Alien Invasion A Great Lakes Dilemma
Some 180 exotic species have found their way into the lakes during the past 200 years, jeopardizing the entire ecosystem; can we stop them?
ON A BRIGHT August afternoon last summer, an armada of 78 small craft pulled away from the Boat Tavern in Bath, Illinois, for an Illinois River fishing tournament in which no one was permitted to use a fishing rod. They returned three hours later with a staggering 1,804 fish that ranged from 5 to 20 pounds, every one of which either jumped into a boat or was scooped out of the air like a monstrous butterfly by people wielding landing nets.
The Redneck Carp Tournament was an attempt to focus national attention on a developing environmental disaster—silver and bighead carp from Southeast Asia that have invaded Midwest rivers and that may soon move into the Great Lakes, where experts already have tallied more than 180 exotic species from around the world. If they do reach the lakes, they could wreck the $5-billion commercial and sport fisheries that the governments of two nations have spent 40 years and hundreds of millions of dollars trying to restore after the last biological disaster there.
The first exotics to enter the Great Lakes were probably sea lampreys and alewives, initially recorded in Lake Ontario after the opening of the Erie Canal in 1825. The massive barrier of Niagara Falls kept invasive species out of the four Upper Lakes—Erie, Huron, Michigan and Superior—until the Welland Canal in 1829 opened a waterway between Lakes Ontario and Erie, beginning a slow but steady progression of new creatures that threatened the survival of native species.
Lampreys are eel-like, jawless relics from the earliest days of fishes. With the hooked teeth of their suckerlike mouths they clamp onto the sides of other fishes, drill holes with file-like tongues and suck host body fluids. Aided by overfishing and pollution, lampreys by the 1940s had driven lake trout to the brink of extinction.
Alewives are small, silvery prey fish from the Atlantic that can live in fresh water. With the decimation of the top predators that might have fed on them in the Great Lakes, alewife populations exploded, until they accounted for up to 80 percent of the lakes' fish biomass.
The lakes also were filling with algae as phosphates and other nutrient pollutants, poured in by everything from washing machines to chemical factories, stimulated plant growth. By the 1960s, the ecology of the lakes was so disrupted that many people had written off Erie as the American Dead Sea. Every summer, beaches were covered with windrows of rotting algae mixed with millions of rotting alewives that died when the algae used up all the available oxygen in the water.
The Clean Water Act of 1973 was the first major step in turning around the pollution problem, and within 20 years it resulted in enormous improvements in water quality. The states around the lakes also attempted to control the alewife problem—somewhat dubiously—by introducing yet other exotics: predatory salmon that would prey on alewives. Pacific chinook and coho, first stocked in 1966, immediately won the hearts and minds of hundreds of thousands of anglers.
But these steps took place during a period of rapidly expanding global trade, bringing into the Great Lakes exotic species that made sea lampreys look relatively benign. The disintegration of the Soviet Union in the 1980s compounded the shift in commerce, yielding new trading partners for the United States and Canada and a huge increase in the number of ships entering the lakes from the Baltic. Those ships brought in a cavalcade of invasive species, including quagga mussels, spiny water fleas and fish such as the round goby and European ruffe. A new nonnative species is discovered in the Great Lakes about every seven months. "As the influx continues, the damage mounts, but it doesn't have to be this way," says Jeff Skelding, senior manager of NWF's Great Lakes Restoration Campaign. "Congress can pass federal legislation to protect the Great Lakes from invasive species." (See "NWF in Action" box, below.)
Among the first of the recent newcomers to gain national attention was the zebra mussel, a bivalve from the Baltic Sea area that feeds by filtering tiny organisms out of the water. About the size of a fingernail, it first showed up about 1985 and spread rapidly. Within 10 years, water clarity in the lakes had increased 50 to 200 percent. Unfortunately, the mussels achieved that seemingly desirable result by removing vital nutrients from the bottom of the food chain. Lake Huron became so sterile by 2003 that alewives disappeared, starving the salmon fishery into collapse.
Many of the more recent invaders arrived as hitchhikers that had been sucked into ship ballast tanks along with water needed to provide stability. Most of the creatures are small, from dime sized to microscopic, but inspectors have seen minnow-sized fish in the tanks. When ships dump ballast in the lakes to take on cargo, many organisms in the tanks wash out. Enough survive to create biological chaos.
U.S. and Canadian regulations require ships to replace ballast water offshore before entering the lakes, flushing out most of the potential invaders and theoretically poisoning invasive freshwater species with salt water. However, many creatures can survive such measures and stay in the tanks, and enforcement of the regulations is ineffective. Ships that declare they have no ballast on board are largely exempted, even though they can carry invasive organisms in tank sludge. Equipping ships with chemical or heating systems to kill unwanted hitchhikers is no more than 90 percent effective. The 500-some oceangoing ships entering the lakes yearly leave a huge opening for potentially disastrous introductions.
