The future of sportfishing and the survival of native aquatic plants and animals in the Great Lakes may depend on what happens in the next few years in a narrow stretch of water that was cut through the Illinois prairie more than a century ago.
About 30 miles west of the shore of Lake Michigan, in what is now the far southwest suburbs of Chicago, state and federal agencies are laying electrical cables with powerful pulsating currents across the bottom of the 150-foot-wide Chicago Sanitary & Ship Canal. The canal was completed in 1900 to reverse the flow of the Chicago River and carry Chicago’s wastewater away from the lake and the city, to the Illinois River.
Canals Link Carp to Great Lakes
The canal thus provides a link between Lake Michigan and the Mississippi and Illinois River systems, and moving up those systems toward Lake Michigan are at least three voracious species of Asian carp. Experts fear that if the carp enter Lake Michigan, they will rapidly overrun the entire Great Lakes.
Asian bighead, silver, and black carp “are the biggest threat to the Great Lakes right now,” said Mike Conlin, acting director of the Illinois Department of Natural Resources (IDNR) and, for 30 years, Illinois’ director of fisheries. “If they get in, the results could be devastating.”
“We’re seeing huge numbers in the Illinois River,” Conlin said. “We found one 20 miles below the current electrical barrier, about 50 miles below [Lake Michigan]. As their territory expands, they take over the river.”
The carp are fit for human consumption, and some people enjoy their taste, but their appeal to anglers is not nearly great enough to arrest their advance toward Lake Michigan and the inevitable crowding out of other species.
Isolating the Great Lakes
Invasive species long have been a problem in the Great Lakes–about 160 alien organisms have been identified, many of which cause serious problems–but experts say the threat from Asian carp may be the greatest of all.
The Asian carp eat mussels, snails, plankton, and plants. Because of their bottom-feeding habits, they were imported into the American Midwest to clean up weed-choked ponds and commercial catfish farms. However, flooded streams spilled their banks, connected with the carp ponds, and allowed the fish to escape into the wild.
To stop the advance of the carp, workers recently began constructing a permanent electrical barrier near a temporary one that became operational on the Chicago Sanitary & Ship Canal in April 2002, near the town of Romeoville. The barriers create an invisible “electric fence” experts hope will stop the fish. The cost of the permanent barrier will be about $8.5 million.
The original barrier was constructed to block round gobies–a small alien fish with an appetite for fish eggs–from moving from Lake Michigan into the Illinois River. That barrier failed to stop the advance of the gobies, though some may have been beyond the barrier before it was finished. The new permanent barrier will emit much stronger electrical pulses and have its own backup power sources.
Carp Eliminating Other Species
The black carp was bred to be sterile, but several have been caught by fishermen in the Mississippi River, and there is some worry they may be reproducing, according to a November 2000 Project Status Report of the Upper Midwest Environmental Sciences Center. The report noted, “Asian carp are becoming abundant and persistent residents of the lower reaches of the [Upper Mississippi River System] and the Illinois River. … These recent Asian carp invaders are increasing in population and expanding in range.”
The biggest worry is from the bighead variety, which can weigh up to 100 pounds and reproduce in huge numbers. In some stretches of the Illinois River, more than 90 percent of the fish are bighead carp. Four or five years ago, there were none, IDNR’s Conlin said. They entered the Illinois River by swimming up the Mississippi River.
The fear is that the carp could ultimately take over the Great Lakes. Because they are voracious bottom grazers and multiply rapidly, the carp could eliminate the small organisms that feed the fry of other fish, Conlin said.
Cooperation Among Governments Needed
The threat of Asian bighead, silver, or black carp reaching the Great Lakes was one of several topics that occupied the minds of mayors, other government officials, and private agency experts at the 18th Annual International Association of Great Lakes and St. Lawrence Mayors’ Conference, hosted July 14-16 by the City of Chicago. Other topics included water and port security, stormwater management, and Great Lakes restoration strategies.
More than 200 officials from some 40 Great Lakes communities attended the conference.
Marcia Jimenez, commissioner of Chicago’s Department of Environment, said she believes the most important message from the conference of mayors may have been a call for more local, state, federal, and international cooperation to combat the carp and other invasive species.
Chicago Mayor Richard Daley complained that the 40 government agencies and 140 regulations that govern the Great Lakes are often in conflict. “There was a very clear, loud call to simplify and get better coordination,” Jimenez said.
“EPA Administrator Michael Leavitt was there and he agreed we’re not making progress in cleaning up the Great Lakes because we’re so busy figuring out rules,” Jimenez said. “There was resounding agreement on that. Invasive species is a good example. Since the 1800s, over 160 have been identified. They will never stop unless we agree to rules and jurisdictions and the federal government helps put enforcement behind stopping their introduction.”
Clean Water Aids Carp Takeover
Perhaps ironically, improved water quality has increased the threat. Conlin said that several decades ago when ships took on or emptied ballast water, the ports were so polluted many of the invasive organisms died before they could reach clean water and get into the ecosystem. Now, with cleaner water as a result of efforts that began in the 1970s, they survive.
Over the past 40 years, another newly established invasive species population has been found in the Great Lakes approximately every eight months, according to mayors’ conference officials.
The Illinois River is also cleaner than in the past, further enabling the movement of carp toward Lake Michigan, according to Conlin. “We used to have a dead zone in the Illinois,” he said. “There was no oxygen. These fish couldn’t have gotten through the dead zone.”
Other Strategies Being Considered
In addition to the electrical barrier to keep carp out of the Great Lakes, other strategies are being considered. One is heavy commercial fishing of the species.
“We’re trying to get some harvest going to see if we can knock them back,” Conlin said. “A company is interested in harvesting 23 million pounds or more a year for a protein source (mainly animal feed). They’d also use part of the by-product as plant fertilizer.”
He said the company is considering locating a plant in Illinois.
“If that would happen, that would stimulate the harvest,” Conlin said. “There’s a market for these fish now, but the price being paid is so low it doesn’t pay commercial fishermen to harvest. They’d have to invest in heavier gear. These fish are so big they’d just tear up the equipment.”
Conlin noted a price subsidy would attract more commercial fishermen. The company interested in harvesting the invasive carp is also trying to develop equipment and netting techniques that would make the harvest more efficient so that the added volume of fish caught would make the per-pound price profitable, according to Conlin.
Conlin said government agencies addressing the problem also plan to use applications of chemical deterrents to kill carp near the barrier.
Other Means of Escape Possible
Even if the electrified barrier works, there are other worries to consider. The nearby Des Plaines River has flooded into the canal many times in recent years. In the past, the invasive carp were not far enough up the Illinois River to escape into the Des Plaines during floods. It is now possible, however, that carp could swim from the canal into the Des Plaines River during such flooding, according to Conlin, which would allow them to move closer to Lake Michigan.
Participants at the mayors’ conference noted this as a threat to the lake, though the actual path by which the carp would move from the Des Plaines to Lake Michigan was not specified.
Moreover, there is always the possibility that humans will catch some of the carp and physically relocate them. That may have already happened, Conlin said. On June 24 a man caught a 43-inch, 45-pound bighead carp from the McKinley Park lagoon, some 30 miles from the barrier, said Conlin. That was the second bighead carp caught there within the past year.
“There is a lot of intentional movement of fish,” Conlin said. “No question it’s a big problem.”
Steve Stanek ([email protected]) is an Illinois-based freelance writer.
For more information …
The November 2000 Project Status Report of the Upper Midwest Environmental Sciences Center is available online at http://www.umesc.usgs.gov/reports_publications/psrs/psr_2000_05.html.