The Aliens Are Coming! 

Strange mussels, fish, plants, and diseases—and their clueless human helpers—could decimate Montana waters

At 2:30 p.m. on Friday, March 4, Erik Hanson got an urgent call from the state of Idaho: A sailboat was on its way to Montana, destined to hit Dayton Harbor, on Flathead Lake, at 10 a.m. Saturday—and it might have dangerous cargo.

Hanson took off from Missoula the next morning. Within minutes of the sailboat's arrival at Dayton, he spotted the cargo. It was clinging to the worn, blue keel of the 33-foot sailboat: a pea-sized quagga mussel.

Quagga mussels are an invasive species in North America.

Hanson is an invasive species expert for the intergovernmental Flathead Basin Commission. John Wachsmuth, Montana Fish, Wildlife and Parks regional coordinator for invasive species, joined him that morning. After Idaho's state invasive species coordinator, Amy Ferriter, tipped Hanson that the sailboat might not have been adequately decontaminated when it left quagga-infested Lake Mead, Nevada, Hanson called Wachsmuth, who coordinated the inspection of the boat. Although they'd learned the night before that the sailboat's owner was not going to put the boat in the water immediately, the need to be sure impelled Hanson and Wachsmuth to Dayton. The discovery of just one living quagga mussel was enough to stop inspecting and start the process of decontaminating the entire boat.

"If we get these mussels here, there is nothing that we can do," says Hanson. "They're going to spread everywhere, and there's going to be no way to contain them."

In the eastern United States and the Midwest, zebra mussels have disrupted aquatic ecosystems and caused billions of dollars of damage to water and hydropower systems. The zebra mussel's close cousin, the quagga mussel–"a zebra mussel on steroids," Hanson calls it–has also invaded the East. Then the quagga appeared in the West for the first time at Lake Mead in 2007. Since then, quagga mussel infestations have taken hold in dozens of other lakes and rivers in the West, fouling dams, water lines, boats, and anything else that remains in the water too long.

click to enlarge Eating up to three times its weight daily, the invasive grass carp can grow to 40 pounds.
  • Eating up to three times its weight daily, the invasive grass carp can grow to 40 pounds.

Montana is extremely vulnerable to zebra and quagga mussels as well as other aquatic invaders. The state has an enormous amount of fresh water that's popular with in-state and out-of-state recreationists who could bring such invaders into the state or move them around. With an extensive irrigation and hydropower infrastructure as well as a tourism industry that's solidly hitched to immaculate bodies of water and fishing, Montana ought to be afraid.

Frenzied carp hordes

In the spring of 2006, the white-bellied corpses of thousands of drum, a silvery-gray fish, floated just below the surface of Lake Erie. As waves pushed them to shore, the bodies piled up, forming walls of fish four feet high. The carcasses showed the signs of Viral Hemorrhagic Septicemia, or VHS: Bulging eyes, as if their heads had been cranked down in a vice, and skin that looked like it had been tattooed with red ink. The virus killed millions of fish in other places that year and has since spread to more lakes and rivers, killing still more fish.

Excessively lively fish, on the other hand, plague the Illinois River. There, and in many other drainages of the Mississippi River, Asian carp have taken over. The fast-growing, ravenous fish vie for food with the river's existing aquatic life; scientists have documented declining body sizes in native fishes such as the gizzard shad and the commercially important bigmouth buffalo since Asian carp appeared in the Illinois River in 1995. But scientific measurement isn't necessary to detect this invasion. Engine noise disturbs the carp, which can reach a density of over 4,100 fish per mile, causing frenzied carp hordes to fill the air in a motorboat's wake. That phenomenon has given rise to videos in which shirtless dudes motor down the river smacking the creatures out of the air with bats. A quick search on Youtube for "Asian carp baseball" or "zombie fishing" turns up dozens of such movies from across the Midwest.

Texas, meanwhile, is struggling with mussels. The North Texas Municipal Water District's pump at Lake Texoma has sat idle for two years due to fears that recently arrived zebra mussels will get into the district's water supply. The inoperable pump has reduced the district's water supply by almost a quarter; this April, the 1.6 million-strong district had to start conserving water. The precaution stems from experience in the Great Lakes where zebra mussels rapidly colonized water intake facilities, encrusting screens and pipes with billions of bodies at densities up to 70,000 per square foot. In 1989 and 1990, the town of Monroe, Michigan experienced severe water shortages and several outages due to the mussels. Other water facilities on the Great Lakes have spent millions trying to deal with the invasion.

