Fishing is continuing to pick up on the Henry’s Fork. Bring some streamers, nymphs and Blue Wing Olives. The streamer fishing has been really good below Ashton Dam. Box Canyon is fishing well, however its all wade fishing unless you want to beat up your drift boat. Things have slowed down on the Ranch. I would look for a cloudy day for action to pick up on the ranch. This is a great time to catch some big fish and have a little bit of solitude on the river.
BWOs are active almost everywhere during afternoons when shadows begin to extend. If we get into cloudy weather, fish will respond to BWOs in better numbers, and hatches will be more intense. It is also the time of year to present streamers for migrating browns. The section between Ashton Dam and Chester backwaters is a popular place to wade fish. There are also locations for wade fishing below Chester Dam downstream to below St. Anthony. From Warm River to Ashton Reservoir backwaters a boat will get you into the best fishing. Pattern choice is not critical at these locations so long as your fly box includes somber and bright ties.
Fishing has been good on the Henry’s Fork. Nymphing and Streamer fishing have been the main tactics for hooking fish. BWO hatches have been few and far between but look for those flies to pop during overcast and rainy days. The fishing below the Ashton Dam have been really good as well as Warm River to Ashton. Stonefly Nymphs and a variety or bead head nymphs. I personally like a large #14 or #12 Pheasant Tail below a rubberleg.
Mayfly emergence events on the upper river are diminishing quickly with colder weather setting in. Soon that of BWOs will be the only one available. Almost on key flying ants are coming on to provide action from trout which seem to crave them. So add ant patterns to your terrestrial pattern roster when you venture to the Last Chance , the Harriman State Park reach, and the river around Hatchery Ford.
If you look at our experience fishing the lower Blackfoot River in our Small Streams report today there are words on the effects of aquatic weeds breaking up. Those words apply, as well, to sections of the Henry’s Fork that “weed up” during the growing season. That includes such as the Harriman State Park reach, the River above Mack’s Inn, above Coffee Pot Rapids, and others. What is important regardless of the water you fish, weeds breaking up this time of year release life forms that therefore become more easily available to foraging fish. Thus because of availability they will key on these life forms and your response should be to simulate them in the flies you offer.
Cooler and longer nights, lower flows out of Island Park Dam, and less daylight are making for changes. Streamer and two-fly nymph rigs fishing is picking up in Box Canyon. Mahogany Duns and BWOs are showing on the river below as tricos and callibaetis decrease. Terrestrial patterns still work, but their days are coming to an end as we cool of further. So make some changes in your fly box!
Now that cooler weather is here mayfly hatches, though still significant, are not the only game in town. If you tend toward the river in Harriman State Park this time of year, a good strategy for presenting larger flies are long, drag free as possible, drifts. Present in this manner around bank side cover, sweepers (which are relatively rare here), rocky shorelines, and timbered shorelines. Terrestrial patterns are best for using this technique, and those, especially hopper patterns, tied with traditional materials seem most effective within these. Don’t expect to catch a huge number of fish using this strategy, but do expect to encounter some of the larger fish here.
If you venture to the Last Chance-Harriman State Park reach the fishing sequence is trico spinners and egg layers in the AM, flying ants later in the morning, terrestrials through the day to caddis in the evening. Not may anglers will be present, so you can pretty much choose your waters. Flow out of Island Park Dam has dropped considerably making for easier wading conditions in Box Canyon. Below Riverside campground go with terrestrial patterns along banks, and your favorite bead head nymph in deeper water. Streamers should be effective below Coffee Pot Rapids and the best choice if you fish above Mack’s Inn.
With Labor Day weekend passing some welcomed happenings are coming. Crowds fishing the river will decrease substantially, waters will cool thanks to shortening and cooling days, and flow out of Island Park Reservoir will drop in preparation for winter storage. These will result in better fishing conditions all along the river. Likely the lower river will “come back to life” with renewed BWO hatches, continuing terrestrial insect and caddis activities, and increased effectiveness of presenting streamer patterns during low light conditions. The upper river will benefit as decreased flows in Box Canyon will make for safer wading and better approachability there. Above the reservoir big rainbows are moving into the river to feed on kokanee spawn. and throughout terrestrial insect pattens will remain effective until killing frosts. So it is a great time to be fishing just about anywhere on the river.