Is there anything left to say about Henry’s Fork of the Snake River that hasn’t already been said? Few rivers have been more thoroughly discussed, written about and acclaimed. Is it the best fly fishing steam in the world? Impossible to say. But the mere fact that it has been so frequently cited as such has earned it a place on any angler’s bucket list.
One thing is for sure: it’s the most famous fly-fishing river in Idaho. From its source at Big Springs and the Henry’s Lake outlet, the river stretches from West Yellowstone through Rexburg, at times a mere stone’s throw from Yellowstone National Park. Eventually, it merges with the South Fork to form the Snake River proper.
Getting the Lay of the Land
One reason the Henry’s Fork Snake River enjoys such a sterling reputation is that it is, in many ways, several rivers in one. Spring creek, freestone stream and tailwater are all valid descriptors of various sections. Brook trout, brown trout, cutthroat trout and rainbow trout all call the river home, and depending on which section you fish, your experience could be wildly different. Before getting into specific flies and techniques, let’s take a closer look at some of the most well-known sections of Henry’s Fork.
Upper (Big Springs/Henry’s Lake Outlet)
The part of Henry’s Fork above Island Park Reservoir—including the Henry’s Lake Outlet and waters just below Big Spring—includes open grassy sections as well as narrow rapids. There are lots of quality rainbows here, plus the highest cutthroat trout numbers anywhere in the river. Some parts are closed to fishing, but areas near Mack’s Inn and Coffee Pot Rapids attract anglers. In Henry’s Lake, fly fishing opportunities include some of the biggest brook trout in Idaho, with access through Henry’s Lake State Park.
Box Canyon
Below Island Park reservoir and the confluence of the Buffalo River lies a long tailwater section of Henry’s Fork. Three miles of near-continuous rocky runs tumble through a stretch known as the Box Canyon, with tall pine-studded canyon walls and some of the biggest (and hardest to catch) trophy rainbow trout in the river. The Box Canyon section ranges from 100 to as little as 50 feet wide. Wading is not recommended in these tricky waters, but it’s a nymph fisherman’s dream come true. The Forest Service operates Box Canyon Campground and Box Canyon Boat Ramp.
Harriman State Park/Railroad Ranch
Perhaps the most famous section of Henry’s Fork, the 6-mile stretch known as Railroad Ranch or simply “The Ranch” flows through Harriman State Park. Here the river widens and slows down, its placid surface meandering through open, grassy meadows with views of the Tetons and the Centennial Mountains. Prolific weed beds produce legendary insect hatches that feed the abundant rainbow trout. This spring creek-like section has earned Henry’s Fork a reputation as the best dry fly stream on earth. Osborne Bridge is a key access point.
Mesa Falls
One of the less-fished sections of Henry’s Fork, the Mesa Falls section of Henry’s Fork has only a few access points on secluded roads that head west off the Mesa Falls Byway. This is mostly swift current and pocket water, with nymphs and streamers being effective. Some sections are navigable by drift boats, and the Riverside Campground is a good access point above upper and lower Mesa Falls.
Lower
With additional nutrients added by the Warm River and other tributaries, the lower Henry’s Fork also offers tremendous fly fishing opportunities. You’ll find many kinds of water in this stretch, including large flats as well as classic riffle-pool-run configurations. Brown trout are much more abundant here, with prime fishing below Ashton Dam and Chester Dam. There are numerous access points as the river flows from Ashton to Anthony, including opportunities for walk-and-wade fishing as well as drift boats.
Henry’s Fork Hatch Guide & Fly Selection
Fertile water makes Henry’s Fork the setting of explosive insect hatches. Available insect forage—and, as a result, fly selection—vary widely by season. Henry’s Fork is a highly pressured river, so being able to match the hatch with pinpoint precision will serve you well. That said, with so many anglers on the water, there are also times when throwing a completely unexpected pattern can give you an edge.
May-June
Salmonflies are among the first big hatches of the year, starting around St. Anthony in May and gradually making their way upriver to Island Park Dam. Golden Stones follow, making May and June great months for big dry flies. There are major Green Drake, Little Green Drake, Brown Drake and Grey Drake hatches throughout June, and a variety of caddis species hatch around this time as well.
July-August
As the Drake hatches wind down, Pale Morning Duns take off in July. Tricos can also hatch at various times throughout the summer, and various baetis species that are often lumped together as Blue-Winged Olives can hatch at virtually any time. Summer is also terrestrial season, especially on open, grassy sections of Henry’s Fork, so don’t get caught without Ant, Beetle and Hopper patterns.
September-October
Terrestrials continue to be crucial through the end of September. A variety of caddisflies are also on the menu well into fall, and there are several hatches of smaller mayfly species on various parts of the river. Mahogany Duns and Blue Winged Olives can pop up here and there.
November-December
Midges are available year-round, but they become increasingly important in late fall after many other insects stop hatching. Streamers and big nymphs can tempt trophy trout in Henry’s Fork and Henry’s Lake this time of year, and as winter approaches, the crowds recede and hardy anglers can find success targeting relatively unpressured fish.
Essential Fly Patterns:
- Dry Flies – Parachute Adams, Renegade, Elk Hair Caddis, Hemingway Caddis, Royal Wulff, Blue Winged Olive
- Nymphs – Pheasant Tail, Copper John, Zebra Midge, Hare’s Ear, Prince Nymph
- Streamers – Matuka Streamer, Wooly Bugger, Zonker, Sculpzilla
- Terrestrials – Black Beetle, Foam Beetle, Foam Golden Stone, Chubby Chernobyl, Chernobyl Ant, Parachute Ant
- Emergers – Soft Hackle, RS2, Barr’s Emerger, No Hackle, Sparkle Dun
Hatches can vary widely in timing depending on what part of Henry’s Fork you’re fishing. When in doubt, stop in at a local fly shop and chat about what’s working at any given time. Henry’s Fork Anglers, TRR Outfitters and Drift Lodge Fly Shop are all good bets
Know Before You Go
A 5w or 6w fly rod is ideal for most situations on Henry’s Fork. Floating lines with long leaders and a light tippet are standard-issue. The Harriman State Park section of the river opens to angling on June 15, but the majority of the river is open year-round. Some special regulations vary by season; see the Idaho Department of Fish and Game for details.
Access to Henry’s Fork is abundant, and there are public spots to get on the water throughout all of the best fly fishing sections. The Henry’s Fork Foundation is a great resource for access maps and other information.