The Department of Natural Resources is declaring the state's fourth-largest lake and its connected waters as infested after two larval zebra mussels were found in a water sample.
The water samples were collected from Lake Winnibigoshish over the summer by DNR fisheries staff, and a recent examination found two zebra mussel veligers in a sample taken near the middle of the lake in the middle of July.
Officials say June, July and August are the prime months for zebra mussel reproduction because the water temperatures tend to stay above the mid-50s.
Fourteen other sets of water samples from the lake did not find any other veligers, and no adult zebra mussels have yet been found; however, the DNR says the sheer size of the lake may make it difficult to find them -- especially since winter conditions don't allow for inspection.
"Although no adult zebra mussels were found, it is prudent and proactive to list Winnibigoshish Lake as infested," said Invasive Species Specialist Rich Rezanka. "The presence of veligers suggests there is likely a reproducing population in the lake."
Rezanka said the listing will allow recreational boaters and anglers to take additional precautions that will prevent any spread, and the DNR is urging all lake users to be vigilant about cleaning water equipment thoroughly before leaving a lake access point.
Lake Winnibigoshish covers 58,544 acres and is visited by thousands of anglers seeking walleye, yellow perch, northern pike and muskie throughout the year -- and it also has several connected waters that are also now designated as infested as well.
Connected waters now designated as "infested" by the DNR are as follows:
More samples will be taken during the spring and summer months, and collection methods will include plankton tows, dives, shoreline searches and coordination on the downstream waters to monitor for potential spread.
Restrictions on bait harvesting and water transportation are already in place for those waters due to a previous infestation designation regarding faucet snails; however, DNR officials say further bait harvest restrictions may be put in place on Feb. 12.