The sallys and jimmys (female and male blue crabs) are running. A cool spring meant a late start to the season, but now the waters of the Chesapeake Bay region have warmed up. The most coveted crabs in the country, soft-shell blue crabs that have molted and shed their hard shells, are available in local stores. (The kickoff of the soft-shell season is traditionally marked by the first full moon in May.)

Shedding an old shell is how a crab grows in size. Throughout the summer and early fall a crab will, on average, shed its shell six times, each time increasing in width by 25 percent during a life span of 24 to 30 months. The shedding process takes from one to three hours. Soft crabs must be removed from the water quickly or the shell gradually hardens and reduces their quality.

How do you pick a good one? At the fish market, choose only crabs that are still alive. Take a crab with little bubbles streaming from the mouth. Ask the seller to run his hand along the ones on display--then single out the ones that move. If crabs on ice don't show bubbles, ask the seller to remove them from the ice; in a few seconds, live crabs will show movement in their appendages. All appendages--claws, feelers and flippers-- should be intact.

The softer the crab the better. Avoid "paperbacks"--crabs whose shells have just started to harden. If the fishmonger allows you to touch them, do it. Rub your finger along the front points to make sure they are still supple. The large points should be bendable as well. Experts say that smaller female crabs are sweeter and more tender.

Perfect soft-shell crabs do make it to the big city. But for the freshest of the fresh at a lower price, take a trip to one of the following shedding operations or retailers where watermen bring their catch.

Always call ahead for availability and directions. Prices vary, but average about $24 per dozen at:

CANTLER'S At this authentic crab house restaurant, patrons, elbow to elbow, pick cooked crabs on tables covered with brown paper. Kids happily wait for dinner by peering into the 10 shedding boxes on the dock. 458 Forest Beach Rd., Annapolis; call 410-757-1311.

PAYNE'S CRAB HOUSE Catherine Via catches crabs in the Rappahannock River. Her sister Beatrice Taylor sells them at their retail crab house that has 22 shedding floats on Urbanna Creek. They can supply recipes and crab-cleaning tips. Urbanna, Va. call 804-758-5301.

PEARSON'S SEAFOOD Since 1935 the Pearson family has sold crabs. School groups often ask for a look at the 36 shedding tanks behind the retail outlet, where hard crabs and the softest of the soft-shells are sold. 610 Colonial Ave., Colonial Beach, Va.; call 804-224-7511.

PIER STREET RESTAURANT AND MARINA Look for the red roof with a giant crab on top. Then, order a cool drink and feed the rockfish school right from your dockside table while your soft-crab order is boxed up. Oxford, Md. (10 miles southwest of Easton); call 410-226-5171.

P.T. HAMBLETON SEAFOOD Ask "Just-call- me-P.T." to show you how he moves his "peelers" from tank to tank according to the color changes on the back flippers. Hambleton has 40 tanks atop an old pier in Grace Creek. Bozman, Md. (six miles west of St. Michael's); call 410-745-5181.

ROBERT H. EVANS SEAFOOD For a look at Evans's two-tank closed system (water temperature and quality are monitored), ask him to take you around back to the garage. He also sells hard crabs and local fish. 5527 Muddy Creek Rd., Churchton, Md.; call 410-956-3327.

SEA PRODUCTS Crabber Louis Whittaker maintains 101 shedding tanks. But he has all of them in operation only at seasonal peaks. Locals shop here for "nuggets"--cleaned, meaty portions of crabs that died while shedding ($8 a pound). Readville, Va. (70 miles east of Fredericksburg); call 804-453-6433.

SHORE SEAFOOD Local watermen in the town of Saxis bring their catch from Pocomoke Sound and the Chesapeake Bay to Shore Seafood, a wholesale and retail crab broker. Shore also sells frozen soft crabs, 24 to a box. Saxis, Va. (20 miles west of Chincoteague); call 757-824-5517.

WOODFIELD'S Essentially a wholesale operation, Woodfield's has drawn seafood lovers to Galesville on West River since 1917 for soft crabs as well as freshly picked crab meat and local fish (croakers, spot, rockfish, perch and bluefish). Galesville, Md.; call 410-867-3421.