An invasive species we don't often hear much about - the spiny waterflea - has infested one of Minnesota's most popular fishing lakes.
The Minnesota Department of Natural Resources announced Monday that spiny waterfleas have been found in Lake Vermilion, a large and pristine lake on the Iron Range in northeastern Minnesota.
Anglers who were fishing on the lake found some of the tiny creatures and turned them in to the DNR for identification.
Because of the discovery, Lake Vermilion and the Vermilion River are now considered infested waters, and lake users will need to take extra precautions to avoid spreading the species to other bodies of water, the DNR said.
Spiny waterfleas are tiny crustaceans that grow to only 1/4 of an inch or so as adults. They have a single long tail that has small spines along its length, and because of their spiky tail they aren't eaten by predators.
The DNR says spiny waterfleas are considered invasive because they eat zooplankton, an important food source for small fish, and because they reproduce in large numbers.
In some lakes, spiny waterfleas have “caused the decline or elimination of some species of zooplankton," the DNR notes.
The tiny creatures are also an annoyance for anglers, because they collect in large numbers on fishing lines and other water equipment, looking like "gelatinous globs," the DNR said. Those globs can become so large they can clog the eyelets on fishing poles.
Spiny waterfleas have been present throughout the Great Lakes for nearly 30 years; they were introduced by ballast water discharged from ocean-going ships that came from Europe and Asia.
The species has been confirmed in about 60 Minnesota waterways, according to the DNR.
On Lake Vermilion, signs will be posted at all public access points to alert anglers and recreational boaters. Anyone who uses the water will need to clean their boats, trailers and equipment afterward to get rid of any spiny waterfleas, zebra mussels, aquatic plants and other invasive species.
They also must drain the water from their boats and livewells, and dispose of any bait they don't use.
The DNR's aquatic invasive species website has more information on the rules that boaters need to follow to keep from spreading the unwanted plants and animals to other lakes in the state.
Another aquatic invasive - the zebra mussel - has been found in several more waterways in Minnesota this year.
Here's a list of all Minnesota waterways the DNR lists as "infested" with an invasive species.