Henry's Fork Report - August 31, 2023

Henry’s Fork Streamflows

Island Park Dam:  594 cfs

Ashton Dam:  1300 cfs

St. Anthony:  849 cfs

Fall River:  355 cfs

Anglers on the Henry’s Fork are being treated to an August with unsettled weather and unpredictable opportunities, and the forecast through Labor Day weekend looks to bring some cloudy weather and cooler temperatures.  Adjusting to the opportunities the day provides will help you maximize your success out there.  Keeping an eye out for insects on the water will guide you in fly selection and approach.  Water clarity is changing depending on the day, but turbidity has generally increased out of Island Park Reservoir, and is not as noticeable in the Ranch and below.  The Henry’s Fork Foundation has some great real-time turbidity information on their website www.henrysfork.org that is helpful for keeping an eye on things when planning your day.

Box Canyon

The Box has continued to put smiles on anglers’ faces out there, providing them with good action and beautiful scenery.  Water clarity is getting worse in here, but it seems to moderate about a mile down.  Keep an eye on the weather and the bugs you see to guide your fly selections here.  Baetis are present and likely to be around more consistently with the upcoming forecast in mind.  Midges are more difficult to observe at times, but are generally present in the mornings as well as active at various times throughout the day.  Current flows keep it sporty for rowing out there, plenty of boulders to avoid, but the canyon’s waters are more easily read and its runs more easily plied with rigs of lesser weight.  For indicator nymphing, it’s helpful to rotate between BB, B and no shot at all depending on the depth of the water you’re fishing.  We are liking the following patterns down there at this moment, but there is room for experimentation and exploration:   PTs, Tactical R/L PTs, Split Back PMD 14-18, Rubberlegs and 101 stonefly nymphs 8-12, olive Hungarian Partidge Caddis Pupa 14-16, red and brown Zebra Midges 14-18, as well as your favorite perdigons (Jake’s SH, Tungsten Jig PMD, Juju Baetis, Olive Hot Spot, Bullet Quill, Spanish Bullet, Redneck and Frenchie 14-18).

Railroad Ranch

The Ranch has been fishing well, overall, but remains a day to day affair.  Yesterday’s successful fishing does not necessarily relate to today’s.  Keep a keen eye on the bugs out there, this will help and give you clues as to the opportunity you can target.  Rising trout can be hard to come by and sparsely rising when you do.  It’s a good idea to be prepared to make a cast to a single riseform, the quicker and more efficiently this can be accomplished, the greater your chance of success.  Spinner eating trout are generally more steady targets, while those eating the occasional ant or hopper can be just as willing to take a fly but give little clue as to their whereabouts in between sparse rises.  We are seeing small baetis, pseudos, occasional caddis, flying ants, hoppers and even some mahogany duns out there.  Generally looking for a spinner fall in the mornings, followed by some activity reflecting the insect activity that the day’s weather provides.  A well-prepared angler will have a good selection of spinners in rusty and yellow in 14-20 (we like the Copenhaver and Harrop’s Paraspinner), a handful of brown caddis 14-18, some flying ants 14-18 (Harrop and Heames’ Honey Ants, Shimazaki are all good ones), a handful of different hopper patterns 6-10, CDC Biot Duns in PMD 14-18 as well as Mahogany 14-16, and some Mahogany Thorax patterns 14-16.  A few gray drake duns out there as well, nice to have an imitation or two in a size 12.

Canyon Country

The canyons remain a good place to spend a day in search of some solitude and entertaining trout fishing with the possibility of a larger trout.  Dry/dropper rigs with rubberlegs stoneflies or quick-sinking nymphs 12-14 are still the most reliable choice, but it doesn’t take long to reach for the streamer rod when things are overcast.  Bring warm and dry layers on any excursion down here, getting stuck in inclement weather while deep in the canyon country is no fun if you don’t have the right gear.  Inflatable rafts are the safest watercraft choice down here.

Warm River to Ashton

Solid forecast this week for continued fun down in the reach above Ashton Reservoir, water temps are cool and the trout are generally active and hungry down here for most of the day.  This is a great time of year to consider ditching the indicator rigs for half the day in order to try and target a larger trout on a streamer or grasshopper pattern.  There is water enough down here to experiment with sink tips as well as the standard floating lines while stripping streamers.  Indicator rigs will do well to reflect the recommendations for the Box Canyon.

Below Ashton Reservoir

The lower river has been a day to day affair, depending on what the weather serves you up.  Cloudy weather is preferable, but a warm and sunny day can bring the terrestrials back to life.  Variable weather will keep water temps in better shape overall and keep it interesting down there.  Not a lot of bugs on the lower river yet, but cloudy days in the forecast bring baetis to mind.  This will likely still be a week of some nymphing and streamer opportunity but limited in the dry fly realm. 

Good luck out there and have fun!