Great Lakes Solutions–Asian Carp

Photo: USFWS

What weighs 60 pounds, jumps when startled and could destroy the Great Lakes? You guessed it: Asian carp.

Asian carp are marching their way steadily toward the Great Lakes, where they could upset the ecological balance on a scale that could make the Great Lakes zebra mussel problem seem insignificant. These prolific filter feeders escaped from fish farms and government breeding programs in the 1990s, and have been marching up the Mississippi River ever since. They are currently about a two-day swim from Lake Michigan in the Illinois River and are being held at bay by an electric barrier that is intended to permit barge traffic while blocking the invasive fish. The threat to the Great Lakes from Asian carp is real, but there are some potential solutions.

Asian Carp

When most people think of carp, they imagine the brown bottom feeders that fill churn up sediments on the bottom of murky rivers. These common carp were imported from Europe in the 1800s and widely stocked as a food fish. Carp is a delicacy in many parts of the world, and government stocking programs hoped to plant the fish in local waterways to provide a cheap source of food for Americans. The imported fish soon turned into pests, breeding prolifically, fouling waters by disturbing the bottom and uprooting plants, and displacing native species. These days, carp aren’t seen as a source of food, they are seen as a problem.

Silver, grass and bighead carp. Photo: USFWS/Bill Reeves, Tennessee Wildlife Resources Agency

Well, there is a new carp in town, and it poses a far greater threat to the waters of the Great Lakes than the common carp ever did. Four species of Asian carp have been imported into the US, and two (bighead carp and silver carp) are making their way up the Mississippi River toward Lake Michigan.  Bighead are prolific breeders and can grow to 100 pounds in weight. Silver carp are smaller but are similarly fertile, and have a habit of jumping clear of the water when startled. Both fish feed on plankton: the tiny organisms that form the foundation of the web of life in the Great Lakes.

If you start doing the math, the potential for disaster becomes obvious. Each female carp is capable of producing up to five million eggs, and once hatched, carp fry rapidly grow to a size that makes them immune to native predators. Bigger carp eat more plankton (bighead can eat up to forty percent of their body weight each day and sliver carp consume two to three times their body weight). It is easy to see how millions of carp eating tons of plankton could easily throw a monkey wrench into the Great Lakes ecosystem.

Consider the trouble that zebra and quagga mussels have caused by filtering plankton in the Lakes. The huge filtering capacity of the invasive mussels has simultaneously cleared waters and caused toxic algae blooms that foul beaches. Outbreaks of botulism in waterfowl have been linked to the mussels, and their persistent sucking has dramatically reduced the population of zooplankton in the Great Lakes, which has in turn stunted whitefish and reduced forage fish populations. The addition of another fertile filter feeder could be the straw that breaks the back of the Great Lakes fishery.

Where did the Come From?

Ironically, Asian carp were imported into the US as an environmentally benign alternative to chemical weed control in southern lakes. Tracing the history of the fish, it appears that weed eating grass carp were imported first, followed by the filter feeding silvers and bigheads and the mollusk-eating black carp. Various experiments were conducted during the 1970s to find uses for the new fish. Some were deliberately stocked into native waters, while others escaped from fish farms where they were cleaning catfish ponds. The bighead and silver carp have been moving steadily northward up the Mississippi River ever since, and are now banging at the door of Lake Michigan forty miles southwest of Chicago at the confluence of the Chicago Sanitary and Shipping Canal and the Illinois River.

Asian carp are knocking on the door of Lake Michigan. Graphic: USFWS

Chicago Sanitary and Shipping Canal

The Mississippi River basin is not naturally connected with Lake Michigan. The Chicago River used to flow east into the lake, while the Illinois River flowed southwest into the Mississippi. The two watersheds are connected by a massive canal that was created in the late 1800s to solve Chicago’s growing sewage problem. Then, as now, the city’s sewage was dumped into the Chicago River, but in the 1890s, sewage treatment was nonexistent. City officials were growing increasingly concerned that the outflow from the river would foul the city’s drinking water intakes, so they hatched an ambitious plan: reverse the flow of the Chicago River to send the waste downstream to the Mississippi and away from the lake. (Peter Annin’s book, The Great Lakes Water Wars outlines the history of the canal and the associated Chicago Diversion from Lake Michigan). Today, the canal handles not only Chicago’s treated sewage effluent, but 50,000 tons (.pdf) of barge traffic per day.

While the Chicago Sanitary and Shipping Canal is seen as the primary path for Asian carp to reach the Lakes, there is a back door to be guarded as well. As bighead and silver carp advance upstream toward the Wisconsin River, they have the potential to enter Lake Michigan through the Fox River system. The Wisconsin is blocked at Sauk City by the Prairie du Sac dam, but a fish ladder has been proposed for the dam to allow spawning sturgeon move up stream. Such a ladder would also work for Asian carp, which then would have access to the river as far as Portage, where the river was once connect to the Fox with a canal. The canal has been plugged with levees, but it is possible that a major flood could open a pathway from the Wisconsin to the Fox.

