Thunder Bay

Zebra mussels threaten Lake of the Woods, Rainy River

Minnesota researchers have discovered zebra mussels in a lake with a connection to the Rainy River — and now there are worries the invasive pest could get into Lake the Woods.

Northern Minnesota camp owner finds zebra mussels on dock in waterway that connects to Rainy River

Zebra mussels are often moved on boats, equipment, bait bucket water, and bilge water. (Supplied)

Minnesota researchers have discovered zebra mussels in a lake with a connection to the Rainy River — and now there are worries the invasive pest could get into Lake the Woods.

An invasive species specialist with the Minnesota Department of Natural Resources said a camp owner found some dried up zebra mussels while putting in a dock in Itasca County in the northern part of the state. 

And Richard Rezanka suspects anglers may be responsible.  

"This is the furthest north we've got them," he said. "We've got pretty heavily fished lakes in the central part of the state, so it wouldn’t be outside of the realm of possibility for water or zebra mussels to have been moved."

The waterway they were found in connects with the Rainy River.

The aquatic invasive species outreach liaison with the Ontario Federation of Anglers and Hunters said if zebra mussels migrate to Lake of the Woods, their habit of straining out plankton could be disastrous to the sport fishery there.

"If you take out the energy in the bottom of the food chain, as you move up the food chain, there will be less energy for your walleye or lake trout," Matt Smith said.

‘Natural buffer’

Rezanka noted that, so far, he's found no further evidence of zebra mussels in the chain of lakes. But he said eradicating them in any water body that's become infested with them has proven impossible so far.

According to Jeff Brinsmead, a senior invasive species biologist for Ministry of Natural Resources, the MNR doesn't have a method to eradicate zebra mussels, so the strategy is to prevent them from being introduced to a new water bodies in the first place.

Because zebra mussels are often moved on boats, equipment, bait bucket water, and bilge water, the MNR conducts educational outreach to anglers and boaters about preventing the spread.

Brinsmead noted the zebra mussel problem is most serious in the Great Lakes and there has been some spread into inland lakes in southern Ontario.

He added zebra mussels haven't spread into lakes in northwestern Ontario, largely because many Canadian Shield lakes don't have enough calcium for zebra mussels to form their shells 

"There are some areas that are vulnerable, but because there's [a] … buffer of the Canadian Shield around those areas it's kind of stopped the movement [of zebra mussels]," Brinsmead said.

The concern now is that they could move into vulnerable areas of northwestern Ontario without crossing the shield, as there may be some lakes that have high enough calcium levels.

But Brinsmead said he believes the calcium levels are quite low in Lake of the Woods and Rainy River that offer a "natural buffer that protects a lot of these lakes from zebra mussels."