Province on alert for zebra mussels

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A cluster of zebra mussels from Lake Michigan in 2007. (JOHN L. RUSSELL / THE ASSOCIATED PRESS)

Zebra mussels -- to the uninitiated, the name conjures up a cute image but to people concerned about water and the environment, they are an alien species capable of massive destruction.

And, they've now been confirmed in the Red River basin.

"They are a harmful, invasive species," Dwight Williamson, the assistant deputy minister of Water Stewardship and the province's expert on the tiny mollusk, said. "They are an excellent example of the need to take all water-management initiatives that will keep invasive species out of our water system."

The province recently issued an alert zebra mussels had been confirmed in Pelican Lake, Minnesota -- the closest the creatures have come to Manitoba.

Zebra mussels attach to smooth surfaces, like water intake pipes, boats and underwater equipment. They are blamed for causing millions of dollars in damage annually.

Williamson said the zebra mussels have proved problematic for facilities that draw water from lakes and rivers, including water-treatment plants. The mussels clog the intake pipes, affecting inflow rates and driving up the cost of maintenance.

To compensate, some utilities have had to enlarge the intake pipes and increase the number of pipes so they can keep water flowing when pipes are shut down for maintenance.

You may have seen the big billboards at the Manitoba-Ontario border urging motorists to do everything possible to keep them out of Manitoba.

Now, the province will erect similar signs along border crossings at North Dakota and Minnesota. Williamson said for the past 10 years, the province has employed inspectors during the summer season at border crossings who examine boats coming into Manitoba for the zebra mussels.

"Since the early 1990s, we've believed that it was inevitable that zebra mussels would find their way to Manitoba," Williamson said. "We thought that through these preventative measures, we could slow down or significantly delay their entry into the province.

"We don't know when they will reach Manitoba but we expect they will."

Pelican Lake is about 800 kilometres south of the Manitoba border in the Detroit Lakes area, but water from that lake can reach the Red River through a circuitous route -- from Pelican Lake to the Pelican River, to the Ottertrail River to the Red River at Fargo, N.D.

The zebra mussels have spread from the east coast harbours, where ocean-going vessels dock, right across the interior of the United States to California and the Great Lakes, both in Canada and the U.S.

Nothing has been able to stop their spread.

Williamson said their only predators in North America appear to be the small-mouth and large-mouth bass but those fish species can't eat the zebra mussels fast enough to slow them down.

"The small-mouth and large-mouth bass will feed well (on the zebra mussels) but not enough to control the population," he said.

Once introduced into a waterway, Williamson said, one of the first changes is an increase in water clarity. While that may appear beneficial, he said that's not natural and will result in the growth of rooted plants in the bottom of lakes. That alters the environment for fish species, he said, meaning that in some areas northern pike will replace sauger and walleye.

Williamson said scientists don't know yet how zebra mussels will fare in the colder rivers of northern Canada, adding the thinking is they won't do well above the 50th parallel.

He said that should stop the spread of zebra mussels into waterways in central and northern Manitoba but the southern part of the province will likely prove inviting.

Williamson said there have been reports of zebra mussels in Lake of the Woods but those always proved false.

Williamson said that now the zebra mussels are in Minnesota, the province will step up its campaign to inform boaters to be on the lookout and to take measures to prevent them from being brought to Manitoba.

aldo.santin@freepress.mb.ca

Republished from the Winnipeg Free Press print edition September 28, 2009 A4