Dan Smart was on his hands and knees, dressed in camouflage and stalking big game. It was Sunday, on the Patuxent River in Montgomery County, and Smart was hunting trout with a fishing rod eight feet long and caution worthy of a Green Beret.

"You have to be sneaky," said Smart, who was wearing dark sunglasses on a rainy day. "They don't get big by being stupid."

Trout may look, swim and smell like fish, but to the men and women obsessed with their capture, they are a breed apart. Ask how trout are caught, and you get a lecture that is equal parts science and mysticism. Talk strategy and most fishermen will glumly admit they are overmatched.

"A trout always has the advantage," says Smart, 36, who gave up a job selling television sets at Woodward and Lothrop two years ago to open a fly-fishing store in Gaithersburg. "He knows the rocks and the trees, the shadows and the food. If you can deceive him it's the ultimate Agatha Christie."

Since 1496, when Dame Juliana Berner authored the first known treatise on the catching of fish, there have been more books and breathless poetry written about trout than any other species. Otherwise prudent adults have been known to walk neck deep into fast-flowing water to better tempt a fickle fish. While other anglers are sitting around the hearth telling fish stories, trout fishermen are in the basement tying rabbit fur, peacock feathers and duck down into imitations of flies and bugs that are more likely to catch a tree limb than a wary trout.

"To become a competent trout fisherman you have to become at least an amateur entymologist. You have to find out what the fish are eating, then imitate it," said Rudy Mattern, who was fishing the Patuxent Sunday with Smart, equipped with 800 artificial flies he had tied with names like Yellow Maribou Streamer and the Maryland Wooly Booger. "If you do everything right, you still might not catch anything. But at least you've narrowed the odds."

This spring the odds will be weighted in Maryland anglers' favor. By the middle of May, the Maryland Wildlife Administration will have stocked hundreds of rivers, lakes and streams with 300,000 brown and rainbow trout. The fish come from state and federal hatcheries supported primarily by fishing license fees. Each spring, the trout are transported in special trucks to waters that are either overfished or no longer healthy enough to support natural reproduction.

Stocking trout is not new. But until recently it was done only by, and for, the rich. Until federal and state governments got into the recreational fishing business during the last two decades, privately stocked ponds were almost the only places to fish for trout with a reasonable expectation. During most of this century, trout fishing was enjoyed by the relatively few who were invited to join exclusive fishing clubs such as The Anglers Club of New York.

In the last 10 years, however, trout fishing has almost become a blue-collar sport.

"Now you hear guys in gas stations quoting the Latin names of flies," said Mattern, the 31-year-old manager of a glass company in Rockville and one of an estimated 50,000 trout fishers in Maryland.

The increased popularity has been accompanied by rapid sophistication in equipment and a new political awareness. Trout Unlimited, a national organization that claims a membership of 24,000, has a political lobbying arm.

"I'd much rather fish than talk politics," said Smart, who is on the board of a local TU chapter. "But what good is the sport if there's nowhere to fish?"

Smart and Mattern spent Sunday on the Patuxent, a river both have fished with uncanny success and failure. The Patuxent, which is stocked each spring with 500 trout, is one of a few dozen rivers in Maryland where live bait is not permitted and from which anglers can keep just one fish per day; that fish must be 15 inches or longer.

"This river is like an old friend," said Smart, walking slowly in rubber hip boots across a shallow, rock bottomed section of the fast-flowing river. "Every time I come back it has changed. Either it's grown a beard, or shaved it off. Gotten fat or skinny."

The Patuxent is one of Maryland's most trout-worthy streams. The river has the cover and nutrients needed by trout. Last month it rated a feature in Field and Stream. But for Smart and Mattern, the Patuxent on Sunday was cold.

"The trout are here, there's no question about that," said Smart, as he tossed cast after graceful cast onto water where trout should have been waiting hungrily. Smart changed flies, moved upstream and studied the river's flow. After five hours, he packed his graphite rod into its case and called it a day.

"I didn't catch anything, didn't even get a bite," said Smart who didn't look the least bit troubled. "But it sure beats working at home."