Dwight D. Eisenhower had a favorite fishing pool on Big Hunting Creek when he was president. During Jimmy Carter's term, or so the story goes, Secret Service agents would use helicopters to stock the water just ahead of the president's casts.

But neither of those trout fishing enthusiasts was any more ardent about the creek than Dick Blalock.

"The first time I fished here, it was like walking into some enchanted wonderland," said Blalock, a retired Foreign Service officer who spends most of his time trying to fool trout with hooks disguised as insects and flies. "I saw mature brown trout feeding on flies. I caught a couple of fish out of the first pool. It was an absolute joy."

From the road that parallels the creek through Catoctin Mountain National Park in Frederick County, Big Hunting appears to be a shallow, fast-moving stream. But climb down a bank to the shoreline and you will find deeper pools of water, shaded by oak and evergreens and crowded with lovely trout.

The setting is so sylvan and the fishing so good, Blalock finds himself drawn here on days he shouldn't be, and wishing he were here on days he can't be.

"This is just 55 miles from Washington, an hour from my front door," said Blalock, the treasurer of the National Capital chapter of Trout Unlimited. "Some people drive this far to go to work."

There are good fishing holes closer to Washington than Big Hunting Creek. But if you want to catch trout, there are few that offer as much opportunity for success, especially this time of year when the creek is stocked with hatchery-grown rainbows and brookies.

Trout purists like Blalock and Ken Miyata, who uses a home computer to store his fishing information, do not approve of stocking streams like Big Hunting that are capable of supporting wild fish populations. The fish raised on trout meal in hatcheries, they complain, are too unsophisticated and too easily caught. If that sounds odd coming from people who spend so much time and effort trying to catch fish, it is because trout fishermen are an odd breed of angler.

They are compulsive as gamblers, as detail-conscious as certified public accountants and almost as knowledgeable on aquatic insect life as your neighborhood entomologist. What they all share is a respect for wild trout that borders on reverence.

"Trout can settle most angling arguments," said Datus C. Proper in his book, "What The Trout Said." "But they don't know much about art; they just know what they like. And you have to be a good listener, because they are bashful."

Not all trout are created equal. I know that as fact because I caught a few of the dumber models last week. Of course, all of them were hatchery trout and all were caught on a fly tied for me by Miyata.

"Cast as close to that ledge as you can and let it drift with the current," said Miyata, after he had positioned me beside President Eisenhower's favorite pool. Four casts later, I inadvertently hooked a 12-inch rainbow trout that twice jumped from the water before being brought to the net.

After coaching me to another catch from the same pool, Miyata set off on his own. Even with a two-fish head start, I knew he would catch more fish that day than I would catch trees. And that, my friend, is a considerable accomplishment.

"The last time Ken and I fished together here he caught 56 trout," said Blalock. "He caught two before I could put my boots on."

The portion of the creek we fished is limited to fly fishing only, and all the fish must be released after being caught. There are parts of the creek where live bait and artificial lures are allowed and anglers can keep three trout seven inches or longer.

If fishing does not appeal to you, there are hiking trails and camping areas in the park. There also is a reservoir that is rumored to be thick with bass.

Because President Reagan is not a trout fanatic, you are unlikely to run into Secret Service agents on the creek these days. But almost all of the veteran anglers here have favorite stories to tell about the Eisenhower and Carter eras.

Blalock's favorite is about a friend who drove to the creek one day during talks at Camp David here between Carter and Israel's Menachem Begin. After being stocked with large trout from a hatchery in West Virginia for the president and his guest, the creek was closed to all other anglers. Somehow, Blalock's friend missed the signs. What he found was a pool filled with giant rainbow trout.

After methodically catching, then releasing just about every trout in the pool, he walked into the ranger station to brag about his good fortune. It was only then that he learned whose trout he had stung.

"He had come along and educated every one of those fish," said Blalock with a big grin.