Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=67265
Story Retrieval Date: 5/23/2013 9:39:20 AM CST
Illustration courtesy of U.S. Geological Survey
In the 1800’s, sewage dumped directly into the Chicago River and Lake Michigan led to widespread typhoid, cholera and dysentery in Chicago.
The city decided a bold solution was needed: Between 1892 and 1900, the Sanitary and Ship Canal was constructed, and the 28-mile canal reversed the flow of the Chicago River system away from Lake Michigan into the Mississippi drainage basin.
The waterway also connects the Chicago River and the Des Plaines River.
It’s not Jaws, but this dangerous fish could take a big bite of the Illinois economy. The Asian carp, a non-native species imported from China and Siberia, is eating its way up the Mississippi River toward the Great Lakes, conquering water ecosystems in its path.
With an estimated $4 billion a year in commercial and sport fishing in the Great Lakes, it’s vital to both the environment and economy that the Asian carp keep out. But it doesn’t just threaten the economy; this giant fish has also injured sport fishers and water skiers.
The U.S. Army Corps of Engineers has constructed an electronic fish barrier along the Chicago Sanitary and Ship Canal, the only defense against the invasive species that feeds on plankton and decimates the fish food chain. However, the barrier is corroding, and funding for its replacement is uncertain. The carp may beat the funding in the race to the Great Lakes.
Here’s what you need to know.
The Asian carp pose a significant threat to both recreational and commercial boaters. The carp eat plankton, which takes the bottom out of the aquatic food chain. This can potentially decimate native fish populations of salmon, bass, perch and walleye, and have a devastating impact on the Great Lakes’ fishing industry. There is currently little market for Asian carp.
“Around 88 percent of commercial fishermen on the Illinois River have been forced out of business because the catfish and buffalo fish they once caught are gone,” said Michigan Sen. Carl Levin (D) in a March 2007 press release detailing the growing danger of Asian carp on the Great Lakes.
The Asian carp are also impressive jumpers, capable of leaping up to 10 feet out of the water. Their water acrobatics pose a safety hazard for boaters, fishermen, and jet skiers; there have been numerous reports of people injured by the fish.
Asian carp include four different species: silver, bighead, black and grass carp.
The fish, which can grow up to 100 pounds, five feet in length, and eat 40 percent of their body weight a day in plankton, were originally imported by southern catfish farmers in the 1970’s to clean algae from fish ponds.
The Asian carp most likely were released into the wild in 1993, when the Mississippi River flooded. “A number of ponds and fish farms went under water in the flooding, so the fish could have swum right out of there,” Chuck Shea, project manager for the Army Corps fish barrier project, said.
TRACKING ITS PROGRESS
A breeding population developed and the carp made their way up the Mississippi River. The biomass, or total amount of fish in a habitat, reached 98 percent Asian carp in some areas of the river, according to several studies.
By 2000, both bighead carp and silver carp had reached the Illinois River. They’ve been spotted just 20 miles south of the Army Corps fish barrier in Romeoville, and a mere 50 miles from Lake Michigan.
Federal and state agencies joined to tackle the threat of invasive species in 1996, when representatives of the U.S. Army Corps, the EPA, Fish and Wildlife Service, Illinois Department of Natural Resources and environmental academics met to discuss options for a barrier. Possible solutions included chemical treatment, heat, sound, dense bubbles and de-oxygenation of the water.
It was vital that the barrier not interfere with the large flow of commercial barge traffic through the ship canal, or with the flow of wastewater away from Lake Michigan. In the end, the electronic “barrier was selected because it was a proven technology and there was a practical way to implement it,” Shea said.
BUILDING A BARRIER
A demonstration barrier was constructed in early 2002 at a cost of nearly $4 million in federal funding. Intended as a research tool rather than a permanent solution, the barrier uses 12 electrodes strung 54 feet along the canal bottom through steel cables. One volt per inch is emitted into the water, a level studies indicate deters the majority of fish.
Shea explains that the barrier “puts an electrical field into the water, strongest in the middle of the canal, so a fish coming in from either side starts to get a shock. [The fish] realizes that if it continues moving forward, it will get an even bigger shock, so they turn away.”
Activated in April 2002, the barrier is continuously operated. It is the largest of its kind in the world, and the first of its type to be used on an open waterway.
Unfortunately, materials used in the demonstration barrier were not long-lasting; the steel cables running the electrical charges have since corroded.
IMPROVING THE SYSTEM
In 2004, the Army Corps broke ground on a second, more permanent barrier to be constructed on the Sanitary and Ship Canal, roughly between Romeoville and Lemont. Budgeted at $9 million, the new barrier is located 800 feet downstream from the demonstration barrier.
The permanent barrier is larger than the temporary barrier, covering 480 feet in total and using 84 electrodes, each with a higher possible voltage.
Solid steel bars, more expensive than the original steel cables, were used to protect against long-term corrosion.
Under construction since 2004, the new fish barrier is being built in two halves. The first half is in a testing phase in conjunction with the U.S. Coast Guard to ensure water safety.
The second half of the barrier has yet to be constructed, however, due to funding problems. Funded 75 percent federally and 25 percent by state agencies, the project ballooned from a projected $9 million to $16 million due to unexpected costs.
The funding needed to complete the second phase of the new barrier is tied up in the Water Resources Development Act, introduced to Congress last March. The barrier is a provision of the more comprehensive $6.7 billion legislation that authorizes multiple water resource development and conservation projects around the nation.
The act has been criticized as pork-filled, so despite being passed by both houses of Congress, it is uncertain whether President Bush will sign or veto it.
“Funding is very much in play, but we cannot move forward until it becomes law. We continue to operate barrier one in the meantime,” Shea said.