a serious problem,” Moberly said.

Thousands of the catfish were already dead Tuesday afternoon, some floating in the water, others washed up on shore.

To kill these catfish, crews will also have to kill the rainbow trout, as the toxin doesn’t discriminate.

“Rotenone, when applied, kills everything with gills,” Moberly said.

The poison suffocates the fish, but biologists say it’s harmless to other wildlife, like mammals and birds. It’s also safe for humans, unless ingested in massive quantities.

Moberly acknowledged some could see the treatment as cruel, but he also said it’s necessary to achieve management plans.

“This is a common fish management tool — it’s used around the United States,” Moberly said.

ODFW has treated several lakes around the state in recent years to rid waters of invasive species. South Twin Lake was treated in 2011.

“It’s very frustrating for all of our staff to repeatedly go out to water bodies and treat them for illegally introduced fish,”Moberly said. “It costs a lot of money, and it’s a lot of time for staff from their normal jobs.”

Fish Restoration and Enhancement Coordinator Kevin Herkamp agrees public money could be spent better, if not for people who break the rules with illegal stocking.

“Like restoring hatcheries and putting in boat docks,” Herkamp said.

After all the fish are dead, ODFW will come back and pick up thousands of them. Others will be left to help improve lake health.

Because of the treatment, the lake will be closed to the public until January. ODFW will stock the lake with rainbow trout in the spring.

ODFW wants to remind people that it is a crime to transfer fish between bodies of water.

“An illegal introduction is a Class C felony,” Moberly said. “If it’s done intentionally, there’s a maximum of five years in jail.”