Combined with maps that seem to show invasive species creeping and slithering across the continent, stories like these make the prospect of invasive species seem like a horror movie, which is perhaps half-right.

Invasive species are not zombies, monsters, or mutants. They are "aliens" only in the sense that they come from somewhere else on the planet. In their home ranges, they're usually either valued by humans or are a normal part of the ecosystem. Where the quagga and zebra mussels originate, near the Black and Caspian Seas, for example, predators and parasites have coevolved with the mussels and keep them in check. Asian carp are valued–indeed, celebrated–in China, where they've been part of the region's food and culture for 1,000 years. There is a common biology to invasive species, however. They're usually extremely adaptable, and can produce lots of young and disperse them widely.

click to enlarge Eileen Ryce, Montana’s invasive species coordinator, conducts boater interviews at a watercraft inspection station on the Fort Peck Reservoir. - PHOTO COURTESY OF EILEEN RYCE
  • Photo courtesy of Eileen Ryce
  • Eileen Ryce, Montana’s invasive species coordinator, conducts boater interviews at a watercraft inspection station on the Fort Peck Reservoir.

Most of the invasive species that plague North America come from the Eurasian landmass. For thousands of years, Old and New World organisms evolved independently of each other. Columbus's voyage initiated a reunion of these worlds that resulted in a massive swapping of organisms, intentionally and unintentionally, which historians call the Columbian Exchange. Since 1492, the human webs of transportation and commerce have only thickened, bringing tens of thousands of exotic organisms to North America. A small percentage has qualities that can make them invasive. But to be invasive, they need human help. VHS can float free in lake water, carp can swim up rivers, and mussel larvae can drift downstream, but none of these organisms can cross land on their own to get into a new drainage.

Mostly, human help is unintentional. But sometimes it's deliberate, even if the consequences are unforeseen.

Kokanee double whammy

In the 1960s and 1970s, Montana Fish, Wildlife and Parks planted the opossum shrimp, Mysis relicta, in the Flathead drainage, hoping to augment the popular kokanee fishery. At its height, in Flathead Lake, fishermen hauled 100,000 kokanee out each year. By the late 1980s, after the establishment and explosion of Mysis, they caught...none. Something had obviously gone wrong.

Fisheries managers had based this ecological experiment on the phenomenal growth of kokanee in British Columbia's Kootenay Lake after the introduction of Mysis shrimp there. But Kootenay Lake had a unique upwelling current that made the shrimp, which normally hide on the lake bottom during the day, available to the kokanee. At Flathead Lake, not only did the shrimp not provide a food source for kokanee, but they competed with kokanee for its main zooplankton prey. The tiny shrimp did provide a food source to one fish, however: the bottom-dwelling, fish-eating lake trout. "Kokanee really got a double whammy," says Bonnie Ellis, a biologist at the Flathead Lake Biological Station. "Not only did Mysis eat the kokanee's favorite food, but Mysis then provided a food source for its major predator."

The destruction of the kokanee fishery reverberated through the Flathead ecosystem, affecting even non-aquatic animals. Flathead Lake kokanee spawned at McDonald Creek in Glacier National Park. When the fishery was robust, this swarm of pink flesh attracted the largest concentration of bald eagles in the United States. In one week in 1983, researchers counted 639 bald eagles at McDonald Creek. In 1989, they counted 25.

"These aquatic invasive species can completely alter the food webs of lakes and rivers," says Ellis. "I've been here [on Flathead Lake] working for 30 years, and it's like I'm working on two different lakes."

The Mysis introduction is an extreme example of a more general phenomenon: Aquatic invasive species are a threat to fisheries, but fisheries management is sometimes at the heart of aquatic invasions. After Mysis warped Flathead Lake's food web, fisheries scientists began noticing declines in wild rainbow trout in the Madison River, in southern Montana, in 1991. By 1994, the fishery had dropped to about 90 percent of its historic average. Lab results on the rainbow trout came back positive for a familiar but unexpected pathogen: whirling disease.

