Zebra mussels are invasive species that compete for food with native mussels and other forms of aquatic life. Their sharp shells also pose dangers for swimmers. They often spread from infected lakes to other areas when they attach to watercraft such as boats.
Areas in Christmas Lake in Minnesota, which were infested with zebra mussels, were first treated in September last year with a bacteria-based pesticide called Zequanox. A copper treatment followed in November and another one in December with the injection of a thousand pounds of potash under the ice.
Efforts to eliminate the invasive aquatic species first appeared to have worked with the Department of Natural Resources initially reporting that there were no longer signs of the zebra mussels in the lake. Ten zebra mussels, however, were found in the lake during a follow-up search outside the treated area.
DNR aquatic invasive species specialist Keegan Lund said that the follow-up searches hint that the treatment in the lake's public area was effective in removing the invasive mussels from the area, albeit this did not fully clear the lake of the invasive species.
Zebra mussels need to be discovered in very early stages so there could be a chance to stop them from spreading. After treatment, inspectors from the DNR extensively searched the ecosystem for signs of the mussels. Officials later confirmed that the treated area was clear although there were zebra mussels that were found in another part of the lake.
"Unfortunately, we found zebra mussels outside the treatment area," Lund said. "These zebra mussels have probably been attached to native mussels in the lake since last summer or fall."
The 10 zebra mussels that were found were removed from the lake, the DNR said, and monitoring will continue. The DNR also said that it will review all the data collected and will determine if further response is necessary and feasible.
DNR representatives likewise admitted that they still do not know if more zebra mussels are lurking because they may still be in their microscopic beginning stages, so preventive measures are recommended.
To prevent the invasive species from spreading, property owners are required by law to follow a 21-day drying period before they can transport docks and related equipment to another lake. Disposing unused bait in the trash as well as cleaning and draining boats are likewise recommended strategies to prevent the spread of the invasive mussels.
