Zebra Mussels Spreading Westward in Lake Minnetonka

Minnehaha Creek Watershed District (MCWD) researchers have found that zebra mussels have become more prominent on the east side of Lake Minnetonka and are spreading to western areas of the lake. These findings, based on data collected from June through September 2011, complete the first year of a three-year study to monitor and measure zebra mussels’ spread throughout the lake.

“The expansion and increased density of zebra mussels are concerning,” said MCWD Water Quality Technician Kelly Dooley. “In just a year, this invasive species has spread to nearly all of Lake Minnetonka’s eastern bays and is moving west. We have been working closely with the DNR and our community partners in efforts to prevent their spread. But we need the public’s continued help to prevent the spread of zebra mussels so we can save Minnesota lakes – one of the state’s most valuable assets.”

Once established, zebra mussels spread rapidly, litter beaches with their sharp shells, damage boats and equipment and alter the food chain of local lakes, rivers and streams. 

The three-year study being conducted by the MCWD, with support from the Minnesota Department of Natural Resources (DNR) and Blue Water Science, began after zebra mussels were first detected in Wayzata Bay in 2010. Early in 2011, the MCWD placed two monitoring devices at each of 32 sites from Grays Bay to Halsted Bay to measure the spread of this invasive species. The findings will help create a more accurate map of where zebra mussels are located in the lake.

During monthly checks of the monitoring devices during spring and summer 2011, researchers found zebra mussels present on the west side of the lake including South Upper Lake and West Arm. At the same time, they observed higher numbers of zebra mussels in the lake’s eastern bays with Grays Bay, Robinsons Bay and St. Louis Bay showing the highest average monthly totals.

Local residents and lake service providers have assisted researchers by providing their observations of zebra mussels on their boats, docks and recreational equipment.  These findings, which were reported to the Minnesota DNR, reflect the results of the MCWD sampling (see attached maps). 

The three-year study will provide scientists with insight into the extent of the zebra mussel infestation and will establish baseline information to help better understand and manage the spread of this invasive species in the future.

“The rapid spread of zebra mussels in Lake Minnetonka shows how prolific they can be,” said Minnesota DNR Invasive Species Unit Supervisor Luke Skinner. “Over time, this monitoring effort and the work MCWD is doing will provide key information on the spread and impact to this lake and other lakes infested in the state.”

For more information on zebra mussels and this research, including study locations, results and photos, visit www.minnehahacreek.org.