HERE'S SOMETHING to do this Labor Day weekend that has all the ingredients of family fun: It's unusual, inexpensive and nearby; it could provide you with a free meal; and it has nothing to do with fish.

Go crabbing -- in Washington.

The Potomac River has been doing some strange things this year. There have been so many of the endangered rockfish -- or striped bass -- in the Washington stretch of the river that you almost can't avoid catching them; walleye have popped up for the first time in years; early in the season shad appeared, another first in years; spot have surfaced as far upriver as Chain Bridge; and now the river is full of blue crabs.

Big ones, too.

"Fishermen can't figure out what's been taking their bait," says Joe Fletcher of Fletcher's Boat House. "Their line rises and moves, and their bait's gone. They can't understand what's taking it.

"Crabs."

One fisherman off Fletcher's said that if he had netted all the crabs he saw swimming, he would have gone home with half a bushel of hardshell crab, Fletcher says.

"There hasn't been crab like this in the river in, oh, 20, 30 years, the last time we had a severe drought like this," he says.

Because of the lack of rain, the river is low, and the salt water from the Chesapeake Bay has been creeping upriver -- and with it, crabs.

To catch crabs, Fletcher recommends using salted eel, which has a super-tough skin. He says you may be able to pick some up at the Maine Avenue fishmarket. Any other fish will do as crab bait, though, he says.

And you might try the old crabbing standby -- chicken necks.

Whatever bait you use, just tie a string around it, add a little weight to it and toss it in the water. After a few minutes -- ever so slowly, hand over hand -- pull in he string.

You should be able to see if you have a crab hanging onto your bait before it gets to the surface (the Potomac isn't that murky). If a crab is there, scoop it up with a net.

In the District, there are no restrictions on crabbing. But you should throw back young ones -- especially females.

How can you tell?

While the crab is still in the net, take a look at its underbelly. The male will have a tab that looks like, well, the Washington Monument; the female's tab is shaped like the Capitol Dome.

If the crab's underbelly doesn't look like any of these, you don't want to keep it.

Where are the best places to go?

Right now, anywhere. But Fletcher recommends going to Hains Point.

The water is saltier there than in his neck of the river, and with the rail along the river bank, you'll be able to crab easily and safely. WHAT'S THE CATCH?

WASHINGTON AND VICINITY

If you can keep your bait away from the crabs, you can expect to catch catfish in the Potomac,says Joe Fletcher of Fletcher's Boat House. But the catfish "aren't any size to speak of." The most effective catfish bait right now is clam snout.

You can also catch the occasional striper, walleye and largemouth bass in the Potomac -- but don't wait up for them.

Fletcher says he expects the crappie to "start up soon. They do when the water cools off." MARYLAND

LOWER POTOMAC -- "It's doing good right now," says Tony Butler of Capt. John's Crab House and Marina on Cobb Island. "It's the best time of year now."

Use softshell crab, and you can expect to catch plenty of big perch and pan-sized spot, Butler says. There also are small blues to be caught in this stretch of the river, as well as "a few croakers," he says.

UPPER POTOMAC -- "The water's high," says Rob Gilford of The Rod Rack in Frederick. "For this time of year, it's up. And it's cloudy. But by the weekend it should clear up."

Catfish are plentiful, Gilford says. And this week there have been "some pretty big smallmouth turned in" to The Rod Rack for weighing, he says.

The black-and-chartreuse Ringworm artificial lure is working well, along with smoke-colored grubs and three- inch twister tails, Gilford says. If you prefer live bait to artificials, use crayfish or shiners, Gilford advises. But don't use hellgrammites if you're after smallmouth, he says. The catfish are gobbling them up.

FARM PONDS -- The farm ponds in the area are hot, Gilford says. If you're lucky enough to have fishing rights in a farm pond, Gilford advises taking along a Ringworm artificial lure. For the ponds, the best color is electric blue with a chartreuse tail, he says. VIRGINIA

LAKE ANNA -- If you can, hold off on Lake Anna for another week or so. "Then you're going to see some really good fishing," says Tom Goodwin of Sturgeon Creek Marina.

"The water's cooled down some, and that's a good sign," Goodwin says. "Small fish are coming up in shallow water, and they always come first before the big ones.

"So I give it another 10 days, and it'll be really good. By the 10th, 15th of September, things should really pick up."

Since that's well after Labor Day, Goodwin predicts that by then most of the water skiers will be gone. "School kids, college students, will be back to school," he says -- and for Lake Anna weekend fishermen that's as good as hearing that the fish have come back.

Until then, expect to catch channel catfish -- "big ones" -- and stringers of crappie.

But the largemouth -- Lake Anna's purported raison d'etre -- have been small, Goodwin says.

OCCOQUAN -- "Overall the fishing has improved," says Phil Mello of The Lynn Co. in Occoquan. "The cooler weather has helped the fishing quite a bit."

In the river, the bass have perked up, going after crankbaits and plastic worms, Mello says. There also are "a few crappie, and plenty of catfish," he says.

In the reservoir, the crappie are "very active," striking small minnows and jigs, Mello says. Bass there are "fairly productive," he says.

And, surprisingly, "there are plenty of blue crabs" in the river, Mello reports. "They're keepers," he says. Mello attributes the large number -- and large size -- to the high salinity.

"And crabbing is even better around Quantico," he says.

Mello says the best place to fish in the Occoquan River right now is at its most accessible place -- underneath the U.S. 1 bridge and about a half-mile from the bridge in either direction.

