Washington ( CNN ) -- The Supreme Court , perhaps for the final time , has rejected a multistate appeal over efforts to keep the invasive Asian carp from reaching the Great Lakes ecosystem . The justices turned aside another request for intervention Monday , the latest chapter in a nearly century-old dispute between 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 that the fish may have already slipped past locks and entered the massive freshwater bodies of water . The fish can grow up to 4 feet in length and 100 pounds in weight , reproduce rapidly and can gobble up to 40 percent of their body weight daily , quickly out-competing less aggressive native fish populations . The high court has refused to intervene in the case twice in recent months . Some activists say Michigan could file another appeal in federal court , but it could take months to resolve . The justices were asked 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 voracious Asian carp have migrated up the Mississippi River to the Chicago suburbs . State officials , businesses , and environmentalists fear that it is only a step away from triggering a swift economic disaster across the Great Lakes , saying that once in Lake Michigan they would spread quickly to Lake Erie , Lake Huron , Lake Ontario and Lake Superior . `` What could be at stake is the multibillion-dollar fishing industry -- commercial , sports fishing , and recreational fishing industries -- in the Great Lakes , '' said Chris McCloud of the Illinois Department of Natural Resources , noting that the lakes constitute `` the largest freshwater body on Earth , and we have to protect it at all costs . '' DNA from the carp was found in December 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 . In a signal of the urgency , Michigan , Wisconsin and New York have repeatedly but unsuccessfully asked the high court to order those locks closed immediately . Among those being sued are Chicago 's local water reclamation agency and the U.S. Army Corps of Engineers , which helped build and maintain the canal system . 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 projects . 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 prolific jumpers , easily spooked out of the water by passing watercraft , and numerous boaters have been injured by inadvertent flying fish collisions . Biologists have been tracking their northern migration ever since they were 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 , 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 . In a filing with the high court last fall , Solicitor General Elena Kagan argued that although allowing the carp to enter the Great Lakes would produce `` grave and irreparable harm , '' it was only `` speculative '' that the harm would occur `` imminently . '' She suggested that Michigan and other states were more interested in relitigating disputes over removal of water from the lakes than seeking to stop fish from entering the lakes . The other states and Canada want the Illinois water diversion projects 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 electric fences -- to ensure that the fish stay away from the lakes . Electric barriers were set up in 2002 in the Chicago Sanitary and Ship Canal , about 33 miles from Lake Michigan . They became fully operational last year , but Army engineers acknowledge that the barrier is not 100 percent effective . It is designed not to kill carp but to discourage them from going further . `` We can control what the fish feels , basically , '' said Col. Vincent Quarles , commander of the Chicago District of the Army Corps of Engineers . `` What they feel is a jolt or a tingle . It 's an electric current in the canal being created by our barriers . '' Another underwater barrier is set for completion this year . The cases are Wisconsin , Michigan , New York v. Illinois and Metropolitan Sanitary District of Greater Chicago ( 1 , Orig . ; 2 , Orig . ; 3 Orig . ) .
Justices wo n't get involved in dispute between six states , Ontario . Some say Illinois water ##way will bring huge fish into Lake Michigan . Million - dollar fishing industry could be at risk , some says . High court has repeatedly been refused to approve canals and dams .