The Minnesota Department of Natural Resources has confirmed the invasive algae starry stonewort in West Lake Sylvia in Wright County.

DNR invasive species staff confirmed sparse to moderate growth of starry stonewort among a heavy population of native plants at the southwest public access on the lake. A wider search indicated the invasive species has apparently not spread beyond the immediate access area. Potential treatment options are being pursued this fall.

Starry stonewort are grass-like algae that may produce dense mats, which could interfere with use of the lake. The invasive algae also may choke out native plants.

Starry stonewort is typically spread by lake users who transport fragments of the plant from an infested body of water. This new infestation reminds boaters and anglers to follow Minnesota laws to prevent the spread of aquatic invasive species:

• Clean aquatic plants and animals from watercraft.
• Drain all water by removing drain plugs and keep drain plugs out while transporting watercraft.
• Dispose of unwanted bait in the trash.

Some invasive species are small and difficult to see at the access. To further reduce the risk of spread, take one or more of the following precautions before moving to another waterbody, especially after leaving infested waters:

• Spray with high-pressure water.
• Rinse with very hot water (120 degrees F for at least two minutes or 140 degrees F for at least 10 seconds).
• Dry for at least five days

More information about aquatic invasive species and how to report them is available atwww.mndnrgov/ais.

Can be introduced from classroom or hobbyist aquariums, crayfish boils

Two red swamp crayfish have been found in Tilde Lake in Clay County in northwestern Minnesota. It is the first time the invasive species have been confirmed in a Minnesota lake, according to the Department of Natural Resources. 

The live specimens have been removed and DNR fisheries staff are searching the lake to see if there are others.

“Many aquarium animals and plants are invasive species that can cause serious harm if released into the wild,” said Heidi Wolf, DNR invasive species unit supervisor.

Wolf said the red swamp crayfish is a good example of a prohibited invasive species that some online retailers ship to unsuspecting teachers for classroom aquariums or to people hosting ‘crawfish boils.’

A permit is required to import crayfish – or almost any aquatic animals – for any purpose, and without a permit it is illegal to import or possess red swamp crayfish in Minnesota, she said. “We recommend people contact the DNR about legal alternative species.”

Red swamp crayfish compete with native species for habitat and eat tadpoles, snails and other small aquatic animals. Their burrowing habits make them extremely difficult to remove and cause damage to levees, dams and water control structures.

Prohibited species like red swamp crayfish cannot legally be possessed, released into the wild, used as bait, or transferred to others. The recommended and most humane method of disposing of them is to put them in a plastic bag in the freezer for a day, then put the bag into the trash.

“We recommend teachers check the prohibited invasive species list before committing to classroom aquarium animals,” Wolf said. “We also encourage teachers to discuss invasive species with their students.”

More information about prohibited and regulated species and what to do with them is available on the invasive species laws page.

Zebra mussels confirmed in 4 Minnesota lakes

Time of year to carefully check docks and lifts

The Department of Natural Resources has confirmed four new reports of zebra mussels in Minnesota lakes: Lake Sallie in Becker County; Lake Andrew in Douglas County; Lac qui Parle in Chippewa, Lac qui Parle and Swift counties; and Big Birch Lake in Todd and Stearns counties.  

“New zebra mussel infestations are often discovered at the end of the boating and fishing season, when docks and lifts are being taken out of the water,” said DNR invasive species unit supervisor Heidi Wolf. “It is important to carefully check for zebra mussels on docks and lifts, and Minnesota law requires that they be allowed to dry for at least 21 days before they can be placed in another body of water. If docks and lifts can be left out of water over winter before being installed in a new water, that’s optimal.”

DNR invasive species specialists confirmed zebra mussels at three locations in Lake Sallie in Becker County. The initial report came from a lake property owner who spotted a half-inch zebra mussel on his dock. Lake Sallie is downstream of Detroit Lake, where zebra mussels were confirmed earlier this year.

DNR invasive species specialists confirmed zebra mussels on offshore buoys in Lake Andrew in Douglas County. In follow-up searches, DNR staff confirmed additional zebra mussels at a public access about a mile from the first confirmed site.

Invasive species specialists also confirmed zebra mussels in Lac qui Parle Lake, a reservoir on the Minnesota River in western Minnesota. The reservoir flows through portions of Chippewa, Lac qui Parle and Swift counties. DNR staff are conducting searches on waters downstream of the reservoir.

DNR invasive species specialists confirmed one adult zebra mussel at the county access on the southeast side of Big Birch Lake, in Todd and Stearns counties. Numerous young zebra mussels were found at a lakeshore property about one-third mile from the access.

Zebra mussels are an invasive (non-native) species that 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.

Less than two percent of Minnesota’s 11,842 lakes are listed as infested with zebra mussels. To protect the state’s waters from the spread of invasive species and the environmental, recreational and economic damage they cause, Minnesota law requires boaters and anglers to:

• Clean their watercraft of aquatic plants and prohibited invasive species.
• Drain all water by removing drain plugs and keeping them out during transport.
• Dispose of unwanted bait in the trash.

Some invasive species are small and difficult to see at the access. To remove or kill them, take one or more of the following precautions before moving to another body of water, especially after leaving infested waters:

• Spray with high-pressure water.
• Rinse with very hot water (120 degrees Fahrenheit for at least two minutes or 140 degrees Fahrenheit for at least 10 seconds).
• Dry for at least 5 days.

More information is available on the aquatic invasive species page.