Henry's Fork Report - August 22, 2024

Henry’s Fork Streamflows

Island Park Dam:  579 cfs

Ashton Dam:  1400 cfs

St. Anthony:  910 cfs

Fall River:  334 cfs

The Henry’s Fork is a changing system at the moment, with irrigation demand decreasing, we’ve seen a stepping down of flows every couple of days out of Island Park Reservoir with mixed bag of resultant opportunity, with flow changes slowing fishing in some areas and slowly increasing activity in others.  Weeds are an increasing presence these next weeks, especially as we have cold nights in the forecast with warm days, this will generate more drifting weeds, anglers will do well to find a way to deal with them without having to bring their flies to hand after every drift.

Box Canyon

The Box is a much bumpier ride than it was last week and will likely continue this trend, albeit at a slower rate of decrease than we’ve been seeing (hopefully).  The flow changes of -100 cfs seem to affect the otherwise relatively stable fishing in there.  We expect to see this week stabilize a bit and fishing to be productive in here.  At current flows, the Box is a great place to spend a quality day’s fishing with attention to technique.  Bugs are getting smaller and the trout aren’t moving as far for them, resulting in subtle visual cues transmitted to strike indicators, be prepared to set the hook at the slightest hesitation and check your flies for bits of weeds often.  In the heavier runs, we like to adjust our split shot, often using a B shot or even a BB in the fast and deep stuff.  In the more shallow, weedy areas, get rid of the split shot and fish the nymphs with their natural weight, this will reduce the number of weeds you hook and ultimately keep your flies in front of more fish.  6’ from indicator to point fly should be enough in here in most cases.  Patterns are getting smaller and should resemble baetis, PMDs, caddis and midges.  Larger food items present are stonefly nymphs, leeches and baitfish resembling small whitefish, rainbow trout, and sculpins.  We like to keep our boxes full with Rubberlegs #6-10, Bouface Leeches #10, SJWs #10-12;  PTs, Tactical R/L PTs, Micro Mays, Red and Brown Zebra Midges #16-18, HP Caddis Pupa, Hare/Copper, Soft Hackles #16-18.  Perdigons are a great addition and we still like the Olive Hot Spot, Bullet Quill, Spanish Bullet, Red Jig Napoleons, Frenchies, and Duracells #16-18. 

Railroad Ranch

The activity in here remains day to day, but we are seeing a slow increase in the number of targets out there, most activity is occurring in the morning hours and it has generally been sparse, so be prepared to cover some ground when in search of rising trout.  We have been seeing honey ants and their associated counterparts, little black winged ants as well as tricos, callibaetis, caddis, and PMDs.  Caddis are present in the mornings, during periods of stormy weather, and in the evenings, but are small in size and number.  Tricos are around, but there haven’t been many fish eating them, callibaetis are sparse but a solid food source.  PMDs have been spotty and respond to the cloudy weather, you’ll want to be prepared with a variety of flies that match size and all life stages when targeting fish feeding on them, these will be some of the more technical targets of the year.  There are plenty of terrestrials around, so be thinking of throwing a few hopper and beetle patterns into your fly boxes.  We like to see boxes stocked with some of the following flies for success down there:  Harrop’s Paraspinner and Copenhaver spinners in rusty, cream, and black #16-20, Harrop’s and Heames’ Honey Ants #14-16, Shimazaki Black Ant #18-20, Half Back, Heames PMD Klinkhammer, Harrop’s CDC Biot Dun, Last Chance Cripple #16-18.  It wouldn’t be a bad idea to make sure you have a handful of mahogany duns should we begin to see some early hatches this week as the air and water temperatures cool down.  Baetis patterns are a good addition as well during stormy periods.  Exposed weed banks can be a bother when it comes to landing fish and getting good drifts, but they can be an advantage to anglers who use them to conceal their approach, as they break up the wakes we transmit when wading.  Use them to your advantage!

Canyon Country

This remains a great time of year to head into the canyons of the Henry’s Fork, where anglers can find some solitude and generally fun fishing.  With the decrease in flows, rafts are the watercraft of choice, and much of the water is now reachable with flies.  A dry/dropper is a great rig down here on most days, but don’t be shy about tying on a heavy streamer, fishing it creatively by dead drifting and stripping to keep it off of the rocks, large trout inhabit these sections and anglers who find them more frequently are hunting them with fly rigs that both reach and entice them.  Keep an eye on the weather forecast, being stuck in these sections during a heavy storm isn’t as fun as being in there on a warm summer day.

Warm River to Ashton

Lots of fun still being had down here on generally smaller trout, but with some larger surprises mixed in there.  Indicator rigs armed with the nymphs that reflect those recommendations for the Box Canyon will be successful here, but anglers wishing to explore their more creative side can play with grasshopper patterns and streamer rigs.  Brown trout are beginning to color up and get more territorial, the possibility of tangling with large trout is real on any excursion down here.

Below Ashton Reservoir

Though there are a handful of anglers fishing down here these days, the action is sparse with terrestrial flies and generally flattens out in the afternoons.  Please keep a close eye on water temperatures down here, when the mercury in your stream thermometer hits 70 degrees, it’s a good time to wind up and head somewhere else.  Streamers are an option in the morning hours as well.  We’re a few weeks away from a major shift in the seasonal pattern down here.

Have fun out there and good luck!