2019 Boat Launch AIS Inspection Hours

Aquatic Invasive Species (AIS) inspections are done May 1 – December 1 by DNR trained AIS inspectors during the following hours. The public boat launches are locked during non-launch hours.

Zebra Mussel Sampler

May 1 – September 15
Daily:  6 am–10 pm

September 16 – October 14
Daily:  6 am–9 pm

October 15 – November 3
Daily:  7 am–8 pm, Inspector On-Call*

November 4 – December 1
Daily:  8 am–6 pm, Inspector On-Call*

*On-Call Program (October 15 – December 1)

During our fall on-call inspection program please call the following numbers to get an inspection.

  • Bde Maka Ska (formerly Lake Calhoun): 612-346-5547
  • Lake Harriet: 612-346-5547
  • Lake Nokomis: 612-346-5428

Boat launches will be open for each boater who calls for entry and exit inspections. Wait time is generally less than 10 minutes. Appointments not accepted. Boaters not exiting the lake by closing time must secure their boat and return for it the next day.

Help Protect Your Waters

If you are a lake user please do your part to prevent the transport of AIS from one lake, river or creek to another. Protect Minnesota’s waters by following the state AIS laws.

MPRB’s Watercraft Education and Inspection Program

In April 2013 the MPRB implemented a Watercraft Education and Inspection program. All watercraft and water related equipment passing through boat launches at Lakes HarrietNokomis, and Bde Maka Ska are required to have inspections looking for aquatic invasive species (AIS).  Boats launched from the shoreline are not required to have an inspection. Boat launches are closed when inspectors are not on site. Be sure to check for current boat launch hours prior to your visit. In addition to watercraft inspections, the MPRB also implements the following actions to prevent the spread of AIS:

  • AIS education and outreach
  • Boat launch usage data collection at the launches
  • Signage and additional trash receptacles to encourage proper bait disposal at launches, fishing docks, and high use shoreline fishing areas
  • Early AIS detection monitoring
  • Staff education
  • Developed an AIS Rapid Response Plan

AIS Prevention in the Future

Park Board staff will continue to evaluate and improve its AIS prevention program from year to year. AIS inspectors collect data during inspections to help inform decisions about future efforts.


Under Minnesota law, it is illegal to transport aquatic plants and animals as well as water, to and from water bodies. Failure to comply with Minnesota AIS regulations can result in fines up to $1,000.

You Must:

Clean visible aquatic plants, zebra mussels and other prohibited species from watercraft, trailers, and equipment before transporting from any water access. Drain water from bilge, live well, motor, ballast tanks, and portable bait containers before leaving water accesses or shoreline property. Dispose of unwanted bait in the trash or refill bait container with bottled or tap water. Keep drain plug out and water-draining devices open while transporting watercraft.

You May Not:

Transport aquatic plants, water, or prohibited invasive species such as zebra mussels or Eurasian watermilfoil.

Dump live bait into state waters, on shore, or on the ground.
Launch, or attempt to place watercraft, trailers or equipment with aquatic plants, zebra mussels, or prohibited invasive species into any state waters.

SCUBA Diving Permits

If not properly cleaned, drained, and dried, SCUBA diving equipment has the potential to spread aquatic invasive species between waterbodies. Once a lake is infested with zebra mussels or other invaders, SCUBA diving can be hindered by increased plant growth, dense mussel growth on underwater attractions, and sharp mussel shells that may damage dive clothing and equipment. If you plan to SCUBA dive on any MPRB waterbody, you must first obtain a permit and take the necessary precautions to prevent the spread of AIS.

SCUBA and Aquatic Invasive Species Brochure [PDF]
SCUBA Permit Frequently Asked Questions [PDF]

Apply for a SCUBA diving permit

Additional Recommended Precautions:

To remove or kill hard-to-see aquatic invasive species before moving to other water bodies the following is advised:

  • Spray watercraft and water-related equipment with high-pressure water and rinse with very hot water and/or
  • Dry boats and water-related equipment for at least five days
  • Report new sightings of aquatic invasive species. If you suspect a new infestation of an invasive plant or animal, save a specimen and report it to a local natural resource office.

