Henry's Fork of the Snake River

- The Upper Henry's Fork -

The Henry's Fork is one of the premier fly fishing rivers in the world. The river is famous for its prolific aquatic insect hatches that draw fly fishers from around the globe to it's banks. On any given day during the summer, large trout can be found sipping these insects from the river's surface.

Besides it's outstanding fly fishing, the Henry's Fork is known for its beauty. The river starts at Big Springs where 480,000 gallons of water a day flow out of the ground. The water here is crystal clear and large trout can be seen feeding in the gentle current just below the springs (this area is closed to fishing!). Moose and other wildlife visit the area regularly.

From Big Springs, the river winds slowly through heavy willows and deep channels until it reaches the Mack's Inn area. The river is shallow and very easy to access at Mack's and the slow current makes this an ideal area to introduce a beginner to fly fishing.

A few miles downstream, the river flows into Island Park Reservoir. The reservoir holds some of the largest fish in the area and hooking into one of them can certainly be a rewarding experience.

The river flows out of Island Park Reservoir and into the Box Canyon. The steep canyon walls and heavily wooded banks of the canyon provide terrific nesting habitat for osprey and eagle alike. Hikers and fishermen can often see these majestic birds flying over the river. Blue herons also live here, silently stalking fish in the shallows. Moose, deer, otter, beaver and marmot can also be seen in the canyon. The fish that live in the Box Canyon can grow to enormous proportions and a trip through "the Box" is often the highlight of a trip to the Henry's Fork.

- Henry's Lake Outlet -

Henry's Lake Outlet is a small, meandering stream that winds across the vast meadow of Henry's Lake Flat on its way to the confluence with the main stem of the Henry's Fork a short distance below Big Springs. The Nature Conservancy's Flat Ranch is on this stretch of river.

The fishing in Henry's Lake Outlet can be very good early in the season. This is due primarily to the fact that during high water years many large fish are carried out of Henry's Lake and into the outlet. These fish tend to congregate toward the upper end of the outlet and they are generally easy to catch.

The Nature Conservancy of Idaho is doing some work to improve trout habitat on this section of stream. In the past, winter flows have been close to non-existent and cattle have damaged some of the riparian areas. Over the last couple of years, the Nature Conservancy has managed to keep water in the stream through the winter months and they have begun work to repair riparian areas. Hopefully, in the near future this fishery will become more viable.

Access to the Outlet is limited mainly to points where a road crosses the river. Highway 20 crosses the outlet about five miles north of Mack's Inn. The Big Springs Loop Road crosses the outlet about two miles east of Highway 20. The Nature Conservancy also provides access to the outlet from its property.

- The Upper River -

Besides its outstanding fly fishing, the Henry's Fork is known for its beauty. The river starts at Big Springs where 480,000 gallons of water a day flow out of the ground. The water here is crystal clear and large trout can be seen feeding in the gentle current just below the springs (this area is closed to fishing!). Moose and other wildlife visit the area regularly. Generally, we define the upper river as the stretch from the confluence of the Henry's Lake Outlet and Big Springs down to McCrea's Bridge at the inlet to Island Park Reservoir. This part of the river is generally shallow, slow moving and protected from the wind. It can be a great place to take beginning fishermen. In fact, this part of the river is stocked regularly at Mack's Inn and McCrea's Bridge and most of those fish will eat anything, including a poorly presented fly.

For the experienced fly fisher, there are some beautiful spring creek areas on this section of river but, often, the fishing can be disappointing. There are several reasons for this. The huge number of recreationists sometimes makes fishing difficult. Another reason is that the general limit is in effect on this section of the river. This means that anglers can take home six fish a day. Needless to say, with all the pressure this part of the river gets, such a liberal bag limit can make quite a dent in the fish population. Many of the hatches that occur on the better known downstream sections of the river also occur here. Blue Winged Olives, Pale Morning Duns, Green and Brown Drakes and caddis flies are all present. We have found that attractor patterns work particularly well on this section of the river since the fish, generally, are less selective. Royal Wulffs, Parachute Adams and Elk Hair Caddis are all good choices.