Whirling disease—so named because it attacks the nervous system and causes fish to swim in a spiral—had been a known problem in U.S. fish hatcheries since the 1950s, but it wasn't considered a threat to wild populations. The discovery of the disease and its role in decimating wild trout in Montana and Colorado rivers in the 1990s shocked fisheries scientists. Funding at state and national levels kicked research into high gear, resulting in rapid progress on the biology of the disease, with the ultimate goal of eradicating it.

click to enlarge Can you find it? A pea-sized quagga mussel hitched a ride from Lake Mead on this sailboat hull on March 4. “If we get these mussels here, there is nothing that we can do,” says Erik Hanson. “They’re going to spread everywhere, and there’s going to be no way to contain them.” - PHOTO COURTESY OF ERIK HANSON
  • Photo courtesy of Erik Hanson
  • Can you find it? A pea-sized quagga mussel hitched a ride from Lake Mead on this sailboat hull on March 4. “If we get these mussels here, there is nothing that we can do,” says Erik Hanson. “They’re going to spread everywhere, and there’s going to be no way to contain them.”

Yet despite millions spent on research, agencies have not been able to halt the expansion of the disease, let alone stamp it out. It continues to spread to other drainages; and though rainbow trout in the Madison have recovered from their low, they are still 30 to 40 percent below historic levels.

The deadliest fish disease

On March 15, at Polson, on the shore of Flathead Lake, dozens of scientists and land managers gathered for the Crown Managers conference. It's an annual event for agencies involved in the Crown of the Continent, a 28,000-square-mile ecosystem that encompasses much of northern Montana, including Glacier National Park and Flathead Lake, as well as neighboring lands in Canada. Present were representatives from the Forest Service, Glacier, the Confederated Salish and Kootenai tribes, and many state and local government agencies from Montana, British Columbia, and Alberta. The discussions were consumed by the past, present, and future of aquatic invasive species. The introductory speaker, Mary Sexton, director of Montana's Department of Natural Resources and Conservation, set the tone for the conference: "We have an opportunity to collaborate before aquatic invasive species become a full-blown crisis," she said.

For the next three days, the scientists and managers hashed out the status of aquatic invaders in Montana and the Crown, and how future invasions might be averted. According to Eileen Ryce, the keynote speaker and Montana's invasive species coordinator, many aquatic invaders are already in the state. In addition to Mysis shrimp and whirling disease, Montana has several aquatic invasive plants. Since 2007, Eurasian water milfoil has spread over the Noxon and Cabinet reservoirs, where it now covers 400 acres. An environmental assessment of the reservoirs indicates that the weed has the potential to cause damage. Eurasian milfoil forms dense canopies that shade native aquatic plants. It can reduce food for fish, and it may particularly affect salmon and trout by covering the gravel beds where they spawn. The weed also ruins swimming areas, clogs water intakes, and fouls the air when it decays. Milfoil invasions have reduced lakeside property values by 15 percent in the Midwest, according to invasive species educator Doug Jensen, hurting not only property owners but state coffers.

Western Montana has other aquatic invasive weeds. Yellow flag iris is well established in four counties in northwest Montana, and flowering rush covers over 2,000 acres in western Montana. Like Eurasian milfoil, these plants threaten native fish and can ruin swimming areas. They can also be very costly to irrigation systems. In Idaho, canals infested with flowering rush have to be chained every two to three years to maintain proper water delivery.

Still other, potentially more destructive invaders loom on the horizon—and Montana may be particularly susceptible to them.

click to enlarge Zebra mussels cling to nearly any hard surface, leaving boat props, shorelines, and irrigation lines encrusted with thousands of the crustaceans anywhere they’ve been introduced. - PHOTO COURTESY OF NATIONAL PARK SERVICE
  • Photo courtesy of National Park Service
  • Zebra mussels cling to nearly any hard surface, leaving boat props, shorelines, and irrigation lines encrusted with thousands of the crustaceans anywhere they’ve been introduced.

