Invasive Species

A person kneels on a dock taking notes on a clipboard, while a diver is in the water beside them.
Research can help us understand, remove, and stop the spread of invasive species.

NPS Photo

Invasive species are considered to be one of the top threats to the ecological integrity of our national parks. While the Upper Midwest has numerous troublesome invasive species, many of these are not present on Isle Royale. Three quadrillion gallons of cold Lake Superior water create a formidable barrier, making it difficult for new species to reach the archipelago.

But invaders do arrive. They are most often found around developed areas, docks, along trails, and in campgrounds; where exposure from the mainland is high. And though a lone seed or zebra mussel may seem insignificant, if unnoticed, can lead to the establishment of a sizable population. Depending on the species and size of the population, such an event could lead to a decrease in island biodiversity and compromise ecosystem integrity.

Please take the time before and during your trip to do your part to repel the invasion.
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Lynette Potvin, Ecologist at Isle Royale National Park, and Julie Van Stappen, Chief of Resource Management at Apostle Islands National Lakeshore, describe the threats zebra mussels pose to Lake Superior waters. They also share precautions people can take to help stop the spread of these invasive species during this 60 second video.

A small, shiny white and black zebra mussel sits atop a rock covered in algae.
With proper care, further zebra mussel invasion in Lake Superior can be mitigated.

Paul Brown

Aquatic Invaders

Isle Royale waters, like all Lake Superior waters, face a growing threat from the invasion of non-native species. Once species like zebra mussels, spiny water fleas, and sea lamprey enter an area, they cause large scale changes in the ecosystem.

Zebra Mussels

In 2009, zebra mussels were documented for the first time in Isle Royale waters. Their potential to cause catastrophic change cannot be overstated. If zebra mussels were to enter the inland lakes it is estimated that they would cover nearly every habitable surface on an inland lake floor in two to four years.

Spiny Water Flea and Sea Lamprey

Two invasive species, the sea lamprey and the spiny water flea, have already established a presence in Isle Royale waters. The spiny water flea is presently found only in Lake Superior. The park is concerned it may enter the inland lakes. Once established, its spines harm predator fish and the fleas disrupt the zooplankton population, the basic food source for many fish species.


Viral Hemorrhagic Septicemia

The exotic virus Viral Hemorrhagic Septicemia (VHS) has reached Lake Superior. This disease affects more than 40 species of fish including lake trout and coaster brook trout. The incredible genetic diversity of Isle Royale's lake trout would be at risk if VHS was introduced to Isle Royale waters.

A dead brown moth
Defoliation from spongy moth invasions can leave forests in poor health, promoting things like disease or wildfire.

NPS/Catoctin Mountain Park

Spongy Moth

Spongy moth is one of the most challenging insect pest species in North America. With hundreds of known plant hosts, many of which are completely defoliated during outbreak years, the spongy moth has no shortage of food. The species was first captured on Isle Royale in 2002, and its numbers continue to rise. However, there are no known reproducing populations on the island. Spongy moth larvae travels by wind, but can also be transported on people or gear.

A large National Park Service sign reading "Stop Invasive Hitchhikers!"
Wiping off your boots on a boot brush before heading to Isle Royale is a good way to stop the spread of invasive species.

NPS Photo

Stop the Spread

Vessel owners are legally responsible for Aquatic Invasive Species decontamination prior to entering park waters (extending 4.5 miles from Isle Royale and the outer islands). This applies to all vessels (power and sailboats, canoes, kayaks, etc.) regardless of size or configuration.

Make sure that all gear and clothing brought to the island are clean and free of any seeds or plant material. Familiarize yourself with non-native invasive plants. Visitors are encouraged to report sightings and locations for any suspicious plants.

Please take the following steps to prevent the transport of zebra mussels and other aquatic invasive species to Isle Royale waters.

Before Traveling to Isle Royale


Drain live wells and bilge on land - remove transom water, lake water, and unwanted bait from your boat. Wash your boat, including bilge and equipment with either: a) hot (greater than 104 degrees F) water, b) high pressure water, c) disinfectant OR clean and dry your boat and equipment in the sun for five days. Rainy days do not count.


Prior to departure, clean your tent, backpack, camping gear, clothing, and boots.

Canoeists and Kayakers

Remove weeds, algae, and other plant and animal materials from your boat. Wash your boat and equipment with either: a) hot water (greater than 104 degrees F), b) high pressure water, c) disinfectant OR clean and dry your boat and equipment in the sun for five days. Rainy days do not count.


Clean fishing gear before island departure.


Wash all dive gear in warm chlorinated tap water. Disinfect your wetsuit with a special-purpose shampoo. Dry all dive gear and wetsuit for seven days before island departure.

While on Isle Royale

Canoeists & Kayakers

Wipe down your boat and associated gear before moving from Lake Superior to inland waters.


When moving from Lake Superior to inland waters, clean gear and change line spools.


Last updated: December 6, 2023

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800 East Lakeshore Drive
Houghton, MI 49931


906 482-0984

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