Lake Trout Threaten Yellowstone Wildlife Officials To Lay Down Gill Nets In Bid To Stop Invasion

Beginning next month, wildlife officials in America’s oldest federal nature preserve plan to start laying down a gantlet of gill nets in a desperate attempt to catch and destroy schools of exotic piscatorial invaders.

Their first option called for unleashing swarms of sterile sea lampreys. The National Park Service then considered dumping tons of poison into the lake.

The nets are the latest tactic being deployed to combat what’s being called the greatest ecological threat to Yellowstone National Park in recent years. The problem stems from the illegal stocking of lake trout in Yellowstone Lake and the impact that these foreign fish are likely to have on the park ecosystem.

“To say we’re on the verge of an ecological disaster here is stating it mildly,” explains John Varley, director of the Yellowstone Center for Resources, which coordinates scientific research in the park. “When I received the confirmation that lake trout were present in Yellowstone Lake, I felt physically ill.”

Lake trout’s large size and voracious appetite for other fish have convinced biologists that unless emergency measures are taken, Yellowstone’s pure genetic strain of cutthroat trout is facing possible annihilation.

Cutthroat trout also happen to be a prime nutritional staple for 43 species of mammals and birds in the park, including federally protected grizzly bears and bald eagles, river otters, osprey and one of the largest inland colonies of white pelicans in North America. The disruption to the park’s food chain could be extreme, officials warn.

So next month, an extensive web of deadly gill nets, some nearly half a mile long, will be placed in key lake trout breeding areas. Holes in the webbing will be big enough to allow the smaller cutthroats to escape.

Further, park rangers are encouraging anglers entering the park to ignore normal fishing regulations and catch as many lake trout as they can. In fact, in an odd twist, it now is illegal to land a lake trout in Yellowstone Lake and return it to the water.

Across the West, Varley has witnessed the devastating effect that lake trout - also known as Mackinaws - have had on native fish populations in hundreds of lakes. It is just part of a growing problem caused by zealous anglers who illicitly transplant all kinds of nonindigenous sport fish into lakes and waterways where previously they did not exist, Varley said.

“This whole business of stocking exotic fish is an epidemic throughout the West,” he said. “It’s gotten so bad and widespread that in 10, 20, maybe 30 years there won’t be a decent-sized lake with wild trout left in it.”

Behavioral traits of the two species are distinctly different.

In late spring and early summer, cutthroat trout move from the lake to spawn in the shallow confines of the Yellowstone River and various tributaries where they are eaten by predators.

Lake trout, meanwhile, spawn in deep water, inaccessible to the animals on the surface looking for food.

The latest fish surveys indicate that about 4 million catchable cutthroat trout thrived in the lake. But Lynn Kaeding, a fisheries biologist with the U.S. Fish and Wildlife Service, says that a proliferation of lake trout could reduce the cutthroat trout population by 90 percent, causing ripple effects across the ecosystem.

Compounding the problem is “whirling disease,” a congenital ailment that leads to deformities in the skeletal system of certain trout. It’s been found in the Madison River and is moving upstream into the national park.

Ron Cooper, northern Rockies field representative for the Pacific Rivers Council, a conservation organization, said the lake trout invasion and whirling disease shatter the myth that Yellowstone is an impenetrable natural fortress immune to threats from the outside world.

“For a long time we have relied on our public lands to serve as refuges,” he said. “Unfortunately, it has gotten to the point where humans have so altered the lakes and waterways at such an accelerated rate that entire fish populations are being compromised. If we can’t save the cutthroat population in Yellowstone Lake there’s little hope that we’ll be successful in saving wild trout anywhere else.”