Solutions

Startled silver carp jump in the wake of a passing boat. Photo: USFWS

Dam that Canal

The obvious solution to the problem of the Sanitary and Shipping Canal is to permanently block the waterway with a dam or plug. Re-reversing the Chicago River so that it flows into Lake Michigan once again would create a permanent barrier to Asian carp, and would also prevent Great Lakes invasives like the round goby from spreading into the Mississippi River Basin. A report (.pdf) was issued in November of 2008 by the Alliance for the Great Lakes outlining potential locations for ecological separation and economic impacts of the move. Separation offers the best chance of stopping the movement of Asian carp into the Great Lakes, but has the potential to cause tremendous impacts on Chicago’s sewage system and the shipping industry. These costs pale by comparison to the potential impact of Asian carp on the ecology and economy of the Lakes, but it may be difficult to gain support for what is seen by some as an extreme measure.

Electric Barrier

The US Army Corps of Engineers has recently activated a permanent electric fish barrier in the canal. This new barrier replaces the aging experimental barrier that was installed in 2002 to stop the spread of the round goby out of the lakes. The Corps is currently running experiments on the device to determine what the safe operating limit of the barrier will be. There are concerns about the possibility of arcing electric current between the barrier and barge traffic and about the potential for harm to people who might fall into the river near the barrier. But, there are also concerns about the ability of the barrier to hold back Asian carp at lower levels. At best, the electric fish barrier is a temporary solution to the problem, that may buy critical time to build support for permanent separation of the two watersheds.

If You can’t Beat ‘em, Eat ‘em

One possible solution to the Asian carp problem is to convert the fish into useful food products or fertilizer. Fishing won’t prevent the spread of carp into Lake Michigan, but it could help to reduce their impact in areas where they currently flourish.

Commercial fishermen have already begun to fish for bighead and silver carp, and yields on the Illinois River have reached as high as 12,000 pounds in a single day. At current market price of 14 cents a pound, hauls like this one can be commercially viable. The problem has been finding a market for the fish.

There is not much demand right now, but carp boosters are hoping that US consumers will develop a taste for the fish, which are highly sought after in Asia. In blind taste tests, the meat has compared favorably with canned tuna or freshwater trout.

If American’s can’t be convinced to eat the invasive fish as fillets, they might end up gulping them as nutrition supplements. Silver and bighead carp are high in omega-3 fatty acids and can be readily converted into fish oil. At least one Illinois entrepreneur has made the jump into processing machinery that will flash convert fish into frozen meal, ready for the oil press. A recent batch, sent to a USDA test facility and tested for toxic residues, was found to be free of contaminants. It appears that because they feed on plankton bighead and silver carp don’t pick up contaminants, even if they are living in the polluted Illinois River.

Lawmakers are divided about what to do to combat the fish. Some in Illinois favor an aggressive fishing program to knock back the invaders, while others want to see all sales of Asian carp banned to prevent the transfer of live fish into the Great Lakes. While it is important to prevent the buying and selling of live fish, a complete ban on the sale of Asian carp would eliminate commercial fishing as a management tool on waters that already harbor the invaders.

Closing the door to Asian carp is critical to protecting the ecology of the Great Lakes. Now that the electric fish barrier is up and running, steps must be taken to separate the two watersheds permanently. It may be difficult to generate the political will to close the canal, but nothing short of separation will insure protection from this new threat. Likewise, Asian carp must be prevented from working their way up the Wisconsin River and into the Fox River basin. This may mean sacrificing native fish populations that would benefit from fish ladders in order to protect the ecosystems upstream from damage. Considering the impact the Asian carp could have on the Great Lakes, this choice is an easy one to make.

Additional Resources

• Asian Carp Management: http://www.asiancarp.org/

• Asian Carp Recipes: http://www.lib.niu.edu/2002/oi020509.html

• Carp Busters: http://carpbusters.com/

• USACOE Chicago Sanitary and Shipping Canal Electric Barrier Homepage. http://www.lrc.usace.army.mil/projects/fish_barrier/index.html

• The Great Lakes Water Wars. Peter Annin. http://www.greatlakeswaterwars.com/ REVIEW

• Management and Control Plan for Bighead, Black, Grass, and Silver Carps in the United States: http://asiancarp.org/Documents/Carps_Management_Plan.pdf

• Preliminary Feasibility of  Ecological Separation of the Mississippi River and the Great Lakes: http://www.lakemichigan.org/page.redir?target=http%3a%2f%2fwww.greatlakes.org%2fDocument.Doc%3fid%3d473&srcid=642&erid=0

• Troubled Waters: Great Lakes Special Report. Milwaukee Journal-Sentinel: http://www3.jsonline.com/index/index.aspx?id=12