“It’s unquestionable that the Asian carp challenge and issue has probably gobbled up 90 percent of the attention of the Great Lakes challenges, and other matters probably have not gotten as much national attention,” said Pat Quinn, the governor of Illinois and the co-chairman of the Council of Great Lakes Governors, one of many groups representing interests of the lakes. “Locally, in the Great Lakes states, almost any conversation about the Great Lakes begins with the Asian carp, ends with the Asian carp.”

For at least a decade, people in the Midwest have worried about the arrival of Asian carp, which was first imported to the United States in the 1970s to help fish farmers in the South clean up their algae-filled ponds. Two types, the bighead and silver carp, are viewed as such ravenous eaters that many feared they would travel up the Mississippi River and through the waterway system that leads to Lake Michigan, where they could wreak havoc with the lake’s ecosystem and fishing industry, then spread through the other Great Lakes.

The concerns were quieted, at least for a time, by an elaborate multimillion-dollar electric fence system the U.S. Army Corps of Engineers built in the Chicago Sanitary and Ship Canal, which links the Great Lakes to the Mississippi River and its tributaries. Some officials say the barriers (combined with intensive carp-fishing efforts farther south) have kept the carp from making their way north into the Great Lakes. But others were alarmed by the recent DNA tests of water samples that detected genetic material of Asian carp (results that have themselves been the subject of a debate over their true significance) beyond the barriers.

“This is what boggles the mind here: We can send a man to the moon but we can’t stop a carp from reaching the Great Lakes?” said Bill Schuette, the attorney general of Michigan, which has led a legal and political fight to close locks that allow water to flow between the Mississippi River and the Great Lakes and, ultimately, to separate those two water systems entirely.