Sunday was the start of rockfish season on the Potomac River below Washington and the end of a six-month-long wait for Mel Welch and his fishing partner, Art Cather.

The wait was a just a few minutes too long, in Welch's view. "Sun's coming up," he muttered as Cather sped down Route 301 just after 5 a.m. on the last leg of the 60-mile journey from the Washington suburbs. "We're late."

Half an hour later, Cather was at the wheel of his 25-foot fishing boat and Welch was in the stern, bouncing three bucktail lures along in five feet of water over rocky bottom, with the current streaming downriver and the sun rising huge and fire-orange behind the Pepco plant. Welch felt his rod tip go down with a strike, then down again with another, and his half-year wait was over.

"Oooh," he said, relishing the tugs of twin rockfish, "it feels so good."

So it continued for four hours until the ebb tide gave out, as Cather, Welch and a guest boated about 60 rock, 13 of which exceeded the legal minimum size of 18 inches and went clattering into the icebox, to be taken back to Washington and sold.

What's this, you say? Rockfish killers on the Potomac, selling their catch? Isn't there a ban on catching rock? Isn't it a protected species?

Indeed it is, but not in the Potomac, which lies in a curious bureaucratic crack where Maryland laws don't apply, even though the river technically is Maryland territory.

Because the tidal Potomac historically has been fished by Marylanders and Virginians, it is presided over by a bistate agency, the Potomac River Fisheries Commission, which has elected not to adopt Maryland's ban on rockfishing, designed to restore stocks of the beleaguered state fish.

The PRFC instead chooses to follow the lead of Virginia, where relatively mild rockfish conservation measures stand in contrast to generally stringent coastwide efforts at restoration of the prized fish, including the four-year total ban in Maryland.

Of 12 states on the Atlantic States Marine Fisheries Commission's striped bass (rockfish) advisory board, for example, only three -- Virginia, North Carolina and Massachusetts -- still allow commercial exploitation of rock, according to Paul Perra of the ASMFC. Today, Virginia and the Potomac offer the longest commercial rockfish season anywhere in the East and probably will produce the biggest commercial catch this year, Perra said.

That's good or bad, depending on your perspective. Perra has problems with the Virginia/Potomac rules, fearing they may hurt efforts to protect young female rockfish until they have a chance to spawn. But for folks such as Welch and Cather, who love the rockfish game, the loophole leaves one last place to play, and signs they see on the Potomac point to no great damage to the rockfish stocks yet.

"Last November we saw more rockfish than I've ever seen in 10 years here," said Welch, a federal government weatherman. "The big flood last fall drove them downriver, and they bunched up below Cobb Island. We took a five-mile ride in the boat, and all you could see from shore to shore was birds working over breaking rockfish."

"It was unreal," agreed Cather, a licensed charter skipper who began fishing the Potomac in the early 1950s. "I never saw anything like it in my life."

Even Maryland officials agree that rockfish throughout the Chesapeake Bay and its tributaries, including the Potomac, are on an impressive rebound. They attribute the resurgence to the Maryland ban, now 1 1/2 years old, and conservation measures up and down the coast.

"We're seeing the beginning of the recovery of striped bass in the bay," said Louis Rugolo, chief of Maryland's estuarine fisheries program.

For now, the only human beneficiaries of this resurgence around the Washington area are those who fish the Potomac, where sport anglers are allowed five rockfish per day over 18 inches and folks such as Cather and Welch, who hold $25 commercial Potomac fishing licenses, can catch all they want, just like the regrettable days of unchecked plunder not too long ago.

There is a catch: Maryland's ban extends to possession of rockfish, which means one in your cooler or the freezer at home puts you in peril of a $500 fine and confiscation of equipment. So he who catches had better land and eat his fish either in Washington, D.C., where there are no rules at all, at least for the next month or so, or in Virginia.

Cather and Welch, ever the pragmatists, have neatly sidestepped even that problem. They live in Maryland, dock there and transport their fish over Maryland roads, so they have obtained a $150 seafood dealers' license to keep it all legal. The license entitles them to transport rockfish through the state as long as it's destined for sale elsewhere, which is exactly what they do.

Which all just bears out what Maryland Natural Resources Secretary Torrey C. Brown said 18 months ago, to explain why he decided on a complete ban: "Anything else you try, people will find a way around."