We’re now being told that the battle has been lost. The provincial government has conceded that zebra mussels will probably never be eliminated from Lake Winnipeg, despite an earlier eradication effort. Actually, the battle was probably lost as soon as the aquatic pests were first found to be present in the lake. But there is still time to save other Manitoba lakes from infestations by the invasive mussels, although it will take stringent preventative measures and education programs to inform Manitobans on how they can help out.
Last fall, zebra mussels were, for the first time, found in Lake Winnipeg at the harbours at Gimli, Willow Point, Boundary Creek Marina/Winnipeg Beach and Balsam Bay. The tiny filter-feeders were discovered clinging to the hull of a private boat and a dock at Winnipeg Beach, and on some fishing boats dry docked at Gimli. In the spring, the province spent $500,000 on eradication efforts using liquid potash at the affected sites, which we now know was only partially successful in stemming the invasion.
In a press release, Conservation and Water Stewardship Minister Gord Mackintosh said results of monitoring of Lake Winnipeg turned up a small number of larval zebra mussels. “Although the treatments of the harbours this spring were successful and slowed the spread of zebra mussels in Lake Winnipeg, unfortunately there is evidence that a localized population of this highly invasive species exists outside the treated areas,” said Mackintosh. “Further monitoring is taking place for the rest of the open water season and I’m strongly urging fishers, boaters, cottagers and other lake users to remain vigilant and report any findings.”
The microscopic larva are known as veligers. While no zebra mussel veligers were detected at locations in or near the treated harbours, out of the more than 60 samples taken so far, nine larva were found in three samples taken from the southeast and eastern portion of the South Basin including east of where the Red River enters the lake, offshore from Grand Marais and in Traverse Bay and north of where Black River enters the lake. The samples were collected by department staff and by researchers on the Lake Winnipeg research vessel MV Namao.
The minister said the Zebra Mussel Science Advisory Committee will continue to advise the province on the best methods of managing the infestation. Results from enhanced monitoring efforts that will continue throughout the summer and fall will further help the advisory committee to assess the situation and provide recommendations, the minister said.
To prevent the spread of zebra mussels from Lake Winnipeg to other water bodies, all individuals who boat on Lake Winnipeg are being asked to ensure they clean, drain and dry their equipment and dispose of any bait and water every time they leave the lake, before entering another harbour on the lake or going to another water body. Overland transportation of recreational watercraft and water-based equipment is the main way zebra mussels spread.
Three decontamination units purchased by Manitoba Hydro are in place at Gimli Harbour, Winnipeg Beach and Selkirk Park, and will operate during peak boating times. Two other decontamination units will continue to travel to high-traffic boat locations, such as Grand Beach, for the rest of the summer. The minister also announced a new awareness campaign, “Don’t Move A Mussel,” to encourage boater to be vigilant and check their water crafts/boats for zebra mussels.
The minister announced that the province is working on developing new laws similar to those now in place in Minnesota to reduce the spread of zebra mussels. This would include laws about transporting water, introducing requirements to drain water before leaving a water body and requiring watercraft be transported with the drain plug removed and drain all water from boat and bait containers. Enforcement powers and fine levels are also under review, he added.
It was just a couple of years ago that zebra mussels were reported to be just across the international border in North Dakota. Earlier, the mussels were found by a local resident at Pelican Lake, Minnesota, about 800 kilometres south of the border. Then zebra mussel larvae were reported to have progressed from Minnesota to North Dakota into the Red River at Wahpeton, where the river begins its northward journey to Lake Winnipeg. It was a mere 635-kilometre leisurely drift on river currents for the larvae to reach Emerson at the U.S.-Canada border. How the mussels actually made their way into Lake Winnipeg is still a matter of speculation. Since adult zebra mussels can survive out of water for several days or weeks, if the temperature is low and humidity is high, they could have been transported on a boat’s hull after it was used in mussel-infected waters, or the larvae could have drifted into Manitoba. Whatever the scenario, they’re here, they’re alive and they’re an extremely serious threat to the lake.
Zebra mussels, a species native to southern Russia, was first noticed in North America in Lake St. Claire, near Detroit, Michigan, in 1988. It is believed mussel larvae hitched a ride in the ballast water of a transoceanic ship. Since that fateful ballast discharge, zebra mussels have rapidly spread across North America.
The prolific and plankton-devouring mussels use a special byssal gland to secrete highly-adhesive threads that attach it to rocks, debris, water pipes, fishing nets, boat hulls and native mussel species. The attachment ability of the mussels results in bio-fouling — masses of mussels clogging pipes and choking off oxygen and the food supply of other organisms.
Researchers from the Great Lakes Environmental Laboratory in Ann Arbor, Michigan, also documented basic changes in the food-chain in the zebra-mussel-infested waters of Lake Huron’s Saginaw Bay. Zebra mussels also release nutrients that encourage algae growth, especially toxic blue-green algae, according to research by the U.S. National Oceanic and Atmospheric Administration. In Lake Winnipeg, hundreds of square kilometres of gooey blue-green algae blooms have been a growing problem in recent years. While the toxins secreted by the algae stress native species of mussels, a study has found that zebra mussels are unaffected; thus, they have a free rein to outcompete their competition.
The disruption of the food-chain by
zebra mussels can seriously impact Lake Winnipeg’s commercial and recreational fishing industries. Another potential blow to the local economy is that the mussels can foul recreational beaches.
As an invasive species, zebra mussels have no native predators other than small- and large-mouth bass and crayfish, which cannot eat enough mussels to make a significant dent in their numbers.
As yet, no one can predict the exact outcome of the invasion of Lake Winnipeg and potentially other Manitoba waterways, but the experience in other jurisdictions has shown disasterous ecological changes can be expected.