2021 Madison dewatering hard to attribute to lower fish populations, FWP survey concludes

Volunteers wade through a channel of the Madison River in December 2021 with a Fish, Wildlife & Parks biologist as they work to save trapped fish in sections that were cut off from the main river flow. 

MEAGAN THOMPSON, The Montana Standard

It could be difficult to attribute any decline in the upper Madison River’s trout fishery to an accidental dewatering that occurred in November 2021 when a Hebgen Dam gate failed.

“In general, sampling conditions, normal fluctuations in abundances, and the lack of baseline data could confound our ability to attribute future changes in the trout populations to the gate failure,” according to a report by a Montana Department of Fish, Wildlife & Parks crew.

Matt Jaeger, a Region 3 fisheries biologist for FWP, said the survey proved the dewatering didn’t wipe out an entire year class of fish, which was encouraging.

“We definitely observed affects to the reds and to a lesser degree fish” following the dewatering, he noted. “We know there was some level of effect, but we’re relying on future years to figure out what that was.”

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