Access to this section of the river is pretty good. You can park and fish at Mack's Inn if aesthetics aren't too important to you. Another great access point is Upper Coffee Pot Campground. There is a parking area just outside the entrance to the campground and it is just a short walk to the river. You can also access the river in the area of Coffee Pot Rapids. To get there, turn off of Highway 20 at the sign for Upper Coffee Pot Campground and then, instead of turning into the campground, follow that road west until it dead ends. This is the fast and narrow section of the Upper River and it can fish very well. One last access point is at McCrea's Bridge where the river flows into Island Park Reservoir. Park at the bridge and walk upstream.

- The Box Canyon -

The river flows out of Island Park Reservoir and into the Box Canyon. The steep canyon walls and heavily wooded banks of the canyon provide terrific nesting habitat for osprey and eagles alike. Hikers and fishermen can often see these majestic birds flying over the river. Blue herons also live here, silently stalking fish in the shallows. Moose, deer, otter, beaver and marmot can also be seen in the canyon. The fish that live in the Box Canyon can grow to enormous proportions and a trip through "the Box" is often the highlight of a trip to the Henry's Fork.

Box Canyon is a short stretch of fast water about three miles long. The bottom is covered with basalt rocks of every shape and size. The current is fast and coupled with the rock-strewn bottom, wading is treacherous. Always wear a wading belt and we recommend that even strong waders consider using a wading staff!

Early in the season the stream flows are high until the snowmelt is over. The river usually runs low in mid-June, making wading less dangerous until the irrigation demand increases the flows. Maximum flows occur during the peak irrigation season from mid July through mid August. At the end of the irrigation season the outflow normally matches the inflow at the Island Park Reservoir for the remainder of the season. Stream flows will vary according to snow pack and irrigation demand.

The rainbows of the Box Canyon are fat, healthy and fast growing. The water is full of many types of trout food from stoneflies, mayflies and caddis to crayfish, leeches and sculpins. There is so much food available that large trout will rarely expend the energy to rise to the surface except early in June when the giant salmonflies are on the water. Large streamers, leeches and heavy nymphs are usually needed to interest the giant rainbows. The most popular fly in the canyon has to be the Brown Rubberlegs. In the early season, we fish the large version of these nymphs (sizes 4 and 6) because there are many fully mature nymphs in the water at that time of year. Once the salmonfly hatch is over, we start to use smaller Rubberlegs (sizes 8 and 10). Other flies that work reliably in the Box are Serendipities, Electric Caddis, Pheasant Tail and Hare's Ear nymphs, and tungsten-beaded Zebra Midges. Anything with a bead head seems to work well, also. Streamer fishing is good most of the summer. Favorite streamers include Zonkers,Bunny Leeches, Matukas, and Sculpin imitations.

When the water is low, wade fishing is usually very productive because you can cover the holding water. When stream flows are high the wading can be very dangerous and drifting the river in a McKenzie boat is the only effective way to properly cover the water.

Most anglers understand the importance of the salmonfly hatch on this special stretch of the Henry's Fork. In early June the large rainbows will move out of their deep hiding places in search of the large stoneflies. While the canyon fishes well throughout the summer, many anglers miss out on two excellent periods to catch a big rainbow. From mid June on, many Henry's Fork anglers fish in Harriman State Park leaving the Box Canyon with little fishing pressure. Even though the salmonfly hatch is usually over, the larger trout are still looking at the surface and there are plenty of golden stoneflies on the water. In the autumn the water is low and easy to wade and fishing pressure is light. The big trout are more accessible and hungry.

There is a great deal of access to the Canyon. The most popular access point is at the head of the canyon, just below Island Park Dam. Here you will find a boat ramp and a parking area that allow quick and easy access to some of the best fishing in the canyon.

The next access point as you move downstream is at the Box Canyon Campground. There is a fisherman's parking lot just outside the entrance to the campground and the river is just a short walk away.

Further south on the old highway, there are a couple of other access points on the west side of the road. These turnouts are unmarked and lead to parking areas located near the canyon rim. The trails to the river from these lots are steep but navigable by most anglers.