Additional AIS Prevention Information

AIS Threat to Minneapolis Waters

Minnesota’s waterways are threatened by a number of aquatic invasive species (AIS). AIS are not native to Minnesota. They can cause economic and environmental harm as well as having negative impacts on human health. Once an AIS is established it is nearly impossible to eliminate. The Minneapolis Park and Recreation Board (MPRB) is taking steps to ensure that our water resources can be enjoyed for years to come by committing to AIS prevention efforts. The MPRB has been actively monitoring AIS since the late 1980s when Eurasian watermilfoil was first discovered in the Chain of Lakes. Some of the City’s water bodies do contain AIS, such as Eurasian watermilfoil, zebra mussels, and common carp. There are, however, several species that have not established themselves in our lakes. New infestations of AIS occur in neighboring lakes and rivers throughout the state and MPRB’s inspection program is designed to slow the spread of those species as long as possible without restricting boater access to the lake. Visit the DNR’s website for the most up-to-date infested waters list, detailed biological information and current regulations on aquatic invasive species. Successful aquatic plant management is key to providing recreational opportunities in Minneapolis lakes. Plants that grow in and around water can have an impact on the long-term health of our area lakes. For this reason, the MPRB completes aquatic plant surveys on lakes every two to three years. These surveys document the increase or decrease in current aquatic plant species and changes in biodiversity.

View the MPRB Water Resources Report for detailed annual monitoring data, data collection methods, and more.

mechanical harvester boat

Mechanical Harvester

AIS Management Methods


Harvesting is currently the best management option that the MPRB has to control aquatic plants, including Eurasian watermilfoil, an aquatic invasive species that is prevalent in many Minneapolis lakes. Minnesota DNR-issued permits limit the area of milfoil that can be harvested each year. Harvesting is done primarily in swimming areas and around boat launches. A machine called a mechanical harvester removes plants that are in the top six feet of water. This temporarily allows for trouble-free boating and swimming, and allows sunlight to penetrate to native plants below.

divers pulling eurasian watermilfoil
Divers using SCUBA gear hand pull plants in areas that are inaccessible or hard to reach with a mechanical harvester.

MPRB uses a variety of early detection techniques to search for newly established populations of AIS in Minneapolis lakes and streams. Some of the techniques are specific to zebra mussels while others can detect a variety of plant and animal invaders. The following early detection techniques were used in 2019:

Zebra Mussel Settling Plates

Zebra mussel settling plates are devices that are hung from docks and used to detect zebra mussels after they complete their juvenile veliger life stage. MPRB staff and volunteers from the Friends of Lake Nokomis monitored zebra mussel settling plates at the following lakes in 2019: Wirth, Bde Maka Ska, Harriet, Nokomis, and Hiawatha.

No zebra mussels were detected at Wirth, Bde Maka Ska, Harriet, and Nokomis. The Lake Hiawatha sampling plate was covered with several thousand zebra mussels by the end of the open water season. This was expected since Lake Hiawatha has been heavily infested with zebra mussels for several years. Despite this, a settling plate continues to be deployed in Lake Hiawatha to monitor the population.

Buoy Inspections

Similar to settling plates, beach buoys and sailboat buoys serve as a suitable growing surface for zebra mussels. MPRB watercraft inspectors inspected all of the beach buoys from Cedar Lake, Bde Maka Ska, Lake Harriet, and Lake Nokomis after they were removed from the lakes in the fall. No zebra mussels were observed.

MPRB watercraft inspectors were also able to inspect 90% of the sailboat buoys at Bde Maka Ska, Lake Harriet, and Lake Nokomis as they were removed in the fall. No evidence of zebra mussels or any other unexpected AIS was observed.

