Trout Fishing Tips - Henrys Fork of the Snake River

HENRY'S FORK

By the first week of June the salmonfly hatch should be in the canyon section above Mesa Falls and starting to show in the Box Canyon. The rainbows of the canyon are some of the fastest growing anywhere and with catch and release, the prospect of catching a lunker is good. This is demanding fishing and you have to really cover the water. The big rainbows can be holding anywhere. Black Rubberlegs, Kaufman’s Stone Nymph and Peacock Simulators in sizes #2, 4 and 6 are my favorite weighted nymphs for this time of the year. For streamers use Woolhead Sculpins, Wooly Buggers and Zonkers with a sink tip line.

Golden stoneflies start showing up in mid-June. This hatch isn’t concentrated in the Box Canyon and the peak of activity doesn’t start until mid-July. These flies are smaller and patterns in size #6-10 work best. You won’t see many golden stones on the water because the hatch extends over about two months, the fish get pretty accustomed to looking for them. Some of the best action on golden stone dries is the last two weeks of July. After the golden stonefly hatch is over your chances of catching a big trout on a dry fly in the Box Canyon are diminished. The canyon is so rich in aquatic life that the larger fish won’t waste time holding near the surface looking for smaller insects. Sculpins, minnows, stonefly nymphs, caddis larva, leeches, crayfish, mayfly nymphs and other aquatic creatures are abundant.

From early August through October your best chance of catching a lunker rainbow will be with nymph and streamer patterns. Use smaller stonefly nymph patterns later in the season after the adults have hatched. Best nymph patterns include Black Rubberlegs, Kaufman’s Stone Nymph, Golden Stone Nymph, Prince Nymph, Zug Bug, Peeking Caddis and Hare’s Ear. Favorite streamers include Wooly Buggers, Flasha-Buggers, Woolhead Sculpins, Zonkers, Bunny flies, Muddlers and Marabou Leeches.

The fishing is good throughout the entire season in the Box Canyon. The rainbows are strong and in excellent condition. Early in the season in June and late season in September and October offer the best chance at a really large trout.

Lower Henry's Fork

From the Riverside Campground, which is about four miles below the Harriman State Park, downstream to the confluence of Warm River, the Henry’s Fork drops about 1000 feet in elevation. This includes about 15 miles of water. Most of this area is inaccessible and requires some hiking into a steep canyon. The water is very similar to the Box Canyon and the same flies and fishing techniques apply. The best time to fish this section is early in the season when the salmonflies are out and again in autumn. Below Warm River the river takes on a different look with more defined pools, runs and riffles. The salmonfly hatch is a major event here and occurs when the season opens in late May. This is a good area to float, but if you can’t float the access is very good and most of the water is wadeable. This section of river has a large population of trout, but since it isn’t under the protection of special regulations, the size is small. There are some real lunkers, however, with browns, rainbows and a few cutthroat trout.

This part of the river is not greatly influenced by insect hatches. You will find the smaller trout eager to take attractor dry flies throughout the season and your best success at big fish will be with nymphs or streamers. Use the same patterns as described for the Box.

Henry's Fork

The character of the river changes again from the town of Ashton down to St. Anthony. The power dam at Ashton turns the water below into a tail water. The water temperature is constant providing a fertile environment for abundant aquatic life. I believe this part of the river is richer than any place else, including Box Canyon. Even though it doesn’t enjoy the protection of special regulations, there are still plenty of large trout. Much of this water has the look of a large spring creek with long flats and numerous weed beds. Many of the same hatches occur here as are found in the upper river including salmonflies, tremendous caddis hatches, Green Drakes, Pale Morning Duns, Flavs and Blue Winged Olives. In addition you’ll find an excellent Grey Drake spinner fall during the evening hours in late June. The only drawback of this part of the Henry’s Fork is during the mid summer when irrigation demand is at its peak, there is too much flow for the fish to hold at the surface and too many weeds to fish underneath. The fishing will be good through early July and then again from mid-September on.

