Henry’s Fork Fishing Report- September 17, 2026

Henry’s Fork Streamflows as of 9/16/26 8:00pm

Island Park Dam:  1150 cfs

Ashton Dam:  1620 cfs

St. Anthony:  1730 cfs

Fall River:  417 cfs

The middle of September in Henry’s Fork country always brings transition with it; the signs of fall are setting in but the last days of summer are holding on and the fishing falls somewhere in the middle, depending on which conditions prevail.  Lately, beautiful weather and sunny conditions have dominated but cloudy weather is on the way.  Not only is the weather in a state of flux, but the flows on the Fork are about to start changing as well.  Expect decreasing flows over the next part of this week and improving water conditions along with it.  Remember that this time of year, the Henry’s Fork Foundation’s Water Quality site is a terrific reference for conditions, especially turbidity.

Box Canyon

The Box has been running high and off color this past week and fishing opportunities have been pretty slim.  We expect this to change for the better once flows decrease over the next few days.  Changing flows can be disruptive to good fishing, but by Sunday we should see things start to improve over here.  Flows will be low, so anglers should expect weedy conditions and a bumpy ride, it’s best to take your time in the Canyon during these periods.  Indicator nymphing will be the most successful, but streamer fishing can be a worthy endeavor as well.  For fly selection, we’re liking 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.  For streamers, we generally like black and olive or a combination of the two, but a copper Zonker is an old time favorite as well.  Try a BFE or BSA Bouface to get things started.

Railroad Ranch

Things have been pretty sleepy on the Ranch lately, with high flows and turbid water prevailing.  Sunny weather has kept hatches to a minimum.  We are hopeful that the changes in the next few days will improve fishing conditions.  Now is a great time to be on the lookout for mahogany duns, baetis, pseudos and even the odd flying ant or grasshopper.  Mahoganies should drive the bite with larger trout, baetis and small spinners can keep them rising when the bigger bugs begin to fade.  A well-stocked Ranch box includes the following at the moment:  Harrop’s and Heames’ Honey Ants, Shimazaki Black Ant, a range of small spinners like Paraspinners and Copenhaver spinners, CDC thorax Mahogany, CDC Biot Dun Mahogany and Quigley’s Flag Dun BWO. 

Canyon Country

The canyons have been running high lately, but should benefit from the decreasing flows over the next few days.  Generally, these sections fish well in the fall with sunny weather and low flows, conditions that should be in place by early next week.  Streamers and dry/droppers will offer the most success, it’s hard to beat a Chubby Chernobyl and a large perdigon or stonefly varietal dropped off.  We especially like Rubberlegs, 101 Stones, Two Bit Stones, Firestarter and Roza Pinks #8-14.

Warm River to Ashton

This section has been a safe bet for a quality day’s fishing with decent action on small to medium sized trout, and should remain so for at least a couple more weeks.  Indicator rigs are the most reliable rig, but dry/droppers and streamers shouldn’t be overlooked.  Brown trout are moving around in the system and can show up unexpectedly, streamers are a good way to search for them this time of year.  The diversity of water types in this section makes it ideal for experimenting with different sink tips and lines.  Nymphs should be similar to those recommended for the Box Canyon and for streamers your imagination can run a bit.  We like BFEs, Goldielocks, Bangtails, Sparkle Minnows, Thin Mints and BSA Boufaces.

Below Ashton Reservoir

The lower Henry’s Fork is slowly springing back into action, with a few more trout eating each day.  Most fishing is subsurface at the moment, but cloudy weather in the near future holds the promise of rising trout.  Anglers should be ready with a variety of baetis and Mahogany patterns, we like to have Flag Duns, CDC Thorax Mahoganies, and Purple Hazes on hand.  A few hoppers can come in handy and nymphs should include small rubberlegs #8-12 and mayfly patterns #16-20.

Good luck out there!!