The annual spring perch fry went off on schedule last week at Fletcher's Boathouse on the Potomac, despite a spitting rain and a cold northeaster. The river was too high and muddy to fish but plenty of white perch had been caught and cleaned the day before, and herring were so thick you could net them even in flood.

Picnic in the rain? Why not? "It won't be the first time," said Ray Fletcher, who guarded a frying pan full of sizzling yellow herring roe, a delicacy as sweet as shad roe and infinitely more abundant. "Get away from my gold," he warned the two dozen trenchermen who hovered nearby, ready to pounce. "I'll let you know when they're done."

The Potomac in spring is pure, delicious abundance, and Fletcher's perch fry, a glutton's delight for the lucky ones invited, is a fitting tribute. This time of year, the river abounds with perch, herring, a few shad, crappies, largemouth and smallmouth bass, sunfish in the quiet water, catfish, the occasional walleye and yellow perch. And rockfish are on the way.

You never know what you might hook, and for centuries nobody cared. There never has been a law worth mentioning to regulate fishing in D.C. waters and there isn't one now. But those days are ending.

A visitor to this year's perch fry, conspicuous in his tweed jacket and bureaucrat's pallor, was Jack Buckley, who intends to end the anarchy.

Buckley, fisheries biologist with the D.C. Department of Consumer and Regulatory Affairs, intends within a month or so to put into effect limits on the size and numbers of certain species caught in Washington waters. Then, in January, his agency will introduce the first D.C. fishing license, costing $5 for residents and $7 for others.

Notable among rules to go in effect immediately is an 18-inch minimum size, two-fish-per-day creel limit on rockfish (striped bass), the beleaguered state fish of Maryland. For the last 1 1/2 years, the District has been in the embarrassing position of having no limit at all on rockfish, while neighboring Maryland had a total moratorium and Virginia imposed strict limits and closed certain seasons.

"They had to do something," said Phil Evans, who runs a rod and reel repair shop in Mount Rainier and is a regular Potomac fisherman. "They had a free-fire zone down there where people could do anything they want, like Tripoli."

Even Joe Fletcher, who a year ago expressed serious reservations about fishing limits and licenses in D.C., agreed regulations were needed. He said fishermen during the height of the rockfish run last year were taking home stringers of 100 and more, including many fish under 12 inches long.

George Boswell, who goes by the nickname "Tidal Basin George," for his skill at hoisting fish out of that Washington landmark, agreed. "It's a good deal," he said. "The law should be the same all over."

Buckley said there will be no size or creel limits on perch, catfish, carp, sunfish or herring, but there will be limits on largemouth and smallmouth bass, walleye, American and hickory shad, and for chain pickerel and great northern pike, both extremely rare. The law also makes commercial fishing in D.C. waters illegal.

Buckley said the regulations have been published as a proposed rule, the public comment period has ended and, barring unexpected problems, the package will go into effect in 30 to 60 days. The rules include the call for a license, but no license will be required this calendar year, he said.

Buckley said fees generated by the license must by law be plowed back into fisheries programs, and will be matched at a 3-to-1 rate by funds from the federal Wallop-Breaux program, which taxes fishing tackle and boating gear. That means for every $5 license, the programs will get another $15 from the United States, up to a total of $400,000 a year.

Buckley wouldn't hazard a guess on how many licenses might be sold, but he said a recent Gallup poll showed that about 14 percent of urban people fish, which translates into some 90,000 potential license-holders in the D.C. area.

Buckley, who has a staff of four biologists and a $275,000 budget this year, has big plans for improving fishing in Washington, including extensive surveys of fish populations, a youth education program, better boat ramps, artificial reefs to provide habitat, fishing piers and, possibly, some fish-stocking.

Fishing, which according to the Gallup poll was the most popular recreation among adult U.S. males in 1985, with 44 percent participating, has been booming for a decade in Washington.

Bass tournament anglers and guides and their bass parties are commonly seen on the lower portion of the Potomac and around the Washington Ship Channel; Fletcher's continues to do a land-office trade during spring spawning runs, and striped bass anglers and catfishers dot the waters from Wilson Bridge to Chain Bridge during summer and fall.

The increased activity is largely attributed to the improved water quality, which in turn is attributed to improvements at Blue Plains treatment plant, the huge sewage facility that spews 315 million gallons a day of treated effluent into the river a few miles below Hains Point.

Blue Plains is one of the few plants in the nation that has been upgraded to remove phosphorus from treated effluent and, evidently as a result, the algae blooms and stagnant water that made the river repugnant 15 years ago have largely disappeared. Submerged aquatic grasses have taken root again in broad areas and fishing is on the upswing.

Buckley hopes the D.C. fisheries program will wind up as a model for other U.S. cities as they, too, clean up their waterways and reap the resulting fishing benefits.

Let's see, what would one wear to a perch fry on Wall Street?