Zebra Mussel Veliger Sampling

MPRB staff use nets to search lakes for juvenile zebra mussels called “veligers” during late-summer months. The nets collect water samples which are sent to a specialized laboratory that can search for veligers using microscopes. Water samples were collected and analyzed for veligers according to the following schedule in 2019:

Late-June Late-July Early-August Late-August Early-September
Bde Maka Ska X X X X X
Harriet X X X X X
Nokomis X X X X X
Cedar X X X
Isles X X X
Wirth X X X

X = Sampling occurred; Samples tested negative for zebra mussel veligers
Blank cell = Sampling did not occur

As depicted above, all samples tested negative for the presence of zebra mussel veligers.

Weekly Boat Launch Surveys

Once per week from July to September, specially trained staff conducted surveys of the boat launches at Bde Maka Ska, Lake Harriet, and Lake Nokomis. The surveys involved entering the water while wearing waders and a life jacket and inspecting the dock, the boat ramp, plants, rocks, sticks, and other debris for approximately a half hour. The staff used the surveys to look for a variety of plant and animal AIS. No unexpected AIS were observed during the surveys.

Meander Plant Surveys

MPRB staff performed meander surveys of aquatic plants at Brownie Lake, Cedar Lake, Lake of the Isles, Bde Maka Ska, Lake Harriet, Lake Nokomis, and Lake Hiawatha in June. For each survey, staff boated around the entire perimeter of each lake and periodically collected rake toss samples of the aquatic plant community. Rake tosses from shore were also performed at Diamond Lake, Grass Lake, Powderhorn Lake, Spring Lake and Wirth Lake. Relative abundancies of native and invasive plant species were made via visual observation and rake toss sampling and recorded on a lake map. No new invasive plant species were detected.

SCUBA Survey

Staff from MPRB and partner organizations conducted SCUBA and wading surveys for zebra mussels at Bde Maka Ska and Lake Harriet on September 19th. In all, 9.3 hours of searching was conducted at Bde Maka Ska and 2.2 hours of searching was conducted at Lake Harriet and no zebra mussels were found.

Environmental DNA (eDNA) Study

MPRB received an $8,000 AIS Prevention grant from Hennepin County to conduct environmental DNA (eDNA) sampling for zebra mussels in 2019. Sampling was conducted on the following schedule:

July September
Bde Maka Ska X X
Harriet X X
Nokomis X X
Cedar X
Isles X
Hiawatha P

P = Sampling occurred; Samples tested positive for zebra mussel DNA
X = Sampling occurred; Samples tested negative for zebra mussel and quagga mussel DNA
Blank cell = Sampling did not occur

All samples were filtered by MPRB staff at the Southside Operations Center and sent to a molecular biology laboratory for analysis. The samples were analyzed for zebra mussel and quagga mussel DNA using quantitative polymerase chain reaction (qPCR). The only samples that tested positive for zebra mussel DNA were those collected from Lake Hiawatha. No samples tested positive for quagga mussel DNA.


MPRB uses a suite of early detection tools to search for zebra mussels and other AIS. Early detection techniques did not detect any new AIS infestations in 2019 and only found zebra mussels in Lake Hiawatha – a lake that was already known to have an established population. That said, it is nearly impossible to prove that zebra mussels are not in a lake, so MPRB plans to continue treating Bde Maka Ska, Lake Harriet, and Lake Nokomis as if they are infested with zebra mussels. This will help prevent the spread of zebra mussels to other lakes.

MPRB’s AIS early detection program will continue in 2020.

Species Currently Found in Minneapolis Waters

Eurasian Watermilfoil (Myriophyllum spicatum)

eurasian watermilfoil
Eurasian watermilfoil is a non-native aquatic invasive species that has been an ongoing concern in several Minneapolis lakes. From an ecological standpoint it outcompetes native species and alters the habitat for fish and other organisms. Milfoil grows vigorously in water less than 16 ft. and often forms dense floating mats that interfere with boating and swimming. The MPRB participates in aquatic plant management to allow for the many recreational opportunities available on our Minneapolis lakes. Eurasian watermilfoil can be easily transported from one lake to another on boats and trailers. Boaters should be aware of this problem and clean all aquatic vegetation from boat, trailer and motor parts before leaving the boat launch.

