For a couple of years now Parks Canada has taken significant steps through the Clear Lake Conservation and Restoration project to prevent aquatic invasive species (AIS) such as zebra mussels from entering waterways in Riding Mountain National Park (RMNP).  

All watercraft and/or water-related equipment entering RMNP waters were required to undergo an inspection for AIS since that time. The service is free of charge and watercraft passing inspection received a permit from Parks Canada watercraft inspectors. 100% compliance was necessary to ensure the ecological integrity of park waterways as it only takes one contaminated watercraft to transport zebra mussels and other AIS into park waters.

However, in January 2023, Parks Canada was notified that one water sample taken in August 2022 tested positive for mussel eDNA, and more steps were taken to stop the spread into RMNP. 

This week Parks Canada confirmed the presence of live zebra mussels at Boat Cove on Clear Lake. This is the first time that zebra mussels have been found in Riding Mountain National Park.

When it comes to zebra mussels, Healthy Lake Committee Chair, Trevor Maguire, says he and his committee have worked extremely hard to share the detrimental effects of zebra mussels to thwart the spread of zebra mussels into Pelican Lake, and all Manitoba lakes.

He says the confirmation of zebra mussels in Clear Lake affects every water body downstream of that lake, including Rapid City, Rivers, and the Assiniboine River right down to the Red River.  It's important to note that the Red River has been contaminated with zebra mussels for years.  The fact that zebra mussels are in the Westman Region, means all of the lakes in the southwest corner of the province are at an even greater risk of this infestation.

So, what are zebra mussels?

Zebra mussels are small, clam-like aquatic animals native to Eastern Europe and Western Asia. 

They were discovered in Lake Erie in the mid-1980s and were accidentally transferred from their native range by cargo ships. Within a decade, the mussels had spread throughout the Great Lakes and many inland water bodies in the Mississippi watershed to the Gulf of Mexico.

Since then, they have spread to hundreds of other water bodies, mainly in eastern North America.

Facts about zebra mussels:

  • Aggressively invade new areas and reproduce quickly. Females produce upwards of one million eggs per year.
  • Colonize almost any hard underwater surface, including watercraft hulls and can interfere with engine cooling systems.
  • Power plants, water treatment plants, and cottages can be negatively affected by clogged intake structures.
  • Threaten native fish and wildlife by reducing algae and food resources at the base of the food chain.
  • Costly nuisance to boaters, commercial fishers, anglers, and beach-goers. They can reduce recreational potential by littering beaches with sharp shells and producing foul odours from decaying, dead zebra mussels.
  • Adult zebra mussels can survive out of water up to 30 days depending on temperature and humidity. Zebra mussel veligers (larvae) are not visible to the naked eye and can survive in very little water.

So, what's the big deal?  Don't zebra mussels just make the water clearer?

"The main issue of the zebra mussel is that it has no known natural predator.  It's an invasive species, so it comes in and it dominates the environment," explains Maguire. "They'll mass produce and lakes like Pelican Lake, Killarney Lake, Lake Winnipeg, are ideal for them.  They need calcium and nutrients, like suspended food (zoo plankton and phytoplankton).  Anyone who know these lakes know they can get pretty green in the summer and that's what zebra mussels love. Plus, they'll occupy every available structure to grow on."

Zooplankton and phytoplankton are what feed the entire food chain, critters like freshwater shrimp, clams, aquatic bugs and freshwater fish.  Zebra mussels will strip the water of these very nutrients, thus literally starving our natural critters of their food.  It's interesting to note that zebra mussels do not feed on the blue-green algae that we're trying to get rid of, or decrease, in our prairie lakes.  So no, they will not clean up a prairie lake of its blue-green algae.

Pelican Lake and Killarney Lake are just two of the prairie lakes that have installed a micro-bubbler aeration system to decrease the number of blooms of blue-green algae over the summer months. And both lakes have seen positive results.  Zebra mussels like plastic objects to attach to and moving water, two of the very features of any aeration system.  Zebra mussels would literally choke out the movement of air through the aeration system by plugging up the lines and the heads.

When Parks Canada detected the eDNA why didn't they take stronger measures?

"When they detected the zebra mussel eDNA there was one of two possibilities," explains Maguire, "you would have dead zebra mussel material which wouldn't cause an infestation, or you already had live zebra mussels.  So, RMNP went very draconian to protect their lake in case it was just the eDNA from dead ones. It usually takes a couple of years from first infestation till the point where you are actually seeing them physically."

And this is where they're at now, a confirmed presence of the actual zebra mussel. 

What can be done to stop the spread of zebra mussels, or any aquatic species?

"The only mechanism that will work is not moving boats, not moving life jackets, not moving fishing equipment," says Maguire. "That's the only thing that's going to work.  They've tried everything else, everywhere else and this species has moved through Minnesota, Wisconsin, all through the southern states. They've tried inspection, decontamination, it's just too easy for these things to slip by."  

"Manitoba has an advantage," he adds. "It freezes in the winter and that's a 100% kill.  So, you keep your boat on your lake for the year and if you want to move to another lake, then do it next spring. That's a 100% guarantee. But if people don't want to accept that reality and abide by that then zebra mussels will be in every lake in Manitoba eventually. It's just a matter of time."

This draconian measure would apply to every watercraft (pontoon boat, kayak, sailboat, inflatables) and every piece of fishing and swimming and water recreation equipment.  Something to note is that as soon as the water temperature is 10C degrees and higher, zebra mussels spawn millions of eggs (veligers) that live in every part of that water body. 

If freezing kills the veliger 100% then throwing your fishing, swimming, water recreation gear into the freezer for a few days before heading out to a different lake is a great idea!  However, your boat, motor, live bait tanks, trailer, vehicle - anything that has come in contact with that infested lake water is potentially carrying millions of veligers.

Please listen to more with Trevor Maguire on zebra mussels and the detrimental effects on Manitoba's water bodies.

The boat launch area at Clear Lake is closed until 2024. Parks Canada is working with partner organizations to analyze these results and determine the best course of action for Riding Mountain National Park.

Public engagement sessions will be held this winter. More information will be shared when it is available. At this time, no decisions have been made for next year’s boating season.

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