After years of a full-scale attempt to rid Yellowstone Lake of nonnative trout that feed on native cutthroats, Yellowstone National Park experts say they’re succeeding in reducing the lake-trout population.
Lake trout were probably introduced to Yellowstone Lake in the 1980s and first discovered in 1994. They’re a natural enemy of the native cutthroats: the larger lake trout both eat cutthroats and compete with them for other food. It’s been estimated that at one time there were 4 million cutthroat trout in Yellowstone Lake, but that number is down significantly, and the number of cutthroat trout migrating to tributaries has decreased dramatically as well. That creates a domino effect, as predators like bears rely on cutthroats as an important part of their diet: some 42 mammals and birds in Yellowstone rely on cutthroats.
It’s not been an easy effort. Those fishing in Yellowstone Lake were educated on the necessity of keeping any lake trout caught. Electrical system were set up on the bottom of the lake to kill spawning. And the last two summer saw the hiring of commercials crews to net the lake trout. Some 1.4 million lake trout were removed in the $2-million netting program, and both Park officials and researchers at Montana State University see evidence the effort is succeeding:
“The goal was to crash the lake-trout population to a point where they are no longer adversely affecting Yellowstone cutthroat trout,” [YNP Center for Resources Chief Dave] Hallac said. “We have evidence now that our suppression program is sufficient to cause the population to decline.”
Hallac said the lake trout population appears to be declining because they were harder to catch in 2013 than in 2012 when the program started.
Each year, biologists netted and killed around 300,000 lake trout, but they had to work harder in 2013, hauling in only five lake trout a night as opposed to eight a night the previous year.
As noted, it costs $2 million a year just for the netting, a cost that’s borne by the Park (via fishing fees), the Yellowstone Foundation and Trout Unlimited.
The experts say it will be virtually impossible to totally eradicate lake trout; the goal is reaching the point where cutthroats are thriving and the lake-trout population is manageable.