- Last Chance and Harriman State Park, "The Ranch" -

The Harriman State Park contains about 7 miles of the Henry's Fork, including 2-1/2 miles of water south of the Osborne Bridge. The river flows out of the Box Canyon at Last Chance and across the open meadows of the largest volcanic caldera in the country. The currents are spring creek-like which makes this section of the Henry's Fork some of the finest dry fly water in the world. Two miles below the park, just south of the Island Park subdivision of Pinehaven, the river changes character as it cascades its way down towards the village of Ashton. The river will drop 1200 feet in elevation in fifteen miles.

The rainbow trout of the Henry's Fork are some of the fastest growing of the species. They are also the longest living. The waters of the Harriman Park are so rich in aquatic insects that these trout continue to rely on mayflies and caddis as their primary food source even after they reach very large proportions. It is not unusual to see trout well over 20 inches feeding softly on tiny mayflies.

The fishing season on this part of the river has always opened on June 15 to accommodate nesting waterfowl. This water closes to fishing on November 30. While most anglers consider the first three weeks of the season the best fishing, there are several other periods which offer the dry fly angler greater opportunity to catch some of the great rainbows of the Harriman Park.

From mid June to early July the river produces some of the most important mayfly and caddis hatches of the entire year. On opening day anglers can expect to find good numbers of pale morning dun mayflies, small baetis mayflies and plenty of caddis. The large green drakes start showing up in significant numbers soon after June 20 and continue until the end of the month. These insects hatch throughout the morning hours and into early afternoon. On cloudy, cool days they hatch all day. The largest mayfly of the Henry's Fork, the brown drake, hatches at dusk in the very slow sections of the river. Bonefish Flats, the Millionaire's Pool, the Dog Hole and Wood Road #16 are some of the most popular areas for the brown drake.

Even though early season produces some of the greatest hatches, there are also disadvantages to fishing the ranch at this time of the year. The river is usually crowded in late June. The combination of opening day and the green drake hatch brings a lot of anglers to this part of the Henry's Fork. Another factor is most other streams in the region are in the middle of spring run-off while the Henry's Fork is running low and clear.

In July the crowds move on to other rivers. The pale morning duns continue to hatch throughout the month producing good spinner falls in the morning. The duns hatch in the middle of the day and the trout get ultra selective. The small western drake, Ephemerella flavilinea, is the most import hatch in July. It resembles its larger cousin in color and shape but is two hook sizes smaller. Flav imitations should be tied in sizes 14 and 16. This mayfly hatches in the late afternoons during the first part of July and produces some furious feeding activity when afternoon thunder clouds roll in over Thurmon Ridge. When the flav activity slows down in mid July, another important mayfly begins appear. The Callibaetis, a pale grey mayfly with speckled wings, produces excellent dry fly fishing from mid July through early September. Beetles and ants are also important and the big trout are always on the lookout for these terrestrial insects.

In August, the morning hours bring the Tricos followed by the Callibaetis. Best fishing is in the middle and lower sections of the park. The trout really get after these mayfly spinners and rise freely from early morning until mid afternoon. In addition to ants and beetles, hopper patterns are also very productive, especially on warm afternoons. The evening produces one of the greatest insect hatches of the year, yet it is unknown to all but the most dedicated Henry's Fork anglers. The slow water caddis is a size 16 with a very dark grey wing and pale amber body. It emerges in clouds in the Bonefish Flats stretch from mid to late July.

Late September through mid October is by far the best time to fish the Harriman Park. Not that early September isn't good, it's just that the fishing continues to improve as the month slips by. The fishing pressure is light, the weather is usually comfortable, the insect hatches are great and the trout rise throughout the day. Three aquatic hatches make up the September fishing. There are two small blue winged olives, Baetis and Psuedocloeon, which are matched with size 20 and 22 imitations. The Mahogany Dun, Paraleptophlebia, is larger, size 16 or 18 and the trout will usually be on the lookout for them even if they are gorging themselves on the smaller mayflies. Ants and beetles are usually killers and the trout will also take a properly presented size 18 Parachute Adams or Royal Wulff.

