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Aquatic invasive species: more than just zebra mussels

Even a small piece of Eurasian watermilfoil is enough to start a new plant in a previously uninfected lake.

Between billboards on the highway and notice signs on boat landings, zebra mussels get a lot of attention as an aquatic invasive species (AIS).

Though zebra mussels are the most common AIS in the lakes area, it is important to be aware of other species that can be harmful to a lake's fragile ecosystem. Many AIS can be unwittingly transported from lake to lake by boats or fishing equipment, posing a danger to lakes seemingly distant from infested waters.

"There is a value in being aware of these species as well as being able to spot them," said Mark Ranweiler, an assistant aquatic invasive species specialist for the Minnesota Department of Natural Resources.

Eurasian watermilfoil, for example, is an aquatic plant that can grow so thickly both underwater and on the surface that it can interfere with water recreation, and has the potential to crowd out important native water plants.

It can be tricky to identify, because it looks quite similar to the native northern watermilfoil. The key is that the Eurasian variety has 12 to 21 pairs of leaflets on each leaf, whereas the northern variety has only five to nine.

"Any of these species can spread fairly easily," said Ranweiler. "For example it only takes a small plant fragment of Eurasian watermilfoil to start a new plant."

The spiny waterflea gobbles up zooplankton, which are an important food for native fish. The Minnesota Department of Natural Resources reports that in some lakes, spiny waterfleas have "caused the decline or elimination of some species of zooplankton."

The critters like to collect on fishing lines and downrigger cables in gelatinous globs, and often clog up the eyelets of fishing rods. They are whitish with black spots, and appear bristly.

Faucet snails, on the other hand, are dangerous because of their role as a host organism for fluke worms that can cause death in ducks and coots. When birds eat the snails, the worms are able to develop and attack internal organs.

The tiny mollusks can also compete with native snail populations, and potentially clog water intake pipes and other equipment.

Hard to identify for non-experts, faucet snails are generally smaller than a half inch in length, are light brown to black, and have four to five whorls in the shell. They're often found on rocky shorelines, plants, docks, and the bottoms of water bodies.

Ranweiler said anyone who thinks they may have found an AIS should take a specimen in a bag or container to keep it intact, take a photo of the suspected infestation, mark the exact location on a map or GPS, and contact a local DNR office immediately to arrange transport to the office.

For more information about area aquatic invasive species visit