FRESHWATER fishing has busted loose in most of the lakes and rivers in and south of Washington. Largemouths, smallmouths, crappies and white perch are all on their spawning beds and attacking anything that invades their territory. This translates into some dynamite fishing just a few minutes' drive from home. And if the weather holds, you can expect the action to last for the next several weeks.

On the saltwater scene, offshore fishermen are hooking up with fantastic catches of Boston mackerel along the Atlantic coast from Maryland to North Carolina. The mackerel run this season could be the best in recent history, judging by the reports from several charter captains. Some of the mackerel will tip the scales at nearly three pounds, and the sizes of the schools are now measured in square miles. WHAT'S THE CATCH? WASHINGTON AND VICINITY

POTOMAC RIVER -- White perch have invaded the Potomac during the past few weeks and you don't have to be an expert to catch all the fish you can handle. Dan Ward at Fletcher's Boat House reports loads of 10- to 12-inch white perch are being caught by local anglers using bloodworms fished on the bottom. In addition to the perch, some fair-sized crappies and largemouths are being taken in the same area. Live minnows and small twisters are taking these fish when fished slowly close to the bottom. Scattered catches of catfish are also being made by anglers fishing with nightcrawlers in the deeper areas. However, it's difficult trying to keep the perch from hitting your bait. MARYLAND

COLUMBIA LAKES -- Excellent catches of crappies and trout are being made at the lakes in Columbia along U.S. 29 by anglers using small jigs trimmed with live minnows and fished under a float, says Bob Griffith of Fishing and Archery Outfitters in Laurel. These fish are moving onto their spawning beds and average nearly 10 inches in length -- not bad for the first week in April.

TRIADELPHIA & ROCKY GORGE RESERVOIRS -- Some fair-sized crappies are falling prey to a minnow-jig combination at both of these WSSC reservoirs. In addition, some fair-sized bass are hitting crayfish-finished crankbaits worked slowly close to the shore. The bass should be migrating in from deep water to spawn within the next few weeks. If you're thinking about fishing on the WSSC lakes, you must purchase a Watershed Use Permit in order to keep your boat docked at the facility. The cost is $25. Daily use permit fees remain at $2.. For more information, call The Washington Suburban Sanitary Commission at 301/699-4172.

DEEP CREEK LAKE -- Although the lake is now ice free, the water is still a bit too cold for good fishing. Within the next few weeks, walleyes and smallmouths should move into the shallows and provide excellent fishing in the mid and upper portions of this reservoir.

DEER CREEK -- Although some trout are being caught, the fishing hasn't been nearly as good as expected. Apparently, the sludge spill last fall wiped out most of the holdover trout. Just how long the stream will take to completely recover is anyone's guess at this time. But the Fisheries Division of the Maryland Department of Natural Resources reports that a maximum restocking effort will take place within the next few months.

CONOWINGO LAKE -- Most of the fish are on the Cecil County side of the lake, said Peggy Young at Glen Cove Marina. Crappies are biting well at Conowingo Creek and at the mouths of the small tributaries entering the lake. However, there are some large crappies in Glen Cove. Butch Young reports all the piers are in place and the launch facility is open. In addition, a full supply of live bait, including nightcrawlers and two sizes of minnows, is now available for early-season bass fishermen. Although the main body of the lake is still a bit muddy, most of the coves are reasonably clear and should provide good crappie and bass fishing action.

SUSQUEHANNA RIVER -- The river level has dropped to normal spring levels and should be fishable by the weekend, reports Grace Rhudy at Conowingo Bait in Darlington. A few anglers have been fishing from the catwalk for early-run catfish, but the water's still a little cold for this kind of action.

NORTHEAST RIVER -- A few crappies are still lingering in the back end of the river, says Herb Benjamin at Herb's Tackle Shop in the town of North East, but it's still a week or two away from the annual run of branch herring. The branch herring usually arrive about the first or second week of April and stay around until sometime in early June. The best concentrations of tidewater largemouth bass also show up about the same time.

GUNPOWDER & DUNDEE RIVERS -- White perch fishing is still holding up well in Salpeter Creek, according to Sue Demaf at Gunpowder Bait and Tackle in Essex. Grass shrimp and bloodworms fished on the bottom have been the most productive baits. Scattered catches of largemouths are still being made in the same area by anglers using large, live minnows for bait. The majority of these are in the three- to five-pound category. VIRGINIA

LAKE ANNA -- The water temperature is now in the lower 60s, which is perfect for bass, crappie and striper fishing. Pete Sprague at Lake Anna Sporting Goods has been checking in lots of citation-sized crappies during the past week -- some of which tip the scales at nearly two pounds. The best action has been at the submerged brush piles close to shore. Live minnows and small jigs have accounted for the better catches. Bass guide Gene Hord reports he has been fishing nearly every day and hooking up with some dandy crappies near beaver huts, brush piles and piers. In addition, scattered catches of fair-sized largemouths and stripers are also being made at some of the points using small, white bucktails trimmed with a white grub. As the water gets warmer, the fishing will improve dramatically.

