Zebra Mussels Found in Lake Sarah

Lake Sarah, located in northern Murray County, was among a string of Minnesota lakes to be newly added to the list of infested waters within the last week. The discoveries were made as people pulled their docks and boat lifts from the water before winter.

Allison Gamble, DNR invasive species specialist, said the agency has been keeping an eye on the spread of zebra mussels ever since monitoring began. Keeping the aquatic invasive species out of a lake is particularly challenging on popular recreation lakes because so many people use the resource.

Minnesota law requires individuals to clean, drain and dry watercraft before moving from one lake to another. While it isn’t known how zebra mussels were spread to Lake Sarah, unintentionally transporting water from infested lakes could certainly be the culprit.

Gamble said another, perhaps lesser known, way the zebra mussels could have spread was through the purchase of used equipment, such as docks or boat lifts, from someone who used the items in an infested lake. State law requires such equipment to be dry-docked for 21 days before being put in a different lake.

“The best way is to let it overwinter — that’s going to kill everything,” she said.

With this new infestation, Gamble said it’s become clear there is still a segment of the population that needs to be reached with information about the spread of aquatic invasive species.

“It’s still about not moving water, pulling a boat plug, not moving zebra mussels from one lake to somewhere else,” she said.

Less than 3 percent of Minnesota’s lakes are listed as infested with zebra mussels, but once a lake is added to the infested waters list, it’s unlikely to ever be removed.

“At this point, zebra mussels are something you end up dealing with in a lake,” Gamble said. “It’s not really been on the radar for southwest Minnesota. I was hoping it would never have to be on the radar, but unfortunately it is.”

Gamble encourages people to take a photo if they see something they think may be a zebra mussel and submit it to the Minnesota DNR.

Based on the size and quantity of zebra mussels found, it’s believed they’ve been in the lake for at least a full year, maybe longer.

“One lift had 16 attached mussels, which is a lot for a new infestation,” she said.

Because Lake Sarah connects with Lake Shetek through long and winding stream channels, Gamble said a day-long search has already been conducted of the stream channel.

“We’ve searched all the hard surfaces we can find,” she said. “So far we haven’t turned up any zebra mussels, but that doesn’t mean we can be lax.”

On Thursday, a K-9 trained in the search for zebra mussels will be at Lake Sarah and then will be taken to the marina and places on Lake Shetek to check equipment there.

The discovery of zebra mussels in Lake Sarah will lead to some changes in the lake. For one, people will want to wear swimmer socks or some sort of protection on their feet when they are in the lake because the zebra mussels have sharp edges and can cause cuts to skin. Second, the zebra mussels feed on phytoplankton.

“One zebra mussel can filter a liter of water a day. They’re taking that and using it for their growth,” explained Gamble. “That’s the same kind of food juvenile — very young fish — would be eating.

“Lake Sarah is a highly productive lake — there’s a lot of food,” she added.

Gamble is hopeful that research will be done on Lake Sarah to see where the zebra mussels came from. The University of Minnesota is doing a lot of work on zebra mussel genetics in its aquatic invasive species program.

“They can tell, generally, what the source population is, whether from Mille Lacs, Lake Superior, the Mississippi,” Gamble said.

The nearest zebra mussel-infested water body to Lake Sarah is the Iowa Great Lakes at Spirit Lake.