Zebra Mussel Information and Updates
Riding Mountain National Park
NEW - Zebra mussel observations in Clear Lake:
During 2025 monitoring for aquatic invasive species in Clear Lake, one zebra mussel veliger (microscopic larvae) was detected for the first time. Parks Canada also found 2 adult zebra mussels and roughly 15 juveniles.
Monitoring
In 2025, Parks Canada used multiple methods to monitor for aquatic invasive species throughout Riding Mountain National Park, including substrate samplers, veliger tows, and environmental DNA (eDNA) monitoring. From June 16 to October 6, 2025, 251 eDNA samples were collected.
AIS monitoring 2025 (1.4 MB)Clear Lake
In Clear Lake, 21 samples tested positive for zebra mussel eDNA, collected from the Wasamin Creek outlet, the water treatment system, and the 61A dock. Zebra mussels are now reproducing in Clear Lake, which means future tests will always detect their environmental DNA (eDNA). For this reason, Parks Canada will stop testing for zebra mussel eDNA in Clear Lake and redirect efforts to other lakes in the park.
Other lakes
In 2025, aquatic invasive species were not detected in any of the outlying waterbodies in Riding Mountain National Park. There is currently no evidence of zebra mussels in Lake Katherine, Grayling Lake, Moon Lake, Lake Audy, Whirlpool Lake, Bob Hill Lake, or Deep Lake.
Other aquatic invasive species
The aquatic invasive species prevention program focuses on two key priorities: preventing zebra mussels from spreading to new waters and preventing other invasive species from arriving in Riding Mountain National Park. Aquatic invasive species of concern in Manitoba include quagga mussels, spiny water flea, black algae, rusty crayfish, Asian carp, and Eurasian water milfoil - each posing serious risks to ecosystems and visitor experiences.
Inspection and decontamination
Parks Canada staff inspected 7,561 non-motorized watercraft between May 14 and October 19, 2025. Each inspection included a risk assessment questionnaire, decontamination when necessary, and education on preventing the spread of aquatic invasive species.
- 84% of permits were issued for Clear Lake
- 16% of permits were issued for the outlying lakes
Of the non-motorized watercraft inspected:
- 86% required no further action before issuing a permit
- 11% required decontamination before issuing a permit
- 3% were denied a permit, most often due to a previous launch in a whirling disease zone
Collaboration and next steps
Riding Mountain National Park will keep working with Manitoba’s aquatic invasive species team to prevent zebra mussels from spreading beyond the park. This includes boat inspections, decontamination, and monitoring Wasamin Creek.
To guide a winter decision on motorized watercraft use in Clear Lake, among other items, Parks Canada will consider:
- Monitoring results from 2025 and previous years
- A third-party literature review on impacts of motorized watercraft on inland lakes
- Feedback from management planning consultations
- Engagement with others, including consultation with Section 35 rights holders
Parks Canada is aiming to make a decision on watercraft management for Clear Lake by February 2026.
Monitoring of freshwater mussels in Clear Lake
Parks Canada, in collaboration with Brandon University, has completed the first year of a new freshwater mussel survey at Clear Lake. The survey covered 34 sites around the lake and included water quality sampling at each location.
This program aims to:
- identify native freshwater mussel species
- assess how many mussels are present and where they live
- document habitat characteristics to locate possible refuge areas
- monitor the spread and impact of invasive zebra mussels
By understanding where native mussels currently thrive, Parks Canada can better protect these habitats, guide future restoration or relocation efforts, and track long-term changes in mussel populations and water quality.
