Through its Federal Energy Regulatory Commission (FERC) license, NorthWestern Energy is required to provide mitigation funds to protect and enhance Madison River basin fisheries. FWP’s report details how these mitigation funds were applied last year. Here are some highlights from that report.
FWP used mitigation funds in 2019 to enhance a 1,000-foot reach of South Meadow Creek. The project was initiated to increase adequate pool habitat, improve spawning gravels at pool tail outs, add sinuosity to the reach to help dissipate stream energy during high flows, reconnect the floodplain, narrow the stream channel and improve cattle operations.
Not only did the project improve habitat for fisheries, but it also aided the landowner along South Meadow Creek in their cattle operation by providing off-stream water that does not freeze. Due to the project’s success in eliminating flooding of calving pasture, a neighboring landowner is interested in pursuing similar measures to improve stream habitat.
FWP discontinued stocking rainbow trout into Hebgen Reservoir in 2016 and began managing the reservoir as a wild trout fishery. Monitoring in 2019 showed an increase in the catch of rainbow trout. A year-long creel survey was initiated this month to evaluate angler use and satisfaction of the fishery.
Mitigation funds also helped FWP complete fish population monitoring in 2019 for two sections of the Madison River: the Varney and Pine Butte sections. FWP uses these estimates — which have been conducted since the 1960s — to monitor the health of the river’s trout populations.
In the Pine Butte section, which is the 3.5 miles of river upstream of Lyons Bridge, estimated totals of brown and rainbow trout declined from 2018 to 2019, and counts for both species are below their respective 20-year averages. Estimated abundance of small trout have generally increased in this section since 2014.
In the Varney section, which runs from Varney Bridge to just above the Eight Mile Ford Fishing Access Site, estimated totals of brown trout remained relatively stable from 2018 to 2019, but rainbow trout numbers declined. Both species are below their respective 20-year averages. Estimated numbers of small rainbow trout have varied from year to year, while numbers of small brown trout have been increasing since 2014, similar to trends in Pine Butte.
Despite good numbers of juvenile trout in both sections, larger trout have declined. While brown and rainbow trout larger than 19 inches have historically represented a small portion of fish in the Pine Butte and Varney sections, those fish became increasingly rare during recent sampling efforts. It’s unclear what is causing the decline.
FWP will be collecting otolith bones of trout throughout the monitoring sections in 2020 to obtain accurate age information. These data will then be used to estimate annual mortality rates for rainbow and brown trout. This information will be compared among sections of the Madison and other rivers to better understand mortality rates and help provide insight on causes. FWP will continue to monitor trends in fish numbers and size structure in the Madison River.