CHICAGO - Chicago's seasonal ritual of boat parades may be scuttled as five states ask a judge to head off an invasion of Asian carp by blocking access to Lake Michigan.

Boats come out of winter storage along the Chicago and Calumet rivers each spring and motor through locks into the lake. The city schedules lifts of movable bridges twice a week to accommodate tall masts.

Michigan and four other states will argue at a Tuesday hearing that one way to shut out the carp is to close the locks. Boaters in the nation's third-largest city say that would strand them in dry dock or, for sailboats, cost thousands of dollars to have vessels transported overland.

"Closing off the locks just seems like cutting off a lifeblood for a lot of boaters in this town," said Glennon Schaffner, 45, who keeps his 30-foot Chris-Craft powerboat, the Maru II, at the Goose Island Boatyard on the north branch of the Chicago River, about 3 miles from the lake.

Boatyard owners are concerned that customers will abandon their facilities close to the city for those far enough away that they wouldn't be affected by carp-fighting measures.

"We are very nervous about the situation," said Rick Haislip, general manager of the Goose Island Boatyard, which stores as many as 400 powerboats.

Asian carp, which grow as big as 100 pounds, escaped into the Mississippi River after being imported to cleanse fish ponds and sewage lagoons. Their diet includes the plankton that native species need to survive.

Michigan, Wisconsin, Minnesota, Ohio and Pennsylvania contend that the carp threaten the region's $7.09 billion sport and commercial fishing industry. U.S. District Judge Robert Dow in Chicago will hear evidence in the lawsuit filed in July by attorneys general for those states, charging that Illinois and the U.S. Army Corps of Engineers haven't done enough to keep the fish out of the Great Lakes.

"We have here a carp highway," Robert Reichel, an assistant attorney general for Michigan, said in an appearance before Dow last month. The Great Lakes and Mississippi are connected by the Illinois River and by the Chicago Sanitary and Ship Canal and the Cal-Sag Channel.

Closing the locks is one of several proposals put before Dow. The states' other suggestions include additional netting and screens as well as poisoning the fish.

The Army Corps already has installed two electric-current barriers along the bottom of the canal to prevent the fish from passing, and a third is under construction.

"Closing the locks would certainly be the swiftest and most powerful solution, but certainly not the only step that can be taken to protect the Great Lakes," said Joy Yearout, a spokeswoman for Michigan Attorney General Michael Cox.