American Fly Fishing

Famous for Trophy Trout
By Bryan Anglerson

On maps, the Continental Divide extends westward from Yellowstone Park toward Henrys Lake Flat, but then it detours in a giant horseshoe-shaped arch up and around Henrys Lake before continuing westward again from the southwest side. Nestled into the divide, the lake’s outflow is forced south toward Island Park, Idaho.
   However, 1.3 million years ago, a volcano erupted where Island Park now sits. The explosion blew off the cone’s top, the liquid center then cooled and collapsed, leaving just the outer ring, the stubby mountains surrounding Island Park today. Satellite imagery on Google Earth clearly shows the caldera’s circle of mountains.
   Henrys Lake and Island Park Reservoir lie north of the caldera. The Continental Divide pushes Henrys Lake’s outflow into the caldera through a gap in the mountain ring at Box Canyon. After a leisurely meander through the flat center of the caldera, the Henrys Fork of the Snake River leaves through another notch in the mountains where Mesa Falls tumble down a basalt gorge.
   Inside the Island Park Caldera and on Henrys Lake Flat to the north, winter lasts into May. Ice does not leave Henrys Lake until early May usually. I drive through Island Park a dozen times each spring to fish the Madison River while Henrys Lake’s trout are swimming safely under the ice. Henrys Lake opens for fishing on the Saturday before Memorial Day. Fishing is excellent during the weeks after the much-anticipated opening day while trout gorge along the shore after ice-off.
   Simultaneously or immediately afterward, the lake’s native cutthroat trout start their spawning activity as they prepare to ascend the tributaries in June. The cutts’ staging at the mouths of tributary creeks also attracts the lake’s brook and hybrid cuttbow trout, a cutthroat/rainbow cross locally referred to simply as “hybrid.”
   In the heat of midsummer, trout go deeper, but because the lake is shallow, trout remain accessible to fly anglers with sinking lines. The lake’s dam raised the water level by 6 feet in 1922, and the deepest parts are now about 20 feet, but trout can typically be found on top of the weedbeds 12 feet deep. During July and August in low-water years, trout may concentrate again in the shallows near stream inlets for the cool, oxygenated water. Lake-wide fishing success picks up in October and continues until ice once again forms sometime in November.


October False Spawn
I recently fished Henrys Lake in mid-October with TroutHunter cofounder and co-owner, Rich Paini, and his wife, Millie. Millie had to scramble to find a sitter for their 8-year-old daughter because her school in Ashton, the self-proclaimed seed-potato capital of the world, was unexpectedly closed for a third week in a row. Typically, the school kids get two weeks off to harvest potatoes, but in 2014, it rained much of the first week, forcing the school to extend the potato-harvest (aka spud harvest) “vacation” to three weeks.
   As we launched a small fishing boat at the Idaho Parks & Recreation ramp on the south shore, the area around the ramp and dock was crowded with anglers and cutthroat trout. In one of the strangest phenomena I have experienced, large cutthroat congregate around the boat ramp in October.
   Like a piscatorial Woodstock, it seems every hippie cutthroat in the lake camps out on the gravel beds around the boat ramp. Why? Perhaps they gather for some false spawn (the cutthroats’ real spawn is in June in the tributaries). Or, perhaps they gather because the boat ramp area is one of a few locations in the lake that has clean gravel. Or, perhaps the trout imprint on the location when they are stocked at the boat ramp as fingerlings. Or, perhaps there is a concentration of food. The day before our trip, a local acquaintance of Rich’s had kept a limit of two cutts and reported that their stomachs were full of scuds.
   Whatever the reason, it is an event to experience. As we launched the boat, Rich and I each caught 18-inch cutts from shore by casting scuds on a floating line to visible, cruising cutthroat. Later, at sunset, as we pulled the boat off the lake, Millie hooked a number of these large, false-spawning cutts on both scuds and midges from the ramp.


