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Zebra Mussels Found On Historic Ship

Isle Royale National Park

National Park News

On July 26th, the Niagara, a historically accurate reconstruction of Commodore Oliver Hazard Perry's victorious 1813 flagship, entered park waters under the terms and conditions of a special use permit. One of the terms of the permit was that the ship would be free of aquatic invasive species, especially the zebra mussel.

The captain of the Niagara assured park staff that the vessel had been cleaned by a team of volunteer scuba divers while in its home port of Erie, Pennsylvania, and that it was clear of zebra mussels. The ship is owned by the State of Pennsylvania’s Erie Historic Maritime Museum, a nonprofit educational association striving to preserve and further the education of historic sailing techniques, environmental stewardship, and outreach education programs. 

On the morning of July 27th, park divers inspected the hull of the Niagara while it was docked at the headquarters dock on Mott Island. They discovered several colonies of zebra mussels attached to the hull of the ship aft of midship on the keel and rudder assembly (pintel).  Evidence suggested that the mussels had been attached to the vessel for a considerable length of time, which meant that the volunteer divers missed them. The park divers cleaned about 80% of the zebra mussels off the hull before deciding that further cleaning of the ship in a clean harbor might seed the harbor and further spread this fast moving invasive species.

The ship left the harbor the next morning with a new level of appreciation for what is necessary to ensure that a ship is 100% clean of aquatic invasive species. The Niagara then sailed to Duluth, Minnesota, to attend the annual Tall Ships Duluth Festival, where it is hoped that the crew of the Niagara will educate the crews of other tall ships and vessels about the issues related to aquatic invasive species such as the zebra mussel.    

Zebra mussels are a species that are thought to have originated in the Baltic Sea and are believed to have been transported to the waters of North America in ballast water discharged from commercial shipping vessels.  Zebra mussels can attach themselves to nearly any surface, including wood, fiberglass, aluminum, steel, rocks, and pipes, and can be transported to a number of other bodies of water, remaining alive for up to a week out of the water. These fingernail-sized mussels can quickly out compete native species, change water chemistry and turbidity, change oxygen content, and have significant impact on native fish species.   

Efforts to contain the spread of aquatic invasive species such as the zebra mussel are well underway, Rules to help contain the spread of aquatic invasive species are found in Isle Royale National Park’s superintendents compendium.


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