Idaho officials describe lake trout suppression efforts

Idaho’s Lake Pend Oreille is often cited by advocates of lake trout suppression efforts in Flathead Lake, which the Confederated Salish and Kootenai Tribes have begun implementing to protect Flathead’s threatened bull trout population.

Like Flathead Lake, Idaho’s Lake Pend Oreille experienced a spike in lake trout populations after the introduction of non-native mysis shrimp.

As the population of lake trout rose dramatically in the 1990s, they began out-competing and preying on the historically well-established populations of kokanee salmon and Gerrard rainbow trout. Both of those species’ populations crashed, with the kokanee salmon fishery closing in 2000.

“We were faced with two choices,” said Jim Fredericks, Panhandle regional fisheries manager for Idaho Fish and Game. “We could either go ahead with suppression efforts or face the loss of our bull trout, rainbow trout and kokanee populations.”

Fredericks spoke to the Flathead Valley chapter of Trout Unlimited in Kalispell on Jan. 20. Lake trout suppression is a controversial issue for Flathead Lake. He said he was not advocating for either side of the issue but merely presenting the results of work in Lake Pend Oreille.

Larry Timchak, president of the local Trout Unlimited chapter, noted his organization supports similar suppression efforts in Flathead Lake but it’s opposed by many in the recreational fishing industry whose livelihoods depend in part on the lake’s plentiful supply of lake trout.

Beginning in 2006, Fredericks explained, Idaho chose to implement a program combining lake trout “bounties” for anglers to target populations of mid-sized fish, trap-netting to target large adults and gill-netting to remove juveniles.

“It’s important that we had both of these [angling and netting] tools at our disposal,” said Andy Dux, principal research biologist for Idaho Fish and Game. “They both removed a lot of fish. If we had only done one or the other, it’s hard to say if we would have had as much success, but it would have taken us much longer to get there.”

Dux said efforts for the past eight years have netted 177,000 lake trout, with research indicating the population has fallen by between 75 and 80 percent, accompanied by a surge in the kokanee salmon population to its highest point since the 1970s. Rainbow trout also appear to be thriving.

The lake’s bull trout population fluctuated significantly over that period, but appeared to be rising overall. Dux noted significant bull trout bycatch, with about 11,600 caught and a mortality rate potentially as high as 50 percent.  

Several people at the Kalispell meeting, however, were clearly not impressed by the results in Idaho. During the question-and-answer session, several people noted the dissimilarities between Flathead Lake and Lake Pend Oreille, particularly the presence of kokanee and rainbow trout in Lake Pend Oreille that took the place of lake trout in sport fishing. Neither species is a factor in Flathead Lake, although a kokanee salmon population had existed until the rise of mysis shrimp.

“If they had an alternative to lake trout to catch, that would be one thing,” said Norm Brewer, who owns a charter boat businesses on Flathead Lake. “When I started chartering eight years ago, I’d take people out and we’d catch 15 to 20 lake trout. … Now I’m telling people we might catch two to seven — on a $350 fishing trip.”

After getting the green light to begin an aggressive lake trout removal program last March, the Confederated Salish and Kootenai Tribes began a similar process. With the goal of restoring bull trout to historic levels, the tribes hope to remove up to 75 percent of Flathead Lake’s lake trout over a 50-year period.

Since 2009, Montana Fish, Wildlife and Parks has been using gill netting in Swan Lake, home to one of the most robust bull trout populations in the Columbia River Basin. Last October, an environmental assessment by the National Park Service supported similar efforts to suppress lake trout populations in Quartz Lake and in the Logging Lake drainage.