Montana Fish, Wildlife & Parks closed a 19-mile stretch of the upper Big Hole River today to all angling due to extremely low water conditions that threaten the survival of the river's native Arctic grayling population. Today's closure encompasses the upper-most reach near Wisdom a 19 mile stretch from Rock Creek Road to the mouth of the North Fork of the Big Hole, about 14 miles downstream of Wisdom. This stretch includes most of the river's critical grayling spawning and rearing habitats.
The closure will take effect tonight at midnight and will remain in effect until the flows improve to 40 cfs for seven days in the upper reach of the river and FWP acts to reopen the stretch.
"While the flows and water temperatures in the upper Big Hole River near Wisdom are at levels that are detrimental to the river's native grayling, there are many miles of river that remain open to anglers," said FWP Fisheries Division chief Chris Hunter.
Open reaches include the stretch from the headwaters downstream to Rock Creek Road and the 102 miles of popular sport fishery from the North Fork down to the mouth of the Big Hole at Twin Bridges.
The USGS gage at Wisdom, on the upper reach, shows that the average daily flow has declined below 20 cfs, which is the "critically low" flow level specified in the Big Hole Drought Management Plan for an angling closure. The plan separates the Big Hole River into three "drought emergency" reaches. The Big Hole Drought Management Plan was developed by the Big Hole Watershed Committee, a group of volunteers from agriculture, municipal, business, conservation, angling and government interests.
"Last year it was June when we hit critical low flows in the upper reach of the Big Hole and closed this stretch to angling, so we are in significantly better shape this year," Hunter said.
Hunter said irrigators in the basin participated in the drought planning again this year, playing an important role in helping to keep water in the Big Hole River this summer. Most irrigation is over for the summer at this time.
"We want to express our gratitude again this year to the watershed's irrigators and anglers for the sacrifices they made during this and past summers," Hunter said.
The Big Hole River holds the last remaining native population of river-dwelling Arctic grayling in the lower 48 states. Introductions of grayling into some Missouri River tributaries have recently been made to expand its present range.
The remaining two reaches of the Big Hole River, which encompass the vast majority of the sport fishery of the Big Hole River, are still open to angling and flows have held up fairly well this summer. Closure triggers for the middle reach, based at the USGS Mudd Creek gauge are 60 cfs, and for the lower reach gauged at Melrose 150 cfs. Instream flows today at the Mudd Creek gage were 130 cfs and 225 cfs at Melrose gage.
FWP is asking anglers to be alert to declining flows in these reaches and the potential for stress to fish. Anglers can do their part to help fish by fishing in the morning hours and by not fishing when fish are stressed by high temperatures and low flows.