Alien Invasion

In the ballast tanks of transatlantic cargo ships and on the currents of river flows, alien predator species are invading the Great Lakes.

South of Chicago, electrodes stretch across the bottom of a canal that links the Mississippi River with Lake Michigan. They create an electric field—the only thing protecting the Great Lakes from the menace of three species of Asian carp.

The silver, black and bighead carp escaped from aquaculture lagoons in Arkansas in the 1990s and have since been making their way steadily northwards. Along the way, each carp has been vacuuming up 18 kg of plankton per day. Already, they have devastated sport and commercial fisheries in the lower Mississippi. Now they’re threatening similar damage to the US$4.5 billion Great Lakes fisheries.

Fully-grown carp can be 1 m long and weigh as much as 50 kg, too large for most predators to attack. Moreover, silver carp have a habit of leaping out of the water when they are startled, striking boaters and even knocking one unfortunate jet-skier unconscious.

It may sound like the plot of a B movie, but the US government is spending hundreds of thousands of dollars each year on the electric field to keep these fish out of the Great Lakes. If this barrier fails, Asian carp will join nearly 200 other aquatic invaders currently thriving in the Great Lakes basin, a list that includes zebra mussels, sea lampreys, spiny water fleas, round gobies and dozens of other fish, invertebrates and plants.

AN INVASION CRISIS

Aquatic invaders are arriving in the Great Lakes at a rate of one species every seven months, says
McGill aquatic biologist Anthony Ricciardi—the highest rate ever recorded in a freshwater eco-system. They are hitching a ride in the ballast water of ships, escaping from water gardens or fish farms, travelling up canals or being negligently or deliberately released.

While not all the aliens that arrive become established, those that do can wreak havoc in the absence of natural predators, diseases, or competitors to keep them in check.

Rusty crayfish, for example, are voracious feeders, clear-cutting beds of aquatic plants. Eurasian watermilfoil, a noxious aquatic weed, develops into a dense mat of vegetation that chokes out native plants and clogs waterways. And in nearby Lake St. Clair, where as many as 100 small bottom-dwelling fish called round gobies can be found in a single cubic litre of water, populations of native fish have plummeted.
Even more troublesome, such invaders can create havoc through synergistic effects with the rest of the ecosystem. Zebra mussels, for example, have passed along a rare form of botulism bacteria to the gobies that feed on them. The gobies, in turn, have passed it to fish-eating birds such as loons, gulls and mergansers. As a result, tens of thousands of these waterfowl are dying each year from botulism.

“The more of these species you put together, the more chance you’re going to get something like this happening,” Ricciardi says

It all adds up to an expensive problem. Zebra mussels alone have inflicted more than a billion dollars in damage by clogging the intake pipes of drinking water plants and industrial cooling systems.

In effect, invasive species are a hidden tax, Ricciardi notes. “They’re going to cost us something, but you don’t know what it’s going to be,” he explains. “You do know that like most taxes, once they’re here, they’re not going to go away and they’re only going to increase.”

SHIPBOARD STOWAWAYS

The invaders’ most common route into the Great Lakes is in ballast water from ocean-going ships. Since the St. Lawrence Seaway opened in 1959, 65 per cent of the invasive species that arrived came in the water used to stabilize these vessels.

An estimated 3,000 aquatic species, from microscopic creatures to plants and fish, are transported around the world each day in ballast tanks. When the ships arrive in port to pick up cargo, they empty the ballast water, releasing a potential biological time bomb.

In order to slow the onslaught, the United States passed a regulation in 1993 forcing ocean vessels to exchange their ballast water with sea-water before entering the Great Lakes, based on the premise that freshwater creatures couldn’t survive the salty inundation. Recently, Transport Canada passed similar regulations for ships entering Canadian waters.

However, by virtue of ballast tank design, the ballast water exchange process is never perfect.
Some freshwater from previous ports is usually left in the ballast tank. That allows the possibility that some organisms could survive and enter the Great Lakes.

Perhaps the biggest concern is that both nations are relying on voluntary guidelines to deal with so-called NOBOBs—ships with no ballast water on board—according to Jennifer Nalbone, campaign director of the bi-national Great Lakes United coalition that is working to protect the Great Lakes. “It’s a major loophole, because 90 per cent of the ocean-going ships entering the Great Lakes are filled with cargo, so they don’t carry ballast water.”

