Plan to remove Diamond Lake fish OK'd

Tuesday, December 21, 2004 2:37 PM PST

Published December 21, 2004

By DYLAN DARLING

The U.S. Forest Service has decided to remove all fish in Diamond Lake - including an explosive population of non-native chubs - in the hope of stopping a recurring bloom of toxic algae.

The agency announced Monday it has settled on a plan to draw down the lake's water level, gather as many fish as possible, poison remaining fish and then replant the lake with native fish. As part of the plan, federal and state wildlife officials will begin lowering the level of the lake in the fall of 2005.

Rotenone will be used to kill fish that can't be gathered in nets, said Kirk Haskett, a Diamond Lake fish biologist for the Oregon Department of Fish and Wildlife. The poison will kill all fish in the lake.

The lake will then be restocked with native fish species.

 

The plan was signed by the Umpqua National Forest supervisor Monday, and the Oregon Department of Environmental Quality has approved the use of the poison.

Tui chubs are native to Upper Klamath Lake, but not to Diamond Lake, 50 miles to the north.

"The tui chubs were brought in by anglers to mimic bait-like minnows," Haskett said.

He said it's hard to say when the tui chubs were brought in, but wildlife officials noticed them in the early 1980s. Diamond Lake, which covers about 3,000 acres, now has an estimated 20 million chubs.

Tui chubs help bring on toxic algae blooms because they have a heavy appetite for zooplankton, which normally eats anabaena, or blue-green algae. Without the zooplankton, the blue-green algae goes unchecked and makes the water toxic, he said.

"It increases to levels that are actually dangerous to human health," Haskett said.

As the population of tui chubs has topped out, blue-green algae blooms have boomed at the popular fishing and recreation lake.

"The last four or five years it's been elevated," he said.

The high algae levels have caused restrictions and closures to the lake. Haskett said officials considered other options, and have tried to curb the tui chubs by netting the fish. But some chubs hidden in reeds and weeds escape the nets.

Lowering the water level and poisoning of the lake proved to be the best option, officials said.

Rotenone is a fish toxicant that cuts off oxygen to the fish. It's been used at Diamond Lake before.

Tui chubs also boomed in the 1950s, leading wildlife officials to draw down the lake and use rotenone to eradicate the introduced fish in 1954, he said. Officials plan to reconstruct the canal used in 1954, draw down the lake during fall and winter 2005 and 2006, and then add the rotenone in fall of 2006.

The plan is subject to a month-and-a-half long appeal period, according to a U.S. Forest Service release.

On the Net: www.fs.fed.us/r6/umpqua