Discovery of zebra mussel near Mactaquac raises alarm over spread of invasive species

CBC

10-03-2025

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The recent discovery of a live zebra mussel near Mactaquac, west of Fredericton, is raising concerns the invasive species is spreading in New Brunswick, with potentially damaging impacts on ecosystems, infrastructure, boats and even beaches.
The Department of Fisheries and Oceans found an adult zebra mussel on a dock in the St. John River just north of the Mactaquac Dam in December, said Terry Melanson, team lead for the department's aquatic invasive species program.
The single mussel doesn't necessarily mean the species has taken hold in that part of the river, but it does suggest the mollusc has spread from the Edmundston region, where it was first discovered in the province in 2023, Melanson said.
"Now, will it get bad? That we don't know," Melanson said in an interview.
"We could see localized impacts and we could see very little [impact]. That's kind of the mystery behind this ... that though we're employing several methods to detect the zebra mussels, there's no way to know to what extent they're going to establish in the St. John River."
A creeping threat
Zebra mussels are native to eastern European waters but entered the Great Lakes in the late 1980s through ballast water discharged from ships, according to the Department of Fisheries and Oceans.
They've since spread through much of eastern Canada and the United States.
The threat to New Brunswick first came in 2022, when zebra mussels were detected in Quebec's Lake Temiscouata, which drains into the Madawaska River, a tributary of the St. John River.
WATCH | Why spreading zebra mussels could hurt infrastructure:
What the spread of zebra mussels in N.B. could look like
23 minutes ago
Duration 1:27
What could happen when zebra mussels, an invasive species that is spreading in New Brunswick, pile up. Terry Melanson of the Department of Fisheries and Oceans explains.
As feared, the mussels were discovered the following year in the Madawaska River, including on infrastructure connected to Edmundston's Madawaska Dam, said Melanson.
Last summer, samples by the Department of Fisheries and Oceans found zebra mussel larvae in several locations in the St. John River as far south as the Mactaquac Dam, Melanson said..
Danger to native species
Melanson said once zebra mussels take hold in an environment, they can propagate in clusters numbering into the thousands.
If that happens in New Brunswick, the species could pose a serious risk to the yellow lampmussel, which has been labelled a species of "special concern" by the Committee on the Status of Endangered Wildlife in Canada.
"They're filter feeders, mussels, so they would filter the same organisms or organic matter as the yellow lampmussels. So in that respect [zebra mussels] risk impacting negatively that species."
According to the Fisheries and Oceans, the yellow lampmussel is only found in two Canadian watersheds, the St. John River and Sydney River in Nova Scotia, making it particularly vulnerable to changes in those ecosystems.
Damaging to humans
Aside from the threat they pose to New Brunswick's aquatic ecosystem, zebra mussels are also known to wreak havoc in spaces affecting people.
Melanson said municipal intake and drainage pipes along the St. John River could become clogged by clusters of zebra mussels and the same can happen to infrastructure for hydroelectric dams.
"And when they do stick to these hardened substrates, they really form dense mats," he said.
"We're talking something perhaps [the size of] the end of your small fingernail, but take hundreds or thousands of those in dense clumps, you can already imagine the impacts that can happen just on, on infrastructure alone."
Melanson said zebra mussels have been found on the Madawaska Dam, but the dozen or so that were found are considered a small number.
Melanson said swimming spots could also become hazardous if zebra mussels spread and multiply in the St. John River, given their shape and size.
"The shells being small by their very nature are very sharp, and ... a person walking barefoot, it could cut their feet."
Stopping their spread
Once zebra mussels have entered a water body, there's not much that can be done to eradicate them, said Sarah Cusack, a project co-ordinator with the New Brunswick Invasive Species Council.
Cusack said part of what makes them so proliferous is that in their larval stage, zebra mussels can travel long distances on their own just using the natural flow of a body of water.
On top of that, the larvae are impossible to see with the naked eye and can get accidentally transported from one waterway to another by boaters and kayakers.
Cusack said in light of that, her organization emphasizes to recreational boaters to thoroughly clean their boats, drain any captured water, and let them dry out before putting it back in the water — especially if they're going to be in a different water body.
"I do believe that this is something that should be taken very seriously," Cusack said.
"Zebra mussels have caused billions of dollars of damages and management requirements elsewhere where they've been introduced," she said.
"They're not native to North America. So we are going to see potentially changes in our ecosystem, in our freshwater systems, and a cascading effect that will happen because of that because they do move so quickly."