SMITH MOUNTAIN LAKE -- The lake has come alive with big stripers and largemouth bass, says Curtis Wolwine at J&W Sporting Goods in Manetta. The stripers are taking white bucktails in 1/4- to 3/8-ounce sizes trimmed with a white plastic worm. Some of these fish will tip the scales at nearly 10 pounds. The largemouths seem to prefer the same-sized jigs with a black finish and trimmed with a chunk of pork rind. Crappies weighing nearly a pound are spawning at the submerged brush piles and taking live minnows fished close to shore. The best areas have been close to the main channels in five to 15 feet of water. Points and bluffs are also a good bet when the winds are blowing up the lake.

STAUNTON RIVER -- The fishing is red hot for smallmouths and walleyes on the river below Leesville Dam, says Earl Coppage at Timberlake Sporting Goods in Lynchburg. The river is running clear and low, which is unusual for this time of year. The most productive baits have been small crank baits and live minnows fished on the fast water.

RAPPAHANNOCK RIVER -- Charlie Wingard at All's Hunting and Fishing in Salem had an extremely good catch of catfish come into his store this past week. Fredericksburg residents Butch Thomas, Cecil Perin, Dave Orrock and Joe Beavers landed 24 catfish with a combined weight of more than 253 pounds. Seven of the catties were citation-sized, meaning they tipped the scales at more than 20 pounds. In addition to the cats, some dandy white perch are also in the river and they're taking bloodworms fished on the bottom. The shad run is in full swing, and several anglers are now catching loads of hickory shad and river herring on small spoons and shad darts. Fair catches of smallmouths are also being made in the same areas; they are biting on live minnows and small crankbaits.

JAMES RIVER -- Scattered catches of muskies are now being made here by anglers fishing with large, golden shiners. The muskies will remain active only while the water is reasonably cold, so it's a good idea to hit this area soon. Smallmouths are also active in the river, and they are taking live minnows and small crank baits fished in the fast water. The best times have been early in the morning and late in the afternoon, according to Carl Gentry at Chesley's Sporting Goods in Fredericksburg. KERR RESERVOIR & BUGGS ISLAND LAKE -- The fishing has been outstanding for the past week or more, says Jim Abers at Jim's Guide Service at Kerr Reservoir. Abers says he's been hitting good catches of medium- to large-sized crappies weighing up to more than a pound. Live minnows and small jigs are responsible for the better catches of these fish. Stripers weighing up to seven pounds are now taking bucktails and live shad at the mouths of the major creeks. The best areas have been at Eastland, Butchers Island and Grassy. These fish are holding in five to 15-foot water depths at some of the secondary points. Largemouths are in these same areas, but a bit closer to shore, where the water is somewhat warmer. The best lures have been Speed Shad and white bucktails trimmed with a white plastic worm. Redfins are also a good bet when worked close to the surface during the early morning and late evening hours. CHESAPEAKE BAY MARYLAND PORTION

UPPER BAY -- The first of the white perch have shown up in the tidal ponds on Bellgrove Road and they are taking grass shrimp or bloodworms fished on the bottom, reports Clyde's Sport Shop in Baltimore. Some of these fish are tipping the scales at more than a pound.

BAY BRIDGE AREA -- The colder nights have slowed the white perch run down a bit in the upper end of the Chester River, according to the Angler's Sport Center on U.S. 50 in Annapolis, but conditions are rapidly improving. Several of the small tidal creeks are now reporting fair concentrations of smaller white perch, which means the larger females can't be far behind. Grass shrimp, bloodworms and live minnows are the ticket to success in these areas. PATUXENT RIVER -- The yellow perch run is over at Allens Fresh. According to folks at The Tackel Box on Route 235 in Lexington Park, the run was short-lived but one of the best they've seen in several years. Scattered catches of white perch are now being made in place of the yellows, and these are big spawners. Grass shrimp and bloodworms fished on the bottom have been productive. Chalk Point's power plant is still producing good catches of jumbo white perch on grass shrimp. Many of these fish are tipping the scales at more than a pound.

CHOPTANK RIVER -- The fishing has been pretty good for the past week, reports Tommy's Sporting Goods in Cambridge. Excellent catches of white perch are now being made at Little Blackwater; mixed with them are some fair-sized crappies. The perch fishing is also good at Marshyhope, the upper end of the Nanticoke and Vienna. Grass shrimp fished on the bottom has been the most productive bait. CHESAPEAKE BAY VIRGINIA PORTION

CAPE CHARLES -- The tautog fishing is coming on strong, says Captain Otis Asal on The Bucaneer at Kings Creek Marina. The tog usually remain in the lower Chesapeake throughout the winter and early spring months. When the water temperature hits the upper 60s, these tasty fish will migrate to deep water. The most productive baits have been chunks of fresh crab fished on the submerged rock piles. Captain Monty Webb of Eastern Shore Safaris had a successful day fishing offshore for Boston mackerel this past weekend. These silver speedsters are just migrating up the coast toward their New England spawning areas and will remain here for the next few weeks. The larger concentrations, schools greater than two acres in size, are now only 10 to 15 miles offshore and accessible to smaller boats on calm days. Both captains have a few open days on their books for mackerel fishing and can be reached by calling Kings Creek Marina at 804/331-2058.