A funny thing happened when Minnesota Department of Natural Resources fisheries scientists John Hoxmeier and Doug Dieterman documented the decadeslong population trend of brook trout in southeast Minnesota.
The study period covered the early 1980s to 2017, during which air temperatures rose in the southeast, as they did throughout the state and much of the nation. Certainly, some lake and river temperatures rose correspondingly.
Assuming those temperature increases continue, they could threaten some of the state's important warm-water fish such as walleyes, as well as ciscoes, yellow perch and other prey species.
Wholly dependent on very cold water, brook trout are perhaps Minnesota's most vulnerable finned species to ever-warming temperatures.
Yet Hoxmeier and Dieterman found in their study that in East Indian Creek in the southeast's "Driftless Area,'' brook trout in recent decades have actually increased in number and size, not decreased, and that they've displaced brown trout.
"Brook trout in the southeast also have expanded their range,'' Hoxmeier said. "In the 1970s, 3 percent of our southeast streams had brook trout. Today, 68 percent of streams in the same area have brook trout.''
The region's improved land conservation practices have contributed to the brook trout rebound by lowering stream-water temperatures. Contour planting, grass waterways and riparian buffer strips are increasingly deployed by the region's landowners to conserve soil and decrease runoff. Additionally, more of the region is forested than was a few decades ago.
"Also, we've been in a wet cycle, meaning we've had more rain, and the conservation practices are helping the water to infiltrate the ground and ultimately reach the region's confined aquifers,'' Hoxmeier said.
