(CN) - A bid to prevent migration of the invasive Asian carp, a voracious breed of fish criticized for crowding out native species in the United States, failed to attract the attention of the U.S. Supreme Court on Monday.
The justices rejected a petition to consider the case without comment, leaving a decision by the 7th Circuit intact.
In August, the Chicago-based federal appeals court refused to order an emergency injunction that would close the locks of the Chicago River.
Asian carp escaped into the Mississippi River from containment ponds in the 1970s and are now poised at the brink of a manmade path to the Great Lakes after decades of northerly migration.
"The carp are voracious eaters that consume small organisms on which the entire food chain relies; they crowd out native species as they enter new environments; they reproduce at a high rate; they travel quickly and adapt readily; and they have a dangerous habit of jumping out of the water and harming people and property," Judge Diane Wood wrote for the 7th Circuit.
The carp population in the Mississippi River has grown out of control. From 1994 to 1997, commercial harvesting of carp increased from five tons to 55 tons per year. As of 2007, commercial fishers were catching 12 tons of carp each day, according to court documents.
As the carp threaten to enter the Great Lakes, experts fear that they will cause ecological disaster and bring down the billion-dollar industries that depend on the existing ecosystem.
Michigan, Minnesota, Ohio, Pennsylvania and Wisconsin filed suit, seeking a number of measures to prevent the carp's entry into the Great Lakes, specifically Lake Michigan.
The suit named the Army Corps of Engineers and the Metropolitan Water Reclamation District of Greater Chicago, which operate a system of locks, canals, channels and dams known as the Chicago Area Waterway System. The city of Chicago and two business and tourism entities were also named.
In federal court, the states asked for a preliminary injunction closing in the locks, placing screens over sluice gates and nets in nearby rivers, using rotenone to poison fish, and expediting a study of how to best protect the watersheds permanently.
U.S. District Judge Robert Dow Jr. declined to grant the preliminary injunction, finding that the states were not likely to succeed on the merits of the case. Dow determined that "it is far from certain that Asian carp can survive and reproduce in the Great Lakes."
While the 7th Circuit affirmed the ruling, the three-judge panel based its decision on different grounds.
"We part company with the District Court when it comes to the assessment of the states' likelihood of success on the merits," Wood wrote. "The magnitude of the potential harm here is tremendous, and the risk that this harm will come to pass may be growing with every passing day."
"Given the magnitude of the harm, we are inclined to give the benefit of the doubt to the states on the question whether they have shown enough of a risk of nuisance to satisfy the likelihood-of-success requirement at this preliminary stage," she added.
"In our view, the proper inference to draw from the evidence is that invasive carp are knocking on the door to the Great Lakes," the decision states. "We need not wait to see fish being pulled from the mouth of the Chicago River every day before concluding that a threat of a nuisance exists."
"Unlike many nuisances that can be eliminated after they are discovered, this one in all likelihood cannot be," Wood added. "The fact that it would be impossible to un-ring the bell in this case is another reason to be more open to a conclusion that the threat is real."
But impending threat does not justify an injunction, according to the court.
"In light of the active regulatory efforts that are ongoing, we conclude that an interim injunction would only get in the way," Wood wrote, noting that "there is a powerful array of expert federal and state actors that are engaged in a monumental effort to stop invasive carp from entering the Great Lakes.
"The last thing we need is an injunction operating at cross-purposes with their efforts or imposing needless transactional costs that divert scarce resources from science to bureaucracy," she added. "Furthermore, from an institutional perspective courts are comparatively ill situated to solve this type of problem."
A preliminary injunction would reduce, but not completely eliminate, the risk of carp migration, the panel found. And it would impose substantial costs on the defendants.
"The balance of harms at this stage of the litigation favors the defendants," Wood wrote, noting that the injunction may not help if the invasive carp descend on Lake Michigan in the future.
To prevent the carp's spread, the corps has already adopted several measures, such as the installation of barriers between the Des Plaines Rive and Chicago Sanitary and Ship Canal, which would prevent carp from washing between them during floods. It has also introduced three electric barriers operating at maximum-safe strength and installed two additional screens at Chicago-area sluice gates.
There are also some nontraditional safeguards in the works. The corps is planning to build "an acoustic, air-bubble, and strobe-light curtain (more or less a disco screen), which would be designed to frighten fish back toward the Mississippi," the judges said. Meanwhile, the Obama administration has named an "Asian carp czar" and announced plans to install "a high-intensity water cannon that would deter fish by firing huge, underwater blasts of water across Chicago Ship and Sanity Canal."
"Whatever happens, the plaintiff states will continue to have a seat at the table as these and future plans are made and implemented," Wood wrote.
"We take very seriously the threat posed by the invasive species of carp that have come to dominate parts of the Mississippi River basin and now stand at the border of one of the most precious freshwater ecosystems in the world. Any threat to the irreplaceable natural resources on which we all depend demands the most diligent attention of government."
The Supreme Court noted in its brief order that Justice Elena Kagan did not participate in the consideration of the case.
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