While industry touts the Great Lakes oceangoing trade as an economic benefit, others say it is a classic example of penny-wise and pound-foolish. John Taylor, an economics professor at Grand Valley State University in Michigan, completed a study in 2006 of saltwater shipping into and out of the Great Lakes and reports that the costs are five to ten times as great as the benefits. He estimates that if saltwater ships were banned, the cost to the economy would be about $55 million a year, while "we estimate that existing invasive species on the Great Lakes are costing us $250 to $500 million a year."
The Asian carp threatening the lakes today didn't arrive in ship ballast or via the St. Lawrence Seaway. Arkansas commercial fish farmers imported bighead and silver carp in the early 1970s to eat algae in fishponds. When the Mississippi River flooded the ponds in the 1980s, carp escaped into the wild (some authorities believe that fish farmers also deliberately released carp that had grown too large). Jerry Rassmussen, a U.S. Fish and Wildlife Service biologist, warned his bosses about the escapes and the threat nearly 20 years ago, but his warnings were largely ignored. Officials in the states where the fish escaped also paid little attention because the aquaculture industry had a lot of political clout and resisted any efforts to impose strict regulations. Asian carp were still escaping from flooded Missouri fish farms in 1994.
Silver carp and bighead carp grow to about 70 and 110 pounds, respectively, in their native waters in Southeast Asia, but in North America the maximum sizes seem to be 20 pounds for silvers and 50 for bigheads. Silver carp attract the most attention, because they leap 10 to 15 feet out of the water when spooked by boats, sometimes blasting through the surface in shoals (bigheads rarely jump, although they can). Several boaters have suffered injuries that include broken jaws, noses, ribs, arms and legs after being hit by flying carp.
Neither species will bite a baited hook. They feed by sucking up more than half their own weight in algae and zooplankton every day. Fisheries scientists fear they could completely disrupt the food web in the Great Lakes. Everywhere they have turned up, Asian carp have stifled native species, including bass, crappies, bluegills, buffalo fish and catfish, to become overwhelmingly dominant. About 80 percent of the commercial fishermen on the Illinois River quit after carp eliminated most of the buffalo fish and catfish that were the fishermen's bread and butter.
In an ironic twist, commercial fisheries may be adapting to the carp and could complicate measures to control the fish. About three years ago a few fishermen began netting Asian carp for sale to markets in Asian neighborhoods around the continent. Steve McNitt, sales manager for Schafer Fisheries in Thomson, Illinois, sold more than 2 million pounds of Asian carp in 2005 and hopes that amount will increase tenfold. Such commercial development is the last thing biologists want to see, fearing that if Asian carp become commercially valuable, people who make money from them will oppose their eradication.
A major concern now is that the carp will reach the Great Lakes. "These are species that could be as destructive or even more so than sea lampreys and zebra mussels," says Marc Gaden, a spokesman for the Great Lakes Fishery Commission, the joint Canadian-American body that manages the sport and commercial fisheries. "We know that they can handle the climate, and they do well in bays, estuaries and marshes. There are thousands of places like that around the Great Lakes."
The carps' gateway to the Great Lakes is the Chicago Sanitary and Ship Canal, which connects Lake Michigan with the Illinois-Mississippi River system. When Illinois researchers set nets in 2003 in the Illinois River a few miles upstream from Bath, which lies about 250 river miles from Lake Michigan, it took only 30 minutes to fill the nets with several tons of silver and bighead carp. Such abundance prompted Betty DeFord, the owner of the Boat Tavern in Bath, to organize the Redneck Carp Tournament in hope of prodding government at all levels to find a fix for the carp problem. "We started this a couple of years ago to try to get some attention and some help," DeFord says. "I don't even take my grandchildren out on the water any more. If a 20-pound carp came into a boat and landed on a 2- or 3-year-old child, it could kill them."
The only thing keeping Asian carp out of the Great Lakes as of the winter of 2006 was sheer luck. The fish have been seen in the Chicago Sanitary and Ship Canal about 30 miles below Lake Michigan, but not until early 2007 did Congress introduce legislation to provide funds for completing a permanent electronic barrier on the canal. The bill had not yet passed at the time of this writing. Ed Landmichl, a Chicago angler and activist, said he and others who are worried about the carp reaching the Great Lakes have gone out in boats when a temporary barrier now guarding the canal is supposed to have been working. "We have [sonar] fishfinders, and we can see fish of all sizes swimming right over it," he says. "Either it isn't turned on some times, or it's not effective."
The U.S. Army Corps of Engineers, which runs the barrier, admits that the agency has sometimes turned it off for maintenance and construction because of design errors that threatened the safety of passing barges. In addition, the present barrier, installed two years ago, was supposed to be a temporary structure until a better, more effective barrier could be built. But as of mid-March, Congress had not passed the legislation needed to build the new barrier.
Some people fear that the temporary electric barrier is ineffective and that the carp have already reached the Great Lakes. Since 2000, anglers in eastern Lake Erie, about 900 miles from Chicago, have caught four adult bighead carp up to 50 pounds each. The origin and ecological significance of these fish remain unknown.
