A freshwater mussel that has infested lakes and rivers around the world is creeping closer to Maine, with confirmed sightings in Canada less than 30 miles from the Maine border.

The Maine Department of Inland Fisheries and Wildlife issued a warning Monday, calling attention to a new law requiring boaters to drain any water that might contain microscopic larvae and bring zebra mussels into Maine waters.

“Zebra mussels have not yet been confirmed in any water of the state of Maine, but represent a high threat level to the health of our waters, fish and wildlife,” the agency said. “Zebra mussel infestations result in irreversible negative impacts on native species and water body systems and are nearly impossible to eradicate once introduced.”

The small striped mollusks are considered one of the most dangerous invasive species because they can quickly spread throughout a water body, attaching to rocks, docks and other shellfish, clogging water intakes and boat hulls and propellers.

Invasive zebra mussels have been found in moss balls sold in pet stores in southern and central Maine. Photo courtesy of Maine Department of Inland Fisheries and Wildlife

“Zebra mussels filter and hold a substantial amount of important food and nutrients that native organisms require, negatively impacting all native fish and wildlife in the water body,” the MDIFW said.

They are native to Eastern Europe and reached the United States in the ballast water of ships before spreading through parts of the country. Once a water body is infested, little can be done to reduce or contain the spread.


Sightings of the mussels have been confirmed in waters that drain into the Saint John River in both Quebec and New Brunswick. The species also could be in the Madawaska River, closer to Maine, it said.

Mary Jewett, director of education and invasive prevention for the Lakes Environmental Association, a regional group in western Maine that also lobbies for healthy lakes statewide, said it’s difficult to prevent the spread of zebra mussels, but the state and local groups are trying to do so and hope a new law can help.

“It could have catastrophic impacts if we don’t prevent them from coming in,” Jewett said.

The new law took effect in June and requires boaters to drain their vessels of any standing water before moving from one body of water to another to help prevent the spread of zebra mussels or other invasive species. The larvae are tiny and translucent and difficult to spot in water.

“In Maine, we’re working on preventing them from getting here to begin with,” Jewett said. “But we need to operate under the assumption that zebra mussels are everywhere.”



Jewett said the association and others are focused on educating boaters on the need to drain their boats and raising awareness of the new law, called the “Clean, Drain, Dry” law.

Young zebra mussels can attach to vegetation that gets caught up in propellers or anchors, and larvae can be brought on board in ballast water or bait tanks. The mussels, which grow to about 1 inch long, can survive out of water for several days.

Before entering a water body and when preparing to leave launch sites, boaters are now required to remove or open any devices designed for routine removal or opening, including hull drain plugs, bailers, live wells and ballast tanks. This must be done in a way that does not allow drained water to enter any inland water of the state. Boats also should be dried out for at least two days.

Similar laws are already in effect in more than 20 other states, including New Hampshire, Vermont and New York.

“Once we explain it to them, people will do it, once they’re aware of it,” Jewett said.

Zebra mussels spread rapidly in the Great Lakes in the 1990s, and also have been found in many rivers cross the country, including the Mississippi, St. Lawrence, Hudson, Missouri and Colorado.


Zebra mussels were discovered in some plants sold for use in fish tanks by Maine pet stores in 2021, which triggered warnings against dumping the plants or flushing them down toilets. The state urged anyone who purchased the plants to destroy them with bleach or by boiling them. Since then, there have not been any confirmed sightings in Maine waterways.

Rep. Walter Riseman, an independent from Harrison, sponsored L.D. 92, an Act to Minimize the Propagation of Invasive Aquatic Plants, and Gov. Janet Mill signed the bill into law in June. Riseman described zebra mussels as a “very dangerous invasive species” that he said would be very difficult to stop if it gets into Maine waterways.

Riseman said the best plan of defense is to educate the public on the dangers of not just zebra mussels but all invasive species. He attributes the increased threat from what he has observed to be more boat traffic on lakes.

“Boat traffic is definitely increasing,” said Riseman, who lives a half mile from Long Lake. He said manufacturers started making larger boats three or four years ago and all you have to do is go to a marina to see how large they are. With bigger boats comes the increased risk of having someone infecting a lake with zebra mussels.

“The lakes are so important to the economy of the region where I live. If we lose the lakes as a financial resource it will have dire consequences,” Riseman said.

Staff Writer Dennis Hoey contributed to this report.

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