According to Jensen, 14 million boaters move frequently between water bodies in the United States. Montana's ample and attractive waters are a destination for many of them. The state contains 750,000 acres of recreational water, said Ryce. Forty-one percent of anglers licensed in Montana are non-resident, and all told, non-resident use adds up to a total of 800,000 angler days—which means a lot of fishermen coming and going from the state. And one third of Montanans are licensed anglers, which means there is a high potential for in-state anglers to transport invasive organisms on boats, bait, or fishing gear. Popular water bodies used by these anglers can serve as stepping stones to spread aquatic invaders across the Continental Divide. "The two most likely introductions for mussels in Montana are Fort Peck Reservoir and Flathead Lake," said Ryce. "Canyon Ferry Reservoir [near Helena] links these two together. It's usually rated number-one by resident anglers."

If viral hemorrhagic septicemia, Asian carp, or invasive mussels made it into Montana, they'd find a welcoming habitat in much of the state—and their effects would be alarming. "VHS would be deadly to pretty much all the fish species we have here in the state," says Ryce, whose scientific training is in fish diseases.

"It's the deadliest fish pathogen we've ever seen."

Those fish that don't die from what has been called the ebola of fish could spread VHS and re-infect fish populations. "Typically what you see when it gets introduced into a new population is a very dramatic fish kill, and then survivors within the population act as carriers for the virus," said Ryce. "During times of stress, after the population has rebounded, you'll see another die-off or fish kill, but it never completely leaves the systems. So you often see this cyclical event of large fish kills."

Several species of fish are categorized as Asian carp, and at least three of these could invade parts of Montana. "The silver and bighead carp are more of a concern for the lower Missouri and lower Yellowstone, but the grass carp can survive in western Montana and we know they have in the past," said Ryce. "They are certainly a threat."

VHS and mussels are likely to come into the state in boats or bait, vectors that could also introduce Asian carp. Another route for some invasive species is aquarium shops and pond supply stores. Aquarium stores in Montana have sold Eurasian water milfoil in the past, and aquatic gardeners have introduced aquatic weeds like yellow flag iris to Montana. Selling and buying invasive species in the state is illegal, but even as agencies work with commercial sources in the state, there is only so much they can control.

click to enlarge Mary Sexton, director of Montana’s Department of Natural Resources and Conservation, set the tone for the conference: “We have an opportunity to collaborate before aquatic invasive species become a full-blown crisis,” she says. - PHOTO BY CHAD HARDER
  • Photo by Chad Harder
  • Mary Sexton, director of Montana’s Department of Natural Resources and Conservation, set the tone for the conference: “We have an opportunity to collaborate before aquatic invasive species become a full-blown crisis,” she says.

"We have found grass carp in private ponds. That is where we have the most problems with them," said Ryce. "People introduce them to control aquatic vegetation. It would be illegal to buy them, but you know you can get anything online."

Most websites that sell grass carp are frank about which states require grass carp permits or have banned grass carp altogether, and none mention delivery to Montana. But other states, including Wisconsin and Texas, have had instances of illegal shipments of grass carp into their state. Arkansas in particular has been a source of these illegal shipments.

Whatever their route into the state, their potential for spread and damage is unsettling. Grass carp are extremely mobile, fecund, and voracious. Biologists have documented them migrating 1,000 miles in one season. Like zebra and quagga mussels, they can produce millions of eggs in a year. And they're pigs. They can increase in size by 45 percent in one month. The intestine of an adult grass carp is two and a half times the size of its body.

"The grass carp eats all the vegetation in a system," said Ryce. "So in terms of habitat, they are very destructive...You can end up with a sort of pea green soup of algae left over."

Grass carp only process about half of what they eat, however. The rest is expelled as feces, which can contribute to toxic algal blooms. After the introduction of grass carp into Devil's Lake, in Oregon, toxic algal blooms linked to the fish resulted in a "Red Level" alert in 2009 in which "contact with the water by people and pets" was not advised.

