Glacier National Park: Latest effort to preserve a native trout species a success

A project to rid a couple of high mountain lakes in Glacier National Park of non-native fish and replace them with native species was a success, Park fisheries biologist Chris Downs said.

Biologists last year treated Camas and Evangeline lakes and a portion of Camas Creek above Arrow Lake with Rotenone, a fish toxicant to kill non-native Yellowstone cutthroat trout.

In turn, pure strain westslope cutthroat trout from Hay Creek, which is just outside the Park and a North of the Flathead Tributary, were raised in a local hatchery.

Last spring, 1,000 fingerlings were stocked in both lakes. The idea was to establish a sustainable population of pure strain westslope cutthroats in the lakes and the stream.

The upper end of the drainage is protected by waterfalls that keep non-native trout and hybrids such as rainbow and westslope cutthroat crosses from migrating upstream.

The Park eventually will stock bull trout from Quartz lake into those small lakes as well.

It’s part of an overall larger effort to preserve native species in Glacier.

Locally, treating streams and lakes to rid them of non-native species is not new — a multi-year project did the same thing in the Bob Marshall Wilderness to preserve westlope cutthroat trout there.

The Park also continues to suppress non-native lake trout in Logging and Quartz lakes, netting the fish with gill nets.

The idea there was to suppress the lake trout population to the point where the native bull trout can rebound.

IN QUARTZ, the effort is working particularly well, Downs noted, though the problem now is finding enough lake trout to catch and while still limiting “by-catch” of native species such as westslope cutthroat and bull trout.

The question in Quartz is how to get the last few remaining lake trout out of the lake. Lake trout, once they enter a waterway, decimate native bull trout, by both eating them and outcompeting them for food.

At Grace Lake, which is just upstream from Logging Lake, the Park has introduced bull trout propagated from stock from Logging Lake. The bulls are now feeding on non-native Yellowstone cutthroat trout in that small lake and there is early evidence that they may be spawning. The hope is they establish a self-sustaining population as they were first introduced in 2017. Today, some of the bulls are 24 inches or longer.

Could the bull trout eat all of the Yellowstone cutts?

“That would be a really good outcome,” Downs said. “It would be nice if that worked out as a biological control story.”

Grace Lake, like Camas and Evangeline, is protected from upstream migration of non-native fish by a waterfall.

The Park plans on continuing its effort to re-establish or in some cases, create completely new refuges for native fish.

As climate change continues to impact the Park, high alpine lakes and streams could prove to be key to preserving and protecting native species.

Downs said the next lake biologists are examining is Gunsight Lake. The high mountain lake is perched just on the east side of the Divide and is fed by Jackson glacier as well as huge snowfields.

But Gunsight isn’t formalized, Downs noted.

“It’s just in the idea stage,” he said.