A good way to start fly-fishermen arguing is to ask them to name the best trout water in Idaho. Up north in the panhandle there's the St. Joe and the Coeur D'Alene, great places to catch native western cutthroat on dry flies. The Middle Fork of the Salmon is unmatched for its remoteness and sheer beauty, while Silver Creek, near Sun Valley, gets the vote of skilled anglers with an eye for big rainbow cruising in water clear as gin. Floating the South Fork of the Snake is a good way, using a grasshopper pattern, to catch trophy browns lurking beneath the banks. The Clearwater...the Blackfoot...the list goes on. With its sparse population and vast mountainous terrain, Idaho boasts more great trout fishing than any other state in the Lower 48, all of it open to the public. If you can get to it without trespassing, you can wade it. Adventurous fishermen willing to hike can spend a lifetime in the Gem State and never fish the same pool twice.
But if one name stands out, most agree it's the Henry's Fork, Idaho's signature fly-fishing river. With its variety of water, prolific hatches, scenery and selective, big-shouldered rainbow, the Henry's Fork is one of the great treasures of the American West. Named after a trapper who settled the area in the 1820s, the Henry's Fork—sometimes called the North Fork of the Snake River—is a giant spring creek whose flow is controlled by a series of dams. It originates at Henry's Lake in a notch of the Continental Divide, a few miles south of the Montana border, just west of Yellowstone Park. The primary headwaters of the Henry's Fork, however, flow into the river at Big Springs, some 12 miles south of the lake, where 120 million gallons of 52� water bubble to the surface 365 days a year, making it one of the 40 largest springs in the U.S.
Big Springs serves as both spawning area and nursery for the brawny rainbow that dominate the trout population in the Henry's Fork (they were introduced to the watershed in the early 1900s, and soon overwhelmed the native Yellowstone cutthroat), so fishing has been prohibited in Big Springs since 1919. But on the viewing platform wide-eyed fishermen can ogle giant rainbow as they cruise through the mossy tendrils that wave in the current like long locks of hair. Trout weighing more than 18 pounds have been caught in the Henry's Fork, and several exceeding 10 pounds live at Big Springs. Thousands of their offspring in the four-to five-pound range can be found in the 117-mile stretch between Henry's Lake and Menan, where the Henry's Fork joins the main branch of the Snake River. That's why anglers from as far away as Southeast Asia come to fish.
"The Henry's Fork offers every kind of fly-fishing there is," says Pat Bennett, a guide for Hyde Outfitters, one of seven guide services licensed to float the river in drift boats and rafts. "Spring creek, freestone, tailwaters, rapids. Nymphs, dry flies, streamers. Wading, drifting, sight fishing."
Bennett, who spent 22 years in the U.S. Army before retiring in 1997 as a lieutenant colonel, has been fishing the Henry's Fork since 1970. "The upper portion of the river was incredible then," he says. "It goes in cycles."
The cycles, many guides believe, are directly related to the amount of water released from the Island Park Dam (some 30 river miles south of the Henry's Fork's headwaters), which was built in 1935 for irrigation purposes. In a dry year the level of the Island Park Reservoir is kept up all winter so potato farmers will have access to its millions of gallons during the growing season. Less water flows downriver, which adversely affects the populations of both the trout and the insects they feed on. In a wet year, when the snow pack is deep, the volume of water flowing out of the dam in the winter months increases, and the level of the river rises. "In '98, '99 and 2000 there were good flows all winter long, and those years we were catching 35 to 40 fish a day," Bennett says. "With the drought, we're in a down cycle now. A good day is 20 hookups."
Twenty hookups of strong, wild rainbow is a good day for most fishermen, and we had such a day in the first week of last July. Bennett took my wife, Sally, and me down Cardiac Canyon, a tumbling 19-mile stretch of the Henry's Fork just below the Mesa Falls. Upper Mesa Falls drops 114 feet, Lower Mesa Falls 67 feet; there's no campground or boat access along the stretch below them, so Cardiac Canyon is a tough place to get into or out of. Bennett skidded his raft down to the river on an impossibly steep slope—I was certain the man was suicidal—but once we were floating, we were rewarded with wild solitude. A moose and her calf bounded along the banks of the river. A bald eagle perched watchfully in the top branches of a ponderosa pine. The water was a trout-friendly 58�, and the current so strong that the few times we got out to wade, we staggered and braced ourselves against being washed away with every baby step. In the raft we drifted swiftly between the boulders, casting into the riffles and seams. We landed a couple of whitefish, which are prevalent throughout the river, and the first trout I caught was my best of the day. It was an 18-inch rainbow whose silver body was so thick I could barely put my hands around it. It looked almost deformed, the salmonoid equivalent of a linebacker with no neck. It was a classic Henry's Fork fish.
The next day we began our float farther upstream, through Box Canyon, which begins just below the Island Park Dam. It is easily accessible from a boat launch and thus more heavily fished. But it begins an unforgettable 20-mile stretch of water. For the first three miles the canyon walls press upon you, and great pines grow to the water's edge. Giant boulders are scattered in the river, creating pockets and eddies that hold big fish. Gradually the canyon walls begin to break down, and the river starts to open up. The water is loaded with stone fly nymphs—big, brown cockroach-sized bugs—and our guide this day, 62-year-old Ken Soares, regaled us with stories of what it's like when those stone flies hatch in late May or early June. "The trout eat so many, you can see the outline of the nymphs in their stomachs," Soares said. "They throw up on you when you're unhooking them, or sometimes two or three real flies are in the trout's mouth with your artificial, trying to crawl out and get away. Piggy, piggy"
Soon the river grows even wider, the current slackens, and the vistas begin opening up. At the mouth of the canyon is a curve of wadable water called Last Chance Run, which flows into the most famous stretch of water on the Henry's Fork: the Railroad Ranch.
The Ranch, as it's affectionately known, is part of Harriman State Park, donated in 1977 to the people of Idaho by the Harriman family of Union Pacific railroad fame. A waterfowl refuge whose species include the rare trumpeter swan, the Ranch is open for fishing only after nesting season, from June 15 to Sept. 30. But once open, this nine-mile stretch of meandering flatwater is as good as dry fly-fishing gets. At dusk, as the sun turns the Western sky to fading embers, the surface of the river comes alive. Thousands of trout and whitefish, many trophy-sized, quietly and rhythmically begin to sip down hatching insects, dappling the water's dark surface like drops of rain. "These trout all have Ph.D.'s," Soares had warned us. "They've been fished over so often that they're very smart. You go in with the idea of catching one fish. You see one working, figure out what he's doing, and it's very, very fun."