At the end of June, water tests taken at Clear Lake’s Boat Cove at Riding Mountain National Park (RMNP) proved positive for environmental DNA from zebra mussels. Water testing and vigilant visual studies in Clear Lake continued for more evidence of zebra mussels.
Last week Wednesday while conducting a visual survey, Parks Canada snorkelers found one partial shell and one living, adult sized zebra mussel attached to a rock. This evidence confirmed a building presence of zebra mussels in Clear Lake.
In response, an impermeable containment curtain was ordered and will be installed July 29th once all the equipment has arrived at the site. The curtain will be installed from Boat Cove to the pier to isolate the area where the zebra mussel was found, from the rest of the lake.
This morning, External Relationship Manager, Dameon Wall, and RMNP Ecologist, Tim Town spoke with stakeholders and the media on this developing situation.
"I want to start by saying that Parks Canada is continuing on the path that was set in May of this year. Staff continue with water monitoring and sampling, and the search for evidence as we move towards the containment and potential eradication of zebra mussels in Clear Lake,” shares RMNP External Relationship Manager, Dameon Wall. “
“Parks Canada continues to be an evidence-based decision-making organization that uses the best available science and indigenous knowledge in managing this situation.”
“Riding Mountain National Park staff are moving forward with efforts to contain the area with the goal of preventing the spread and preparing for a potential eradication attempt. This is a continuation of the decision made in May of this year, as Parks Canada knows zebra mussels present a real and significant threat to the ecological integrity of water bodies both inside and outside the park.”
Wall says beyond the installation of the containment curtain no decision has been made to attempt a further eradication method at this time as Parks Canada is awaiting the results of further visual surveys and water sampling from other areas of the lake before determining the best course of action.
He adds any decision will be widely communicated before actions are taken. In the meantime, the temporary rules for all watercraft for Clear Lake remain in place.
How do you measure success in your eradication methods?
“The goal here is to isolate that area and then to make a decision on what happens next after we get more evidence and data,” explains Wall. “We’ll be able to determine the efficacy once we’ve gone through the whole process. The ultimate goal of course is that if it's feasible for us to do a treatment of potash to eradicate zebra mussels then that’s our goal. But it would be premature to say much more at this point until we’ve got more data back from our investigations.”
Wall notes the scientific literature on containment curtains shows success in smaller water bodies.
“It was used in the early invasion of Lake Winnipeg and was considered highly effective in the areas where it was applied. However, the containment curtains that were used there, or the application didn’t get all the mussels. Some of them were outside of the treatment area.”
“Health Canada has approved potash for such an application in open water environments for the treatment of zebra and quagga mussels,” explains RMNP Ecologist, Tim Town. “Currently, we're only looking at zebra mussels here in our situation, and they've done quite a bit of testing in regards to the effects on other species and it's fairly targeted, especially at the concentrations that would be required for a treatment, in our case, which is for zebra mussels. The concentrations are about 100 parts per million, or the equivalent to 100 milligrams per liter, which really would be only targeting freshwater mussel species, so extremely effective for the eradication of zebra mussels.
Should the containment curtain have been installed as soon as the ice was off the lake? Is it too late for this strategy?
“Our approach has been consistent on this since the beginning,” says Wall. “The plan was always to have that containment curtain arrive. We're trying to strike a balance here in the actions and timing we're taking. Even if that curtain was here and installed already, we still don't have all the evidence we need to make a prudent decision about a potential treatment,”
“We're very confident that the curtain will be able to separate the water column. So really minimizing the potential spread of any zebra mussel veligers that may be present, or eDNA that may be present in that containment area,” continues Wall. “So regardless of if that curtain was in place or not, until we've got the evidence and the data to back up the decision, we would not be moving forward with any actions until we had that. We're waiting for more of that data to come back from our water sampling and veliger sampling.”
Tim Town says they’re working closely with the Department of Fisheries and Oceans Canada (DFO), which is well versed in aquatic invasive species and detection. “And we are doing quite intensive sampling within the proposed containment areas and just outside and we haven't found any further evidence other than just that small isolated area in and around the boat launch there at Boat Cove, so we're pretty confident that things are still fairly isolated in terms of the establishment of zebra mussels, but we're still awaiting around 78 test results to come back, hopefully next week from DFO.”
What determines the decision to deploy potash?
“That decision will be made once we've got more data back from our efforts outside of the containment area,” explains Dameon Wall. “The primary goal here initially is to isolate that space where the zebra mussel was found. And then depending on what we discover outside that containment area, that will help us determine the next step. So, if we have multiple data points or evidence suggesting that there is an invasion underway in many locations inside or in the waters of Clear Lake then a determination will have to be made as to whether it's feasible to go ahead with a potash treatment. And I will say that the more areas that have established populations, the less feasible any kind of treatment becomes.”
“If we find multiple locations of zebra mussels outside the area that we're going to be containing, then the likelihood of a treatment goes down considerably,” explains Wall. “It would not be prudent to treat the whole lake. That is certainly not something we're considering. That would not be cost effective, and it wouldn't be scientifically driven, right? We want to make good use of taxpayers' dollars in a potential application. So just sort of [half-hazardly] throwing stuff into the lake to try and deal with that is not the approach we're going to take. So, we will be looking at the data and that will dictate the next step.”
RMNP Ecologist, Tim Town agrees.
“I think it's prudent just to wait till the next round of samples comes in, just to ensure that we do have an isolated population, which we're assuming that we do based on our current testing results that we received. Like Damien said, if we did find evidence in further locations in the lake, the situation becomes much more complex.”
“In saying that we are preparing for a potential treatment, and we do have a contractor lined up to come as soon as possible if a treatment is triggered,” adds Town. “But that's where we're at; ensuring that we're making the right decision because obviously the ecological and economic impacts can be pretty profound. So, we want to make sure we have the right information and we're doing the right thing.”
Have you determined how zebra mussels were brought into Clear Lake?
“There is really no way to determine the specific location of how this zebra mussel arrived in Clear Lake,” says Wall. “Certainly, as you know, we are within about an hour and a half drive of other lakes that have zebra mussels in them. But I don't want to speculate on how it may have arrived at our lake. And in some ways, while I appreciate there's a lot of interest in that we're really focused on where we're going next and what we're doing now. Determining the point of origin of that zebra mussel doesn't help us necessarily. There are next steps, and my understanding is it would be very difficult to pinpoint source location scientifically.”
Tim Town says the identified zebra mussel was collected out of the water and sent to the DFO for inspection and testing. "So, we don't have any further information in regards to where it may have come from. I think there is some analysis that could be done in terms of like isotopes to look at certain elements within different water bodies, but I don't have that information.”
Dameon Wall says thus far in the 2024 boating season there have been several charges laid against several individuals who were unlawfully using a personal watercraft on Clear Lake. “I don’t have specific information about the number, or the charges laid, but again that’s not telling us where these mussels have originated.”
Wall adds the other important aspect of this is for Manitobans to continue to be vigilant to Clean, Drain and Dry all watercrafts when leaving any waterbody in and beyond our provincial borders.
Please listen to more with Golden West reporter Betty Sawatzky and Dameon Wall and Tim Town discuss the importance of Manitobans and visitors to our province to do their part.
“Parks Canada, thanks the community for its ongoing support for the Aquatic Invasive Species Program at Riding Mountain National Park and for the commitment to working together to attempt to further identify and possibly eradicate a population of zebra mussels in Clear Lake,” adds Dameon Wall.
(photos below submitted by Riding Mountain National Park)