There are several points from which you can access the water in Harriman State Park. The most popular access point is the parking lot at the northern border of the Park. The parking lot is on the west side of Highway 20 at the southern end of Last Chance. Anglers can park their cars here and walk downstream to fish.

The "mailbox" is another common access point. As you head south from Last Chance on Highway 20, you will see a large mailbox on your right. There is a parking area across the highway from the box. You must park here and walk one mile to get to the river.

Another common access is at Osborne Bridge. There is a large blacktop parking lot, which is accessed by turning east about ¼ mile south of the Osborne Bridge.

The last access points to the Park are going to cost you a few well spent dollars. Afterfound by turning right after you cross Osborne Bridge (heading south), turn right on to Green Canyon Road. Head due west for about 100 yards and turn right at the sign for Harriman State Park. Be sure to stop at the gate and pay the entrance fee. Season passes are available and highly recommended. Once through the gate, you have two choices. If you take your first left, the road will take you down to the river at the lower end of the Park. If you continue on the main road and go past the visitors center on your left and across the Silver Lake Dam, the road will dead end at the parking lot for Millionaires Pool. This is probably one of the most scenic spots on the whole river. It doesn't take too long to figure out why the Harriman's chose to build in this area.

- Riverside -

Riverside Campground is about seven miles south of Last Chance on the east side of Highway 20. There is a fisherman's parking area right down near the water. At Riverside, the river begins to cut through the side of the huge volcanic caldera that forms the Island Park area. The water is fast and the bottom is rocky. As a result, the wading is difficult, particularly downstream.

Use the same fishing techniques and flies here that you would use in the Box Canyon. Though they tend to be a little smaller than the fish in the Box, tThe trout here are strong, fat and well worth the effort.

- Cardiac Canyon -

Perhaps the least known part of the Henry's Fork is the canyon stretch below Riverside Campground. Below the Pinehaven subdivision the waters of the Henry's Fork start to gain velocity. From Riverside Campground to the confluence with Warm River, the Henry's Fork cascades through a deep canyon. Access is limited to this part of the river and only two stretches can be floated.

Access to this canyon stretch of the Henry's Fork is from the Mesa Falls Scenic Byway. The first access point to this part of the river is at Hatchery Ford. The road is well marked and in good condition. The road goes right to the river and ends at the best boat ramp on the entire river. At Hatchery Ford the river is quiet and easy to wade. I recommend walking up or downstream to find better fishing. The water is very fast and rough in this stretch. The best fishing is early in the season when the salmonflies and golden stones are out and late in the summer when the hoppers are on. The stretch also offers some great float fishing (with Hatchery Ford being the last takeout before the big waterfalls). There are several rapids to negotiate so I don't recommend floating unless you are an expert oarsman. This float offers scenic beauty that is unsurpassed as well as the opportunity to view lots of wildlife. It's common to see moose, deer, osprey, bald eagles, and marmots. You'll also see elk on occasion.

Below Hatchery Ford the only access is by foot. Several rapids and small waterfalls prohibit floating. This is the place to go if you really want some solitude and you don't mind hiking. The canyon is pretty deep which keeps most people away. One access is at Sheep Falls. This can be reached from the Sheep Falls Road from highway 20. Another good access is on Wood Road #6 from the Mesa Falls Road. There are a lot of deep fast runs in this section with some large trout. My favorite fishing is when the salmonflies are on but you always have a good chance with large stonefly nymphs and streamers throughout the season.

Upper Mesa Falls is one of the most popular scenic attractions in Island Park. This area also offers some excellent fishing. Walking up the river above the falls offers some excellent water. You can also walk down a trail below the upper falls and fish down to the lower falls. This stretch is known as Cardiac Canyon. This area was my favorite place to fish during my high school years. We would hike down below the falls and then wade across the river in jeans and sneakers. Waders would have been a disaster because we'd get washed downstream a time or two before we reached the other bank. Then we fished the deep water below the falls and hooked some enormous trout. We couldn't land most of the big fish even with 20 lb. tippet because we couldn't follow the fish downstream because it was too rough. Favorite flies were a weighted olive wooly worm and a Bar-X wet fly. Those types of flies are still good in this stretch.

