Bighead and silver carps, commonly known as Asian carps, are posing a serious threat to Ohio sport fishing. The big fish have voracious appetites, and biologists fear that, once established in the Great Lakes, the invasive species would seriously deplete the population of sport fish such as perch and walleye, imperiling the area’s 7 billion dollar a year sport fishing industry. The state of Michigan, supported by Ohio, Minnesota, Wisconsin, and the Canadian Province of Ontario, asked the Supreme Court to shut down the Chicago Sanitary and Ship Canal in order to prevent the carps from entering the Great Lakes. However, the Supreme Court refused yesterday to issue such an injunction. Just hours after the court ruled, The U.S. Army Corps of Engineers announced that DNA from the invasive carp was detected at the breakwater of Calumet Harbor, leading to the waters of Lake Michigan.
How many carp make a breeding population?
While DNA from invasive carp species has been detected beyond the barriers, so far only a few individual bighead carp have been reported in Great Lakes waters. How many individuals would it take to be considered an invasion? Evidence of a breeding population would not depend upon the presence of a specific number of the fish, but upon evidence that the fish were reproducing in the Great Lakes rather than entering from other waterways. Bighead and silver carps require large biomasses of plankton for food, and most Great Lakes waters do not provide ideal conditions for the establishment of the carps. However, the areas that would support bighead and silver carp populations are the same areas that support large numbers of sport fish. As to whether the genetic material detected indicates that the fish are making their way into Lake Michigan, according to Eugene C. Braig IV, Assistant Director of the Ohio Sea Grant College Program, "It’s just too soon to know...but it’s not too soon to work against any more 'genetic material' or the carp themselves getting into the lakes."
What will happen next?
Government agencies, environmental activists, and sport fishermen continue to monitor the situation. Electric barriers remain in place, and Michigan continues efforts to force the closing of the Chicago Sanitary and Ship Canal. The lawsuit as filed requested the court to issue a preliminary injunction to close the Canal, and to reopen the original case (Wisconsin v. Illinois, 278 U.S. 367 (1929) involving the Canal. The court has yet to rule on reopening Wisconsin v. Illinois.