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FOR IMMEDIATE RELEASE
June 28, 2004

Source: John Chick, 618-466-9690 or chick@illinois.edu

Asian Carp May Compete with Key Mississippi River Fish

URBANA--Invasive Asian carp consume similar food as a native fish that is a major component of the Mississippi River ecosystem, according to preliminary results of an Illinois-Indiana Sea Grant study. If populations of Asian carp species go unchecked, they may adversely affect numbers of gizzard shad, the most abundant fish in the river.

Brought to the U.S. for use in aquaculture, Asian carp escaped into the Mississippi River in the 1980s. They are now plentiful in much of the river--in fact, they have moved into the Illinois River and are approaching Lake Michigan. At this point, an experimental electric barrier stands between these fish and the Great Lakes. But, concern is high because Asian carp consume zooplankton, which all fishes typically feed on in their larval stages, so they have the potential to adversely affect many species of fish in the Mississippi River and Great Lakes.

John Chick and Mark Pegg, biologists at the Illinois Natural History Survey, are assessing the potential impact of Asian carp on several native Mississippi and Illinois River fish who feed in a similar fashion to the carp, by filtering suspended food particles from the water current through their gills.

By analyzing stomach contents, the researchers compared the diet of two Asian carp species, bighead and silver carp, with the diet of paddlefish, bigmouth buffalo and gizzard shad. “We sampled these fish in back-water habitats during spring flooding, which is a good way to find all these species in the same location,” said Chick. They also collected zooplankton samples at the same site.

Despite the fact that Asian carp can grow to more than 50 pounds in the Mississippi River, the researchers found that these species typically eat zooplankton smaller than 200 microns in length, as do the prevalent gizzard shad. “On the other hand, in our samples, paddlefish and bigmouth buffalo primarily ate larger prey, including crustacean zooplankton, insects and fish larvae,” explained Chick.

“At this point there’s no evidence that Asian carp are reducing abundance of zooplankton in the Mississippi River; it is a very productive system,” said Chick. “But if populations of bighead and silver carp go unchecked, zooplankton numbers may drop, impacting gizzard shad. The shad are eaten by all predatory fish--channel catfish, blue catfish, flathead catfish, largemouth bass, walleye and more.”

“If Asian carp populations are able to take off in Lake Michigan, the impact will likely be even more detrimental,” said Chick. “The lake is a less productive system, and its zooplankton populations have already been depleted by zebra mussels.”

In addition to their preliminary data collection, the research team has sampled fish from locations in the Mississippi and Illinois Rivers throughout the spring and summer. When analyzed, this data will provide a thorough picture of the diet of Asian carp and native filter-feeding fish in these waterways.

Early detection of Asian carp in new waters can help control their spread. You can help with the monitoring of these fish by learning how to recognize them and reporting any sightings. To order a free Bighead and Silver Carp Watch ID Card from Illinois-Indiana Sea Grant, visit www.iisgcp.org/products/free.htm on the Internet, or call Susan White at 217-333-9441 or email white2@illinois.edu. Report sightings in new locations online at www.iisgcp.org/il-ans or call 847-872-8677.

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The Illinois-Indiana Sea Grant College Program is one of more than 30 National Sea Grant College Programs. Created by Congress in 1966, Sea Grant combines university, government, business and industry expertise to address coastal and Great Lakes needs. Funding is provided by the National Oceanic Atmospheric Administration (NOAA), U. S. Department of Commerce, the University of Illinois at Urbana-Champaign and Purdue University at West Lafayette, Indiana.