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Rainbow trout back in North Twin Lake

ODFW thanks anglers for their patience

August 25, 2016

BEND, Ore. – State fisheries managers will stock North Twin Lake with rainbow trout again after tests indicated the water is safe for the fish.  The lake was chemically treated last fall to remove unwanted brown bullhead catfish.

Beginning as early as tomorrow morning, 2,500 legal-sized and 1,000 trophy trout will be stocked in the lake.  Additional stocking will occur next month.

“It has been a long wait for anglers to get back out on the lake to fish,” said Erik Moberly, assistant district fish biologist.  “We appreciate everyone’s support and patience.” 

The plan was to re-open the lake Jan 1, 2016 and restock with hatchery rainbow trout in the spring.  However, the treatment didn’t occur until late fall due to late delivery of the chemical by manufacturers.  Once the lake was treated, an early winter storm arrived and froze the lake; high snow levels prevented access, delaying efforts to evaluate the effectiveness of the treatment and test whether the waters were safe to re-stock the trout. 

“Rotenone breaks down when exposed to heat and ultraviolet rays, none of which was available at North Twin until nearly May,” said Moberly.

Over the last few months local staff have monitored the concentration of residual rotenone every few weeks through collection of water samples for lab analysis. As a result of the rotenone treatment, Moberly believes that brown bullhead catfish population has been killed. 

The treatment of North Twin comes nearly five years after the successful treatment of nearby South Twin Lake, where illegally introduced brown bullhead had also decimated the trout fishery.  Today trout fishing in South Twin has fully recovered.

“We have demonstrated that rotenone projects can improve trout fishing and increase angler satisfaction,” Moberly said. “We hope North Twin recovers as well as South Twin.”

Rotenone is often used to remove undesirable fish species because it is an affordable and effective treatment with little threat of long-term environmental damage. Rotenone has been approved as a fish toxicant by the Environmental Protection Agency.




Erik Moberly, Bend (541) 388-6145

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