Zebra Mussels Just Turned Up in Two More Canadian Lakes: What Boaters Need to Know
Updated: 1 hour ago
The recent discovery of zebra mussels in two Manitoba lakes has triggered new decontamination requirements and renewed attention to the role recreational watercraft must play in preventing the spread of aquatic invasive species.
Two Manitoba lakes are currently under increased monitoring after zebra mussel larvae were detected in Lake Winnipegosis and Waterhen Lake.
The Manitoba government announced September 14 that zebra mussel veligers, the free-swimming larval stage of mollusks like the zebra mussel, had been detected in both lakes. In response, the province's Aquatic Invasive Species Early Detection Rapid Response Plan was activated.
The Lake Winnipegosis discovery was kickstarted by a report from a local fisherman who discovered adult zebra mussels attached to his boat after removing it from the water. The Manitoba Wildlife Federation subsequently analyed the mussels and confirmed that zebra mussel veligers were in Lake Winnipegosis near the town of Winnipegosis. They were also discovered in nearby Long Bay, as well as in Waterhen Lake. The three locations are all connected.
Lake Winnipegosis drains into Waterhen Lake through the Little Waterhen and West Waterhen rivers. Waterhen Lake then drains south through the East Waterhen River into Lake Manitoba.
The Manitoba Wildlife Federation is currently trying to determine the extent of the infestations.
Boaters leaving the lakes face new requirements
In response to the discoveries, Manitoba immediately required all waterway visitors, including both powered and unpowered vessels, leaving Lake Winnipegosis and Waterhen Lake to decontaminate their watercraft and equipment before launching into another waterbody.
The requirement applies to recreational powerboats and non-motorized watercraft like canoes, kayaks, and paddleboards.
The province's aquatic invasive species watercraft requirements instructs boaters to clean their vessel and equipment, drain all standing water, and dry the equipment completely before entering another waterbody. The requirement checklist specifically mentions areas on a powerboat that can retain water, including ballast tanks, bilges, motors, live wells, and trailer components that come in contact with the water during launching.
Manitoba also requires all drain plugs to be removed while watercraft are being transported over land, with the exception of plugs for onboard kitchen facilities and/or washroom holding tanks.
The problem can be difficult to see
Adult zebra mussels are relatively small and generally grow to about 25 millimetres, or approximately 1", and attach themselves to underwater surfaces using what's called byssal threads—small fibers on the mussel's foot. These sticky threads extend from underneath the shell to anchor the animal firmly to hard surfaces like rocks, docks, or boat hulls.
The more difficult threat to detect is the mussel's larval stage. Known as veligers, the larvae are microscopic and free-floating, making them impossible to identify by simply looking at a boat's hull or trailer. According to Ontario Parks' Clean, Drain, Dry guidance, zebra and quagga mussel veligers can survive for weeks in standing water inside watercraft.
That means water left in a boat can potentially transport microscopic organisms to another lake days or weeks after visiting a contaminated location.
To minimize the risk, Ontario Parks recommends draining water from bait buckets, ballast systems, bilges, coolers, internal compartments, and live wells before leaving a waterbody.
Recreational boats are a recognized pathway
Given the ongoing circumstances in Manitoba, the province has identified the overland travel of watercraft on trailers and its related equipment as the main pathway zebra mussels are using to spread.
According to Manitoba's own zebra mussel information guide, the mussels were introduced into the south basin of Lake Winnipeg in 2013. The province says it is suspected that an uncleaned watercraft that visited Lake Winnipeg was responsible for the introduction.
But the concern is not limited to Manitoba.
In May 2026, Fisheries and Oceans Canada (DFO) and the Manitoba government conducted roadside inspections along Highway 1 near the Manitoba-Ontario border to check vessels for aquatic invasive species and compliance with the Clean, Drain, Dry requirements.
During the inspection blitz, officials stopped 136 westbound vehicles transporting 167 vessels or related equipment. Sixty-eight watercraft failed the Clean, Drain, Dry inspection, 14 required decontamination, and one had visible zebra mussels, according to Fisheries and Oceans Canada.
A second inspection operation in June 2026 involved 455 vehicles transporting 502 watercraft or related equipment. Officials reported 120 watercraft that had not been properly cleaned, drained, or dried, and 13 that required decontamination. One vessel contained visible zebra mussels, according to DFO's report.
A third inspection blitz in July involved 519 vehicles transporting 616 watercraft or related equipment. Officials reported 137 watercraft that failed the Clean, Drain, Dry inspection and 15 that required decontamination, according to Fisheries and Oceans Canada.
Officials emphasize prevention
During the June inspection blitz, Fisheries and Oceans Canada Minister Joanne Thompson said prevention is an important part of stopping aquatic invasive species from moving between waterbodies.
“Healthy lakes and rivers are essential to the communities that rely on them,” Thompson said in the DFO news release. “Through joint inspection efforts with the Government of Manitoba, we are working to protect those waters from aquatic invasive species and preserve Canada's freshwater ecosystems for generations to come,” she added.
Manitoba Environment and Climate Change Minister Mike Moyes also highlighted the ability of invasive species to cross provincial boundaries.
“Aquatic invasive species can easily cross provincial borders,” Moyes said in the same release.
What boat owners can do
The basic steps are straightforward, but officials emphasize that they need to be followed every time a boat moves between waterbodies.
Clean: Remove plants, mud and any visible aquatic organisms from the boat, trailer and equipment before leaving the water. Manitoba advises boaters to inspect submerged surfaces, including the hull, motor's lower unit and trailer.
Drain: Remove all standing water from the boat and equipment. This includes bilges, live wells, ballast tanks, bait buckets, compartments and the motor.
Dry: Allow the boat and equipment to dry completely before entering another waterbody. Manitoba notes that drying takes longer during spring and fall because of increased humidity and lower temperatures.
Decontaminate when required: Watercraft or equipment subject to applicable control-zone requirements may need additional decontamination before entering another waterbody.
For boaters, the challenge is that a vessel can appear clean while still containing water in areas that are difficult to see, inspect, or drain. Microscopic zebra mussel veligers can be present in remaining water trapped in bilges or storage compartments even though they are not visible to the eye.
The Clean, Drain, Dry process is likely to become a more recognized part of recreational boating in Canada as industry advocates and stakeholders measure of the risk. If zebra mussels continue to appear in new waterbodies, particularly across provinces, boaters can expect to see more available training and guidance to limit the possibility of cross-contamination in their region.
Comments