On our left as we go, crumbly sandstone bluffs topped with a thick cap of yellow loess rise steeply from the edge of the river; on the right, Russian olive, and beyond them, a cottonwood-studded prairie stretching to a hilly horizon. All very exotic to a New Englander.

But there’s something familiar about it: the water. I was raised on limestone terrain – the Helderberg Formation and later the Onondaga Limestone – and came to love what it did for the meadow streams of my youth. It nurtured swarms of aquatic arthropods that in turn fed seemingly endless numbers of brook and brown trout, and provided us kids with long days of stealthy walking and crouching as we approached our favorite holes. It also encouraged luxuriant beds of aquatic weed that snagged and entangled our hooks and trembled when we pulled free, frightening every trout within a hundred feet. The Bighorn, a so-called tailwater fishery because it’s fed here at Fort Smith from the bottom of a big hydrodam, mimics those conditions perfectly, if on a much larger scale. A local outfitter’s web site describes it: The Yellowtail Dam, built in 1967, created the perfect trout habitat. Behind the dam is a 72 mile long lake in which limestone from the canyon walls leaches into the water to give the river the perfect PH and nutrients for producing large trout. It is essentially a big spring creek in both clarity, vegetation, and demanding trout. That’s as close as words can get to describing a trout fisherman’s heaven – as long as you don’t miss the word, “vegetation.” The Bighorn is grassy. Its trout are the strongest I’ve ever seen.

My friend Baird and I go back to the mid-50s, when I first arrived in his native village in the Adirondacks, looking for work. I had whiskers and nobody knew me, so I was instantly called “the hippie.” Baird was in high school then, and with a friend came occasionally to visit, talk, and sing the songs (I knew six or seven guitar chords) of the budding folk music movement. We’ve been friends ever since, and we’ve fished together whenever possible. Now that he’s moved West, we fish pretty much beyond the Mississippi.

We fly fishermen in the East tend to use flies that we can see – mayflies, big nymphs, caddis flies, and streamers. Here on the Bighorn, the guides use flies that are almost invisible to the human eye. Our guide this week has fingers the size of German sausages. How he manages to tie those little devils – three in a row on a 5X tippet (six-thousandths of an inch in diameter) – is beyond me. They’re generally all different flies, and when either Baird or I catch a fish, he notes which one it “took.” He has a fish stomach pump, too, that he can use to determine what pattern’s best. I’ve decided that what I can’t see is but an abstraction, so defer cheerfully to his judgment and let him change them whenever he thinks it a good idea.

The standard technique here is to fish those flies underwater in a dead drift, easy to do if the boat you’re in is also drifting with the current. It’s called nymphing, after the stage of the insect just before adulthood. Because the strike of a fish on a nymph can be feather-light, the guides attach a tiny brightly colored plastic ball to the line above the flies. It’s called a strike indicator. With my distaste for euphemism, I call it a bobber, a term not popular with most guides.

But that’s what it is. You keep your eye upon it constantly, and if it twitches, you strike back instantly. If you don’t, your guide shouts, “Hit it!” or some variation of it. Baird, who’s fairly intense when attached to a fishing rod, never has to be prompted. I get distracted, and frequently attract the shouts of the guide, who has, after all, an interest in how many fish we catch. I’m not convinced that the instant reflex is all that important; twice today I’ve hooked fish I didn’t even know had struck. and once didn’t react until after the third cry of “Pull up! Pull up! Pull up!” I still caught the fish, however, a lovely brown. And, never without repartee, I turned coolly toward the guide as the fish streaked across the river and said, “I was just waiting for the third shout.”

We spotted a side channel at one point, where the current rippled over a slope of stones and slowed in a shallow pool perhaps a hundred feet in diameter. Trout were rising for tiny dark caddis flies. There were so many of them that for the first time I could see clearly the pattern of the hatch occurring on the bottom of the pool: first a patch here, then a lull, and then a patch there, with the fish moving back and forth to intercept each as it began. Baird and I ended up taking turns at them. The guide, clearly as delighted as we were, netted each one, removed the almost-invisible barbless hook, put the fish back into the pool, and watched it swim off to rejoin its peers.

The Bighorn is considered by some aficionados the best fishery in the world. I don’t have enough experience to argue that. But it is hard to see how it could get any better. It’s a nearly perfect system, from the ideal pH of the river, the masses of invertebrates and the fish that feed on them, and the kingbirds and tree swallows that patrol the space above the river. I’ll remember for a long time a drift boat that swept past us in fast current. A small boy, held by his father from being pulled overboard, leaned back against the pull of a big fish. His laughter rang across the water.