DNR Researching Effectiveness Of Beaver Dam Management On Trout Populations

Sep 2, 2020

USDA Wildlife Services workers remove a beaver dam on a trout stream in Langlade County.
Credit Ben Meyer/WXPR

For years, many wildlife managers have assumed removing beaver dams on streams helps trout populations.

It allows the streams to run colder and more free, conditions trout generally like.

In an episode of The Stream last month, we showed you how wildlife managers often use explosives to remove dams.

“It’s really important to have these free-flowing from the very top, the cold-water sources, in many cases, all the way through to the larger systems,” said Jeremy Irish, who works with the USDA Wildlife Services program, as part of that story.

But now, a DNR researcher is testing just how true the management theory is.

“We’re trying to fill in the gaps in the understanding of how beaver are affecting these streams and trout populations in them,” said DNR fisheries research scientist Matt Mitro. “The trout population itself, if you have a beaver interrupting flow in a stream and creating different types of habitat, are you increasing trout population? Decreasing trout population? Changing the size structure?”

The assumption about positive impacts for trout is based on decades-old data from one part of the state.

Mitro is now studying 15 streams statewide, manipulating some to allow for beaver dam-building and having dams removed on others.

He said his research could change how the state manages its beaver dams and trout streams.

“Wisconsin DNR fisheries management expends a certain portion of their budget for maintaining this program. Are we wisely spending that money? Or are there ways that we could improve how we’re doing it?” he said.

Mitro hopes to release data as he gets it.