Invasive Species

Youth volunteers remove invasive thistles from the park.
Youth volunteers remove invasive thistles from the park.
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.

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.

Spiny Water Flea & 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.

Zebra mussel on the bottom of Lake Superior.
Zebra mussel on the bottom of Lake Superior.

NPS/Paul Brown

Zebra Mussels

In 2009, zebra mussels were documented for the first time. 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.


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.


Stopping the Spread - Visitor Responsibilities

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: November 17, 2020

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Houghton , MI 49931


906 482-0984

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