Curly Leaf Pondweed (Potamogeton crispus)

Curly Leaf Pondweed (Potamogeton crispus)
Curly leaf pondweed was first documented in MPRB lakes in 1974. This species likely hitchhiked to North America with European carp, an intentionally introduced species.  Both have subsequently become invasive throughout Minnesota. Curly leaf pondweed has an unusual life cycle in that it is an annual that begins growing under the ice and dies off in June. In a spring that follows a mild winter curly leaf pond weed can produce mats of vegetation that cause a nuisance for lake users. In harsh winters this plant shows lower levels of growth.

Purple Loosestrife (Lythrum salicaria)

Purple Loosestrife (Lythrum salicaria)
Purple loosestrife (Lythrum salicaria) is a perennial featuring long spikes of colorful purple-pink flowers that begins blooming in July. Records show that Purple loosestrife has been in North America since the 1830s. The plant came to North America in the ballast of ships from Europe and was also introduced as a medicinal and ornamental plant. In Minnesota, records show that in the 1920s several garden clubs introduced purple loosestrife into wetlands for “beautification” purposes. Purple loosestrife invades wetland and lakeshore habitats, displacing native plant communities and destroying habitat and food sources for waterfowl and other wetland wildlife. Producing half a million seeds per square meter allows purple loosestrife to easily re-establish itself.

Yellow Iris (Iris pseudacorus)

The yellow iris is a regulated invasive species in Minnesota. This Eurasian species is sold commercially for use in garden pools but when it escapes it competes with native shore land vegetation. Residents should take care not to allow aquarium and landscape plants or animals to escape into the surrounding environment.

Flowering Rush (Butomus umbellatus)

Flowering Rush (Butomus umbellatus)
Flowering rush is actively expanding throughout southern Canada and the northern United States and is on the Minnesota DNR Prohibited Invasive Species list.  This Eurasian plant has been sold commercially for use in garden pools. Flowering rush is very aggressive and competes with native shore land vegetation.

Reed Canary Grass (Phalaris arundinacea)

Reed canary grass is a major threat to natural wetlands. It outcompetes most native species and forms large, single-species stands, with which other species cannot compete. This Eurasian species has been planted throughout the U.S. since the 1800s for forage and erosion control. While many Minnesota state agencies have removed it from their planting lists, it is still being planted in the state.

Zebra Mussels (Dreissena polymorpha)

Zebra Mussels (Dreissena polymorpha)
Zebra mussels are freshwater bivalve mollusks native to southeastern Russia. They hitchhiked to North America in ballast water from the Black Sea and were first identified in the Great Lakes in 1988. By 1990 they were established in all of the Great Lakes and began to move into major river systems.  By 1992, zebra mussels became established in the Mississippi River. In 2010, zebra mussels were confirmed in Lake Minnetonka and at the outlet to Minnehaha Creek. Lake Hiawatha is directly connected to Minnehaha Creek and Nokomis has close proximity but is physically separated by a weir. Both Hiawatha and Nokomis were designated infested due to their connection/proximity to Minnehaha Creek. Zebra mussels were discovered on a sampling device in Lake Hiawatha in 2013 confirming the designation. One live, adult zebra mussel was discovered on September 8, 2017 by MPRB staff on a boat cover recovered from the bottom of Lake Harriet. After the initial discovery, no additional zebra mussels were found after 67 hours of searching.  Lake Harriet has been designated as infested and will continue to be monitored closely as part of the MPRB AIS early detection program.  Learn more about the zebra mussel in Lake Harriet. Zebra mussels spread easily because of their biology. Unlike native mussels, zebra mussels do not need a larval host. Faster growth rates and a shorter time to maturity also give non-native zebra mussels an advantage over native mussels. They can attach themselves to any solid surface (including: pipes, boat hulls, rocks, wood, vegetation, other mussels) and can significantly alter the ecology of a waterbody. There are no practical ways to eradicate zebra mussels from a natural system once they are established. The DNR website provides additional useful information about the infestation of zebra mussels in Minnesota. The MPRB has developed a Zebra Mussel Action Plan [PDF] to guide the organization on prevention efforts against further infestations.

