Henry's Fork Report - August 8, 2024

Henry’s Fork Streamflows

Island Park Dam:  1020 cfs

Ashton Dam:  1780 cfs

St. Anthony:  974 cfs

Fall River:  237 cfs

Hot weather prevails in Henry’s Fork country and looks like it this trend will continue, interrupted by afternoon thundershowers and partly cloudy conditions.  Overall, water temps are holding up throughout the river upstream of Ashton Dam, and water quality is holding close to average for the time of year.  Flows out of Island Park are keeping up with irrigation demand and we don’t expect to see large fluctuations this week, looks like things should be relatively stable in that department.  Hot and sunny conditions on the Henry’s Fork make for good morning fishing excursions, but anglers will need to have a plan for the afternoons, either heading to faster, more oxygenated water, or areas of colder water inputs.

Box Canyon

No huge changes here from last week, flows are holding about the same and at a nice flow for fishing the Box Canyon.  Plenty of water coming through to help the trout feel comfortable and in a good feeding rhythm.  Water clarity coming out of the dam has been a bit off, but this mixes and moderates after the first major bend below the river and the section is fishable from top to bottom.  Dry/dropper, indicator nymph, and streamer rigs are all useful at the moment.  There are still a few golden stones around, but just enough to use one as the dry component of your dry/dropper rig.  A grasshopper pattern is a good choice as well, especially in the second half of the float.  At this time of year, we are often seeing small insects like midges, PMDs and caddis hatching in the morning hours, when imitating insects with your fly selections, keep the #16s and #18s handy.  This is an excellent time of year to throw a leech or SJW under an indicator as a point fly, with a small something or other tagged off, lots of leeches in the river and they seem to be active at this time of year, they make a tasty morsel for some of the Box’s larger trout.  For nymphs, we like PTs, R/L Tactical PTs, Split Cases, CDC Jig PTs, Red and Brown Zebra Midges 14-18; Two Bit Goldens, 101 Stones, Rubberlegs #6-10.  Perdigons like the Spanish Bullet, Bullet Quill, Olive Hot Spot, Frenchies, PMD Bombs, and Red Jig Napoleons  14-18 are all good choices as well.  We generally like heavy streamers on floating lines in there:  Olive/Black, White, and Black BFEs, Olive and White Bouface Leeches, and Olive, White and Copper Zonkers are all good choices.

Railroad Ranch

The Ranch has seen a slight picking up in bug activity with the stability in flows.  Keep in mind that even in the best of years, this time of year is characterized by sparse targets that show themselves infrequently.  This is always a challenging time of year to fish the Ranch, and anglers must be prepared to act on the infrequent visual clues that reveal where trout are located.  A single rise is now something to key in on, anglers may need to throw a cast over an area where they have seen a trout rise once or twice, and not necessarily wait for it to show itself a second time.  Considering that some of the trout are on the move, anglers should give generous leads to these sorts of targets and keep their drifts going long after the fly has passed over the zone of the last rise.  This can make for a difficult hook set with lots of extra line fed out over the course of the drift, but you will be surprised at how much line you can tighten by setting the hook with a low rod tip, sweeping it to the side, rather than raising the rod overhead to come tight.  This sort of fishing favors flies that trout will eat on the first pass or not at all, an assortment of terrestrials comes in handy.

A spattering of small spinners in the morning, with a chance of flying ants and a breezy afternoon that delivers grasshoppers to the water makes for a decent day out here, choose your days and your locations and let it play out, keeping a keen eye out for the telltale signs of feeding trout at all times.

Trout that are found outside of spring influenced waters will likely be on spinners, flying ants, or grasshoppers.  Trout that are found around cooler water inputs will be keying in on midges, PMD emergers, spinners, ants, and any other tricky semi-emergent fly you may have in your box.  Expect these trout in the cold water inputs to be techy and difficult, but engaging and fun.

Canyon Country

These remote canyon sections of the Fork will respond to the lower flows favorably, these sections are characterized by fast, roiling water that will be more easily penetrated by flies at current flows.  This water stays highly oxygenated even during the heat of the summer.  Dry/dropper rigs are the main choice here, it’s hard to beat the “Chubberlegs” combination, but streamers are an excellent option for those who prefer to target fewer, but larger trout.  Copper Zonkers, Black/Olive/White BFEs, and Bouface Leeches are all good bets, these are best fished on a floating line with 1X tippet.

Warm River to Ashton

Not much has changed down here in the last week, this section is still a good choice for anglers of all skill levels.  Indicator nymphing rigs can provide good action throughout the day on smaller fish, with a few larger surprises mixed in there.  Dry/dropper rigs fished in the transitions can be effective as well, with an occasional brown trout willing to look to the surface to take in a grasshopper pattern.  Streamer anglers will find some willing trout in the morning hours, often a larger fish or two will give it up and make it worth the effort.  Afternoon hours, in the absence of thundershowers, will generally favor the nymphing or single dry fly (terrestrials!) crowd.  The same flies that are being recommended for the Box Canyon will work wonders down here.

Below Ashton Reservoir

There is a little morning opportunity for anglers down here, but with lower flows and hot weather on the horizon, anglers should be looking for alternatives after the clock strikes noon.  It’s a good idea to keep a close eye on water temps down here, usually they will hit 70 degrees by midday and then it’s time to go somewhere else.