Yellowstone Cutthroat Trout
It is curious that the native trout in Henrys Lake are the Yellowstone subspecies of cutthroat trout because the lake is separated from other strongholds of Yellowstone cutts by the Continental Divide. Scientists hypothesize that Yellowstone Lake at one time connected to the Snake River perhaps via Lewis Lake and before Mesa Falls formed. Whatever the natural and geologic history, Henrys Lake cutthroat are closer kin to the Yellowstone cutthroat than to the fine-spotted cutts that currently inhabit the other fork of the Snake River.
   In fact, Henrys Lake serves as a brood-stock hatchery for Yellowstone cutthroat. Idaho Fish and Game’s (IFG) regional fisheries manager, Dan Garren, reports that a thousand of the lake’s cutts are trapped in April and May on Hatchery Creek, a little spring-fed trickle where IFG has a fish trap and a small hatchery. These thousand fish produce about 2.5 million eggs, which develop into 1.3 million fry at Mackay Fish Hatchery. Most of the crop is stocked into Henrys Lake in September as fingerlings. A small percentage (10 percent and growing) is stocked in high mountain lakes and elsewhere.
   Historically, Henrys Lake cutts spawned up the tributaries. However, human development since the 1880s has created numerous barriers to fish passage. Cattle also have taken their toll by trampling the banks, causing smothering sediment to erode into the tributaries and silt up gravel. Consequently, Henrys Lake’s cutthroat fishery has depended heavily on stocking.
   That is slowly changing for the native cutthroat, and increasing numbers of Henrys Lake cutts are hatching in improved gravel habitat in tributaries. In 1982, 100 locals got together and founded Henrys Lake Foundation with the sole purpose of improving the fishery. In his book, The Henry’s Fork, Charles Brooks relates that he spoke in the initial Henrys Lake Foundation meeting and counseled the founding membership that if anyone should want to pursue any purpose other than improving the lake’s fishery, then the foundation should “hand him back his membership money and bid him farewell.”
   Since 1983, Henrys Lake Foundation has improved the habitat in the tributaries to the point that today, 30 percent of cutts in the lake come from eggs deposited naturally in clean gravel in the tributary streams. Henrys Lake Foundation removes culverts, plants willows streamside for erosion control, installs fish screens at diversions, and more. In 2006, Henrys Lake Foundation was instrumental in rebuilding the bridges on State Route 87 over Targhee Creek and Howard Creek to allow fish passage.


Hybrids and Brook Trout
In the early 1900s when it was vogue to stock rainbow trout around the continent, many rainbows were planted in Henrys Lake. They crossbred with the native cutthroat and produced cuttbow hybrids. Anglers soon discovered that these fish grew faster and fought better than either of the parent stock. Large, hard-fighting hybrids made Henrys Lake famous, and its fame as a trophy fishery has not diminished. It is still the premier lake for catching large hybrid trout. 
   However, unlike the naturally occurring hybrids of yesteryear, today’s fish are sterile and managed by stocking. Wildlife officials mix rainbow milt with cutthroat eggs, and then pressurize the eggs to sterilize them. The resulting triploids use all their energy for growth and not for reproduction, allowing them to grow faster, grow larger, and live longer. Ten to 15 percent of the trout in the lake are hybrids, 70 to 80 percent are cutthroat, and 10 to 15 percent are
sterile brookies.
   Brook trout from a nearby hatchery apparently escaped into Henrys Fork in the 1890s and migrated up the outlet into the lake. Because of the incredible amount of food available in the fertile lake, the brook trout grew large and became a coveted catch. Idaho Fish and Game continues the large-brook-trout tradition in an ecologically safe way by stocking only sterile brook trout. Sterility allows wildlife managers to ensure that the brook trout do not overpopulate and stunt or destroy the food base for other species. In the early 2000s, wildlife officials temporarily halted stocking brook trout for fear that the population was not 100 percent sterile. The hiatus lasted only two years until a more effective sterilization procedure became available. Triploid brook trout can exceed 20 inches in the fertile lake, adding to Henrys Lake’s trophy-fish reputation.


The shore of Henrys Lake is mostly private; consequently, anglers must use some sort of watercraft. Small boats with engines allow quick, easy access to new locations where trout may be easier to reach or more active. One way to learn about the hot spots is to watch for groups of boats. Hot spots attract a lot of attention and get crowded, but there are so many fish that crowding rarely affects the fishing if it’s “on.” It is estimated that only 10 percent of the lake’s trout are ever caught.
   Inflatable float tubes and pontoon boats in their many varieties are an easy way for out-of-staters to gain access to Henrys Lake. The only downside of these portable personal crafts is the limited distance that can be travelled efficiently via kicking or paddling. One fellow I know, along with 10 of his fishing friends, used to mount little trolling motors to 2000s-era float tubes and motor around the shore of the lake every September.
   For all sizes and shapes of watercraft, public launch sites are available at the state park on the southeast shore, and at the county boat dock (William Frome County Park) on the west side, which is reached via a road around the north side of the lake. Both launch sites offer camping, restrooms, and tables, and both charge fees. Additionally, several private launch sites are available along the north shore, including Jared’s Wild Rose Ranch Resort. The state fish hatchery has carry-in access for float tubes and such. Finally, there is a primitive launch in the southwest corner via an informal road.
   Another great option, especially for visitors who don’t have all the time in the world, is to engage the services of an excellent guide, such as Paini and his staff—and, at the end of the day, with an arm weary from battling Henrys Lake pigs, retiring to TroutHunter Lodge after a meal at Last Chance Bar & Grill seems the fitting ending to a perfect outing in trout country.
   Because bad weather can be dangerous for small craft, anglers should get off the lake if the wind whips up. The first time I attempted to fish the lake in the 1990s with one of the original primitive float tubes, I was blown off the water before wetting a line as whitecaps churned up the lakebed and muddied the entire lake. 
   Wildlife officials are serious about keeping aquatic invasive species out of Henrys Lake. Thousands of boats are checked annually at lakeside checkpoints for quagga and zebra mussels and other invasives, including plant species like water milfoil. Anglers should be diligent about cleaning boats, pontoons, float tubes, and gear. Wildlife officials are also watching the Utah chub population and the American white pelican population as potential threats to the trout.


