Sunday traffic streamed across the Chesapeake Bay Bridge as the weekend throngs headed into the western darkness, going home from the beach.

One hundred eighty-seven feet down in the shadows, where the sound of the cars was a faint, whistling clatter, three fishermen scurried around a 17-foot skiff.

Two were trying to bring to the net without incident a 15-pound striped bass Kevin Kenno of Rockville had hooked on light tackle a few moments before. The idea was to get it quickly to the boat, remove the hook and ease the fish back into the water unhurt, since keeping or injuring stripers is illegal in Maryland.

The third man was keeping the boat away from the piles of rock rubble that support the main bridge columns. He tossed his lure out whenever he got a chance and ran it back in the shallows along the edge of the rockpile.

In the middle of one such retrieve the lure stopped. The fisherman pulled back and felt the weight of a strong fish shaking its head.

"Rockfish doubleheader," Kenno said triumphantly. "I haven't seen that since 1979."

The point of this exercise was to see whether Kenno's friend, a Bethesda fish salesman named Vernon Lingenfelter, was correct in contending the Bay Bridge these days is crawling with striped bass, or rockfish as they are called locally. The doubleheader and six other rock the trio brought to net in two hours offered pretty good proof he was right.

Lingenfelter, who went into the fish business six years ago because he loves fish, not business, had called a few days earlier to complain about recent articles extolling the striper fishing in Washington, which has been good this summer.

He thinks fishing for the troubled stripers should be banned in all waters of the Chesapeake, not just Maryland portions, and said stories about ways to circumvent the Maryland ban and keep rockfish to eat are counterproductive.

"Anyway," he had said, "those fish around Washington are small. If you want to see some real rockfish, you ought to come down to the Bay Bridge and do some sport fishing."

Theoretically, even the catch-and-release tactics he described are illegal these days in Maryland, where "incidental catching" of rock is permitted as long as the fish are returned immediately to the water, but where continual catching and releasing of rockfish from a single spot is not deemed incidental.

But we had an excuse. Lingenfelter is awaiting the arrival of big sea trout, due any day to share the feeding grounds around the bridge pilings. He figured if anyone asked, which no one did, we could honestly say we were scouting for trout.

But it was big rockfish that turned up, as promised.

We had sped across big water to the middle of the four-mile bridge. Now, in the still of an eddy behind a piling with the motor off, we heard schools of baitfish hitting the surface like hard rain after they leaped to escape attacks by predators.

"Tie one of these on," Lingenfelter said, handing over a seven-inch black-and-silver Rapala floater-diver lure.

"Look at that fin," he said. In a tiny place between two rocks a striper lay in ambush, waiting for bait to swim by, its gray tail fin protruding.

"Cast as close as you can to the rocks," said Kenno, a University of Maryland student.

On the fourth or fifth cast, water swirled around the lure and the rod bent with the weight of a 10-pounder. Lingenfelter smiled, watched, waited and netted the fish neatly when it came to the boat, then turned it loose with a practiced hand.

A bit later, Kenno hooked his first fish of the night. The striper ran straight for the rocks and thrashed about, trying to dislodge the hook. Lingenfelter missed a strike, then missed another.

The darker it got, the better it got, until it was black, moonless dark and you couldn't see to cast.

Lingenfelter and Kenno credit Maryland's 8 1/2-month-old ban on striper fishing with the return of rockfish to the Bay Bridge, their historical feeding grounds. A decade or two ago, evening and nighttime fishermen could hope for the kind of success we enjoyed last weekend, but it's been years since the average soul could cast a lure and expect a strike.

Their opinion is shared by officials of Maryland's Department of Natural Resources, who made the controversial decision to ban commercial and sport rockfishing Jan. 1 after a 10-year, precipitous decline in striper numbers.

"It stands to reason," said Harley Speir, a DNR biologist, "that if fishing mortality reduces the striped bass population by half every year, there's going to be more fish around if you ban fishing."