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Major Zebra Mussel Infestation in Harbor Impacts Native Mussels, Boaters

Map of the St. Louis river before and after the Fond Du Lac dam.

When Dan Kelner went SCUBA diving in the Duluth-Superior Harbor this fall searching for native mussels, he was expecting to see a few smallmouth bass following him around as he incidentally stirred up food for them during his search, and maybe some scattered clusters of zebra mussels. Unfortunately, that’s not what Kelner, a Minnesota Department of Natural Resources (DNR) malacologist, found.

“It was pretty grim. The bottom was completely covered with zebra mussels,” said Kelner. “It reminded me of places in the Ohio and Mississippi rivers.”

Kelner and his team of divers were conducting the first comprehensive survey of native freshwater mussels across Minnesota. They had already surveyed other parts of the St. Louis River below the Fond du Lac Dam (see map) and found few zebra mussels. The native mussels seemed to be doing well there. In fact, they found a rare new species for that part of the river, the creek heelsplitter (Lasmigona compressa). But the native mussels in the Duluth-Superior Harbor were in dire straits.

A zebra mussel watcher on Lake Minnetonka.

A Zebra Mussel Watch volunteer, Linda Boll of Mound, MN, raises a plankton net while checking Lake Minnetonka for zebra mussels. Photo courtesy of the Lake Minnetonka Association.

This fall, zebra mussels were found for the first time in an inland lake in Minnesota. A resident of Zumbro Lake, north of Rochester, brought the mussels to the DNR for identification. If you live in Minnesota and are concerned about the spread, you can help by joining the Zebra Mussel Watch program sponsored by Sea Grant and the DNR. Volunteers across the state look for zebra mussels on boats and docks in the fall and report their findings to the DNR.

Last spring, Sea Grant sent 350 sets of preserved exotic specimens and informative publications to lake association volunteers across Minnesota. We loaned 11 monitoring kits to various lake associations. The kits contain an instructional notebook, training video, labeled sample jars, and plankton net to take water samples. Volunteers use the kits to take water samples twice during the summer. After collecting the samples, the volunteers send them to a lab where scientists analyze them for zebra mussel larvae, called veligers.

“It’s a wonderful idea,” said Dick Osgood, Lake Minnetonka Citizen Monitoring and Education Network Project Manager. “As far as the Lake Minnetonka volunteers go, they appreciate it. Technically, the sampling process is very well put-together and simple, yet credible.”

This program was made possible by funding from the National Oceanic and Atmospheric Administration. Sea Grant programs in Michigan, Minnesota, and Illinios-Indiana are participating.

To get involved next summer, contact the DNR at (651) 259-5100, or Sea Grant at (218) 726-8712.

— Teri LeFaive

“One-hundred percent of the native mussels I found on the bayside of Park Point were heavily infested with zebra mussels,” Kelner said. “A lot of the native mussels were already dead or dying because the zebra mussels make it difficult for them to eat and breathe.”

His findings confirmed suspicions of a major infestation of zebra mussels in the harbor. Biologists and resource managers suspect warm summers and mild winters the last three years have created conditions for zebra mussels to grow. Sea Grant staff using an underwater video camera also noticed heavy colonization of zebra mussels in the Duluth Ship Canal this fall.

This prompted Sea Grant and the DNR to issue news releases alerting boaters to take extra time and care to inspect and remove zebra mussels. In Minnesota, it is unlawful to transport zebra mussels or aquatic plants on a public road or to launch a boat with them attached. Violators are subject to misdemeanor or civil penalties from $50 to $1,000.

“Most boaters are doing a good job of inspecting and cleaning off their boats,” said Jay Rendall, DNR Exotic Species Program coordinator. “But the renewed zebra mussel growth emphasizes the need for boaters to be careful.”

The creek heelsplitter, the new species Kelner and his team found in the St. Louis River estuary, is listed as a species of special concern in Minnesota and is at risk from the increase in zebra mussels. “Based on the 98 percent loss of Lake Erie’s native mussels due to zebra mussel infestation, it doesn’t bode well for the native mussels in the lower part of the estuary,” said Doug Jensen, Minnesota Sea Grant Exotic Species Information Center coordinator.

According to the DNR, more than 70 percent of the mussel species once found in North America are now extinct, endangered, or declining. In Minnesota, more than half of native mussel species are listed as endangered, threatened, or of special concern.

Zebra mussels arrived in the harbor in 1989, likely the result of ship ballast water discharge. Across the Great Lakes they are clogging water intake pipes and eating plankton needed by young fish. Some companies have spent up to $2 million annually to control this invasive mussel. Zebra mussels attach to hard surfaces, such as boat hulls and motors and can also attach to aquatic plants. Microscopic larvae can be transported in bait buckets, live wells, and bilges.

So boaters… be sure to remove all plants from your boat and trailer, scrape or wash any live mussels off your boat, and empty water from livewells and bait buckets on land before leaving infested waters. It’s also a good idea to let everything dry for five days before going to other waters.

These simple steps will help ensure that Kelner sees smallmouth bass and native mussels instead of zebra mussels during his surveys of other Minnesota waters.

By Marie Zhuikov
January 2001

Return to January 2001 Seiche

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