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Battling Common Carp Through the Winter

January 28, 2019

Man holding radio tracking equipment on frozen lakeThis column is part of an occasional series of articles about an unprecedented effort to improve water quality in the headwaters of Lake Minnetonka and the Minnehaha Creek watershed.

Despite cold temperatures, snow, and ice, winter is actually the best time to do certain construction activities, especially projects located on or near lakes and streams. Frozen water and frozen ground make the work easier, and that’s certainly the case in the Six Mile Creek – Halsted Bay Subwatershed this season.

As part of a multi-agency, ten-year focus on the headwaters of Lake Minnetonka to improve water quality and ecological health, the Minnehaha Creek Watershed District is working to control the population of invasive common carp in the region’s lakes. Our goal is to remove 872,000 pounds of carp from across 12 lakes in the system.

Last summer, this work included using baited box nets to remove carp in East and West Auburn and Steiger Lakes. We removed 13,234 pounds of carp from all three lakes! Catch rates were lower in Wassermann Lake, which indicates that the carp population in that lake is near our target number. This is most likely due to a temporary barrier that’s been stopping carp from entering via the lake’s outlet.

Now that winter has set in and the carp have moved to deeper water, our focus has shifted to installing two permanent carp barriers to block carp from accessing their spawning locations. One barrier will be located at Highland Road east of Mud Lake in Minnetrista and the other will be located north of Wassermann Lake in Victoria. Construction of the barriers will be finished in time for the spring thaw and carp migration.

The carp barriers will be physical barriers customized to fit each location. They will have a removable section in the middle that can be raised and lowered to allow gamefish through and that can be used with other equipment to trap carp in stream channels for removal. Barriers will be maintained frequently to clean off debris and allow passage of other wildlife.

This winter, we’ll be aerating Mud Lake and South Lundsten Lake to help maintain oxygen levels in the water. This will prevent winter kill of bluegill sunfish which feed on carp eggs in the spring.

Managing carp is the first strategy in a multi-pronged, multi-agency effort to improve water quality in the Six Mile Creek - Halsted Bay Subwatershed. The other strategies are protecting and restoring wetlands, reducing the amount of polluted stormwater entering local water bodies, and controlling the amount of phosphorus being released from lake bottoms.

To help us make progress on some of these other strategies, the Minnesota Board of Soil and Water Resources has awarded us a $93,879 Clean Water Fund grant to improve the water quality in Wassermann Lake. The funds will be used to treat polluted sediment in a pond adjacent to the lake this spring and for future repairs to an eroded stream channel.

Including the MCWD, ten agencies are participating in the decade-long effort to improve habitat and water quality in the watershed’s headwaters. They are Carver and Hennepin Counties, Laketown Township, the Minnesota Department of Natural Resources, the Cities of Minnetrista, St. Bonifacius, Victoria and Waconia, and Three Rivers Park District.

To keep updated on the work to in the Six mile Creek - Halsted Bay Subwatershed and to sign up for project update emails, visit our Six Mile Creek - Halsted Bay Subwatershed page.