Photo: A carp exclosure experiment showing much clearer water and plant growth inside of a 1-hectare vinyl-wall exclosure as compared to surrounding water in Lake Wingra. Carp were removed from within the study area but present in the remainder of the lake. Photo taken in July 2007 by Mike DeVries of The Capital Times.
Common carp have been discussed by some lake managers as being one of the most destructive and impactful aquatic invasive species. Carp typically live to be 20 years old, and may reach between as much as 30 inches in length 30 lbs in weight. A carp can typically spawn for many years, between 2 and 16 years old. When feeding, the large fish can disrupt rooted aquatic plants and stir up bottom sediment into the water column. This activity causes turbidity in the water and releases nutrients which feed algae growth. Their excrement has high nutrient content as well. Studies from the University of Minnesota have determined that there is an appropriate “management threshold” in which carp begin to have measurable impacts on a lake’s water quality. This occurs when carp reach a density of over 100 kilogram per hectare, or approximately 90 pounds of fish per acre of lake.
The Sherburne SWCD has sought to understand the impacts of common carp on a number of county lakes and has several active carp management projects. Read more about these projects below.
Lake Fremont
In 2023 the Sherburne SWCD worked with the Lake Fremont Improvement Association, City of Zimmerman, and Carp Solutions to assess the carp population in Lake Fremont. Preliminary estimates indicate that the population exceeds the management threshold of 90 lbs/acre with potentially as much as 644 lbs/acre of carp within the lake. In 2024, Sherburne SWCD and Lake Fremont were selected by the Minnesota Aquatic Invasive Species Research Center (MAISRC) for a long-term management program called Lab to Lakes. The goal of the program is to take recent advances in carp management tools and technology and achieve success in a Minnesota lake. From 2024 through spring of 2028, the SWCD, MAISRC, and contractor Carp Solutions will be managing carp and learning more about the impacts of carp management on Lake Fremont.
Follow along for updates on this project by viewing the Lake Fremont Lab to Lakes Story Map and check back often for updates.
Lake Fremont
In 2023 the Sherburne SWCD worked with the Lake Fremont Improvement Association, City of Zimmerman, and Carp Solutions to assess the carp population in Lake Fremont. Preliminary estimates indicate that the population exceeds the management threshold of 90 lbs/acre with potentially as much as 644 lbs/acre of carp within the lake. In 2024, Sherburne SWCD and Lake Fremont were selected by the Minnesota Aquatic Invasive Species Research Center (MAISRC) for a long-term management program called Lab to Lakes. The goal of the program is to take recent advances in carp management tools and technology and achieve success in a Minnesota lake. From 2024 through spring of 2028, the SWCD, MAISRC, and contractor Carp Solutions will be managing carp and learning more about the impacts of carp management on Lake Fremont.
Follow along for updates on this project by viewing the Lake Fremont Lab to Lakes Story Map and check back often for updates.
Photo: Staff from Stantec hold up a Briggs Lake carp for display during the 2024 SWCD Tour of Conservation Practices. Photo by Sherburne SWCD.
Briggs Chain of Lakes (Julia, Briggs and Rush Lakes).
In 2023-2024, the Briggs Chain Lake Association and Sherburne SWCD worked with consultants at Stantec to understand sources of nutrients to Julia, Briggs and Rush Lakes from the watershed and from within the lake. An outcome of this study was that all three of the lakes have a substantial carp population and exceed the management threshold by 4-5 times (between 400 and 530 pounds of carp per lake acre). The study documented that the contribution of phosphorous to the lakes is substantial; in fact, it is likely the largest source to Julia Lake and the 2nd largest source to Briggs and Rush Lakes. Read more on this study here: Briggs Lake Chain Diagnostic Feasibility Study
The Briggs Chain Lake Association and Sherburne SWCD are currently planning further work on carp management for summer of 2025.
In 2023-2024, the Briggs Chain Lake Association and Sherburne SWCD worked with consultants at Stantec to understand sources of nutrients to Julia, Briggs and Rush Lakes from the watershed and from within the lake. An outcome of this study was that all three of the lakes have a substantial carp population and exceed the management threshold by 4-5 times (between 400 and 530 pounds of carp per lake acre). The study documented that the contribution of phosphorous to the lakes is substantial; in fact, it is likely the largest source to Julia Lake and the 2nd largest source to Briggs and Rush Lakes. Read more on this study here: Briggs Lake Chain Diagnostic Feasibility Study
The Briggs Chain Lake Association and Sherburne SWCD are currently planning further work on carp management for summer of 2025.
Photo: Remote camera still-shot of Eagle Lake carp moving upstream to an identified spawning location. Photo by Sherburne SWCD.
Eagle Lake
In 2019-2020 the Big Eagle Lake Improvement Association, Sherburne SWCD and consultants at WSB conducted a phosphorus assessment of Eagle Lake. The study determined that it was likely that carp exceeded the management threshold by roughly two times at 171 lbs per acre and contributed roughly 360 lbs of phosphorus to the lake each year. In 2022 a follow-up study was completed to confirm the population density and identify potential spawning locations for carp. Currently there are no plans for carp management work on Eagle Lake however the studies suggest that carp management is an important element of holistic lake management and to achieve water quality improvements.
In 2019-2020 the Big Eagle Lake Improvement Association, Sherburne SWCD and consultants at WSB conducted a phosphorus assessment of Eagle Lake. The study determined that it was likely that carp exceeded the management threshold by roughly two times at 171 lbs per acre and contributed roughly 360 lbs of phosphorus to the lake each year. In 2022 a follow-up study was completed to confirm the population density and identify potential spawning locations for carp. Currently there are no plans for carp management work on Eagle Lake however the studies suggest that carp management is an important element of holistic lake management and to achieve water quality improvements.
Read more about the Eagle Lake carp studies here:
2019-2020 Nutrient Budget Analysis
2022 Integrated Pest Management Plan
2019-2020 Nutrient Budget Analysis
2022 Integrated Pest Management Plan
Header Photo provided by MAISRC