Mussel invaders

Asian carp and VHS are scary, but the poster creatures for an aquatic invasive species apocalypse are the zebra and quagga mussels. At the Crown Conference, discussion of invasive mussels focused on Flathead Lake, both because of the lake's susceptibility to an infestation and because the lake–the largest natural freshwater lake in the American West, and one of the cleanest large lakes in the world–is an ecological and economic keystone of western Montana.

click to enlarge Thousands of fish carcasses pile on the shore of Lake Erie in 2006, victims of viral hemorrhagic septicemia, or VHS. The virus killed millions of fish elsewhere that year and has since spread even farther. - PHOTO COURTESY OF VERMONT FISH AND WILDLIFE
  • Photo courtesy of Vermont Fish and Wildlife
  • Thousands of fish carcasses pile on the shore of Lake Erie in 2006, victims of viral hemorrhagic septicemia, or VHS. The virus killed millions of fish elsewhere that year and has since spread even farther.

Lakes with lots of calcium are vulnerable to an invasion because mussels need calcium for their shells. Chris Downs, a fisheries biologist in charge of Glacier National Park's aquatic resources, showed that most of the park's lakes had 15 to 20 milligrams of calcium per liter of water. That's a moderate level for mussels, but not necessarily prohibitive. According to Bonnie Ellis, Flathead Lake's calcium level is about 25 to 35 milligrams per liter—which probably makes it good real estate for zebra and quagga mussels. "Zebra and quagga mussels would definitely alter the entire food web," she said. "Every square meter, if it was loaded with mussels, would be filtering the zooplankton and phytoplankton out of the water column at the rate of 100,000 liters per day. So they're removing food for the young fish. Not all fish eat the plankton, but many of the juvenile fish do."

Such dire predictions are born out by research elsewhere. In the Hudson River, for example, biologists found that mussels reduced phytoplankton abundance by 85 percent. The removal of such large quantities of food would dramatically affect any fish that feed on plankton. That would include many native fishes such as the pygmy whitefish and northern pike minnow, and also the lake whitefish, a popular sport fish. The severe competition for plankton would also reduce Mysis numbers, which in turn could cause the lake trout fishery to collapse.

"Basically almost all fish would decline except maybe those that feed in the littoral zone," the area close to shore, said Ellis. "So we might get a lot more suckers, mountain whitefish, pike, bass, and black crappie—meaning more shallow-water angling opportunities for non-native fish."

More beach fishing then?

"The shoreline experience will be really pretty bad," she said. "There will be bacterial mats, green algal mats, toxic algal blooms, and rough, sharp mussel shells."

A mussel invasion in Flathead Lake could also easily spread into the Flathead River. Rhizomes of flowering rush have been steadily dispersing downstream from Flathead Lake since 1964 and have now reached Lake Pend Oreille, in Idaho. Zebra and quagga mussel larvae can likewise float free in the water. It's likely that the downstream drift of these larvae from Lake Mead, for example, is responsible for mussel invasions at several other spots on the Colorado River. This all makes protecting the Crown of the Continent Ecosystem from invasive species even more important. "We have the triple divide here," said Ryce, referring to the point in Glacier National Park where drainages flowing to the Pacific, Atlantic, and Arctic Oceans converge. "And all this crap flows downstream."

click to enlarge Although Montana Representative Verdell Jackson sponsored the state’s first Aquatic Invasive Species (AIS) Act in 2009, the state still lags behind many other western states in terms of funding and capacity to deal with aquatic invasive species. - PHOTO BY CHAD HARDER
  • Photo by Chad Harder
  • Although Montana Representative Verdell Jackson sponsored the state’s first Aquatic Invasive Species (AIS) Act in 2009, the state still lags behind many other western states in terms of funding and capacity to deal with aquatic invasive species.

Even more than the ecological effects, it's the physical presence of invasive mussels–the coating and the clogging–that worries some people. "Mussels are probably different from the other aquatic invasive species because they have that ability to impact more than the ecosystem," said Ryce.

At Parker Dam on the Colorado River, for example, mussels have fouled the dam's spillway, its generator seals, and its domestic water lines. In the East, attempts at mussel control give a sense of what long-term attempts can cost. Ontario's hydropower utility has spent between 15 and 18 million dollars retrofitting its power plants after mussels encrusted them. Between 1993 and 1999, invasive mussels cost the entire North American power industry an estimated $3.1 billion. The broad impact on communities, businesses, and industries was estimated at more than $5 billion.

