Henry's Fork Fishing Report - August 20, 2026

Henry’s Fork Streamflows

Island Park Dam:  736 cfs

Ashton Dam:  1640 cfs

St. Anthony:  1300 cfs

Fall River:  377 cfs

The Henry’s Fork is holding up its end of the deal so far despite a grim outlook in the early days of the season.  Conditions are holding up much better than last year and fishing still ranging from fair to good in many of her reaches.  We are past the real heat of summer and though daytime temperatures will dip into the 90s, they’ll only be there for an hour or two, with most hours of the day being comfortable, overall.  Turbidity remains manageable, flows are low but not extremely, water temperatures are staying in the right range, and happy trout can be found.

Box Canyon

The Box has been fishing well this past week, with cooler water temperatures out of Island Park Dam than the previous week.  Flows are at a great level for anglers to read the water and spend time working through the pockets and runs.  A few golden stones are hanging on and the flows are low enough to keep a few trout looking up here and there.  Dry/dropper rigs and indicator nymphing rigs are still the norm and weeds are about normal for the time of year.  Vegetation is an issue and anglers will need to deal with it in order to keep their flies clean; try less weight and/or shorter lengths in your droppers and between your flies and indicators.  Keep your hooks clean, these trout don’t generally appreciate salad on their flies.  Though the odd stonefly nymph will get eaten, nymphs are generally small in here at this time of year, and we don’t mind a few fluorescent hot spots here and there.  We like the following:  PTs, red and brown Zebra Midges, Split Case PMDs, Rednecks #14-18 and Rubberlegs stonefly nymphs and SJWs #10-12.  Many perdigons will work but we especially like Olive Hot Spots, Spanish Bullets, Jakes’ SH, Black Daggers and red Jig Napoleons #16-18 this time of year.

Railroad Ranch

The moisture of last week seems to have kicked a few winged ants into gear, with nuptial flights occurring here and there.  Anglers will do well to have a few varietals in their boxes:  small winged black ants, honey ants and cinnamon ants.  The Heames and Harrop Honey Ants are good choices as is a Shimazaki black ant.  There are a few mayflies around as well, small PMDs, callibaetis, tricos and pseudos are all being found on most days, but don’t find yourselves without a callibaetis spinner #14-16 down there, it’s likely you’ll put it to use.  A variety of spinners in rusty, cream, yellow, gray and black ranging from #14-20 can be put to use as well.  A few caddis can be found, both tan and dark in size 18.  A small selection of grasshopper patterns comes in handy down here this time of year as well, especially if the wind picks up in the afternoon hours.  There are a few fish around and anglers looking for a day of trophy hunting can usually find a few to dance with if they’re willing to put in the time and mileage.

Canyon Country

This remains a great time to foray into the canyon sections of the Ranch, flows are great for getting flies into difficult lies and there’s plenty of fast, oxygenated water to keep trout happy.  It’s always hard to part ways from the dry/dropper “Chubberlegs” combo in here, but bringing along a few fast-sinking beadheads in a size 12 is generally a good idea.  We like the Rosa Pink, Blowtorch, and Red Tags.  Remember that weather sneaks up on you in here and packing extra layers in the boats is mandatory, as are a raft and a skilled oarsman.

Warm River to Ashton

This section may just be the most consistent piece of water when it comes to providing anglers with a fun day’s fishing.  Good action on small to medium-sized fish in a beautiful setting checks the box for many visiting anglers.  Indicator rigs, dry/dropper rigs, and streamers can all be employed successfully throughout the day.  Find your depth of water and stay with it.  Flies are about the same as those recommended for the Box Canyon, but throw in a few leeches and some streamers as well.

Below Ashton Reservoir

Though there are windows of opportunity to be found down here, they can be brief and risky in the absence of stormy weather.  Anglers will do better to focus on waters upstream, but keep an eye on water temperatures if they do foray into these lower reaches.  It doesn’t take much for temps to get back up to 70 degrees if the day is warm and devoid of clouds.  Most fishing will be subsurface with nymphs and streamers, but the odd trout can be taken on a terrestrial fished with patience. 

Good luck out there!!