FRENCH RIVER, Minn. - For decades, they've been making their way toward the Great Lakes. If invasive Asian carp invade the lakes, scientists say they will be extremely difficult to control.

"I’m concerned like everybody else is, once the invasive species gets into the Great Lakes, its awful tough to control them," said Don Schreiner, Minnesota DNR Area Fisheries Supervisor.

The invasive species has worked its way up the Mississippi and Illinois rivers.  Now, Asian carp DNA has been found in Lake Michigan. 

Schreiner says if they do make it to Lake Superior, the main concern is they could disrupt the food chain. 

"Asian carp are filter feeders," he said. "They filter out the water and mostly they are feeding on algae, plankton in the water and in that way, that's the same food that some of the smaller organisms and the young fish feed on."

Schreiner says the largest Asian carp can reach up to 6 feet in length and weigh anywhere from 40 to 100 pounds, so a secondary concern is they would become a danger to boaters and anglers. 

"Some of the carp will jump as boats come by; folks probably have seen some of the photographs of the carp jumping and actually hitting anglers or boat operators as they motor through areas of high concentrations," Schreiner said.

 But Schreiner doesn't expect the Asian carp would have much impact in Lake Superior itself. 

"I think the biggest impact that we would have would be in places like the St. Louis River, some of the bays like Chequamegon Bay over in Wisconsin, maybe Thunder Bay - that would be the biggest concern locally," he said, along with inland lakes and rivers. 

"The Asian carp do run up fast-moving. larger rivers to spawn, so we may see some of that if they come in any type of numbers," Schreiner said.  "Any of the rivers. The Brule River might be [affected]; it's one of our larger rivers on the western end of the lake here and it's fairly fast-moving. It does have a barrier upstream, which might be a good thing if they actually get into the system."

The U.S. Supreme Court turned down a request to immediately close down locks near Chicago to stop the spread of Asian carp, but it's still considering a broader lawsuit challenging the legality of the locks. 

The White House will host a summit on the Asian carp threat next month.