Two men standing side-by-side on the river bank, both fishermen. Two fishermen wearing moss-green waders, tan vests, blue baseball caps, and using matching fly rods, identical reels, with orange floating flyline, 3X tippet, neon-green strike indicators and sinking nymphs on a No. 10 hook with a split-shot pinched 10 inches up. One taking time out to release a spotted brown, or colorful cutthroat now and then, while the other, standing a few yards upstream, curling his upper lip in frustration.

Two fishermen standing on the same side of the river, dropping flies into the same little riffle, mending out the same amount of line floating in the same current, paying attention to the same school of fish, AND yet one is catching fish and the other only a stiff breeze now and then.Why? Smart fish some say, at least on the Green River, anyway. Because of catch-and-release practices on the river, they've been educated. Those graduated cum laude are there to be caught and released again by smarter fishermen; those who failed exams have been pulled out of classes.

Under this theory, the Green is spawning ground for brainy fish. Scholars in artificial lures and flies and spinners. Graduates at hook detection and avoidance.

As Larry Tullis, a fishing guide with his doctorate on the Green, said earlier this week, as he released one of several dozen 18-inch trout he'd caught that day, "With the number of fishermen that fish this river now, these fish have seen it all."

Translation: A lure's not only got to look like real food, but also act like it, right down to the way it flows and turns with the current.

The least little drag on the lure and the fish won't touch it, Tullis added as he released the next fish.

By drag he means letting the line bow with the drift and be dragged down faster than the flow, or having the line too tight, causing the lure to be held back. Any resistance or pull on the line, even the slightest not-visible-to-the-naked-eye hesitation, and the fish will ignore it.

That's why educated fishermen on the Green can pull in fish like they were dropping worm-tipped hooks in a hatchery pen, while undergraduates merely get sore arms and high blood pressure and usually enough of the dumber fish to keep them casting in desperate hope.

If ever there was a river where a fish should be caught, though, it's the Green below Flaming Gorge Dam. This is the New York City of U.S. rivers. There are more fish per mile here than in any river in the country. By fall, a good estimate would be more than 20,000 trout - brown, rainbow, cutthroat and brook - for ever mile of waterway. For comparison, a river anywhere else with one-third that number of fish would be very highly rated.

Because of the numbers, and the high quality of the water, and the picturesque setting, good fishermen come to challenge it, and the not-so-good come to play the odds - more fish means more chances.

To fish it properly, however, takes an educated hand . . . know the patterns, how to place the lure, keep it natural and set the hook.

Tullis has as much schooling as anyone in natural delivery. In three years, he's spent more than 150 days on the river's edge delivering flies, which is why on a good day he can hook and release 70 to 80 fish - easy.

Which is why, too, he supports so strongly the catch-and-release concept of fishing, which is gaining more and more support from fishermen. It is, says Tullis in a tone drawing full attention of those nearby, "the only way to preserve the quality of the fishing on the Green.

"I sat down one day," he continued with a tone of urgency, "and figured out that if every fisherman that fishes here keeps just three fish, there would be no fish in the river by the end of the year. If only one in 10 keeps fish, there would be a noticeable drop in the population. Catch and release is the only way of preserving the resource, the only way."

Of course, you've got to catch them before you can release them.

That, the fishing guide says, comes from studying and practicing.

Even now, Tullis says, as much as he's fished the river, he learns something new every time he casts a line there.

Easier said than done, especially as you're listening to the guide while your fly, an orange scud, floats very naturally, just like Tullis' had moments earlier before it had hooked to a three-pound cutthroat, and the 20 or so fish visible in the clean-water pool very mannerly move aside and let yours pass - untouched.