The U.S. Supreme Court announced that it will not immediately shut down shipping locks near Chicago that link the Mississippi River to the Great Lakes, denying a request by Michigan that was aimed at keeping away invasive Asian carp.

The court's one-sentence ruling didn't explain its decision, but conservationists were quick to point out that all is not yet lost.

"[This] does not mean that no action will be taken in the case," a spokesman for the National Resources Defense Council says. "There is still a significant possibility that the court will issue a decision regarding Michigan's broader requests for action on this issue."

Asian carp are big, voracious fish that were brought to America in the '70s and have been snaking up the Mississippi River ever since, now threatening the Great Lakes' $7 billion-a-year fishing industry.

Many scientists say the fish could starve out popular species such as trout and salmon. 

Just hours after the Supreme Court's ruling, state and federal officials announced that Asian carp DNA has been found in Lake Michigan, raising the possibility that the fish have already broken in. But the DNA samples could be anything from scales to feces, and don't necessarily indicate the invasion has begun just yet.

"Even if we have a live carp get into Lake Michigan," an EPA official says, "that does not mean they have established a self-sustaining population there."

They also are spooked by passing motors and often hurtle from the water, colliding with boaters forcefully enough to break bones.

Officials poisoned a section of the canal in December after discovering genetic material that suggested at least some carp might have eluded an electric barrier on the Chicago Sanitary and Ship Canal and could be within six miles of Lake Michigan. If so, the only other obstacles between them and the lake are shipping locks and gates.

Scientists fear that if they reach the lakes, they could disrupt the food chain and endanger the $7 billion fishery.

The biggest Asian carp can reach 4 feet in length and weigh 100 pounds while consuming up to 40 percent of their body weight daily in plankton, the foundation of the Great Lakes food web.