Rick Munker had been waiting all morning, on a bridge above a brown river, for his bobber to bounce. So when it finally quivered, Munker jerked to attention like Ahab spotting his white whale.

"That's just your minnow moving around," said a man fishing beside him, flashing a sympathetic smile. "But that's the biggest excitement we've had all day."

Waiting for the annual spawning run of the yellow perch can make a person jumpy. When those gold- and black-striped beauties decide it is time to leave the Chesapeake for cold-blooded spawning grounds up a hundred local rivers and streams, the fishing can get frenzied.

"I've seen days when you could have filled up the back of a pickup truck with perch," said Don Clark, who was waiting with Munker and half a dozen others above the Wicomico River one rainy day last week. "They'll get so thick you can just drop your hook in the water and snag them."

Find a stream choked with spawning perch and you have sure-fire fishing. Some claim grass shrimp are better than worms or minnows as bait. Others swear that streamers and shad darts work best. Last year, I watched a 6-year-old catch perch with bologna, popcorn and Wonder Bread.

But you have to find them to catch them. And that can be a problem. The spawning run can be as short as a few days. If your timing is off, you can spend a miserable spring listening to fishing buddies chatting about what you missed.

"When it's good, it's very good. When it's not good, it's no good at all," said Sam Sherwell, a Maryland state policeman, commercial trapper and perch fisherman who was standing beside the Wicomico this day with an empty fishing bucket.

A yellow perch does not look glamorous enough to arouse such ardor. It is small, bony and puts up about as much fight as the family goldfish. But it tastes great and can be caught in abundance.

And because it is the first fish of the year to spawn, anglers whose fishing habits have been permafrosted by winter regard the yellow perch as the true harbinger of spring.

"We've had people coming in here since George Washington's Birthday asking for live bait," said Betty Goodman, proprietor of Dan's Store, an ancient general goods and fishing supply shop in Newburg, just a few miles from Allens Fresh.

Allens Fresh is one of the more famous spots in Maryland for yellow perch because it is among the first places to experience the run. Within hours of the first fish caught, the news will pull anglers from Baltimore and above to this shallow water 65 miles southeast of Washington, just off Rte. 301.

Last weekend, with the sun shining and temperatures in the 60s, the word went out. The temperature of the water had risen above 44 degrees and the perch had begun to move. By Saturday night, Dan's Store had sold out of fishing licenses, bait and minnow buckets.

The fishing was not overwhelming, just promising. Then the rain began. The water temperature dropped and the streams turned dark. By midweek, when the fishing should have been at a peak, it was dead.

"We haven't done nothin'," said Carroll Clark, who had spent four hours watching his bobber float, and now sat on the tailgate of his brother's truck watching minnows swim in a bait bucket so he wouldn't forget what fish looked like.

The others passed the time with stories of past runs.

"Last year, a friend came in to see me carrying two buckets full of yellow perch he caught on the South River. He wanted me to close the shop and go back with him," said Don Clark, who owns a sporting goods store in Brooklyn, Md. "But I was tired, so I said wait until tomorrow. The next day we went out there and found 50 people and not a fish in that stream."

On a bank below the bridge, Sherwell had begun casting and retrieving a spinner. "I just get bored watching that bobber," he said. Sherwell, who has been fishing southern Maryland waters for 17 years, was the picture of patience in his rain hat and hip boots.

"It's a nice, peaceful way to spend the day," he said. "Anything is better than sitting in an office answering telephones."

The Clark brothers and Munker were not as serene. They had a taste for fish in their mouths that just wouldn't quit.

"I guess we're gonna have to stop by Arthur Treacher's on the way home," said Don Clark.