The Minnesota DNR has discovered spiny water fleas in Lake Mille Lacs.
It's the first time this invasive species has been found in the Minnesota, outside Lake Superior and the U.S.-Canadian border waters.
Individual spiny water fleas are tiny, but they collect in masses, sticking to fishing lines. They're tiny crustaceans that eat other zooplankton, and they often flourish in late summer and fall. Scientists are studying what impact they might have on ecosystems.
Earlier this year, zebra mussels were found in Lake Mille Lacs.
The DNR is monitoring both populations in the lake, and urging boaters to clean their boats thoroughly when leaving any lake.
Spiny water fleas probably came to the U.S. from Eurasia in the ballast water of cargo ships. They were first found in Lake Superior in 1987.