Washington ( CNN ) -- The Supreme Court for a third time has turned aside an urgent appeal from Great Lakes states to close Chicago-area shipping channels so invasive Asian carp wo n't have a doorway into the world 's largest freshwater ecosystem . The justices Monday turned aside without comment another request for intervention , the latest chapter in a nearly century-old dispute involving six Midwest states and the Canadian province of Ontario . At issue is a direct challenge to Illinois ' complex water diversion and sewage disposal network , which some predict will inadvertently allow the non-native fish to enter Lake Michigan . Some environmentalists and lawmakers fear an economic and ecological disaster if the creatures breach man-made barriers . And there are concerns the fish may have already slipped past locks and entered the massive bodies of fresh water . The fish can grow up to 4 feet in length and 100 pounds in weight , reproduce rapidly , and can gobble up to 40 % of their body weight daily , quickly out-competing less aggressive native fish populations . The high court twice before has refused to step into the case . Five states -- Michigan , Minnesota , Ohio , Pennsylvania and Wisconsin -- had filed a new appeal , demanding permanent closure of a drainage system linking the Mississippi River and the lakes . The justices were asked again to grant a preliminary injunction , which would have forced Illinois to immediately close down much of its Chicago-area shipping locks and dams , and would have prompted rapid construction of a fish-proof barrier . The high court refused that petition , but offered no explanation . The voracious Asian carp has successfully migrated up the Mississippi River to the Chicago suburbs . State officials , businesses , and environmentalists fear it is only a step away from triggering a swift economic disaster across the Great Lakes , saying that once in Lake Michigan the carp would spread quickly to Lakes Erie , Huron , Ontario , and Superior . DNA from the carp was found in 2010 closer to Lake Michigan than ever before -- at a Wilmette , Illinois , pumping station along the lake shore -- raising fresh concerns that the fish has breached an electric barrier placed along a maze of canals and locks in Illinois . Among those being sued are Chicago 's local water reclamation agency and the U.S. Army Corps of Engineers , which helped build the canal system and helps maintain it . Illinois officials say other states and the federal courts do not have the legal authority to order the closing of any federally approved water management project . There are fears that shutting down the locks would lead to massive flooding and cripple the area 's commercial shipping industry . The term `` Asian carp '' is actually an umbrella name for at least four large varieties of fish considered nuisance invasive species : the grass , black , silver , and bighead carp . Related to common goldfish , the bigger types are known as prolific jumpers , easily spooked out of the water by passing watercraft . Numerous boaters have been injured by inadvertent collisions with airborne fish . Biologists have been tracking their northern migration ever since they were first imported in the 1960s , traced to an Arkansas fish farmer . Several of the fish escaped during a flood in the 1990s and quickly expanded their range . Their possible presence just miles from the lakes prompted the latest lawsuit over the so-called Chicago Diversion , a project started in the late 1800s to prevent the city 's sewage from contaminating Lake Michigan . The project involved reversing the flow of the Chicago River , and connecting it and two other nearby rivers with the Mississippi River basin . That created a connection between the Great Lakes and the Mississippi , helping fuel an economic boom in the nation 's third-largest metropolitan area . In 1922 , Wisconsin sued Illinois to stop the growing water diversion , since other states relied on the drinking water . All other lake states except Indiana joined suit , and the Supreme Court eventually agreed with them , ordering mitigating effects over Illinois ' diversion . Now several of those states are asking the justices to reopen the old cases . Such interstate disputes over boundaries and shared natural resources are one of the few instances where appeals can go directly to the Supreme Court , instead of first being heard in lower courts . The Obama administration is supporting Illinois . Justice Elena Kagan was actively involved in the cases when she worked as the Justice Department 's solicitor general . Since joining the high court two years ago , Kagan has not participated in any of the current carp-related appeals , including Monday 's order . The other states and Canada want the Illinois water diversion projects to be declared a `` public nuisance '' because of the carp emergency . Of more immediate concern , they want Illinois and federal officials to modify their fish-control facilities , including the electric fences , to ensure the fish stay away from the lakes . Electric barriers were first set up in 2002 in the Chicago Sanitary and Ship Canal , about 33 miles from Lake Michigan . They became fully operational in 2010 , but Army engineers acknowledge the barrier is not 100 % effective . It is designed not to kill carp , but to discourage them from going farther . The current case is Michigan v. Army Corps of Engineers ( 11-541 ) .
Six Midwest states , Canadian province of Ontario want action on Asian carp . They want the court to order Illinois to shut down locks and dams and build a fish barrier . The large , voracious Asian carp is seen as a threat to native species . The fish got into the Mississippi River system from a fish farm during a flood in the 1990s .