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The Chicago Sanitary and Ship Canal serves as a vital transportation corridor for commercial and recreational vessels operating between the Great Lakes and the Mississippi River.
The Chicago Sanitary and Ship Canal, constructed in 1910, connects the South Branch of the Chicago River to the Des Plaines River. The confluence of the Des Plaines and Kankakee rivers forms the Illinois River. Originally, this waterway helped build the Midwest; today it provides a two-way conduit to expand the range of exotic species between the rivers and Great Lakes.
This conduit is how zebra mussels spread from the Great Lakes to the Gulf of Mexico. The grass carp, African water flea and round goby also are expanding their ranges using the canal.
The round goby is of great concern in Wisconsin and has been found in the Duluth-Superior and Milwaukee harbors, and at Sturgeon Bay. Like the zebra mussel it came from Europe near the Caspian Sea and is believed to have arrived in lakes Michigan and Superior from other Great Lakes in ballast water.
The round goby is an aggressive and bottom dwelling fish that can displace native aquatic species. The goby prefers rocky, cobble habitat and preys on mussels, invertebrates, fish eggs or other small fish. They have the potential for rapid population growth since they spawn several times during the summer. It is illegal to possess and transport live gobies at any time, though people in Wisconsin may have one dead goby in possession with the purpose of sharing it with the Department of Natural Resources, University of Wisconsin Sea Grant or U.S. Fish and Wildlife Service staff for positive identification.
Other species that could spread into the Midwest or the Great Lakes through the canal include the black carp, bighead carp, striped bass and their hybrids, three-spine stickleback, fishhook water flea, quagga mussel (a mussel that can survive in deeper and colder waters than zebra mussels) and the spiny water flea, which is a crustacean that is distantly related to shrimp, lobster and crayfish.
The spiny water flea is a European native that came to North America likely in ballast water and took up residence in each of the Great Lakes by 1987. It preys on smaller planktonic animals and may consume as many as 20 organisms in a day. The spiny water flea also targets a small water flea called daphnia that is food for many young fish and native crustaceans.
White perch spread is another concern. White perch already have been found in the Milwaukee harbor and are abundant in Green Bay. White perch, a relative of white bass, yellow bass and striped bass, is a native of the East Coast and entered the Great Lakes in the 1980s.
The fishhook water flea is an invasive crustacean that, like the spiny water flea, was first discovered in Lake Michigan in 1999 by a researcher working in Grand Traverse Bay and near Waukegan. It was introduced into the Great Lakes in the 1980s originating from the Caspian Sea in Eastern Europe and was likely transported to North America in ballast water. It has been found on fishing line near Chicago, although it has not yet been found in Wisconsin waters.
Considering its proximity to the Wisconsin-Illinois border, researchers predict that it is likely to appear in Wisconsin waters. Anglers have reported that fishhook water fleas foul fishing lines, which interfere with retrieving hooked fish. Some anglers have had to cut their lines because they are unable to reel them in. The masses of the water fleas look and feel like wet cotton batting. They also feed on zooplankton, which is an important food source for juvenile fish and invertebrates.
The National Invasive Species Act of 1996 authorized the U.S. Army Corps of Engineers to investigate whether these and other aquatic exotic species could be prevented from moving through the Chicago Sanitary and Ship Canal. The Corps and a multi-agency advisory panel indentified an electric barrier as an option that was commercially available, had the fewest permitting concerns, and would not interfere with day-to-day navigation on the canal.
The first step will be establishing a micro-pulsed DC electric field designed to deter passage up or downstream. Construction of the electric array, located at River Mile 297, near Romeoville, Ill. began this spring, and the barrier should be operational this summer. Monitoring by the Illinois Natural History Survey and the U.S. Fish and Wildlife Service will help determine the barrier's effectiveness.
The electric barrier will run through the water column with the strongest electrical current at the bottom to target bottom dwelling organisms such as the round goby.
"The barrier is one of the few experimental tools we have to limit the spread of exotics through the Chicago Sanitary and Ship Canal," notes Ron Martin, who works with exotics species issues for the Wisconsin Department of Natural Resources. "It probably won't be 100 percent effective on all species but it's the best tool that we have."
Future additions to the electric field may involve an acoustic array, bubble screens or some other technology. To learn more about the barrier project visit University of Wisconsin Sea Grant.
Phil Moy is a fisheries and nonindigenious species specialist in advisory services for the University of Wisconsin Sea Grant.