Fishing newcomers to Washington always wonder how safe Potomac fish are.

The old-timers tell them no problem except during June, when you have to watch out for rockfish fever.

"You know the song, 'Bullet Fever -- Catch It?'" asked Ray Fletcher of Fletcher's boathouse, Washington's only genuine fishing camp. "Well, this weekend people were walking around here singing 'Rockfish Fever.' It's a real problem. It gives you goose bumps."

By Fletcher's unofficial count, some 400 to 500 rockfish (striped bass) were caught out of boats and from the banks of Washington's river between Chain Bridge and Key Bridge last weekend.

"I'd hate to say how many bloodworms we sold," he said. "People don't mind paying $2.35 a dozen when the rock are biting.

"They come marching in here all day, saying 'Gimme some blood, man.'"

The annual run of striped bass comes as good news to Potomac anglers. Up to now, spring has been practically a total washout. High, muddy water from unusually heavy rains kept anglers off the river for the earlier white-perch run, and shad have nearly disappeared from the Potomac.

But water levels began dropping last week and by Thursday the river was fishable, although still slightly muddy.

I dropped in on Dicky Tehaan, one of the regulars at Fletcher's, that day and demanded that he take me striper fishing the next morning.

He had some demands of his own. "Meet me at 4:30," he said. "And bring your cooler."

The river was beautiful, bathed in the light of a full moon with wisps of fog on the water. Tehaan struggled at the oars, working the rowboat against the current to a spot just below a sandy beach on the D.C. side a couple hundred yards upstream from the boathouse.

Ray's brother, Joe, was already there, anchored off and fishing. Tehaan pulled the boat up alongside and dropped the anchor rock overboard. The boat swung downstream and settled in a few yards from Joe's.

The boats were talking distance apart, and talk was about all the fisherman did for the next two hours. Shortly after dawn, Fletcher felt a hard tug on one of the two rods he had dangling over the stern. He set the hook and reeled in a one-pound striper.

But the fishing stayed slow, and by 8 o'clock there were only four fish between three anglers. Tehaan thought a move was in order. Fletcher decided to stay put.

Tehaan rowed through the boiling current almost all the way to Chain Bridge, stopping in at likely-looking spots to drown a few more bloodworms.Nothing doing.

"We better go back," he said, "and see if Joe did anything."

They don't call it Fletcher's Landing for nothing. Joe had been plenty busy landing fish.

"I tried to keep 'em here for you but I didn't have enough bait," he said, grinning. The he pulled the top off his cooler and showed off 10 stripers, mostly in the one-pound size.

"They came through about a half-hour ago -- a whole school of them," he said. "I was catching one on every cast, just as quick as I could reel'em in."

The school did not come back.

Friday was slow but it was a start. The rockfishing broke loose in spectacular fashion Saturday and continued through Sunday and Monday, when some larger fish in the two- to four-pound class were captured.

The theory is that these school-sized stripers move up into the top of the Potomac's tidal water this time of year in pursuit of food. The upper river is still loaded with small white perch, herring and minnows, which the stripers ravage.

The run generally lasts through the first three weeks of June. Then striper catches taper off to a few a day most of the bait and rockfish move back downstream.

The high number of pan-size fish for the remainder of the summer as this year is apparently attributable to the excellent spawning success of the 1978 year class in the Potomac. According to Joe Boone of the Maryland Department of Natural Resources, 1978 was the best striper-spawning year in the Potomac since 1971.

Pan-size fish don't provide the thrilling sport of six,- eight- and 10-pounders that occasonally turn up in the river, but they make a fine meal.

While I fileted the 15 fish we wound up with, Ray Fletcher heated some grease in a skillet and mixed a batch of flour and spices.

He dusted the filets and fried them briefly. So far, the only effects of that feast is a case of rockfish fever.