Map of all zebra mussel observations in Clear Lake 2023-2025
Table of all zebra mussel observations in Clear Lake 2023-2025
| Date | Location Name | Count | Age Class |
|---|---|---|---|
| 2023-09-01 | Boat Cove Dock #1 | 48 | Adult |
| 2024-07-18 | Snorkel Survey | 1 | Adult |
| 2024-09-16 | Lakeshore Dock #3 | 1 | Juvenile |
| 2024-09-20 | Northshore Block 1 | 1 | Juvenile |
| 2024-09-20 | Northshore Block 15 | 1 | Juvenile |
| 2024-09-20 | Northshore Block 17 | 2 | Juvenile |
| 2024-09-20 | Northshore Block 18 | 2 | Juvenile |
| 2024-09-24 | Deep Bay | 5 | Juvenile |
| 2024-09-26 | Boat Cove Dock #1 | 3 | Juvenile |
| 2024-09-26 | Lakeshore Dock #1 | 1 | Juvenile |
| 2024-09-26 | Lakeshore Dock #4 | 1 | Juvenile |
| 2024-09-26 | Lakeshore Dock #5 | 1 | Juvenile |
| 2024-09-27 | Wishing Well Dock | 30 | Juvenile |
| 2024-10-07 | East End Docks | >90 | Juvenile |
| 2024-10-11 | Marina Docks | 3 | Juvenile |
| 2025-07-16 | 61A Dock | 1 | Veliger |
| 2025-08-21 | Snorkel Survey | 1 | Adult |
| 2025-09-09 | East End Docks | 5 | Juvenile |
| 2025-09-15 | Lakeshore Dock #1 | 1 | Juvenile |
| 2025-09-15 | Lakeshore Dock #6 | <5 | Juvenile |
| 2025-09-15 | Lakeshore Dock #8 | <5 | Juvenile |
| 2025-09-17 | Water Intake | 1 | Adult |
| 2025-10-06 | Boat Cove Dock #1 | 3 | Juvenile |
| 2025-10-06 | Marina Docks | 2 | Juvenile |
Background
What are zebra mussels?
Zebra mussels are small, freshwater mollusks (clam-like organisms) that are native to eastern Europe. Zebra mussels entered the Great Lakes in the late 1980s through ballast water discharged from ships. Since then, they have spread through much of eastern Canada and the United States. They were first detected in Manitoba in 2013 and are now found in Lake Winnipeg, the Red River, the Nelson River system, Lake Manitoba, and other waterbodies.
Biology
Zebra mussels are filter feeders that attach themselves to solid surfaces. They breed very quickly, as females can release up to one million eggs each year. Once the eggs are fertilized, they become larvae (called veligers), which you can only see with a microscope. Veligers float through lake or river currents for up to a month before they settle on a solid surface. Zebra mussels have few, if any, natural predators in North America. As a result, they often permanently change the food web and ecosystems they invade.
Negative impacts
Negative impacts on people:
- In Canada, zebra mussels cause millions of dollars in damage every year by clogging intake structures in power stations and water treatment plants, as well as damaging watercraft
- Injury from sharp shells
Negative impacts on aquatic ecosystems:
- Alter food webs by removing native species’ food sources, such as plankton
- Change the surface of rocks and vegetation, which impacts the survival of fish eggs
- Create clearer water, which:
- allows sunlight to penetrate deeper
- increases the growth of submerged aquatic vegetation
- leads to toxic algal blooms because zebra mussels do not feed on cyanobacteria
- increases pathogenic bacteria, avian botulism, and removes oxygen from the water
Zebra mussels are especially harmful to native mussels, many of which are species at risk. They outcompete these species for food and will attach themselves to native mussels, suffocating them.
Frequently Asked Questions
What will happen to Clear Lake going forward?
Over time, zebra mussels are likely to spread throughout Clear Lake. Although veligers (zebra mussel larvae) cannot swim, they move naturally through currents caused by thermal cycling, wind, and gravity.
What does this mean for downstream communities?
Veligers will likely travel downstream via Clear Lake’s outlet, Wasamin Creek, which connects to the Little Saskatchewan and Assiniboine River Systems. It is still unknown exactly how far they may spread and whether they will find suitable habitats to settle and reproduce.
How will Parks Canada manage the impacts of zebra mussels in Clear Lake?
Parks Canada will continue monitoring infrastructure in and around Clear Lake and assess management options as zebra mussels become established. Park staff will track water quality and inspect water treatment systems to ensure safe drinking water for visitors and residents.
What are Parks Canada’s plans if zebra mussels are found elsewhere?