Below Lower Mesa Falls access by trail at the end of the small campground. There is some great water in this area and it's worth the rigorous climb. Boaters can also drag boats down at this point. The float is spectacular and provides some great fishing. The take-out is at Stone Bridge just below Warm River confluence. My two favorite times for dry flies are late May and early June when the salmonflies are on and again in late summer when the hoppers are out.

If you haven't discovered this part of the river you've missed out. Even if the fishing isn't good you'll still enjoy the scenery and the solitude. The fishing can be great. Dry fly fishing is best early in the year and later in the summer. Nymphs and streamers are productive throughout the year.

- Warm River to Ashton -

The Warm River to Ashton stretch of the Henry's Fork provides some of the most scenic trout water in the entire region. It drops out of the deep, narrow chasm below Lower Mesa Falls and opens up into a wide canyon at the Wendell Bridge. Eagles and osprey abound and in the fall the aspen trees light this stretch up with a golden glow. The water has a lot of definition with fast runs, shallow riffles and deep pools. There are also plenty of large rocks with some deep undercuts.

In addition to the resident rainbows there are some nice brown trout in this stretch of the Henry's Fork. In the early 80's the Upper Snake River Chapter of Trout Unlimited, along with the Upper Snake River Fly Fishermen, worked with the Idaho Fish & Game Department to stock these browns. Each year for five years, fingerling brown trout were stocked at various locations from Mesa Falls to Ashton. The browns have established a resident population and have also established themselves in the Henry's Fork below the Ashton Reservoir.

On this section of river, the season really starts with the salmonfly hatch. The hatch generally starts during the last week in May and lasts about a week. Dry fly fishing doesn't get any better than this. The trout gorge themselves on these giant insects as the hatch moves up the river.

Once the salmonfly hatch is over, anglers will have the most success nymph fishing. Small brown rubberlegs, beadhead Prince Nymphs and tungsten Zebra Midges are all good flies for this section of the river. There is still plenty of dry fly fishing to be done, too. Blue winged olives, pale morning duns, green drakes, golden stones and terrestrials can all be found on the water over the course of the summer. Dry attractors such as the Royal Wulff, Parachute Adams and Royal Coachman are good flies all summer long.

Access to this section of the river is pretty good. There is a boat ramp just below the confluence of the Warm River and the Henry's Fork and wade fishing in this vicinity can be productive. Much of the river can be accessed from a road that runs almost parallel to the river on its north side. To get to this road, head south on Highway 20 down the Ashton Hill and turn left just before you cross the Henry's Fork.

- Ashton to Chester -

Next to the Harriman Park, the stretch of the Henry's Fork from the Ashton Dam to the Chester Dam is my favorite. It's a tailwater fishery because it originates below a deep reservoir. It's also a large spring creek because the banks are saturated with springs that seep into the river almost the entire length. You can stop and pick watercress almost anywhere you want. This combination of water types creates an environment rich in aquatic life. It is the most productive stretch of the river. Below the Ashton Dam the river breaks out into a series of runs, riffles and pools interspersed with several small islands. Below the Ora Bridge, a half-mile below the dam, the river starts to slow down. The river backs up at the Chester Dam just upstream from the confluence of Falls River. While the entire reach holds a large population of trout, the Chester Backwaters is the most prolific with lots of large, fat rainbows.

While most of the river flows through private land the access is good. You can take the county road west from the main street in Ashton. This road crosses the river twice before it intersects with Highway 20 at Chester. The road to the Ashton Power Plant is just north of the Ora Bridge. The Ora boat ramp is accessed by turning west on the south side of the bridge. There is a gravel parking area at the top of the canyon, and a dirt road down to the boat ramp. The Vernon Bridge is a couple of miles below the Ora Bridge. We have lost driving/parking access at Vernon Bridge, but thanks to cooperative landowners and the Henry's Fork Foundation, there is a new boat ramp and parking area ¼ mile downstream from Vernon Bridge on the east side of the river. There is another county road that turns north just above Fall River and accesses the Henry's Fork just above the Chester Backwaters at the Seeley Ranch. The boat ramp here is no longer accessible, but there is still a parking area provided by the generous landowner.

