MAMMOTH HOT SPRINGS, Wyo. — Efforts to reduce nonnative lake trout in Yellowstone Lake appear to be working, Yellowstone National Park officials say.
The park recently concluded its annual removal of nonnative trout, and the population is, indeed, declining.
Lake trout are removed in an effort to preserve the native cutthroat trout population, the largest remaining concentration of inland cutthroat trout in existence.
Native cutthroat trout are the park’s most ecologically important fish and the most highly regarded by visiting anglers. It is an important food source for grizzly bears, birds of prey, and other wildlife. The cutthroat decline resulted in several of these species being displaced from Yellowstone Lake or having to use alternate food sources during certain times of the year.
“I want to personally thank the National Park Service team, our partners, and the many people who have philanthropically supported this continuing conservation effort,” said Superintendent Cam Sholly. “There is a considerable amount of work yet to do to build on this progress. This will continue to be one of our conservation priorities.”
Yellowstone National Park and contract crews removed 282,960 fish between May and October of this year compared to 297,110 in 2018, and 396,950 in 2017, a 29% decline over three years.
Yellowstone’s lake trout suppression program is one of the largest nonnative fish removal programs in the United States. Since lake trout were first discovered in 1994, more than 3.4 million have been removed from Yellowstone Lake through suppression gillnetting. The number of lake trout caught in nets continues to steadily decline, from 4.4 per net in 2017, and 3.1 per net in 2018, to just 2.9 per net in 2019.
In order to predict the success of the removal effort and set benchmarks for gillnetting in the future, Yellowstone National Park and Michigan State University collaborate to generate statistical models of the lake trout population. The models suggest there are 73% less lake trout ages six and older in Yellowstone Lake now than were present at the population’s peak in 2011. This is critical because older, larger lake trout have the highest reproductive potential and consume the most cutthroat trout. The models also indicate that the invasive species has been in decline since 2012.
While models and monitoring point to positive trends, a panel of expert fishery scientists in May 2019, estimate that a minimum of five more years of effort is needed to reach the lake trout population goal of below 100,000. They also emphasized that lake trout cannot be completely eradicated with current techniques and will continue to require annual removal and monitoring into the future.
Yellowstone has invested more than $20 million over the past two decades on this recovery effort. Much of that funding has come from the generosity of donations through Yellowstone Forever. “The park will never completely eradicate lake trout but the return on investment is the ecological restoration of Yellowstone cutthroat trout, sustainable angling, and a chance to glimpse a river otter, osprey, or bear catching a cutthroat,” said Dr. Todd Koel, leader of the Native Fish Conservation Program.
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