Flies, Lines, and Tactics
Because leeches, damselfly nymphs, and baitfish account for 50 percent of a typical Henrys Lake trout’s diet, it is not surprising that stripping streamers is the most common and typically the most effective way to fly fish the lake. Leech patterns in brown, red, and black interest fish all season long, but are most abundant and most available to trout from opening day in May through August, peaking in July. Leeches are not fast swimmers, so a slow retrieve is best. When damselflies migrate toward shore to hatch, anglers should use an olive-green Woolly Bugger or marabou damselfly pattern. Damselflies are typically fished moving the fly toward the shore, but from a boat, stripping parallel to shore is an effective compromise, and even swimming damselflies away from shore toward your boat will pick up some fish.
   Larger streamers are effective imitations of baitfish that make up about 15 percent of a typical Henrys Lake trout’s diet. Cutts, brookies, and hybrids are all piscivorous; therefore, minnow-like streamers work equally well for all species. To the trout, streamers represent Utah chub, fry and fingerling trout, or just something that looks edible. For primal fish attracting, Montana Fly Company’s streamer fly called Coffey’s Sparkle Minnow is my new favorite after using it on still water near Henrys
Lake recently.
   Chironomids are legion, as they tend to be in every trout lake. When the fish are on them with vigor, midge larva and pupa patterns may be about the only flies that garner consistent success. Luckily, such selectivity to tiny midges is not the norm on Henrys Lake.
   There are other times—ranging from a brief hour here and there to days on end—when scuds seem to be the favorite target. If the usual arsenal of flies fails to deliver results, consider strip-retrieving a small scud pattern using very short, quick line strips, each series of six or so strips followed by a pause. And hold on tight: when Henrys Lake trout want scuds, they don’t leave any doubt about their intentions. In addition, every once in a while, a small beadhead Prince Nymph or Zug Bug fished in the same manner can be deadly.
   The choice of fly line depends on the depth of the water. For the shallows at the mouths of the creeks, a sinking-tip will keep your offering in the zone. In the deep glory hole area out from Staley Springs or along the cliffs, a full-sinking line in type 2 or 3 will keep flies deeper. Experiment with various countdown times from 10 to 20 seconds until you snag vegetation, then back off by a few seconds. Often, trout hold barely 6 inches off the weedbed.
   When I fished Chironomids and scuds with the Rich and Millie Paini, we used floating lines and worked the shallows near shore. The flies were weighted and they pulled the tippet and leader under to just the right depth. Millie and Rich tried to teach me to strike with the line only and not lift the rod tip. However, I am a lifelong, habitual, rod-tip lifter, and kept forgetting and lifting the rod tip to strike. Thankfully, the Painis spared me the harangue that their Cuban counterparts scold with on Cuba’s bonefish flats when the hook set is not done perfectly. With the rod tip aimed at the fish, the Painis set the hook with a slip-strip yank of the line hand to connect directly and quickly with the trout to drive the fly’s hook into the jaw, hard. 
   As I marveled at the skill required not to break the tippet with this type of hook set, I guessed aloud that they must be using 2X tippet, but Rich said that TroutHunter’s 4X was strong enough. He explained that TroutHunter manufactures its own proprietary tippet material, which has the deserved reputation as the strongest in the industry.
   Dry-fly fishing opportunities are limited at best on Henrys Lake; nevertheless, more and more anglers are experimenting with dry flies there with mixed success. Except for extremely rare occasions, Henrys Lake trout do not feed on the surface. They feed near the surface at times, but not on dry flies. In the shallows, anglers may frequently see fish porpoising with dorsal fins and tails breaking the surface, and may suppose the trout are “rising” to duns, spinners, or some adult floating fly, but they are not. When you encounter porpoising trout, suspend a Chironomid or a scud (or both) off a floating line to pick up these feeding fish.


Morning and Evening
Morning is the best time to fish Henrys Lake because the fish and their foods are most active then. Although fish can be caught at all times of day, anglers who are on the water early and late do best. That kind of timing makes TroutHunter Lodge in the Last Chance area of Island Park an ideal base for Henrys Lake fishing because with minimal drive time, anglers can be on the water early when the fish are
most active.
   TroutHunter Lodge, which includes a fly shop and hot tub, is built on the bank of the Henrys Fork River with a full-length balcony from which to enjoy the river’s charm—and, of course, the charm of that famous fishery includes ultra-selective leviathan rainbows sipping mayflies from the surface and defying anglers to fool them with a feathered forgery. That’s what makes Island Park and surrounds the nation’s most storied trout country: you can test your mettle against the pickiest of trout on the famous river one day, then marvel at the girth and power of the bruisers in nearby Henrys Lake the next.


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