Park controls invasive fish

YELLOWSTONE NATIONAL PARK, Wyo. – An effort to cull invasive species from Yellowstone Lake has removed more than 300,000 lake trout this year.

The number of the fish caught is the most in one year since fisheries managers first discovered it in 1994 in Yellowstone National Park’s largest lake. The presence of lake trout has decimated populations of cutthroat trout, which are native to Yellowstone Lake.

The culling operation is finally reaching kill levels necessary to effectively suppress the ecologically damaging lake trout population, estimated at about 500,000 adult fish, officials said. Some 224,000 lake trout were netted in 2011, but the total kill for the decade before was 500,000.

Yellowstone officials are satisfied with the intensity of the lake trout kill and plan to hold netting at current levels into the near future, Yellowstone spokesman Dan Hottle told the Jackson Hole News & Guide.

“I think we’re about as ramped as we can get right now,” Hottle said. “As far as I know, we don’t have any plans to bring on any additional boats.”

At the same time, monitoring indicated the number of juvenile cutthroat is increasing in the lake.

Cutthroat trout are considered a keystone species in the Yellowstone Lake ecosystem. They historically ran up 60 feeder streams by the thousands each spring to spawn.

The spawn made them an easy catch for predators, and cutthroat were once an important food source for grizzly bears, bald eagles, ospreys and river otters.

The big lake trout, also known as mackinaw, have outcompeted and eaten the native cutthroats since they were illegally introduced into Yellowstone Lake.

Fishermen employ trap nets and gill nets to catch and kill mackinaw on Yellowstone Lake.

“We had a banner year for a couple of different reasons,” Hottle said. “No. 1 is we’re using the tracking telemetry to find out where the fish were spawning and where they’re congregating.”

The kill was also successful this year because anglers fished as long as they could, netting the 139-square-mile lake from just after the ice melted until last week, Hottle said.

In 2011, Yellowstone contractors netted the lake for 17 weeks, but the season spanned just 10 weeks in 2010 and three weeks in 2009, he said.

Restoration efforts for cutthroat on Yellowstone Lake are supported by volunteers and by financial contributions from the Yellowstone Park Foundation, Trout Unlimited, Greater Yellowstone Coalition and the National Parks Conservation Association.