Henry's Fork Fishing Report - September 24, 2026

Henry’s Fork Streamflows

Island Park Dam:  241 cfs

Ashton Dam:  694 cfs

St. Anthony:  923 cfs

Fall River:  411 cfs

It’s definitely “Fall on the Fork” out there with some of the most beautiful days of the year happening right now.  Leaves are deep in change and the colors of autumn will be at their peak this week.  The river is low and getting lower and should reach its minimum flow for the rest of the fall in the coming days.  Clarity is improving with low flows and we are hoping for some fun fishing in the next couple of weeks and into October.  We are expecting a final drop in flows out of Island Park Reservoir to around 80 cfs in the coming days, and flows have dropped over 500 cfs since last Thursday.  Clarity will be pretty poor directly out of Island Park Dam but quickly diluting with clear water from the Buffalo and settling of sediment into the heavy weed growth as one moves through the first miles of river below the dam.  Keep an eye on the Henry’s Fork Foundation’s River Conditions site to keep an eye on turbidity at Island Park Dam and as it moves through Pinehaven and Marysville to have some perspective on clarity. 

Box Canyon

The Box should fish well this week, but things are going to get low in there at 80 cfs.  With the amount of weed life that is in the river at the moment there should be enough displacement to be able to get through but boats will have to be walked through some areas and pushed over rocks along the way.  A small raft isn't a terrible option.  Definitely not a half day’s endeavor and any anglers venturing in to float her waters should plan on making a day of it.  Fishing will get more concentrated in the deeper runs and this can be a good time to go in on foot with a wading staff in hand.  Turbidity is higher nearer the dam but the river will become more fishable downstream of the Buffalo River’s confluence.  Shallow nymphing rigs will be the most productive and you’ll need to keep your flies weed-free!  Flies should be small overall, imitating baetis and mahoganies, but a full selection might include:  unweighted PTs, red and brown Zebra Midges, Split Case PMDs, Rednecks #16-20 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.

Railroad Ranch

The Ranch has had a tough week with high expectations fueled by many years of great September fishing, conditions have been difficult with high water and turbid flows.  Recent decreases have improved the quality of water, especially in the last two days.  Mahogany duns, baetis and pseudos are around and as the water situation stabilizes more trout will be out there eating them.  Expect spooky conditions with low flows and lots of exposed weed beds, using the weed beds to break up the wake of your approach can be a useful tactic.  This is usually a fun time of year for target shooting on the Ranch, plenty of trout can be found rising, and there is always the ability to focus on hunting a large target.  Things are just getting going out there, so keep an eye on conditions for good opportunities, cloudy days will be better than sunny ones!  We recommend having a variety of small spinners, a good selection of baetis emergers and duns, a variety of Mahogany patterns ranging from emergers to spinners, some terrestrials for the occasional warm day (small hoppers and ants), and even a few small dark caddis for the odd occasion that they’re around.  It’s worth taking a walk out there if flows have been stable for over 24 hours, remember, we have one more big drop coming.

Canyon Country

The canyons are on their last opportunities for the season, these sections become more difficult and time consuming to navigate but will fish well in the low flows of fall.  Floating in here will be an all day affair and will be best on days with fair weather.  Hi-viz dry flies with fast-sinking droppers are about all you’ll need for a good time in here as long as you have the layers you need to stay warm if Mother Nature rears her head with some unexpected weather!  Solid oarsmanship and a rubber raft are a must in here.

Warm River to Ashton

This section of the Fork has been the most consistent piece of Henry’s all year.  Good action on small to medium sized fish makes for a fun day of trout fishing for most anglers.  For those wanting to try and target a larger one, streamers can come into play fished on a variety of sink tips.  Fly selection should be about the same as that for the Box Canyon, but be sure to add in some BSA Boufaces, BFEs and a variety of other streamers.

Below Ashton Reservoir

The lower river has been fishing well in the past week with mostly subsurface opportunities, either streamers or nymphs.  Cloudy and cool weather will bring around more dry fly activity in the way of baetis, pseudos and mahogany duns.  Hopper/dropper rigs can come into play for shallow nymphing rigs during other periods and indicators will still come in handy as well.  Low flows are going to make things weedy and spooky out there, so be cautious in your approach for greater success.

Good luck out there, enjoy!!