Westslope Cutthroat Trout and Arctic Grayling Restoration Project FWP-DN-FSH-R3-24-16

May 10, 2024 4:31 PM

With this action, FWP would restore native Westslope Cutthroat Trout (WCT) and Arctic grayling to a segment of Winslow Creek in the Centennial Valley of southwest Montana. Historically, WCT, Arctic grayling, and mountain whitefish were the only salmonid species found in the Centennial Valley. Today, in addition to these native salmonids, the Centennial Valley hosts non-native brook trout and hybridized Yellowstone cutthroat and rainbow trout.

The primary threat to WCT in southwest Montana, including the Centennial Valley, is hybridization, competition for resources, and predation by nonnative fish species. The native WCT population in Winslow Creek has been eliminated through hybridization with rainbow trout. Further, Arctic grayling were once widespread in the Centennial Valley and spawned in over 15 tributary streams; however, current Arctic grayling distribution is primarily limited to Upper Red Rock Lake and Red Rock River. The primary threat to grayling in the Centennial Valley is a lack of over-winter habitat in Upper Red Rock Lake with a secondary threat identified as access to tributary streams.

Under the proposed action, nonnative fish upstream of an existing fish barrier on Winslow Creek will be removed using a piscicide (rotenone), applied over two consecutive years. After the two annual treatments have been completed and the stream has been verified to be fishless using a process evaluating environmental DNA, WCT will be repopulated with fish from nearby streams where nonnative trout introgression is <1% and the WCT population is at-risk. Grayling will be stocked using fertilized eggs or newly hatched fry from spawning efforts at three mountain lakes with a Centennial Valley Arctic grayling origin (i.e., genetic ancestry). Repopulation efforts for both WCT and Arctic grayling will occur over a 2 to3-year consecutive period following the elimination of fish from the affected segment of Winslow Creek.