On July 17 of 2017 zebra mussels were confirmed in Comfort Lake, Minnesota. A vigilant resident discovered what she thought was a zebra mussel on July 12 attached to a piece of submerged wood. The same resident found a second mussel on July 15 at another location on Comfort Lake. The Minnesota DNR then confirmed that the mussels were indeed the dreaded zebra mussel.
Zebra mussels are not native to North America. They came over from their home range in Europe, probably in the ballast water in ships. They were first identified in Lake Erie in 1988. Within a year, they were found in the Duluth harbor.
Zebra mussels are very small when compared to our native mussels. Adults are ¼ to ½ inch long and are usually attached to anything that has been underwater, including native muscles.
It took a long time for zebra mussels to become a problem. This is typical with non-native species. They first arrive and are present in very small numbers. The population grows very slowly for several years before it suddenly explodes.
It’s usually during this explosion that we notice the species and find out that it’s causing harm. Between 1988 and 2014, only about 100 of our 10,000 lakes were known to be infested with zebra mussels. Now, the DNR has over 415 water bodies listed as “infested.”
As the population reaches that explosion point, we could see it move rapidly (or discover that it’s already in many of our lakes).
Boaters might have a say in the spread of this invasive species. If you enjoy floating on Minnesota’s many waters, you probably already know about the precautions that boaters need to follow whenever transporting their boat or docks. Anything that has been submerged in the water of an infested lake could have zebra mussel adults and their offspring, which are nearly impossible to see.
Prevent the spread of zebra mussels by draining all water from your boat, clean off any weeds or wood debris, and dispose of any extra bait in the trash. If you want to move your dock to a different lake, take the dock out for a minimum of 21 days so that it can dry; the zebra mussels will die.
Vigilance is key to keeping our waters free from these aquatic invaders.
You can become a zebra mussel monitor with the MN DNR. Report your findings online at http://www.dnr.state.mn.us/volunteering/zebramussel_monitoring/index.html.
For more information about zebra mussels and to check if your lake is infested, visit the MN DNR’s website http://www.dnr.state.mn.us/invasives/aquaticanimals/zebramussel/index.html.
Susan Humble is administrative assistant at Chisago Soil & Water Conservation District.