RIDGE, Md. - Chesapeake Bay crabber Paul Kellam has advice for the teenage boys who help tend his traps every summer: You better have a backup plan.

It's an anxious summer for watermen harvesting the Chesapeake's best-loved seafood, the blue crab. The way some see it, the crabbing business here isn't just dying. It's already dead.

Crabs have thrived in the bottom muck of the Chesapeake and its tributaries even as centuries of overfishing harmed oysters, fish and other species in the nation's largest estuary. Now blue crabs are in trouble, too, and when they go, a way of life is sure to go with them.

"There was a time when crabbers were only out here from Memorial Day to Labor Day. Now, it's about all we have left," says Kellam, 53, steering his 30-year-old rig "Christy" out of the Potomac River and onto the bay for a day of crabbing. The contradictory decor in the cabin sums up the outlook of today's waterman: a red wooden good-luck horseshoe dangles over a mud-splattered copy of "The Worst-Case Scenario Survival Handbook."

The bay's blue crab stock is down 70 percent since 1990 due to overfishing and water pollution, according to Virginia and Maryland fisheries managers. The states have imposed steep cuts on this year's female crab harvest, aiming to reduce the number of crabs taken by more than a third.

For Kellam and his neighbors in southern Maryland, where the working rigs and crab picking houses that sustained these communities for generations have been replaced by yachts and vacation homes, hopes are dim that the blue crabs will ever come back.

"It's looking worse every year," says Bob McKay, who at 74 is the oldest working waterman in St. Mary's County. He still sells crabs out of a shed in his yard but doubts the industry will live much longer than he does. "I don't know what the solution could be."

Watermen have turned to real estate and automobile repair. They've opened seafood restaurants and bakeries.