Manitoba has declared victory in its first battle with invading zebra mussels but says the unique treatment it used to kill the shellfish doesn't mean the province is free of them yet.
The province sealed off four harbours in mid-May with a silt curtain before injecting liquid potash into the water. The concentration of potash was increased until it suffocated the mussels.
The experiment received global attention because it's believed to be the first time liquid potash has been used in open water. Scientists who study the mussels called it a "golden opportunity" to find a way to prevent their proliferation in water bodies around the world.
Conservation Minister Gord Mackintosh said the treatment was successful and killed the mussels in the harbours. But it was just the first step in the fight to keep the mussels out of the province, he added.
"We've won the first battle in what is likely to be a long war and it must be a hard-fought war," Mr. Mackintosh said Wednesday. "There is a good chance that zebra mussels are still lurking outside of the treated harbour areas. We have got to detect wherever else these zebra mussels might be."
The invasive species, which has been in the Great Lakes for nearly two decades and has spread throughout parts of the United States, was discovered for the first time in Manitoba last October.
The mussels reproduce quickly and can disrupt the food chain, clog water pipes and create algae.
Mr. Mackintosh said the success of Manitoba's experimental treatment, which cost $500,000, has attracted attention from countries such as the U.S. and Spain. He said the province hasn't ruled out using the treatment again.
For now, the province is increasing monitoring on Lake Winnipeg. There are also five decontamination units for boats that could spread the mussels.
"It's been estimated that about 90 per cent of the boats coming into Manitoba come from jurisdictions where there is exposure to invasive species," Mr. Mackintosh said. "So there is a great risk all around us."
He implored boaters and residents to watch for the mussels and to ensure they aren't unwittingly unleashed into Manitoba's waterways.
Laureen Janusz, fisheries biologist with Manitoba Conservation, said the department will spend the summer searching for the mussels deep in Lake Winnipeg. It could take years before the province can declare itself free of zebra mussels, she said. "We have to remain hopeful that we're doing everything we can to stave off, to prevent the spread," she said.
Shannon Martin, conservation critic for the Opposition Tories, said the province appears to be moving in the right direction, but questioned why it took so long to develop a plan.
"This species, in terms of the environmental and economic cost to Lake Winnipeg and our waterways in general, is phenomenal," Mr. Martin said. "It's a bit concerning that we've known about this invasive species being in these specific harbours for almost a year and only now is the government announcing that longer-term strategy."