It is midnight, and along the hard rocky banks of the Potomac there are murmurs of discontent. Sparks drift skyward from campfires: mantel lanterns cast their light across angular stone and the soft forms of sleeping fishermen.

The shore is dotted with men and women who are keeping a timeworn date with the river; it is April and the herring and shad are running; catfish are lurking in the deep, the tide is rising.

"Look at that rock, Wayne," says Ken Sigler, who makes this voyage from Frederick yearly with as many of his kin as he can round up. "She's practically covered up now. Try dippin' over here by the big rock."

Wayne Sigler shoulders the long-handled dipping net and tiptoes across the sharp crevices. His broad workman's black is silhouetted against the pink glow of Georgetown, two miles away.

He dips, knocking the aluminum pole against more rocks hidden in the dark water. "No, Wayne," says Sigler, "run that next downstream. You never dip into the flow."

The net comes up empty, as it has almost without fail since the Siglers began fishing five hours earlier. It is not a good night for herring.

"Water's low," says Sigler. "You never get them close to shore when the water's this low."

Indeed, the anglers who are loading their buckets and bins with the silver-sided eight-inch herring this Saturday night are the ones who are tossing bare weighted hooks deep into the channel. They let the treble hooks sink to the bottom, then heave and reel, heave and reel, hoping to snag their fish deep.

What is it about the little herring that draws hundreds of anglers in the daytime and this small band of die-hards long past dark?

"When they're running right you just take all you want," says Ken Sigler. "I've been down here when we loaded up four washtubs full in three or fours hours. Every time you dip you come up with 10 or 15 fish. I've had the dipping net so full I can't pick it up; I have to drag it back to the rocks and heave it in."

What then?

"Momma always cold-packs them," says Sigler. "But some folks sat them down and others like 'em fresh. What momma does is put them in a big jar with a little bit of vinegar, then she puts them in the refrigerator for a few days. The vinegar softens the bones. Then we grind them up, bones and all, and make, you know, like salmon cakes."

"When you get back home with a mess of them we all set down and clean them. While we're doing that momma will fry up the first ones. You have to make 'em real crisp. And we eat 'em just like that."

That celebration was unlikey after this voyage. The fish weren't there. But down the way Bob Willhite and Bob Anders from Thurmont were doing well on catfish, fishing cut herring bait on the surface. They had a half-dozen or so, two pounds and up, and the waiting for the big one.

And occasionally someone dipped or stagged a shad or pickerel.

The river these days is alive, teeming with fish and people. It is that time of year when the Potomac blossoms to match in bounty the beauty of the redbuds, lilacs and dogwoods that line her banks.

If a river can have her moment in the sun, the weekend upcoming is it for the Potomac.

And Sunday is her day. The dippers and snaggers will jam the rocks; boats will crowd the channel up by Fletchers Landing, where the shad fishing is best and mallards and Canada geese sound exotic notes against the faint background of traffic.

The whitewater canoe people will have their own festival just upstream that day, with the 22d annual Potomac River Whitewater Race. Close to 200 canoeing experts and novices are expected to try their hand across Wet Bottom Chute, Difficult Run, Yellow Falls and Stubblefield Falls.

The 7 1/2-mile course starts with a half-mile portage from the Maryland Great Falls Park, Registration is from 9:30 a.m. to noon at the park, with an entry fee of $5 per paddler. The first of 48 races starts at 1 p.m.

John Seabury Thomson of the Canoe Cruisers Association said entrants should have run the course at least once before racing. He said spectators can get the best view by hiking the Billy Goat Trail from the canal stop lock below Great Falls to the Mather Gorge overlook. The less industrious can watch flatwater stretches from the towpath between Lock 8 and Cabin John Creek or at the finish on Sycamore Island.

Downtown river fans have their day Sunday, too, with the Maine Avenue merchants Aweigh Day program. Clustered along the Southwest waterfront, where picturesque crab and fishing boats jam the bulkheads, will be displays, dancers, music, open boats including a topsail schooner, a boat parade and blessing of the fleet, a fish mongering contest and a sailboat race.

It's the first time for this effort to drum up business and pay homage to the river that provides much of Washington's character. It runs from 11 a.m. to 5 p.m. and is free.

Pick your spot. Washington's spring blessing is a river bursting with life and ready to share it.