If the carp establish populations in the Great Lakes, they will turn the lakes into giant carp ponds in which other key fish species are wiped out. Says Gary Towns, fisheries manager for the Michigan Department of Natural Resources in the southeastern section of the state, "We have to find a way to stop [the carp], because ignoring them is like playing Russian roulette."
Eric Sharp is a reporter for the Detroit Free Press.
NWF in Action
Restoring the Great Lakes
As coleaders of the Healing Our Waters--Great Lakes Coalition, NWF and the National Parks Conservation Association are working with other coalition members to pass federal legislation that will relieve the threat of alien species in the Great Lakes. These bills include:
- The National Aquatic Invasive Species Act, designed to prevent invasive species introductions from the ballast water of oceangoing vessels, migration through the Chicago Sanitary and Ship Canal and importation and trade;
- Great Lakes Collaboration Implementation Act, which seeks to restore the Great Lakes in a comprehensive manner by preventing invasive species introductions, stopping sewage contamination and restoring wetlands and other habitat for fish and wildlife; and
- Great Lakes Asian Carp Barrier Act, which would authorize funding for the last line of defense against the nonnative Asian carp, an electric barrier.
NWF also is working to expand and fully fund programs in the U.S. Farm Bill that are essential to Great Lakes protection and restoration. Farm Bill programs provide farmers with funding and assistance for restoring and protecting wildlife habitat that supports the region's $18-billion annual hunting, fishing and wildlife-watching industry. The programs also restore wetlands and other habitats that serve to filter pesticides, fertilizers and sediment out of water that millions of Great Lakes residents depend on for drinking, bathing, fishing and swimming.
In addition, NWF has joined its state affiliate and other groups in federal district court to stop the shipping industry from striking down a 2005 Michigan law that seeks to protect the Great Lakes from invasive species discharges from oceangoing vessels by requiring the ships to obtain permits for ballast-water discharge.
"The clock is ticking for the Great Lakes," says Jeff Skelding, senior manager of NWF's Great Lakes Restoration Campaign. "NWF is calling upon Congress to act now to restore this resource. By investing in a solution today, we will avoid the higher price of trying to contain this problem tomorrow, and we will ensure that future generations continue to experience the lakes as we know them."
Why We Call 'Em "Great" Lakes
How big are the Great Lakes? Well, when the French navigators who were the first Europeans to put the Great Lakes on world maps initially sailed into Lake Huron's Georgian Bay in 1615, they called the lakes "sweet seas." Keep in mind that these people had recently crossed the ocean in tiny wooden ships, so they knew a sea when they saw one.
So much for impressions. Let's get down to facts. The Great Lakes cover 94,000 square miles and hold 5,500 cubic miles of water within 10,210 miles of shoreline--almost 20 percent of the world's freshwater and more than 95 percent of surface freshwater in the lower 48 states. Only the polar ice caps contain more freshwater.
The greatest of the lakes is Superior. With a name like that, it has to be greatest, or face a lawsuit for false advertising. It holds 2,900 cubic miles of water--or, if you like your water in gallons, 3,000,000,000,000,000 (3 quadrillion) gallons--which is as much as all the other Great Lakes combined plus three more Lake Eries. That's enough to cover all of North and South America with a foot of water. It has the largest surface area of any freshwater lake--31,700 square miles--roughly the area of South Carolina. If Superior's 1,826 miles of shoreline were stretched into a straight line, it would start in Duluth, Minnesota, and end in Miami, Florida.
The bottom of Lake Superior is 700 feet below sea level, a whopping 418 feet lower than Death Valley, making the lake bottom the lowest land in North America.
But all these superlatives aside, the Great Lakes aren't as great as they used to be. Lake trout, once the primary Great Lakes commercial fish, now survive at levels capable of sustaining commercial fishing only in Lake Superior, and even there they are supplemented with hatchery fish. The blue pike, once the top predator in the open waters of Lake Erie, and the Atlantic salmon of Lake Ontario, were major components of the early fishing industry but are now extinct.
And that's not all. Lakes Superior, Huron and Michigan have been shrinking in recent years. Once again, Superior outdoes the rest, dropping back 50 feet or more from its traditional shorelines. Beds of native wild rice, usually inundated, are going dry, sandbars are rising to the surface and cargo ships navigating the lakes have to lighten their loads to avoid running aground. Superior is nearly 20 inches below its normal average depth of 601.92 feet and is closing in on the record low set in 1926--599.92 feet. But at its deepest, Superior is 1,330 feet to the bottom, so the effect of this lowering is felt mainly along the shrinking shores, where boat docks are being left high and dry.
Why the shrinkage? No one's sure, but a likely culprit, say experts, is global warming, which has reduced the amount of time the lakes spend under ice in winter, allowing more water to evaporate during the cold season than would otherwise occur.--Roger Di Silvestro