Low flows, high water temperatures reach closure criteria  

TWIN BRIDGES – A full fishing closure is in effect once again for a portion of the lower Ruby River due to low flows and high water temperatures.  

The closure extends about 14 miles, from the Duncan District Road crossing downstream to the confluence with the Beaverhead River. This is the second time this year a fishing closure has been implemented in this section of the Ruby River.  
Flows in the Ruby River at a U.S. Geological Survey gauge near Twin Bridges dipped below 20 cubic feet per second on June 16, well below the fifth percentile of historic daily flows for that date, which is 45 cubic feet per second. Water temperatures also exceeded 73 degrees for three consecutive days from June 13 to 15.  

These flow and temperature values meet the established criteria for closing this portion of the river to fishing. Low flows and high water temperatures have been driven primarily by very low snowpack, water supply and inflows to the river. Dry conditions are expected to continue throughout the summer. 

Closures of this nature are designed to protect fish that become more susceptible to disease and mortality when conditions, such as low flows and high water temperatures, combine with additional stressors.  

This is especially expedient this year as recent fish surveys found low numbers of trout in the lower Ruby River. Montana Fish, Wildlife & Parks biologists estimate there are about 191 fish per mile at the upper end of the closure area, which has a long-term average of about 700 fish per mile. At the lower end, there are an estimated 31 fish per mile, compared to a long-term average of about 800 fish per mile.  

“From a fisheries perspective, we’re at historically low trout abundances in the lower Ruby,” said Matt Jaeger, FWP’s Hydropower, Native Species and Beaverhead-Ruby Program Manager. “So that, in combination with poor snowpack and low precipitation leading to low flows and high temperatures, is why we feel an angling closure is warranted.” 

Ruby River water users are also taking steps to keep flows above 20 cubic feet per second, in accordance with the Ruby Valley Users Drought Management Plan. Stored water users have taken a 15 percent reduction in allocated water, and decreed water users have taken a voluntary 10 percent reduction in allocated water, according to Bill Wood, the Dam Tender for the Ruby River Water Users Association.  

“We’re trying to balance the needs of users who rely on water from the Ruby while maintaining flow levels that fish need,” Wood said. “Water levels at Ruby River Reservoir peaked at 93 percent of capacity this year, which is the first time since 2003 that the dam didn’t spill.” 

The section of the Ruby River between Duncan District Road and the confluence with the Beaverhead River will remain closed to fishing until daily average flows exceed 40 cubic feet per second for seven consecutive days, or until Oct. 15, 2021.