Stopping European frog-bit

By Connor Ford and Erin Mauk

European frog-bit in the field. Photo credit Sigrid Resh.

Michigan’s Upper Peninsula is uniquely surrounded by three of the five Great Lakes and is home to many ecologically diverse and unique Great Lakes coastal wetlands, rivers, shorelines and lakes, in addition to hundreds of natural aquatic attraction sites across 15 counties. Each year, thousands of visitors flock to the UP to take advantage of these sites for recreation including kayaking, boating, fishing, swimming and hunting. Increased tourism has resulted in an increased introduction of new aquatic invasive species to the region. These species threaten the quality of tourism and ecological health of Michigan’s UP. 

One of these new species is European frog-bit, a free-floating aquatic invasive species that can form dense mats, hinder recreational activities and disrupt the movement of waterfowl and fish. Within Michigan’s UP, the prevention and management of this species is a focus of the organizations within the Cooperative Invasive Species Management Areas, one such organization is KISMA. 

Who is KISMA?

Locally, the Keweenaw Invasive Species Management Area (KISMA) has received funding to survey for and educate about invasive European frog-bit. 

“KISMA is an acronym for the Keweenaw Invasive Species Management Area, which is a specific Cooperative Invasive Species Management Area (CISMA) that covers Baraga, Houghton and Keweenaw Counties,” said Sigrid Resh, KISMA’s coordinator, “CISMAs, in general, are tasked with providing education and outreach to our stakeholders for the prevention, identification and management of invasive species across jurisdictional boundaries.”

Resh also said that “KISMA has 22 partners ranging from Tribal, Federal and State entities, such as the Keweenaw Bay Indian Community, the National Forest Service, the National Park Service and the Department of Natural Resources, to regional and local conservancy groups such as The Nature Conservancy, Gratiot Lake Conservancy and the Keweenaw Land Trust. KISMA also works with private landowners and managers within our tri-county area.”

KISMA’s organizational partners.

What is European frog-bit?

One of the new invaders that has made its way to the UP is European frog-bit (Hydrocharis morsus-ranae), a watch-list species prohibited here in Michigan, according to the State of Michigan’s website. European frog-bit is a free-floating aquatic plant that resembles a small lily pad, usually the size of a quarter, and can be found in low-wave action, sheltered sites such as ponds, wetlands, inland lakes, or coves and bays of a river system. It can form dense mats across the water surface while creating a tangled, interweaving mess of roots below. It is currently found in Chippewa and Mackinac Counties in the eastern UP, in addition to northeastern Wisconsin, not far from the Michigan border, according to a 2021 technical report from the State of Michigan regarding the status and strategy for addressing European frog-bit.

European frog-bit plants resemble miniature water lilies. Photo credit: Michigan.gov/invasives

Why manage this species? Why care? 

European frog-bit has numerous impacts on the landscape. According to the state’s technical report, ecological factors include habitat degradation for breeding waterfowl, elimination of fish passage for spawning species, and reduction of light and dissolved oxygen in the water column. Frog-bit also can get caught in boat propellers and impede boat traffic or collect on kayaks and paddles. Just like other aquatic species, this invader spreads primarily through fragmentation, caused by recreational activities like boating or duck hunting. It does not take much for a segment or whole plant to stick to the side of a boat, a piece to be chopped up and left on a propeller, or stuck to the side of a pair of waders. 

“European frog-bit may act as an aquatic hitchhiker, so boaters, anglers, and hunters can unintentionally contribute to its spread,” the state’s technical report reads.  

Plants can form dense mats, often among cattails or other shallow-water vegetation. Photo credit: Michigan.gov/invasives

What’s being done? 

KISMA is surveying local waterways for signs of European frog-bit in cooperation with other UP CISMAs, the Upper Peninsula Resource Conservation and Development Council, and the state of Michigan.

“This is the second year of this species-specific project, and we have not found any European frog-bit in the KISMA yet,” Resh said. “However, it has been found near the Wisconsin-Michigan border and in the eastern UP, so spread to our area is highly possible if our locals and visitors are not aware of the importance of prevention measures, that is, to clean, drain, and dry their aquatic recreational gear and equipment.”

 Resh said they know that not finding European frog-bit so far doesn’t mean they can let their guard down.

“Early detection will be the key to protecting our coastal habitats for our native aquatic species. The more people who know what to look for the quicker our response can be if it is found,” Resh said.

CISMAs are also providing outreach–via workshops, social media, and interviews centered on proper identification and prevention techniques. According to the state’s technical report, in the eastern UP, where European frog-bit has been found, it is being hand-removed. Plants are carefully collected from the water, drained and disposed of in an approved landfill (eliminating the risk of re-introduction elsewhere). Proper decontamination of all field gear always follows survey and removal efforts. 

Is prevention in the Keweenaw still possible?

According to the state’s technical report, proper treatment of invasive species will help control efforts; however, prevention techniques by recreators are the most economical tools available to stop European frog-bit, sometimes referred to as EFB. 

“Over a five-year period in the Town Farm Bay in Vermont, 55.9 tons (50,711.63 kg) of EFB were removed at a cost of $79,000 and 6,208 hours, reducing EFB cover to less than 6%,” according to the state’s technical report. 

As an invasive species occupies more area, more economic resources and time are required to manage it. The most cost- and time-effective stage is the prevention stage, followed by eradication, then containment. Asset-based prevention requires the most money and time because the invasive species has become abundant and widespread. Credit: modified from Hobbs and Humphreys 1995 and DEPI 2013

It is crucial to clean recreational gear, drain livewells and bilges, and dry all watercraft and associated equipment to avoid having to remove adult mats of the plant from recreational and natural areas later. This “Clean. Drain. Dry.” protocol is vital when moving from one waterbody to another.  For more information about how recreators, hunters, and boaters can prevent the spread of aquatic invasive species, visit https://stopaquatichitchhikers.org/prevention/. 

To learn more about European frog-bit visit Michigan.gov/invasives or to locally get involved contact kisma.up@gmail.com or visit KISMA’s website at https://www.mtu.edu/kisma/.