Pretty much the same as last week. For the lower river fish early and late in the day and concentrate on terrestrial insect and caddis life cycle patterns. A lot of folks are fishing on the upper river where early AM tricos and daytime terrestrial insects (including ants), a few speckled duns, tiny PMDs, and later caddis and spinner falls bring action in the Last Chance-Harriman section. Two fly nymph rigs work well in Box Canyon.
Hoppers are out big time on the lower river, but the fish are after them mainly in the early hours then again during evening. They are also out big time on the Last Chance-Harriman and Flat Ranch sections river where tricos are on during morning hours with caddis during evening. As they fade about late AM, switch to hopper and other terrestrial insect patterns (use long drag-free floats). Fishing on the Flat Ranch section is slowing down as flow out of Henry’s Lake is dropping and warming. It’s still a good idea to have rusty spinners (#16-18) in that fly box anywhere you try the upper river.
If you fish the river below Ashton Dam during daytime, why not just go for a swim. In Island Park terrestrial insects are just as abundant as on the lower river. But with cooler water fish are more active in taking them. They seem to like small (#18) rusty spinners, too. Tricos should be showing in significant numbers soon. Two rig nymphs (big pattern trailed by a small one) are working in Box Canyon. Water is dropping and warming in the Flat Ranch portion. This means larger fish there will be moving downstream.
Hoppers are here anywhere on the river. Unless you fish late or early in the day swimming is more fun than fishing on the lower river. So head to the Last Chance-Harriman, Flat Ranch or Box Canyon sections for the best chance for action from terrestrial insect patterns. With the heat of day, consider wading wet in each of these sections.
If you try the water (it’s a bit high because of downstream irrigation demands) from Last Chance through Harriman State Park the rusty spinner (size 14-20) is the “must have” fly. Afternoon caddis activity offers several types of insects, and hoppers are beginning to show. Fishing on the lower river is slowing down, but crowds have gone over to the South Fork
The best fishing on the lower river is from Warm River to Ashton, but that section is beginning to turn to early and late in the day for the best results. PMDs, a few goldens and flavs are present with caddis providing PM action. Don’t forget to pitch a steamer pattern around overhead cover as the sun sets. Crowds have thinned everywhere on the river. Much of that is because of the activity on the South Fork. On the upper river nymphing seems the most effective way to action in Box Canyon where recreationists will share the water. Further downstream at Last Chance and Harriman crowds have thinned a bit and mayfly hatches are off their peaks. AM and PM spinner falls provide good action with standard rusty spinner patterns being most effective. PMD and decreasing flav activity provide some daytime action with a variety of caddis taking over during PMs.
Time to enjoy what is left of the great mayfly hatches on the upper river. Brown drakes and flavs are beginning to diminish. Soon PMDs and speckled duns will make up the major mayflies. Caddis of many types will be around. But just around the corner terrestrial insects will rule the roost. Ants and hopper will be of major attraction to trout.
Look for the lower river to begin warming to the point that early and late in the day will be the best times to present caddis life cycle patterns as well as those for terrestrial insects. Also look for boat traffic to drop, but an increase in recreational boaters.
We are past the peaks of the big stone fly and green drake activities. Now is the time on the upper river for flavs and PMDs during daytime and brown drakes during evenings. Look for a lot of folks being on Harriman East, especially using Wood road 16 to access the river during evenings. Because of the South Fork turning on crowds are thinning, but enthusiasts remain. This also applies to the lower river where good PMD and caddis activity remains, but the usual summer warming will begin any day.
His book “Fly-Fishing Guide to the Henry’s Fork” says it all for the river.
Along the upper river major mayfly hatches move on from continuing PMDs to include those of flavs and brown drakes. Caddis accompany them during PMs. So the “name of the game” is finding which of these fish are taking: PMDs, flavs or caddis. Go to the water with life cycle patterns for all of these. Brown drakes coming on will most likely be what trout look for during the evening hours. If you fish at twilight, don’t overlook drifting a hair mouse pattern close to banks adjacent to water offering good cover. You could encounter your fish of the year!
The crowds on the lower river are a bit thinner now. The above aquatic insects are important to trout as are gray drakes during evening hours.
The big stoneflies have come and gone from the river. Straggling goldens can be around on upper sections including Coffee Pot and wind blown into the Flat Ranch section. Now the big mayfly emergence array has taken over. Green drakes are diminishing on the lower river, but flavs, gray drakes & PMDs are taking over to be accompanied with PM caddis and a growing amount of sallies. The trick here is to find trout’s preference at a given time then present life cycle patterns for that preference. If you want fly-fishing company, the Box Canyon to Riverside section is for you.
The array of mayfly activity ( minus gray drakes in number) continues on the upper river. From the top end of the Mesa Falls Scenic Highway to view towards the river looks like a massive trailer camp. The Last Chance rest stop is full of parked vehicles, and there you can hear foreign languages and English language accents from all corners of the earth. Dozens of boats will pass you by along the river during a day of fishing. All this is for good reason: this section of the river currently offers arguably the best trout fishing in the country. So be patient and considerate if you plan a visit!