Zebra mussels appear to have made their way into two more Minnesota lakes: Rainy Lake near International Falls and Horseshoe Lake in Crow Wing County.
The Minnesota Department of Natural Resources confirmed that four of five water samples taken from Rainy Lake in July contained zebra mussel larvae, suggesting that there's a reproducing population of the invasive species there.
About one third of the lake, which straddles the Minnesota-Canadian border, is within Voyageurs National Park. The invasive species larvae were found in waters outside the park's boundaries.
The DNR has contacted the Canadian government, the National Park Service and the Bois Forte Band of Chippewa about the discovery.
The samples were a follow-up to a report in July 2020 that a single adult zebra mussel had been found. The DNR, however, didn't find zebra mussels in the lake at that time and none of the microscopic zebra mussel larvae were found in water samples.
The DNR also has confirmed that zebra mussels are in Horseshoe Lake, near the city of Crosslake. A watercraft inspector found adult zebra mussels attached to an aquatic plant that was removed from a boat and trailer at the lake's public access.
DNR aquatic invasive species specialists also found more at opposite ends of the lake's west bay during a follow-up search.
Zebra mussels can compete with native species for food and habitat, cut the feet of swimmers, reduce the performance of boat motors and cause expensive damage to water intake pipes.