“We know that NOBOB flushing will improve the situation,” Nalbone says. “Why didn’t we go straight for the mandatory regulations?”

STOPPING THE SPREAD

Once a species gets established in the Great Lakes, it can quickly spread to inland lakes and rivers via boats, fishing gear and bait buckets. That’s why the Ontario Federation of Anglers and Hunters (OFAH) partnered with the Ontario government to create its Invading Species Awareness Program.

Anglers, cottagers and boaters are often the first to spot an invasive species. Anglers, for example, know when spiny water fleas invade a lake because the tiny creatures get stuck on fishing lines, creating knots that snag when the line is reeled in.

OFAH runs a hotline for reporting en- counters with invasive species and its staff investigates new sightings, working with local Ministry of Natural Resources offices to educate people in the area and halt further spread.

They have also enlisted 200 lake associations and fishing clubs to actively monitor lakes across the province. “It’s an issue that people care about and want to deal with,” Francine MacDonald, who coordinates the OFAH program, explains.

According to MacDonald, public outreach in the US has been hugely successful in slowing the spread of invaders into inland lakes. It’s vital work, she says, because once a species gets established, “there isn’t a heck of a lot that can be done.”

In fact, of the 183 invasive species in the Great Lakes basin, not one has disappeared and only two have been successfully controlled.

One is the sea lamprey, an eel-like creature that latches onto fish and sucks out their blood and bodily fluids. The metre-long parasite decimated a once-thriving commercial lake trout fishery during the mid-1900s. Now they are kept in check thanks to an annual $22-million program run by the bi-national Great Lakes Fishery Commission.

But it’s a never-ending effort. Although the commission has reduced sea lamprey numbers by 90 per cent from their peak in the 1960s, if funding for the program drops in a particular year, their populations increase.

The other successful control program targets purple loosestrife, using a European beetle carefully selected because it feeds on the invasive wetland plant without harming native plants or crops. These beetles have been released at more than 300 sites across the province, reducing the population of local purple loosestrife by 80 per cent.

NEED FOR ACTION

Ricciardi has identified 40 species in major European ports—the origin of many ships entering the Great Lakes—that could be poised to become the next invader based on their ability to withstand ballast water exchange and to spread quickly.

They include the so-called ‘killer shrimp’, a deadly crustacean that shreds its prey to pieces, and the tube-dwelling amphipod, which builds mud tubes that smother rocky bottoms, along with anything living on them.

Even if we can’t shut off the tap completely, Ricciardi believes it’s crucial to stop as many potentially invasive species as possible to limit the damage. “Canada has plenty, plenty, plenty of work to do,” he stresses.

But progress is happening at a snail’s pace, says a frustrated MacDonald, pointing to a stack of reports from the Standing Committee on Fisheries and Oceans, Canada’s Environmental Commissioner, the Auditor General and the International Joint Commission that all call for more action on invasive species.

Chris Wiley, who sets most of the federal policies on aquatic invasive species for Fisheries and Oceans Canada and Transport Canada, is more optimistic. “From a shipboard point of view, I think we have a pretty good program,” he says. “It ain’t perfect, but it’s a whole lot better than it was ten years
ago, and it’s probably the best in the world right now.”

More than 90 per cent of NOBOBs in the Great Lakes are now flushing their tanks, and more than 95 per cent of ballasted ocean-going ships are meeting Canadian and US regulations. Ballast water treatment technologies are also being developed, spurred by a new international ballast water convention.

What does have Wiley worried are invaders that reach the Great Lakes through other methods, including the marine life that clings to hulls and could survive an ocean journey. “How are we going to deal with that?
I haven’t got a clue,” he admits frankly.

Back in the Chicago Sanitary and Ship Canal, the demonstration barrier holding back the Asian carp will soon be supplemented with a more powerful, permanent version. Getting federal operating funds to keep the electricity flowing, however, is an annual fight.

A stop-gap amendment in June provided money for this year, and Nalbone is hopeful that a bill currently moving through Congress will ensure long-term funding in the future.

It appears that the Great Lakes are safe from the terror of one particular invader— the Asian carp—at least for now.

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