Jack Scanlon grew up in New England, where as a young man he kept his sanity on the trout streams and in the grouse woods. He's a Washingtonian now, a pediatrician specializing in newborns. When he has time off it isn't much - maybe a weekday morning once or twice a month.

Scanlon's the kind of person who doesn't feel right about living unless he has some wild place to repair to.

A few years ago some trout enthusiasts told him about a place he could get to in his scarce off-time. He found it, he fell in love with it and it's sustained him since.

Eight years ago Maryland began stocking the Patuxent River above Triadelphia Reservoir with trout each spring. Two years later the Wildlife Achievement Chapter of the Izaak Walton League adopted the stretch as part of its Save Our Streams program and worked to clean it up and shore up the banks.

Today the 10-mile fish-for-fun span of the Patuxent between Route 27 near Damascus and the top of Triadelphia has Scanlon hooked.

He agreed to share it one brisk late-spring morning.

"Meet me at 6 in the morning at Hipsley Mill Road near Laytonsville," he said. He pulled up right on time at the bridge crossing, screeching to a stop in his sports car.

Scanlon bent to the task of rigging up his fly rod, then stopped about halfway through.

"Listen," he said.

We inclined our ears and picked up from the woods across the road the insistent clucking of a bird.

"Wild turkey," said Scanlon, "right here 20 miles from Washington."

It was indeed a turkey - a hen issuing what seemed to be lovesick cries a tom, even though the mating season was long past.

Scanlon vowed there were plenty more suprises ahead. "Walk 200 yards downstream and you'll feel like you're in another world."

He set off at brisk pace along a trail that parallels the stream, He said he didn't often start fishing until he was a mile or two downstream, where the weekend crowds seldom venture.

Scanlon's reason for inviting company was to expose the problem of poaching, which rankles him extremely. The fish-for-fun stretch is carefully posted with signs that command anglers to use only flies or single-hook artificial lures and to keep not more than one trout a day, if they are lucky enough to catch one 15 inches or longer.

But Scanlon says, and others who use the stream verify, that bait fishermen use the Patuxent regularly and strip it of its trout. The protesters claim they've seen the poachers and seen their leavings - prong sticks for holding their rods, empty bait cans. And they've seen the stream denuded of trout after a few good spring weekends.

On our day we didn't see any poachers or any sign of them.

We did see snapping turtles sunning themselves on the banks and in the trail; a furry beast Scanlon is convinced was an otter; a hawk circling overhead on the hunt; a Baltimore Oriole, a beautiful songbird.

A mile down from the road we burst into an overgrown meadow, once an active farm, which Scanlon pronounced "my favorite place."

Wild flowers were blossoming. We followed the beaten grasses where deer made their trails. We found the flattened spots where does and bucks bedded at night and the passageways they made to the stream for water.

Shortly after that Scanlon proved that fish were still available, hoisting a 14-inch rainbow from beneath a fallen tree that was steaming in the morning sun.

By 11, when he had to race back to town for his afternoon appointments, he had landed four trout, turned them all loose and was ready to face the world again.

The Patuxent is not an easy place to catch trout, but it is an easy place to get in these troubled transportation times. And it's wild and different.

There are five road crossings - Georgia Avenue, Howard Chapel Road, Hipsley Mill Road, Mullinix Mill Road and Long Corner Road.

Most of the experts agree that the fishing is best in spring, but htere are holdover trout available through the summer months, best caught on stone fly nymphs, muddler minnows and small imitations of black ants and beetles. The scenery is always excellent and the wildlife abounds.

Says Larry Miller of Potomac-Patuxent Trout Unlimited, "It's really surprising to find something that nice-looking this close to home. There are a lot of riffles and pools; it doesn't look at all like a coastal plain stream."

Adds Jerry Tacinelli of the Izaak Walton League, who helps stock the stream by transporting brown trout in float boxes for release along all 10 miles: "I took three days off in the spring and fished all the western Maryland streams with a friend. When we came back we decided the Patuxent was better than anything else we'd seen." CAPTION: Picture, AT TRIADELPHIA THE PATUXENT RUNS SLOW AND DEEP, BUT UPSTREAM ANGLERS HIT BROWN TROUT. By Douglas Chevalier