The Henry's Fork is open to year round fishing from the Riverside Campground downstream (with the exception of the stretch from Ashton Reservoir to Vernon Bridge, which is open for the general season only). The river rarely freezes up because of the spring water and proximity to the Ashton Dam. Midge fishing is good throughout the winter. In the spring the Blue Wing Olive mayflies come off. They belong to the baetis family and are imitated with size 18 patterns. This hatch produces some outstanding dry fly fishing from mid March through mid April. The first of several important species of caddis start hatching in April. The caddis hatches continue until early July. June is the best month for caddis with blizzard hatches each evening.

The salmonfly hatch on the Henry's Fork usually occurs about May 20th but can vary at least a week in either direction depending on water temperature. I usually start looking for the salmonflies when I see the first blossoms on the chokecherry trees that line the banks of the river.

June and October are the best months to fish this part of the Henry's Fork. In addition to the heavy concentrations of caddis, several mayflies are also important in June. While the Green Drakes generate lots of action, the most important mayflies are the smaller Pale Morning Duns and the larger Grey Drakes. The Pale Morning Duns occur in the morning hours and the Grey Drakes hatch in the evening. Late June also produces good hatches of the Western Olive (Ephemerella flavilinea) or "Flav", which occurs in the late afternoon. In midsummer the stream flows increase due to irrigation demands and the surface activity stops. When the irrigation season is over in September the river again comes alive with feeding trout. Late season hatches include several species of Blue Winged Olive mayflies and Mahogany Duns.

The trout in this section are not as sophisticated as their Harriman Park cousins, although they can get pretty selective if the fishing pressure is high. While a drag-free presentation is essential, the choice of pattern is usually not important. I've found that an Elk Hair Caddis, Royal Wulff, Parachute Adams or Renegade will usually take trout. Of course your odds will increase if you match the hatch with No-Hackles, Thorax or other exact imitations.

- Chester Dam to St. Anthony -

The volume of the river is reduced from a series of diversions between the Chester Dam and St. Anthony. Some of these diversions are almost impassable by boat and require and expert at the oars to negotiate them. There is a lot of private access on this section but we have arrangements with a couple of landowners that provide access for us to take out. Otherwise we would not be able to legally float some of this water.

The fishing can be outstanding in this water. The percentage of brown trout increases the opportunity to hook and hopefully land trophy-sized trout. As with most of the lower Henry's Fork, the fishing dramatically declines during the peak of the summer months in July, August and early September. However, you can have some of the finest fishing in the region from March through June and again from mid-September through November.

There are lots of riffles and runs that provide outstanding dry fly fishing when the caddis and early season mayflies are emerging. Later in June you can expect excellent hatches of PMDs, Green Drakes, Gray Drakes and Flavs as well as some spectacular caddis hatches during the evening hours. Later in the fall the dry fly fishing picks back up with the emergence of several species Blue Winged Olives (Baetis).

Streamer fishing is a good way to go if you're after a trophy-sized trout. Nymph fishing is also very productive in the highly defined riffles and deep runs."

- St. Anthony to the confluence -

There are only four outfitters in the state of Idaho who are licensed to guide on this section of the Henry's Fork. Henry's Fork Anglers is very fortunate to be one of them. Walk-in access is extremely limited due to the fact that most of the river is some distance from the nearest roads. This section has the lowest trout-per-mile population downstream from the Island Park Dam. This may be the reason that the angling pressure is normally light. Yet some of the largest trout of the entire Henry's Fork have been landed in this stretch. We have recorded several measured trout in the 27" - 31" range caught and released by guide clients in this section. Most of these monsters are caught on streamers but June can produce some exceptional dry fly fishing. Hopper fishing can also ring up some of the bigger trout in late August and September."