The first time I saw Dicky Tehaan, he was standing on a dock on a back eddy of the Potomac River fishing through the cracks in the deck.

"Ha, ha, ha," I thought. "Here is a guy with a good sense of humor."

Then Tehaan yanked the little lure he was jigging up through the crack and along with it came an eight-inch crappie. He flipped the fish off, dropped the jig back in and within seconds hauled up another fish - a bluegill.

"I was fooling around off the edge of the dock one day and I caught some fish," Tehaan explained. "I figured if they're next to the dock they're probably under it, too."

"That's Dicky," said one of his cohorts. "He can catch fish when nobody else can, where nobody else can."

Every stream, every lake, every stretch of ocean beach has it specialist, the fellow who keeps track of the daily migrations and habit changes of its residents. Tehaan is the dean of Washington's waterway.

"I try to get down every day for at least a couple hours in the morning," he said, "just so I can keep an eye on where everything is."

At 28, the smiling Tehaan has established the parameters of his concern and they extend from Key Bridge to Chain Bridge. No further.

"I went out on a headboat in the Bay one time but it was real rough. I was seasick for six hours afterwards. That's enough for me."

So now, armed with a pair of light-action Fenwick rods, his battered English bicycle, tattered sneakers and a rental rowboat, Tehaan plies the murky waters of the Potomac and catches more fish than anybody else.

Thursday, he showed how.

"You drive the boat," he said as we pulled out into the surging mainstream just after dawn. "I'll rig you up."

It turns out that the first thing the complete Potomac angler needs is a selection of Dicky Darts, hand-tied lead head jigs with marabou feathers streaming off the back, either yellow or white. Needless to say, if it's not tied by Tehaan, it's not a genuine Dicky Dart.

The dart is used for just about everything, mostly because it catches just about anything the river has to offer.

To wit: In six hours of fishing, the following results: two smallmouth bass, a dozen and a half crappie, several bluegill, three catfish, about 50 white perch and two monster carp.

Our aim was crappie, of which Tehaan had caught 109 during one frenzied afternoon a week before. They had moved up into some of the shallow eddies just below Chain Bridge. Unfortunately, as word spread Tehaan's find became everybody's picnic, and by now the panfish had been raked over by many boatloads of anglers.

By arriving early, we beat the crowds. We pulled the boat up on some rocks and hiked up to a cove. We watched a pair of American merganers barrel up and down the riverbed, saw a kingfisher on the prowl and even a crow feasting on little perch. From time to time, the water would boil and break with the happy leaps of herring and carp.

Tehaan rigged two darts on a three-way swivel, one deep and one high, with a bobber just above. We tossed them out and reeled them back at a snail's pace. Within mimutes, he had a crappie on the shore, and within an hour we'd landed eight or 10. All the fish were good eating size, a half to three-quarters of a pound.

We worked our way up the shore line in silence. Tehaan pointed to a favorite spot near a stump. "You try it first." he said, "might be something good there."

I sloshed out to the stump and popped the little dart rig next to it. Instantly, a crappie hit and quickly was on shore. I looked down to see if there was another.

"Good gravy, look at this."

Sunning itself five inches under the surface and no more than a foot from our feet was a horse of a carp, at least 10 pounds. Tehaan dropped his dart in and tried to postion it smack in front of the big fish's mouth.

The carp snorted and sniffed, then decided against and slowly disappeared into the deep.

On my next cast, my bobber went down with a satisfying suddenness and kept going. When I lifted the rod tip to set the hook, the sweet sound of screeching gear teeth was all we heard as six-pound line tore off the little spinning reel. The monster was hooked.

Seventeen minutes later, by Tehaan's actual count, the gold slabsides of the worn-out carp rolled to the surface. We waded out, Tehaan hooked a finger under a gill plate and I had the biggest fish I'd ever caught in fresh water - 12 1/2 pounds.

"Outstanding," said Tehaan, plucking the little Dicky Dart from the big fish's lip.