Zebra mussels found in Nipigon Bay of Lake Superior

The Ministry of Natural Resources and Forestry (MNRF) has discovered zebra mussels in Nipigon Bay, of Lake Superior.  

Nipigon Bay is home to one of the strongest remaining populations of coaster brook trout, a native fish species in Superior. 

While Lake Superior has not been considered an ideal habitat for zebra mussels — they've been found in a few areas before, including the Thunder Bay and Duluth-Superior harbours, the Apostle Islands, and by Isle Royale — due to its cold temperature, a recent survey showed they've also appeared in the western part of Nipigon Bay.

"It's typically much shallower, warmer, and a lot more productive," said Kyle Rogers, an MNRF biologist with the Upper Great Lakes Management Unit. "We have the Nipigon River, obviously, draining into there, which is carrying nutrients."

The concern now is that anglers who fish Nipigon Bay may inadvertently transfer the invasive species to Lake Nipigon, or other inland lakes.

Zebra mussels — which were originally brought to the Great Lakes by large freighters — are very effective at filtering water, removing nutrients, Rogers said. That can lead to difficulties in finding food for younger fish, which can starve.

"We often see shifts in the fish community once they're established," he said.

Zebra mussels are able to form colonies on hard and soft surfaces, including docks, boats, breakwalls, and beaches.

"They are in Nipigon Bay and Lake Superior, so it's really important for boaters and anglers to wash down their boats when they're taking them out of the water," Rogers said. "Spray them down, spray down their trailers, remove any debris that might have got caught on the boat."

"It's really important to disinfect and rinse out their live wells and bilge pumps," he said. "That's a very important way to mitigate the spread of these organisms."

The zebra mussels, Rogers said, have a microscopic larval form, that can be picked up in a bilge pump or live well, and can be spread to other parts of a lake, or other lakes altogether.

"Once they're there, they'll attack to a hard surface, where they'll form into the adult mussel," he said.

Zebra mussels and other invasive can be reported at the Early Detection and Distribution Mapping System.