Well, chalk up another invasive species in Minnesota's most popular walleye lake.

The Minnesota Department of Natural Resources issued a release this week saying its staff discovered spiny waterfleas in Lake Mille Lacs last week. Zebra mussels, another invasive species, already is in the lake and officials have been trying to educate boaters and anglers about that problem.

Now they have another that could impact the lake. It's the first time s
piny waterfleas have been found in Minnesota outside of Lake Superior and U.S.-Canadian border waters, including Lake of the Woods, Rainy Lake and Namakan Lake. Definitely not good news.

Here's what the DNR news release says:

Spiny waterflea impacts to lake ecosystems are largely unknown. The waterfleas compete with small fish for food called zooplankton. While larger fish eat them, tiny fish may not be able to consume this invader. In certain types of lakes, they can change the species and numbers of zooplankton, which may harm those lake ecosystems.

However the waterfleas can collect in masses, sticking to fishing lines, downrigger  cables and anchor lines. The masses can resemble gelatin or cotton batting with tiny black spots, which are the creatures' eyes or eggs. Individual animals are difficult to distinguish without magnification because they are only 1/4 to 5/8 inch long.

The spiny waterfleas in Lake Mille Lacs were first observed collecting on fishing lines in the water. The find was later confirmed from water samples collected by the DNR.

"Spiny waterfleas can spread when boats, fishing or bait harvesting gear become contaminated with egg-laden females or when water from the infested lakes and rivers is transported," said Rich Rezanka, DNR invasive species specialist. "Although the waterfleas may die between fishing trips, they might be carrying resting eggs that can begin a new infestation."

Spiny waterfleas are zooplankton - microscopic crustacean animals like the Daphnia in lakes. They have a long tail spine with up to three pairs of barbs sticking out of it. As a predator, they eat other zooplankton, and they often can become abundant in late summer and fall.

Anglers are often the first to discover spiny waterfleas because they become tangled to fishing gear. The waterfleas can be a nuisance to anglers, collecting in gobs on fishing lines.

In response to this new infestation, the DNR will:

  • Update the signs at water accesses on Mille Las to indicate the presence of the waterfleas.

  • Continue watercraft inspections and enforcement efforts around the lake that were increased in 2009 due to zebra mussels.

  • Provide area business with information on spiny waterfleas.

  • Regulations prohibiting the transport of water and requiring draining of livewells, bait containers, and bilges are already in effect at the lake due to its zebra mussel infested water designation.

  • Monitor spiny waterflea populations as part of an assessment of impacts to the lake.

Before leaving the water access, boaters and anglers should:

  • Remove aquatic plants and animals, including gelatinous or cotton-batting-like material from fishing lines, downrigger cables, anchor ropes or waterfowling decoy cords.

  • Drain water from livewells, bait containers, and bilges by removing the drain plugs (Those who want to keep live bait must replace lake or river water with tap or spring water).

Boaters and anglers should also:

  • Dispose of unwanted live bait in the trash.

  • Spray the watercraft and gear with hot high pressure or hot tap water for several minutes before transporting to another water or;

  • Dry the watercraft and gear thoroughly for at least 24 hours and preferably five days before transporting to another waterway.

Experts believe spiny waterfleas originally arrived in the U.S. from Eurasia in the ballast water of cargo ships. They were first found in Lake Superior in 1987.


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