For one sun-bright hour early Saturday morning, from a grassy bank of the narrow Corsica River, it looked as though the annual Yellow Perch Run and Fishing Frenzy had begun.

Anglers stood shoulder to shoulder, their backs to a graveyard, and yanked in fish that were swimming up the river to spawn. The fish and the fishers seemed equally ravenous. Then the sun disappeared behind some rain clouds and the river got dark and dead.

"You couldn't get 'em off your line. My friend and I must have pulled in 25 fish," said Robert Fiddes, a 23-year-old truck driver from Baltimore. Fiddes was fishing the Corsica Saturday morning at 7 a.m. when the biting began, and was still there Sunday afternoon, 30 hours after it ended. He looked like somebody had stolen his dog.

To folks who fish, the first sign of spring has nothing to do with songbirds or crocuses. When yellow perch in the Chesapeake Bay decide the water is warm enough for their spawning run up a hundred rivers and streams in Maryland and Virginia, winter is over.

"This is it. It's breaking looose," said Fred Crowley, wetting his line in the Corsica after a winter of unemployment and snow in Baltimore. "Yellow perch starts the season."

A perch out of water seems too small, bony and hard to scale to merit so much ardor. But its meat is white and tasty. And when the fish travels upriver, it is usually in great, tightly packed schools that darken rivers and choke streams. Catching yellow perch on the run can be as easy as dangling a piece of baloney from a bamboo rod.

"It's really something to see when they start running," said Sonny Biedrzycki, 27, who was laid off this winter from the same Baltimore General Motors plant that laid off Crowley. "You can actually see them coming at you up the river."

Biedrzycki, his wife, Deborah, and Nicholas, their 3-year-old son, pooled their energy and expertise Sunday for four hours of serious fishing. They came up with one small perch and a restless kid. Beside Paul Belcher, however, they had a pretty good day.

"I've been here since 8:30 this morning and I haven't had a bite yet," said Belcher, who was one of about two dozen men, women and children sharing the Corsica where it flows under Rte. 213 in Centreville. "Of course, nobody's done anything to brag about."

Yellow perch generally start their spawning run when the water temperature rises above 45 degrees. The females lay milky ribbons of eggs on submerged rocks and branches, then move off to let the males fertilize them. Because the temperatures of coastal rivers and streams vary according to depth and location, a fisherman having a bad day in one spot can be tortured by the thought that, a few miles away, the fish may be moving in convoys.

Last weekend, anglers from Allen's Fresh in St. Mary's County to the Corsica on the other side of the Bay could take some small comfort in the reports that, outside of some brief periods at scattered locations, nobody was catching much of anything anywhere.

"Every place we visit, we give it the kiss of death," said Wayne Powell, who drove to four rivers Sunday with his brother and father before ending up at the Corsica. They caught one catfish that was too small to keep.

If the fishing was bad, the day was a gift. It was warm enough to sit on the bank in a light jacket, drink beer and joke about the fish that they could have caught if they'd really been trying.

"I didn't bring this bucket to put fish in," said Clyde Maness, another Baltimore native who was leaving the river with a 25-gallon plastic bucket light enough to carry in one hand. "I brought it to sit on."

As Maness was leaving the river, Edith and Frank Davis of Centreville were just arriving with Dana Jones, their 6-year-old granddaughter. Dana was fishing with a stick four feet long and an inch square. A line, hooked and baited with a worm, was tied around one end of the stick. Dana held the other end with grim determination, her tongue between her teeth. She kept her legs slightly bent and braced in case some 50-pound perch tried to take her for a ride.

"It's not very fancy," said Edith Davis, nodding toward Dana's homemade gear. "But she's doing about as well as anybody else at this point."