Downstream from Flathead Lake is some expensive water-related infrastructure. Directly below the lake is Kerr Dam and the Flathead Irrigation Project, and beyond the Flathead Valley there are dozens of other dams, irrigation projects, and municipal water systems, all the way down the Columbia River to the Pacific Ocean.

Make sure the eggs are killed

Montana Representative Verdell Jackson is something of an aquatic invasive species crusader. In 2009, he sponsored the state's first Aquatic Invasive Species (AIS) Act. This year, he's introduced a revision to the 2009 AIS Act. Not otherwise known for supporting environmental issues, Jackson has pushed hard for better funding and policy for invasive species. So far, he's had success. His new bill passed the state senate by a landslide and passed a first hearing in the state house more narrowly. Still, even if Jackson's bill is signed into law, Montana will lag behind many other western states in terms of funding and capacity to deal with aquatic invasive species.

Since 2002, Montana has had an aquatic invasive species plan, which includes coordination between agencies and education. The plan received federal approval and funding that was matched by state funds and bolstered by various grants. Jackson's 2009 bill secured more funding to combat aquatic invasive species and gave more power to agencies to regulate boating and recreation activities that could spread them. It also resulted in a large education and outreach campaign that included signs, radio spots, and billboards instructing boaters to inspect, clean, and dry their boats after use.

Jackson's new bill would extend funding and strengthen agencies' ability to regulate activities that could spread invasive species. "This special program is setting up check stations around the perimeter of Montana, around the border, and on the roads especially that come in from other states that are infected," he explains. "Last time these were voluntary check stations and this time they are going to be mandatory check stations...When anything is found [on a boat], inspectors would use the power washer to clean it off. If it's a big boat, and we can't adequately clean it, then it will be impounded. In fact, probably if it has a live mussel on it, it will be impounded because we want to make sure the eggs are killed."

Erik Hanson helped write Oregon's invasive species act, which served as a template for Montana's 2009 AIS Act. He supports Jackson's revision, with a qualification. While the bill allows for mandatory inspections and quarantine, it requires agencies to declare an invasive species management zone first. "Nobody in the state has that authority now unless they declare a statewide management area," says Hanson. "That needs to happen."

Both Hanson and Jackson are looking to other states, especially Idaho, for more policy ideas. "I am a firm believer that this is an issue that lies beyond a single agency or two agencies, and that we need a council to really guide the effort," Hanson says. "Invasive species councils have been one of the major reasons why other states have more successful programs than Montana."

Hanson advocates the sort of coordination that Idaho's Aquatic Invasive Species program has with the state's Department of Transportation. "The fact is, the boat that came up to Dayton [with a quagga mussel], the only reason we knew about it is because Idaho had worked with their Department of Transportation and so the DOT staff notified Idaho and Idaho called us. We don't have that in Montana."

There's still much that can be done at the state level, too, but policies have to be backed up with funding. Jackson's bill contains a budget of about $350,000 per year for aquatic invasive species. Other bills may add to this, making the annual budget around $500,000, but that's still fairly modest compared to the amount spent by states such as Utah and Idaho.

click to enlarge Originally introduced as an aquarium plant, yellow flag iris is well established in four counties in northwest Montana, threatening native fish and ruining swimming areas. - PHOTO COURTESY OF EILEEN RYCE
  • Photo courtesy of Eileen Ryce
  • Originally introduced as an aquarium plant, yellow flag iris is well established in four counties in northwest Montana, threatening native fish and ruining swimming areas.

"Idaho is really ramped up. They spend about $1.2 million and they did 30,000 inspections last year," says Jackson. "They are a little ahead of us right now. We're kind of ramping up as we go. And we're trying to piggyback as much of this as we can on other agencies."

Idaho and several other states have raised money for aquatic invasive species with boat sticker fees, a program both Jackson and Hanson advocate. "It's not that onerous to charge $10 per boat when somebody's putting $50 worth of gas in it every time they use it," says Hanson. "That sort of bill has basically sailed through other state legislatures that are just as conservative as Montana."

"If I carry the bill next time it will be self-funding through boat fees," says Jackson. "We'll be charging out-of-state people as well. People that boat need to step up and pay to keep these mussels out of the water."