Chinese Mystery Snails (Bellamya chinensis)

Chinese Mystery Snails (Bellamya chinensis)
Chinese mystery snails have been identified by the DNR in Loring Pond, Grass Lake, and Powderhorn Lake. This snail is native to Asia, was introduced to California in 1892, and was found on the east coast of the United States by 1915. This species has the capability of growing to high densities and tends to have boom and bust cycles. When the population reaches the bust portion of the cycle, large concentrations of dead snails can ring the shoreline. This species is a popular aquarium snail, and when found, is likely an aquarium release.

European Carp (Cyprinus carpio) and Goldfish (Carassius auratus)

Each of these species can reproduce to very high densities. These bottom-feeding fish are capable of disturbing lake beds to the extent that water quality can be diminished. Lakes with an overgrowth of European carp typically have high phosphorus concentrations, low water clarity, and little to no aquatic plant growth. Carp eat vegetation and can alter or destroy the aquatic plant community in a lake.

Species of Concern to Minneapolis Waterways

Brazilian Waterweed (Egeria densa)

Brazilian Waterweed (Egeria densa)
In August of 2007, Brazilian waterweed was identified in Powderhorn Lake. This species is native to South America and used extensively in aquariums and water gardens. It is likely that it was introduced into the lake through an aquarium release. The DNR treated the stands of waterweed with an herbicide approved for aquatic use, and it has not been seen in Powderhorn since this treatment. Residents are encouraged to dispose of aquarium and water garden plants and animals as recommended by the MNDNR rather than releasing them into Minneapolis waterways where they can do extensive damage to the environment.

Other Aquatic Invasive Species of Concern

The Minnehaha Creek Watersheds Least Wanted list gives detailed information about the following AIS that are of concern to the Minneapolis Park and Recreation Board:

  • Asian carp
  • Hydrilla
  • Brazilian elodea
  • New Zealand mud snail
  • Quagga mussels
  • Round goby
  • Rusty crayfish
  • Spiny water flea
  • Starry stonewort
  • Viral Hemorrhagic Septicemia (VHS)

Frequently Asked Questions about the MPRB AIS Watercraft Inspection and Education Program

What is the goal of the program?

The best way to manage aquatic invasive species (AIS) is to keep them out of water bodies in the first place. Once AIS enter a water body, they are extremely difficult, if not impossible, to remove. The MPRB’s goal is to delay the introduction of AIS into Minneapolis water bodies as long as possible in hopes that techniques are developed to control or reduce their impacts. An MPRB board resolution requires an inspection for AIS prior to entry, and upon exit of any water-related equipment at or near the boat launches on lakes Harriet, Nokomis and Bde Maka Ska. The launch hours have been adjusted to reflect launch use data collected since 2013. The public boat launches will be locked during non-launch hours.

When will the inspections and launch hours be in effect?

Visit the Boat Launches and Rentals section for more information about boat launch hours and AIS inspections.

Why is the Park Board concerned about AIS?

AIS threaten native plants and animals, which in turn alters the lake’s ecology. These changes can significantly interfere with both the beauty and recreational use of lakes. Some AIS, e.g. zebra mussels, can also have social impacts, such as cutting the feet of swimmers on beaches.

Isn't it too late to prevent the spread of AIS?

No. While the lakes are already affected by some AIS, including Eurasian watermilfoil, there are still many species, with far worse impacts, that can be prevented from entering and harming the lakes. States that have implemented similar education and inspection programs have significantly slowed the spread of AIS.

Which AIS is the Park Board aiming to keep out of Minneapolis lakes?

