Trout return to Afton’s Trout Brook

Afton State Park is well-known as one of the best places in the Twin Cities for serious hiking and trail running. The park contains 1600 acres of prairie and woods and is crisscrossed by steep ravines that plunge 300 feet from the bluff-top down to the St. Croix River below. It is home to deer, fox, and badgers, as well as eagles, hawks, and migratory birds. Today, you can also find healthy populations of brown trout and native fish in the park, but that wasn’t always the case.

“When the DNR first conducted a fish survey on Trout Brook in the early 1990s, they only found a few trout,” explains Mark Nemeth, a trout habitat specialist with the Minnesota Department of Natural Resources (DNR). “There hadn’t been any stocking in the stream and the water temps were fairly warm, so fisheries staff guessed the trout had probably come over from the Kinnickinnic, on the other side of the St. Croix River.” By 2018, trout populations had grown significantly and the fish were beginning to reproduce in the stream. Now, says Nemeth, you can find anywhere from 150 to 1100 fish per mile in Trout Brook, depending on where you sample.  

One major reason for Trout Brook’s revival is a series of restoration projects completed by South Washington Watershed District (SWWD), in partnership with the DNR, Vail Properties (Afton Alps), and Great River Greening.  

Most recently, in 2019, the watershed district re-routed a segment of Trout Brook that flowed straight through Afton Alps ski area back to its natural, meandering course and added several features to improve habitat and reduce erosion. The wiggles in the stream create different types of habitat that fish need, including deep pools with slow-moving water, shallow riffles with fast, turbulent water running over rocks, and runs with deep, fast water and little to no turbulence. Project partners also re-created the natural floodplain so that sediment settles out along the banks of the stream instead of in the center. As a result, fertile soil carried by floodwater can nourish plants along the water’s edge instead of burying fish spawning areas. Funding from the Minnesota Clean Water Fund and the Lessard-Sams Outdoor Heritage Council helped to support the work.

Trout Brook’s natural course meanders through a wide floodplain as it nears the St. Croix River.

This spring, SWWD plans to begin a similar re-meander project further downstream along Trout Brook within Afton State Park. “We just awarded a contract to Minnesota Native Landscapes and they’ll begin work in April or May, as soon as the ski season is done,” says John Loomis, who is deputy administrator for the watershed district. The plan is to construct a new, meandering channel parallel to the existing, artificially straightened stream, and then re-direct the water into the new course once the vegetation is fully established next year. “This project won’t just restore cold-water aquatic habitat within the stream,” Loomis explains. “It will also reduce the amount of phosphorus and sediment flowing downstream to the St. Croix River [by 177 pounds per year and 154 tons per year, respectively].”

Brook trout photo in Minnesota Conservation Volunteer. Photo by Mike Dvorak.

Now that things are looking up for Trout Brook, the DNR is considering introducing a small population of Minnesota Driftless brook trout to the stream. The fish, sometimes referred to as “heritage trout,” are Minnesota’s only native stream trout and are genetically distinct from brook trout that are bred in east coast fisheries. Thanks to similar stream restoration efforts in other parts of the state, these native brook trout can now be found in almost 70 percent of the streams in southeastern Minnesota, which is up from 50 percent in the 1990s, and from just a handful of streams in the 1970s.

This year’s Trout Brook restoration project is one of several to receive funding from the newly formed Lower St. Croix Watershed Partnership. The partnership includes 15 local government partners in Anoka, Chisago, Isanti, Pine and Washington Counties and focuses on high-value projects and programs to improve water quality in the region. “This project fits the mission of the partnership perfectly,” says Matt Moore, administrator for the South Washington Watershed District. “We had a stream that didn’t used to support fish and wildlife, and now it does.”