Harriman State Park

The flat meadow water of the Harriman State Park, or Railroad Ranch as it was previously known, encompasses some of the finest dry fly fishing in the world. This kind of fishing is not for everyone, however, as these rainbows can be very selective and unpredictable. They’ve destroyed the egos of some of the world’s finest anglers on more than one occasion. This meadow water extends for about nine miles, starting at Last Chance below the mouth of Box Canyon and extending downstream to the summer home area of Pinehaven. The season on the Harriman State Park property always opens on June 15, but the flat water surrounding the park opens the same as general season. The first hatches to occur on this flat water are caddis and three kinds of mayflies. We always see caddis on the water even before general season opens. There are also plenty of small Blue Wing Olive mayflies. Another larger mayfly of the Rithrogena family, commonly called the Black Quill, hatches in early June. This hatch is usually over by the time the ranch water opens. The Pale Morning Duns normally start the first week of June. If you plan to fish this area prior to June 15, the water above the ranch at Last Chance and from the lower boundary down to Pinehaven provides some excellent early dry fly fishing. Best patterns for this time period include size 14-16 Hemingway Caddis and Peacock Caddis. You’ll also need some mayfly patterns which include size 18-20 Blue Wing Olive No-Hackle and Thorax, size 12-14 Quill Gordon, and Pale Morning Duns in size 14-16. The most famous hatch, the Green Drake, generally has started when the ranch opens. The hatch usually lasts for 10 days to two weeks. Like other large insects it usually takes the big fish a few days to get accustomed to feeding on the big mayflies. The hatch starts about 11 am and will last only an hour or so unless the weather is cool and cloudy, which will extend the hatch. If you happen to be here when the weather is overcast, count your blessings as you are one of the privileged few. For the Green Drake hatch you’ll need some nymphs, emergers, duns and spinners. Most anglers opt for size 10 but I generally lean toward smaller size 12 patterns. My favorite flies are the Green Drake Emerger, Green Drake Cripple and standard Green Drake.

Several other hatches occur during this same time period. The Pale Morning Duns, Blue Wing Olives and caddis usually continue throughout the month. In addition to the previously mentioned caddis hatches, you can expect to find good numbers of tiny micro caddis hatching near the stream banks in the early evening. I’ve found a size 18 or 20 Spent Partridge Caddis to be the ticket when these little flies are out. The big Brown Drakes also hatch in the evenings during this period. Look for them in the slow sections of the river. Best areas include the islands, bonefish flats, the ranch buildings, the gravel pit and woodroad #16. You’ll need nymphs, emergers, duns and spinners for the Brown Drakes. The hatch occurs at the same time as the spinner fall so you may find one fish eating emergers and another keying on spinners. My favorite pattern is Mike’s Brown Drake in size #10. One of the best mayfly hatches of the entire season comes right on the heels of the Green Drake. It’s a slate wing olive mayfly, Ephemerella flavilinea, commonly called a "Flav", that looks like its larger cousin the Green Drake. You’ll find the Flavs hatching in the late afternoon hours on the ranch. This hatch will continue throughout July. The Pale Morning Dun hatch tapers down in early July and then picks up again later in the month. August brings some important changes in the fishing on the ranch. By August many of the large trout which hold in the upper section of the ranch near Last Chance start to move downstream. I don’t know the reason for this, but I’m convinced it happens. If you walk into the ranch from the upper parking lot, you may not find much going on but if you walk into the flats from the mail box, you should find plenty of trout rising in the morning hours. There are two important mayflies to consider during this period, Callibaetis and Tricos. The spinner fall is of the greatest importance with both of these mayfly species. The Tricos get on the water about 8 am. Use size #20 and 22 Trico Spinners. You’ll find the Callibaetis spinners on the water about 10 am. Use a size #14 or 16 Callabaetis Spinner or an Adams. Terrestrials will really gain importance in August. You’ll frequently find ants, hoppers and beetles on the water.

The Callabaetis and Tricos will continue into mid-September, which then brings in hatches of Blue Wing Olives and Mahogany Duns. The Mahogany Dun hatch is of major importance. No-hackles and thorax patterns in size 16-18 work great as well as the standard Red Quill. These hatches will continue until the fishing on Harriman State Park closes on October 15. There are other considerations when fishing the Harriman State Park in addition to understanding the hatches. You need to be able to locate specific trout and stalk them. Just covering the water is usually unproductive. The fish can be difficult to catch, but the excitement is in the challenge.

In addition to matching the many hatches, you should be prepared with a general assortment of patterns. My favorites include Royal Wulff #16-20, Adams and Parachute Adams #14-18, Renegade #16-20, Black Beetle #14-18, Olive Humpy #16-20, Pheasant Tail Nymph #14-18 and Wooly Bugger #6-10.