Lake trout elimination

Posted 7/20/10

Trout Unlimited Council President Dave Sweet of Cody began fishing in Yellowstone in the 1970s, but now lake trout are wiping out Yellowstone cutthroats, and that is having an avalanche effect on other wildlife, Sweet said.

Once there were 4 …

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Lake trout elimination


{gallery}07_13_10/gillnetting{/gallery}Aboard Freedom, Yellowstone National Park summer employees, Jake Boone, left, and Hannah Gundernan, right, prepare to unleash a gill net to capture unwanted lake trout in Yellowstone Lake. Mount Sheridan rises in the distance. Tribune photo by Gib Mathers Extreme measures needed to save Yellowstone Lake native cutthroat troutSince the mid 1990s, the National Park Service has endeavored to eliminate lake trout from Yellowstone Lake. But the race to save native cutthroat trout there could be lost unless the service adopts extreme measures, said a Trout Unlimited member. Park Service personnel say they are working on it and will adopt tougher measures in the future.

Trout Unlimited Council President Dave Sweet of Cody began fishing in Yellowstone in the 1970s, but now lake trout are wiping out Yellowstone cutthroats, and that is having an avalanche effect on other wildlife, Sweet said.

Once there were 4 million cutthroat in Yellowstone Lake and its tributaries, but that number has declined by 10 percent or less, according to Trout Unlimited estimates.

Animals such as grizzly bears, otters, ospreys — 42 species in all — are dependent on cutthroats that swim the lake's tributaries, Sweet said prior to volunteering on a Park Service gill-netting boat June 29. He also volunteered in 2008.

Lake trout, deep water fish, are difficult for wildlife to catch and don't inhabit tributaries, he said.

Lake trout prey on cutthroats, waterfowl and even small mammals. “They are extremely predacious,” Sweet said.

Gill nets are used to capture and kill lake trout.

Since 1995, the Park Service employees have been gill netting in the summer.

In 2009, the Park Service allowed 20 days of commercial gill-netting on the lake. This year, there will be 10 weeks, Sweet said.

“That is not efficient,” Sweet said.

Gill netting has removed 450,000 lake trout in the last 15 years. The recent count was 73,000 in 2007, 76,000 in 2008, and, more than 100,000 in 2009, Sweet said.

Last week, Yellowstone Park Spokesperson Al Nash said the two park service boats had removed 35,000 lake trout so far this year.

But Sweet said, “That gill-netting effort is really a Band-Aid.”

In August 2008, the Park Service convened an impartial scientific review panel to evaluate service efforts and to offer recommendations for lake trout suppression.

One panel recommendation was increasing commercial gill-netting activities from June into mid-October. And, if possible, contract another commercial gill-netting boat.

An environmental assessment is due out this fall for public review, and a key component of it are lake trout in Yellowstone Lake, Nash said.

To double commercial netting, which Yellowstone Fisheries Program Supervisor Todd Koel intends, it must be written in the assessment as part of National Environmental Policy Act guidelines.

The panel also recommended initiating mark-recapture to track lake trout to spawning beds as crucial to their removal.

“They haven't done it,” Sweet said.

The service must locate the spawning beds to destroy lake trout eggs, Sweet said.

“That (mark-recapture) is key to knowing where those spawning beds are,” he said.

In the mark-recapture process, lake trout are caught, marked by cutting a V in their fin, released, and then hopefully captured again at a later date. This process would allow personnel to estimate the population and also trail lake trout to spawning beds.

Panel recommendations included transmitters to track lake trout to spawning beds, low amp electric grids to kill eggs, sonic waves to shatter eggs and carbon dioxide to smother eggs. The research is promising, but it will be two years before these methods are ready, Sweet said.

Electric grids lowered into the water in spawning beds has potential to kill many lake trout eggs, as would pesticides, but the environmental impact must be weighed, Koel said.

Trout Unlimited has contributed $27,000 to Dr. Robert Gresswell's research to eliminate lake trout using methods including sonic waves, electric grids and carbon dioxide.

U.S. Geological Service, Park Service and Fish and Wildlife Service also contributed money to Gresswell's research, Sweet said.

The mark-recapture process can also be used to estimate the population, but is a bit of a double-edged sword from Koel's perspective. First 10,000 fish must be netted, then returned to the lake and netted again to estimate the total lake trout population. And, the estimate would be just that, a population estimate, Koel said.

Another panel recommendation was rebuilding the Clear Creek weir on the east side of Yellowstone Lake. The weir, destroyed by spring run-off in 2008, had monitored spawning cutthroats since the 1940s. In the 1970s and 1980s, the weir counted 70,000 annual spawning cutthroats. At last count, there were 500 spring spawning cutthroats traveling up Clear Creek, Sweet said.

Rebuilding the weir on Clear Creek in 2011 is included in the environmental assessment, Koel said.

The service claims it is getting better at capturing the fish, but Sweet said there simply are more lake trout to snag now.

Although the two Park Service employee boats that are netting approximately 8,000 lake trout per week are industrious, Sweet said the one commercial vessel — snagging 6,000 per week — is more so.

The service must accelerate gill-netting to at least keep the lake trout population in check and thus buy more time for research, Sweet said.

“They need to get as many commercial boats out there as possible and turn them loose,” Sweet said.

This year, the service is spending $1.2 million in its battle against lake trout. That is $320,000 for the commercial operator, $320,000 for park personnel and $600,000 for monitoring, Koel said.

On July 7, Koel said he had just clinched a $600,000 federal grant for 2012 and 2013. The grant was ranked No. 1 in the country for the National Park Service, he said.

Koel has a liquidation green light. Sort of. Nobody is berating the killing of lake trout in Yellowstone Lake.

“We're out to kill every lake trout we can,” Koel said.