Why?

"There's a deep-channel dropoff through there," he says, "and the bridge provides shade and structure."

RAPPAHANNOCK -- Have things gotten better from last week when the rains had washed out the fishing?

"Not really," says Karl Gentry of Chesley's Tackle Shop. "It's still been slow."

"The river's got back into good shape," he says, "and they're catching some fish," but the catches of smallmouth are nowhere near the big sizes that were caught before the rain of two weekends ago.

"That rain put all the water back into the river," Gentry says. "Before the rain, the river was so low you could find the holes the fish were in."

But don't give up on the Rappahannock, Gentry advises. The fishing will pick up, and "should remain good into October."

And that goes for catfishing. According to Roy Edwards of the state inland fisheries commission, before the big rain, two anglers -- David Ratcliff and Phillip Ballard, both of Fredericksburg -- hauled in 48 pounds worth of catfish. Not bad for two fish. Ratcliff caught a blue catfish that was 27 pounds, 2 ounces; Ballard's was 21 pounds, 3 ounces.

Their bait was Ivory soap.

If you use soap to catch a fish, does that mean you don't have to clean it? CHESAPEAKE BAY

CAPE CHARLES -- The run of channel bass, or red drum, "is starting now," says Emmett Bailey of Bailey's Tackle Shop. "A few are being caught now -- starting this week."

"Some folks are catching two or three each evening," Bailey says, adding that two red drum were brought into his shop Wednesday, one weighing 341/2 pounds and the other 391/2 pounds.

If you can't get to Cape Charles this weekend, Bailey says not to worry. The red drum will be around for a while; in fact, since the run is only now starting, the red-drum fishing should be even better next week.

Right now the red drum are being caught "from the tide starting in the evening, around 4 or 5 o'clock, and on up to dark," Bailey says. By next week, you should be able to catch them earlier than that.

DEALE -- You'll need plenty of empty coolers on board if you troll from the radar towers on the west side of the Bay just south of Deale out into the ships channel to marker 28B and then back to marker 71, says Capt. Tim Johnson.

It's Bluefish Heaven out there.

Use spoons, Johnson advises. The bluefish he's been catching are in the three-pound range, and they're full of menhaden in the six-er than what pond fishermen are bringing in," Johnson says.

If the water is rough, troll deep with heavy weights, Johnson advises. If not, you can expect the bluefish to be breaking on the surface.

On Monday, Johnson was sitting at home, which is "right on the Bay," when "through the outside window, I heard what sounded like a thrashing machine," he says.

Blues were breaking "right against the sea wall" outside his home, he says.

They're coming that close to shore.

So what did he do, this professional charter captain who lives, eats and sleeps bluefish this time of year?

He grabbed his spinning rod and a No. 18 Tony, and "my hands were shaking I was so excited. I was acting just like a kid," he says.

"We take people out fishing all the time, but we never get a chance to do any fishing," he says. "It was wonderful. I'd drop the spoon over the side, jig it and I was taking a fish a cast."

POINT LOOKOUT -- Surfcasters on the causeway are hauling in "a lot of fish," small bluefish and small flounder, reports Pat Raley of Sister's Store. The blues are in the three-'re still using alewives and bloodworms for bait," she says.

If you go out in the Bay on a headboat this weekend, you can expect to catch all the bluefish you want, says Norman Bishop of The Lucky Lady. The blues are everywhere. Headboats are chumming for them and having "very good" catches, Bishop says.

People with their own boats also are having luck trolling for blues, and they're catching flounder in the 12- inch range.

Bishop notes one unusual catch: One angler caught a dozen or so sea bass, 10 to 12 inches long, at the mouth of St. Jerome's Creek, where The Lucky Lady is located. The size and quantity of the sea bass are unusual for this part of the Bay, Bishop says. Usually they're smaller than that. ATLANTIC OCEAN

CHINCOTEAGUE -- "It's been kind of slow," says Capt. Bob Pohlmeyer of Capt. Bob's Marina.

Offshore, charters are coming back with trout and croaker -- "about one and a quarter pounds, but they're getting bigger," Pohlmeyer says.

And surfcasters off Assateague Island are catching trout, snapper blues and shark -- "not many of them," he says.

In Chincoteague waters, the flounder fishing is "not too good," Pohlmeyer says. "They're not catching beaucoup right now.

"But next month they should be. It'll pick up. But right now they really have to work for them."

OCEAN CITY -- If you've got the bucks, go by boat. If not, grin and bear it.

In the Baltimore Canyon, the fishing for white marlin and tuna is good, and closer in -- about 20 to 25 miles out -- the bluefish are plentiful, says John Wildeman of the "Mariner" headboat, which operates out of the Talbot Street Pier. Wildeman says the shark fishing is "so-so," and the boats are getting into "scattered dolphin." (Don't worry. These aren't your cute, lovable, almost cuddly "Flipper" kind of dolphin. These are your good-fighting and even better tasting fish variety of dolphin.)

The headboats are bringing in trout, croaker and flounder, Wildeman says. Fishing from the headboats has picked up this week after a few days of calm weather, he says.

"If you've been fishing at all, you can catch a lot" from a headboat now, Wildeman says.

Closer in, on the piers and in the bay, the fishing has been lousy, he says, but it picks up a little in the evening. However, trout are coming in, and "by Labor Day the fishing should be pretty good," Wildeman says.