If evidence of zebra mussels is detected in another lake within Riding Mountain National Park, Parks Canada will initiate a rapid response to confirm whether the species is present. If zebra mussels are confirmed, Parks Canada will then evaluate potential containment and eradication options.
Aquatic invasive species prevention program timeline of events
Timeline
Summer 2011 – Monitoring began for aquatic invasive species (AIS), specifically zebra mussels, in Clear Lake.
Summer 2015 – Mandatory Parks Canada AIS inspections and decontaminations began at Riding Mountain National Park. Water samples from Clear Lake and surrounding waterbodies began to be taken and tested for zebra mussel environmental DNA (eDNA).
January 2023 – Fisheries and Oceans Canada informed Parks Canada of a positive test result for zebra mussel eDNA in a water sample taken on August 4, 2022, from an area known as the Boat Cove in Clear Lake.
May 4, 2023 – Parks Canada announced that trailered watercraft intended for use on Clear Lake must not have been in any other waterbody in 2023 and must undergo an inspection by June 15. Boats that met the requirements had a tag installed that sealed the boat to the trailer. If this tag was removed or tampered with, that boat was not allowed to launch in Clear Lake for the remainder of the 2023 season. All non-motorized vessels (such as canoes, kayaks, stand-up paddle boards) were required to complete a Parks Canada AIS inspection and, if needed, decontamination before launching in park waters.
November 10, 2023 – Parks Canada officials did a physical search at the Boat Cove and found a clump of 48 live zebra mussels, which they removed from the water. Before that, zebra mussels had never been found in Riding Mountain National Park.
May 2024 – Parks Canada implemented watercraft management measures that restricted all recreational watercraft use on Clear Lake for the time required to determine if a population of zebra mussels had been established and for any potential remediation. This included exceptions for emergency vessels, the commercial tour boat, and one vessel from Keeseekoowenin Ojibway First Nation.
August 2024 – Parks Canada closed the Boat Cove for the installation of an impermeable containment curtain in Clear Lake. The curtain was installed around the area where living zebra mussels were found in November 2023 and July 2024. Shortly after installation, the curtain was damaged to the point that it was no longer an effective means of containment and was removed. The curtain could not be repaired or replaced in the same open water season.
September 2024 – Parks Canada found more than a hundred juvenile zebra mussels attached to docks and infrastructure near the east end of Clear Lake.
October to December 2024 - Extensive internal and external review of the evidence and data collected from Clear Lake in 2024.
January to February 2025 – Parks Canada ran a public engagement questionnaire to inform the management of Clear Lake’s aquatic invasive species program for 2025, which received 2,934 responses. During the Winter Adventure Weekend, the Field Unit Superintendent, management, and other staff also engaged in informal conversations with 268 local stakeholders.
May 2025 – Parks Canada made the decision to limit motorboat use on Clear Lake to limit the spread of zebra mussels within Clear Lake, prevent their movement to other lakes, and reduce the risk of new invasive species from entering the park.
June to October 2025 - In 2025, Parks Canada used multiple testing methods including substrate samplers, veliger tows, and environmental DNA (eDNA) monitoring. During this time, 251 eDNA samples were collected throughout Riding Mountain National Park.
July to August 2025 – The first zebra mussel veliger was detected in Clear Lake during a plankton tow. Parks Canada also found 2 adult zebra mussels and roughly 15 juveniles in Clear Lake. There is currently no evidence of zebra mussels in Lake Katherine, Grayling Lake, Moon Lake, Lake Audy, Whirlpool Lake, Bobhill Lake, or Deep Lake.
July to August 2025 – Parks Canada, in collaboration with Brandon University, completed the first year of a new freshwater mussel survey at Clear Lake, which serves as a baseline inventory for native mussels in Clear Lake. By understanding where native mussels currently thrive, Parks Canada can better protect these habitats, guide future restoration or relocation efforts, and track long-term changes in mussel populations and water quality.
October to November 2025 – Parks Canada held public meetings and ran a public consultation survey to update the management plan for Riding Mountain National Park. This included questions about the future vision for Clear Lake.
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