Fishing for Answers: How Do Brook Trout Survive in Rice County?

The sky is clouding over and the wind is picking up. It’s not the best day for capturing and tagging brook trout, but Stephanie Schmidt, an aquatic ecologist from St. Olaf College, straps on a battery-loaded backpack and wades into the thigh-high waters of Spring Brook.

A wand attached to the backpack will deliver a shock to any brook trout swimming near her in the creek, a rare brook-trout stream that she and fellow biologist Paul Jackson are studying as part of a two-year research project.

Over the next few hours, Schmidt and three students will capture, measure, weigh, and insert radio-frequency identification tags under the skin of 35 trout, the largest measuring 10.5 inches, before returning them to the stream. Tagging the trout will enable Schmidt and Jackson to track the fish over the next two years as they travel along the stream, grow, spawn, and die.

The project, which is being overseen by Bridgewater Township and funded through a $110,000 grant from the Minnesota Pollution Control Agency (MPCA), will gauge the health of this rare brook-trout stream, which is the only stream of its kind in Rice County and one of only a few in southern Minnesota.

“The fact that the trout have survived is surprising,” Schmidt said, “but there is so much we don’t know about them.”

‘A Gem of a Stream’

Spring Brook, also known as Rice Creek, has been the subject of environmental concern for several years.

The state has listed it as an impaired waterway due to excessive turbidity (suspended particles in the water), bacteria and nitrates. Its naturally reproducing population of brook trout—the only native Minnesota trout—makes it a “gem of a stream,” says Schmidt.

Researchers hope to assess the health of the trout population from several angles, including the fish size, population growth or decline, food web, habitat and movement as well as the stream's water temperature, quality and flow.

The study grew from concern about how potential development in the area might affect the stream, which is located on the border of Northfield and Bridgewater Township and may be annexed to Northfield in the future.

"The annexation agreement between the township and the city of Northfield requires us to protect Rice Creek as a prerequisite for annexation, and as development occurs," said Township Supervisor Kathleen Doran-Norton. "What we learn about the creek's environment helps us to act responsibly in the future."

According to Schmidt, the project has been a “very collaborative effort,” involving the township, Cannon River Watershed Partnership, the Minnesota Department of Natural Resources, Rice County Soil and Water Conservation, MPCA and Trout Unlimited. Assistance from Northfield city staffer Brian Welch helped the township identify the MPCA grant that is funding part of the study, Doran-Norton said.

While researchers are not sure how the trout got in the stream—one local legend says they were stocked decades ago—they believe that underground springs that feed the stream are one reason the fish have survived.

Brook trout require clean, cold water that is filled with oxygen. Springs keep the water temperature in Spring Brook below 60 degrees year-round and they add oxygen, Schmidt said. In addition, Spring Brook has many “cut banks,” areas where the stream flows below ground, giving the trout cool places to hide. The trout feed on insects, which seem to be attracted to the vegetation around the creek’s banks.

Monitoring the Fish

Researchers plan to insert radio tags, which are similar to the chips used to identify pets, into about 200 trout this spring. As the research project continues, trout will be captured at different times of the year. When the tagged trout are caught, researchers will be able to track their growth and where in the 7-mile long stream they have been.

“I don’t know this, but my sense is the trout move around quite a bit,” says Schmidt.

One concern with residential or light industrial development in the area is the addition of impervious surfaces, such as parking lots and roofs, that encourage faster runoff of rainwater. There are ways to mitigate potential alterations to the stream from runoff, Schmidt noted.

“We’re trying to figure out how we can balance the needs of the people who own land along the stream and sustain the trout at the same time,” she said of the concerned citizens group. “Because the trout are there, we know it has been working so far. We want to see how we can make it work even better.”

“These are a rare and very beautiful fish,” she said. “They are harder to catch than brown trout because they are skittish, so there is something romantic and mystical about them.”

WANT TO LEARN MORE?

To help the public learn more about the project, the Rice Creek Concerned Citizens will be holding an open house from 9:30-11 a.m. May 14 at the Bridgewater Town Hall. Or, you can follow the trout on Twitter—@TroutThatTweet.

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