The spread of zebra and quagga mussels is not just a Great Lakes issue, it's a continental issue. The stories and case studies below explore how places as far as Nevada and California are dealing with an invasion that was discovered twenty years ago in Lake St. Clair.

Great Lakes

“It is with profound regret that the Great Lakes Fishery Commission marks the twentieth anniversary of zebra mussels in the Great Lakes,” said Marc Gaden, Communications Officer for the Great Lakes Fishery Commission. “ Zebra mussels truly changed the ecosystem and the economy in ways not seen since the sea lamprey invaded the upper lakes in the 1920s.” 

Zebra mussels are particularly insidious in that they undermine the very foundation of the Great Lakes’ food web.  Being filer feeders, zebra mussels rob fish and other organisms of the food they need.  They offer nothing in return; they provide no value as a prey organism and throw the natural ecosystem out of balance.  Zebra mussels are implicated in the alarming disappearance of Diporeia, a key native zooplankter that is vital to the diet of many native fish species.  Zebra mussels, when they interact with round gobies, another exotic pest, help produce the conditions that move botulism up the food web, killing Great Lakes fish and birds. 

“Overall, zebra mussels have cost the fishery, the economy, and the people of the region dearly.  It is time to learn from the hard lessons zebra mussels have taught us,” says Gaden. “We must manage the ballast from oceangoing vessels; ballast that has permanently littered our lakes with trash species like zebra mussels.”

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Inland Ontario

Following the discovery of the zebra mussel in Lake St. Clair in 1988, it quickly spread to all the Great Lakes and connected waterways such as the Trent Severn Waterway and Rideau Canal. Using these recreational corridors, in less than a decade zebra mussels had gained access to many of the major watersheds of southern Ontario.

Recognizing the devastating impacts zebra mussels and other aquatic invaders could have on Ontario's 250,000 inland lakes, the Ontario Federation of Anglers and Hunters in partnership with the Ontario Ministry of Natural Resources created the Invading Species Awareness Program.

"Since 1992, we have educated hundreds of thousands of boaters and anglers about this issue; posted signs at over 3000 boat launches, and successfully engaged public participation in measures to stop overland spread from recreational watercraft said Francine MacDonald Invasive Species Biologist for the Ontario Federation of Anglers and Hunters.  "We are also actively involving hundreds of community groups to participate in "Invading Species Watch" initiatives to annually monitor lakes and waterways for zebra mussels and other invaders".

Similar efforts have also been initiated in neighbouring provinces such as Manitoba and Quebec to stop the further spread of zebra mussels across the country.

However MacDonald added "Despite all of these significant outreach and prevention efforts, we are fighting an uphill battle, if action is not taken immediately to stop new introductions to the Great Lakes and Canada's coastal waters from ship ballast and other vectors."

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Rideau River, Ontario

Prior to 1993, the Rideau River was clean of zebra mussels and had a rich diversity and abundance of native unionid clams. But, it would not take long for the invasive zebra mussel to take hold and spread throughout the river.

For six years starting in 1993, André Martel and his team at the Canadian Museum of Nature tracked how the zebra mussel virtually destroyed the native clam population, building huge colonies on the shells of the native clams (sometimes also referred as native mussels), effectively starving them. In only four years the native clam population had disappeared over vast areas of the river and the spread of the zebra mussel was comparable to, if not greater than, the highest spread of the mussel in the Great Lakes. In some downstream areas, densities of zebra mussels exceeded 150,000 individuals per square metre.

 "We knew that the ecological impact of the zebra mussel was severe in the Great Lakes region. Here in the Rideau River, we found the first zebra mussels soon after their discovery in Lake St. Clair," said Dr. Martel. "They were on a large steel ship that had made its way up the Rideau Canal to Ottawa after having spent some time sailing in the zebra mussel-ladden Lake Erie."

André Martel and his fellow researchers and volunteer divers were the first to employ SCUBA-diving techniques to quantitatively investigate and document the long-term impacts of the zebra mussel on a small river ecosystem.

"Ironically, the Rideau River and Rideau Canal would become one of Canada’s Heritage Rivers and a UNESCO World Heritage Site. It is unfortunate that the Rideau River-Rideau Canal system had to lose much of its rich native mussel populations before reaching this status simply because of our failure to properly control or prevent the transport of invasive molluscs like the zebra mussels in transoceanic cargo ships bound for Canada." 

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Nevada
Live zebra mussels were first discovered in Lake Mead in January 2007, though authorities suspect that the invaders were introduced as early as 2005. The detection has raised concerns that the mussel will affect hydroelectric power operations, ruin boat engines, and clog water pipes.

“The big scare for Las Vegas is that about 80 percent of the town’s drinking water comes from Lake Mead,” said Kevin Cabble, president of the Nevada Wildlife Federation. “Also, the Colorado River goes down into California, and it is likely that the mussels will continue to spread, affecting not only Las Vegas’s water supply, but also the water supply of other cities and states.”

Cabble added that the state has initiated an education program aimed at recreational boaters in hopes of preventing the spread of zebra mussels. The campaign focuses on boat inspection both before entering the water and after leaving it.
               
 “Unfortunately, these things are already here, so the best we can do is try and prevent them from spreading,” Cabble said.

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California
In January 2008, California officials confirmed that live zebra mussels had turned up in the San Justo Reservoir in San Benito County. The reservoir is connected to California’s central waterways that feed millions of acres of farmland and provide drinking water.

Similarly, Quagga mussels – a closely-related species – were first detected in the Colorado River system in January 2007 and were later found in San Diego and Riverside counties by California water agencies.

“Quagga and zebra mussels pose a serious threat to California’s vast fishing and recreational boating opportunities, they threaten the state’s extensive water delivery systems and agriculture, and pose a serious threat to California’s diverse  native aquatic resources,” said Susan Ellis, California Statewide Invasive Species Coordinator.

California has adopted measures to prevent the spread of the mussel, including opening a toll-free telephone line for reporting zebra mussel sightings and educating boaters in proper boat cleaning techniques.

Also, a multi-agency taskforce that includes the California Department of Fish and Game, Department of Water Resources, Department of Boating and Waterways, and California State Parks has responded with surface and underwater inspectors to determine the extent of the threat.

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100th Meridian Initiative

The 100th Meridian Initiative is a cooperative effort between state, provincial, and federal agencies to prevent the westward spread of zebra mussels and other aquatic nuisance species in North America.