The MPRB is focusing its prevention efforts against many invasive species of plant, animal and disease, including many that currently do not occupy Minneapolis lakes, but are present in other bodies of water that Minneapolis lake visitors frequent. Learn more about AIS from the Minnesota DNR.

How does the AIS education and inspection program affect kanoes, kayaks and sailboats?

The AIS education and inspection program affects only watercraft entering and exiting the water at or near a public boat launch. Canoes and kayaks entering the water from storage racks, or watercraft carried over the shoreline at other access points will not require an inspection. Launches will be closed when AIS inspectors are not on site. The inspection program focuses on trailered boats accessing the lake through the launches. However, inspectors do have the authority to inspect any watercraft or water-related equipment entering or exiting water bodies. All sailboats (including trailers, dollies, and gear) participating in a permitted regatta must be inspected when entering and exiting the water, even if they are accessing the lake over the shore rather than the boat launch.

How was the inspection/launch season determined?

Based on data collected since 2013, DNR training dates, and average ice off dates; May 1 was determined to be the best date for opening the launches. December 1 is just before ice on, is the last day of muskie fishing season, and was therefore determined to be the best date for closing the launches.

How long do inspections take?

Most inspections are done relatively quickly and completed in less than five minutes. However, if cleaning is required, boaters may be delayed.

What if I refuse to have my boat inspected?

Boaters who refuse inspections will be denied access from launching watercraft into a lake.

Which lakes or water bodies will be affected by the AIS inspections?

AIS inspections will be enforced on watercraft and equipment accessing launches at Lake Bde Maka Ska, Lake Harriet and Lake Nokomis.

What if I want to go fishing on the lakes before the launch opens or after it closes?

The MPRB firmly supports the position that all boats and equipment using the launches must be inspected when entering and exiting MPRB waters. The launch hours were determined through intensive data collection and analysis of use patterns. Outside of these hours the launches are closed. Watercraft users requiring the public boat launch to exit the lakes will be responsible to exit before the boat launch closes. Watercraft users who choose to remain on the lake after closing will be responsible for securing their watercraft and removing it during public launch open hours the following day. Lake users are welcome to access the lake using watercraft that can be carried over the shore at other access points anytime during open park hours which are 6 am-midnight in areas illuminated by artificial lighting, and 6 am-10 pm in areas without established pathways and illumination by lights.

Can I use my gas-powered motor on any of the lakes?

No. Gas powered motors are not allowed on Minneapolis city lakes. Only electric trolling motors are allowed to be used. If you have a gas powered motor on your boat, it must be propped up and out of the water. Boats with gas powered motors in the water and in use without a permit will be reported to law enforcement.

What is proper bait disposal and how does it protect against AIS?

Although some anglers still might not think twice about dumping leftover live bait into a lake or river when they are done fishing, this transport of water is another pathway for AIS to move from one body of water to another. Most bait species are also not native to Minneapolis lakes so could disrupt the ecosystems. The MPRB and DNR encourage anglers to dispose of live bait in the well-marked trash receptacles available for bait disposal at launches, fishing docks, and high-use shoreline fishing areas throughout the park system. It is illegal to release live bait into a water body as well as to knowingly (or unknowingly) transport water from AIS infested waters.

What can I do to stop the spread of AIS?

Under Minnesota aquatic invasive species laws: You Must:

  • Clean visible aquatic plants, zebra mussels and other prohibited species from watercraft, trailers, and equipment before transporting from any water access.
  • Drain water from bilge, live well, motor, ballast tanks, and portable bait containers before leaving water accesses or shoreline property.
  • Keep drain plug out and water-draining devices open while transporting watercraft.
  • Dump unwanted bait in the trash or refill bait container with bottled or tap water.

You May Not:

  • Transport aquatic plants, water, or prohibited invasive species such as zebra mussels or Eurasian watermilfoil.
  • Dump live bait into state waters, on shore, or on the ground.
  • Launch, or attempt to place watercraft, trailers or equipment with aquatic plants, zebra mussels, or prohibited invasive species into any state waters.