Henry's Fork Fishing Report - September 4, 2025

Henry’s Fork Streamflows

Island Park Dam:  350 cfs

Ashton Dam:  990 cfs

St. Anthony:  936 cfs

Fall River:  371 cfs

Turbidity is present throughout the river on a highly variable basis.  For information regarding turbidity, check the Henry’s Fork Foundation’s River Conditions page.  Click on the “Water Quality” link, then select the monitoring station you’d like to view, selecting “turbidity” at the top of the chart for recent and current conditions.  The Foundation is working diligently to understand the complexities of the current situation, but at its core, this is a difficult water year and with a reservoir at 33%, there’s not much clear water upstream to work with.  Stay tuned for updates on current and future projects addressing this issue, the good folks at the Foundation are working hard to consider and develop long term solutions to this issue.

Labor Day has come and gone in Henry’s Fork country and we now enter one of our favorite time frames on this great river, autumn.  Already, we are seeing colors begin to change and frost on the pumpkin feels like a possibility any morning.  Fair weather is in the coming week’s forecast, trending towards more clouds and cooler as we clear the weekend.  This will be a good week to get out there before we’re dealing with the freezing mornings of mid-September.  Dry fly anglers will still have to put some time and miles in to find targets, but anglers targeting faster water sections with nymphs and streamers will find plenty of opportunity.

Box Canyon

At current flows, and likely for the rest of the season, the Box is going to be both a bumpy ride and a good place to spend a day’s trout fishing.  A check on turbidity at the dam should precede any full day’s commitment, but anything 10 NTUs and under should go well.  With the decrease in flows out of the reservoir, the clear water of the Buffalo river will do a better job of dilution as anglers get downstream of the confluence as it now makes up a larger percentage of total flow.  Indicator rigs will provide the most action, but dry/dropper rigs will be effective as well.  Streamers are an option as well, especially during periods of lower light.  Weeds are an issue, so check your flies frequently for hitchikers and choose your rig to keep your flies from hanging up on every cast.  Larger flies will still work, but they’ll catch and hold more weeds than smaller flies.  For nymphs:  PTs, R/L Tactical PTs, Split Case PMDs, red and brown Zebra Midges and Rednecks #14-18, black Zebra Midges #18-20, HP Caddis Pupa and Hare/Copper SH #14-18, Rubberlegs #8-12 and SJWs #12-14.  Streamers:  black BSA Boufaces, Olive and Copper Zonkers will generate some interest.

Railroad Ranch

The slow increase in activity continues, there are a few more rising fish out there, but not many as of yet.  We are holding out hope that mahogany duns will start in earnest and get some trout rising.  The forecast over the next seven days looks promising, especially as we get through the weekend and into next week.  Anglers should be prepared with a variety of offerings:  a variety of small spinners reflective of Tricos, PMDs, Baetis, and Pseudos #16-22; emergent PMDs like the Heames Klinkhammer, Harrop’s Captive Dun, and Lawson’s Halfback PMD.  Terrestrials should include hoppers, small flying ants, and honey ants, all are present in good numbers.  For mahoganies, we like the CDC Thorax Dun, CDC Biot Dun, Captive Dun, and a naked PT.  Mornings will be better than hot afternoons, generally, and anglers should be prepared to cover some ground in search of relatively few targets.

Canyon Country

The canyons of the Henry’s Fork will remain fishable for the next couple of weeks, and are great places to spend a day in periods of fair weather.  Low flows make the pockets more readable and accessible to flies, they also make for a longer float, so plan accordingly and bring extra water, layers, and some food!  Dry/droppers are our preferred rigs, a high viz Chubby Chernobyl with a Rubberlegs hanging below is a good place to start.  Larger beadhead nymphs #12-14 are a good choice as well if pickings are slim.  Streamers are a good option in here, we like a heavy fly on a floating line with 1X as tippet.  Having an indicator nymphing rig will come in handy to work the water more thoroughly when stopping and pulling over.

Warm River to Ashton

As the most consistently fishing stretch of the Henry’s Fork, this piece of water will be a good choice on most days for anglers looking for good action on small to mid-sized trout.  Dry/droppers, indicator nymphing rigs, and streamers will all produce results, so anglers can fish their preference and find some positive feedback.  Browns are on the move and a little more territorial than they were a couple of weeks ago, they can show up anywhere in the system, be prepared for a surprise if a big one ends up on the end of your line!  Refer to the Box Canyon recommendations for useful flies in here.

Below Ashton Dam

With fair weather, the lower river will reward persistent anglers in the mornings more than the afternoons.  Dry/dropper rigs and streamers are the most consistent methods currently.  Ditching the dropper and floating a hopper or other terrestrial can be a liberating experience and one worth trying.  We expect to see a slow ramping up of these lower sections over the course of the month as cooler weather becomes the norm, but good game will be found for those who look for it.  Nymphs should be reflective of small stoneflies #10-12, midges #18-20 and smaller mayflies #16-20.

Good luck out there!