Six Mile - Halsted Bay Habitat Restoration

Project Status: 
Active
About this project: 

Over the next ten years, the Minnehaha Creek Watershed District (MCWD or District) and its partners will engage in one of the Twin Cities metro’s largest habitat restoration and water quality enhancement projects: the restoration of 2,488 acres of in-lake habitat across 14 connected deep and shallow lakes and the creation of corridors of restored wetland and uplands in the Six Mile-Halsted Bay Subwatershed (SMHB), one of the largest tributaries to Lake Minnetonka. 

The SMHB is one of the District’s focal geographies. With our partners (listed below), we’ll be working to align priorities and investments across agencies to accomplish large-scale habitat, corridor, and water resource restoration objectives, including larger-scale wetland restorations, additional rough fish management, in-lake and watershed phosphorus reduction, or others.

Managing the subwatershed’s large population of common carp is the first phase in our comprehensive restoration of the SMHB, which will restore 2,488 acres of shallow lake habitat, benefiting game and non-game fish species, improving wildlife habitat for waterfowl, and address water quality issues for the 14 lakes that are listed by the state as being impaired.

The foundation for this project is a three-year assessment conducted in partnership with the University of Minnesota Aquatic Invasive Species Research Center (MAISRC) which evaluated common carp’s abundance, recruitment patterns, and seasonal movement patterns in the SMHB. This pioneering work and the resulting data (attached below), completed in 2017, has allowed MCWD to develop a well-timed, and targeted management approach with quantifiable goals. As one of the most ambitious common carp management efforts in the state, the project will enhance fisheries and benefit waterfowl and non-game bird communities, improving recreation for fisherman, hunters and bird-watchers.

Project Outcomes

The carp management plan will restore habitat in 14 lakes, totaling 2,488 acres of habitat for game and non-game fish by increasing aquatic vegetation, improving the invertebrate communities, and increasing water clarity.

The management plan will also improve habitat and forage for more than 75 species of birds, including more than 20 species of waterfowl that breed in or migrate through the SMHB.

Overall, this management plan will provide long-term protection from invasive common carp across the system of lakes and wetlands in the SMHB. After implementing the management plan, we will evaluate improvements in the aquatic ecosystem by surveying the abundance and diversity of aquatic vegetation, fish, and macroinvertebrates using scientifically valid best practices. The District will monitor carp populations after implementing the management plan and will respond to any increase in carp as needed to maintain a sustainable population.

Common Carp's Impact on Ecosystems

Common carp were introduced into Minnesota in the 1880s as a game fish because they grow quickly and thrive in our lake ecosystems. However, they have become one of the most damaging aquatic invasive species in our waters. Carp are bottom feeders and when they feed, they uproot aquatic vegetation, dig up nutrient-rich sediment (releasing phosphorus and other nutrients into the water, which contributes to algae blooms), and compete with other fish and waterfowl for food. Common carp can live for many years, lay millions of eggs per year, move quickly between lakes through streams and channels, and tolerate many different environments. This has made them extremely successful, particularly in the shallow lakes of the SMHB, and they can freely move between the subwatershed and Lake Minnetonka.

Managing carp populations can improve habitat and water quality for waterfowl and gamefish and begin restoring the ecological health of these degraded lakes.

University of Minnesota Carp Assessment and Findings

Efforts to improve water quality and restore fish and wildlife habitat are not effective in lakes that are infested with common carp until the number of carp in the lake can be reduced to a sustainable level.  To prevent the carp from undermining the impact of other restoration efforts in this focal geography, we first need to focus on managing carp populations in the area before embarking on other water quality and habitat improvement projects. 

The first step to sustainably managing common carp in SMHB was assessing, over a period of three years, the abundance of carp in the subwatershed, the movement of carp between and within the different lakes, and the locations where adult carp were laying their eggs. MAISRC conducted the study from 2014-2017 and provided a cutting-edge scientific assessment of common carp’s populations, reproduction and migratory patterns in SMHB. This assessment revealed some of the largest carp population densities ever observed by MAISRC. It also indicated that the carp population in the lakes is on the rise. The final report is attached below.

Carp Management PlanProject Strategies

The MAISRC’s carp assessment informed a carp management plan for the SMHB which will be phase one in our restoration of the area.  The carp management plan includes three strategies:

  • Suppressing carp reproduction: installing aeration units in six of the shallow lakes in the subwatershed to prevent freezing during the winter. These six lakes were identified by the MAISRC assessment as carp nurseries. Aerating these lakes will prevent winterkill of bluegill sunfish, which are predators of carp eggs. Several physical barriers will also be installed to prevent adult carp from spawning in other affected lakes.
  • Installing a barrier/trap between Mud Lake and Halsted Bay: The barrier installed between Mud Lake and Halsted Bay will prevent carp migration from Halsted Bay and Lake Minnetonka to Mud and Parley Lakes. This will contain the carp populations and help with removal efforts. The barrier will incorporate a trap to capture additional carp and remove them from the lakes.
  • Adult Carp Removal: Carp will be removed from individual lakes to achieve a target of below 89 pounds per acre of carp in each lake. This threshold is the maximum carp density that the lakes can support before ecological damage may occur. Various strategies will be used for removal including:
    • Winter or open water seining (using large nets that can remove large numbers of carp at a time)
    • Box-net trapping (rectangular nets used with bait during open water season)
    • Trapping carp in stream channels as they migrate from body of water to another