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Battling Lake Trout In The Flathead River System; ‘A Huge Ecological Health Issue’
Posted on Friday, August 24, 2012 (PST)

Glacier National Park officials are proposing a lake trout removal project on Logging Lake and continued lake trout netting work on Quartz Lake, both of which are connected to Montana’s Flathead Lake and river system.

The park is taking initial public comment on the proposals until Sept. 10 to prepare an environmental assessment.

On the west side of the park, lake trout have invaded nine of 12 lakes they are able to reach from the North Fork Flathead River, and they have replaced native bull trout as the top aquatic predator in most of the lakes that have been monitored.

“It’s a huge ecological health issue,” said Clint Muhlfeld, a Glacier-based fisheries scientist with the U.S. Geological Survey. “A lot of the populations are functionally extinct in the park right now.”

In 2005, lake trout were detected in Quartz Lake, a stronghold for bull trout and cutthroat trout.

The park and the U.S. Geological Survey initiated a lake trout netting project on the lake in 2009 to reduce or eliminate the lake trout population, and the results are considered promising.

Muhlfeld said the suppression work has been effective largely because of transmitter-tagged “Judas fish” that have been tracked to two specific spawning areas in the lake located below avalanche chutes.

“If we can increase the harvest rate above recruitment we can kind of collapse the population,” Muhlfeld said.

But he emphasized that Quartz Lake’s native fish populations were still largely intact when suppression efforts got under way, and that is not the case with Logging Lake, which has “phenomenally low” numbers of native fish remaining, Muhlfeld said.

Logging Lake was once considered the most productive bull trout fisheries in the Flathead River basin, and for that reason it is a priority. Due to the growing lake trout population, bull trout are in danger of becoming extirpated, and that could require different strategies, Muhlfeld said.

The park is proposing netting methods on Logging Lake similar to those used on Quartz Lake, and it is proposing to extend Quartz Lake netting operations that are currently only approved through the end of this year.

But there could be another approach to Logging Lake, with the first step being an effort to “rescue” the remaining bull trout population, Muhlfeld said.

That could involve collecting bull trout and eggs to be raised in a rearing hatchery for release back into the lake or possibly transplanting them to Grace Lake, which is upstream from Logging Lake and protected by natural barriers.

Meanwhile, there would be an aggressive netting effort to rapidly suppress the lake trout population.

Information about the proposals and how to comment on them are available online at:


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