Teams of divers this week found a total of 10 zebra mussels in a second search of Christmas Lake. None of the 10 were found in the area treated late last year, the Minnesota Department of Natural Resources said.
“The follow-up searches suggest that the treatment in the Christmas Lake public access area was effective in eliminating mussels from the area,” said Keegan Lund, DNR aquatic invasive species specialist. “Unfortunately, we found zebra mussels outside the treatment area. These zebra mussels have probably been attached to native mussels in the lake since last summer or fall.”
The 10 zebra mussels were removed from the lake, and monitoring will be ongoing. The DNR will review all data collected and determine whether any further response is feasible and necessary.
A search in April indicated successful treatment of a small, isolated infestation of zebra mussels that was detected early. However, the more extensive shoreline and underwater dive searches Wednesday and Thursday revealed the invasive species was present in very small numbers outside the treatment area. The searches were organized by the Minnehaha Creek Watershed District (MCWD), with divers from the DNR, MCWD, Blue Water Science and Waterfront Restorations, and the University of Minnesota.
The treatment in the public access area of Christmas Lake in the city of Shorewood was one in a series of rapid responses by the DNR and other partners that have targeted small, isolated, and recently detected infestations of zebra mussels. Previous rapid response treatments of isolated infestations in other lakes have produced mixed results. Information gained from these treatments and searches will help the DNR determine when, where, and how to treat new zebra mussel infestations most effectively.
To that end, the DNR will be considering pilot projects to manage newly detected, isolated zebra mussels in other bodies of water this season. An assessment framework has been developed and more information will be gathered as the pilot projects are initiated. Lund stressed that pilot projects are only feasible for small, isolated infestations of zebra mussels that are detected early.
DNR officials said the key to any future pilot projects is the partnership between local governments, researchers, and the DNR. In the case of Christmas Lake, the combined efforts of the Minnehaha Creek Watershed District, the city of Shorewood, and invasive species researchers from the University of Minnesota working closely with DNR staff was critical to effectively treating the public access area infestation discovered last August.
Last year’s treatment of the public access area in Christmas Lake consisted of three parts. Zequanox, a natural substance highly selective to zebra and quagga mussels, was first applied to the treatment area in September. That application was followed by a copper treatment of EarthTec QZ in October and November. In December, a contractor working with the DNR injected 1,000 pounds of potassium chloride (potash) under the ice near the public boat access. It was only the third time potash was used for zebra mussel control in the United States. The applications of potash and EarthTec QZ were experimental, off-label uses requiring special emergency permission.
Boaters, anglers and lakeshore property owners have a vital role in the Minnesota partnership to prevent the spread of invasive species. Cleaning boats and trailers, draining boats and live wells, and disposing of unused bait in the trash are the most effective strategies and are required by law. Property owners are legally required to follow a 21-day drying period before transporting docks or related equipment to another lake.
Zebra mussels are an invasive species that can crowd out native mussels and compete for food sources with other aquatic animals such as larval fish. They attach to boat hulls and other water-related equipment, can create a hazard for swimmers due to their sharp shells, and can pose a significant challenge for water intake operators.
For more information about aquatic invasive species, go to the Web page.