"Unless decision-makers understand the issues, money will remain scarce," says Eileen Ryce, Montana's invasive species coordinator.

One way to get them to understand is to show them the effects of aquatic invaders. According to Hanson, an Idaho sheriff who went down to see the mussel infestation at Lake Mead for himself has committed to stopping all boats that come through his check station. Hanson suggested that it might be worth paying for Montana legislators to go down and see Lake Mead.

Another option is to show them the numbers. John Duffield, an economist and speaker at the Crown Conference, was part of a team that helped the Pacific Northwest Conservation Council conduct a study on the economic impacts of a mussel invasion. Duffield's team concluded that the Pacific Northwest should be spending much, much more to prevent a mussel invasion. Currently, spending is around $3 million. Duffield's study suggested spending should be in the tens of millions for benefits—that is, future costs that are avoided—that are probably in the hundreds of millions.

Part of the problem, says Duffield, is that numbers are vague because economic studies of the impacts of invasive species are hamstrung by the lack of detailed ecological information about specific lakes and streams. Only with detailed ecological models can scientists make predictions about the complex effects of invasive species. And only with those predictions can economists make their predictions about the costs of ecological change and the benefits of prevention. "Long-term studies of the biology of lakes are really critical in teasing out indirect effects in changes in the fishery and the biology of the lake," says Bonnie Ellis. "Sometimes those effects are slow and they're not always linear."

This year, however, funding from the state Department of Environmental Quality for research on the food web of Flathead Lake–one of the longest running programs of its kind in the world–was cut for the first time in 25 years.

Scientists and land managers fear that inadequate policies and funding will put Montana in the position of trying to control aquatic invaders after they get into the state rather than preventing their arrival.

"In terms of whirling disease, the biggest thing we've learned is there's no silver bullet to get rid of them," says Ryce. "We're in the position of putting red dots on the map as it spreads."

David Lamb, another invited speaker at the Crown Conference, described how, after years of using herbicides and scuba divers with huge suction hoses to control Eurasian water milfoil at Lake Couer d'Alene, in Idaho, his program had to downgrade its goals from eradication to control. But even that has been too ambitious, he said, as control measures have not kept up with the spread of the weed.

click to enlarge Motors aggravate Asian carp, causing them to jump into the air. This phenomenon has led to “zombie baseball,” or “Asian carp baseball,” as seen in this screen capture from YouTube.
  • Motors aggravate Asian carp, causing them to jump into the air. This phenomenon has led to “zombie baseball,” or “Asian carp baseball,” as seen in this screen capture from YouTube.

The Mysis shrimp has also proved intractable in the hundreds of lakes where managers introduced it. "There have been attempts with commercial harvest, because it's a good feed for aquarium fishes, and they even tried dragging collection devices along the bottom of lakes," says Ellis. "Nothing has worked. They have not been eradicated from any large lake that I know of."

Invasive mussels have been poisoned out of two lakes. At Millbrook Quarry, Virginia, contractors dumped 174,000 gallons of potassium chloride solution to kill the mussels. At Offut Lake, in Nebraska, contractors put 28,000 pounds of copper sulfate in the water, which killed a lot mussels, but also killed a lot of plant life and 48,000 pounds of fish. The fish population rebounded, but zebra mussels also showed up again two years later.

Even putting aside questions of efficacy and ecological harm, such extreme measures would be enormously expensive in a lake like Flathead. Offutt Lake covers 115 acres. Flathead Lake is more than 1,000 times that size. Hanson figures it would cost in the tens of millions or even billions of dollars to do a similar treatment in Flathead Lake.

"Introduction is forever," the US Fish and Wildlife Service's report on grass carp declares. But there are plans to stop the spread of Asian carp: The Army Corps of Engineers is considering reversing the flow of the Chicago River in order to try to keep the fish from getting to the Great Lakes from the Mississippi River.

When it comes to VHS, "there are no control options," says Ryce.

Ryce's agency has plans in place should aquatic invaders arrive, but eradicating them or even controlling their spread is likely to be difficult if not impossible. "Once they become established there are so few tools available to us to control them that our best tool that we have really is prevention," she says.

Besides, she adds, "We'd rather not find out what's going to happen when they get introduced."

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