Agencies ponder dissolved oxygen boost for wintering grayling in Centennial Valley

DUNCAN ADAMS The Montana Standard

Arctic grayling within the Centennial Valley rely primarily on the Upper Red Rock Lake in the Red Rocks National Wildlife Refuge east of Lima for winter habitat.

It’s not a great place for the unique fish to spend the winter.

Given the Arctic grayling’s perilous status in the region, that reality is worrisome for the U.S. Fish and Wildlife Service and Montana Fish, Wildlife and Parks.

The Upper Red Rock Lake is a shallow and “eutrophic” lake that is rich in nutrients supporting plant life that decomposes in winter. The lake is covered for months each winter in ice and snow and that combination reduces dissolved oxygen, leaving the Arctic grayling vulnerable to winterkill.

What can be done?

This week, the U.S. Fish and Wildlife Service and Montana FWP released for public comment a draft environmental assessment identifying six potential interventions that could add dissolved oxygen to the Upper Red Rock Lake.

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Other partners include Montana Trout Unlimited and the U.S. Geological Survey.

“The proposed action would increase dissolved oxygen levels in deeper portions of the Upper Red Rock Lake, where grayling over-winter, improve grayling winter survival and

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