South Fork & Henry's Fork Fishing Reports

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Fishing Reports

Jimmy's All Seasons Angler / Fishing Reports (Page 2)

Main Stem Snake River, March 20th, 2021

The flow out of American Falls Dam was raised from 370 cfs to 1250 cfs on 3/18. That means you’d better hurry if you want to fish the river below with relatively easy access! Wading is still safe, but more flow increases are coming making wading tougher and spreading fish throughout the river. Streamers pitched and retrieved or drifted under an indicator at taking depth remain as effective strategies.


Main Stem Snake River, March 13th, 2021

Flow out of American Falls Dam remains just under 400 cfs, but any day a BIG increase will happen to satisfy Magic Valley agricultural demands. Streamer presentation remains the name of the game. The further downstream from the dam one goes, the fewer anglers will be encountered.


Henry’s Fork, March 13th, 2021

Midge and BWO activities are bringing fly fishers to locations from Ora Bridge downstream to the Fun Farm Bridge area.  Use life cycle patterns for each activity.  Presenting streamer and woolly bugger patterns is effective for encountering post spawning rainbows. Some rainbow spawning remains, so avoid  places where such is ongoing. Stream flow in this area is near normal.


South Fork, March 13th, 2021

Here’s a bit of info if you are considering a float trip during this beautiful weekend.  The Conant boat ramp has enough snow to make getting to the river a bit difficult.  Kitty litter,  tow rope, and shovels may be in order. Other than that, flow out of the dam remains around 900 cfs increasing on downstream to around 1300 cfs at Heise. Water is ultra cold and clear with midges emerging best in backwaters and calm channels. Rubber legs, streamers, etc., best bet for encountering bigger fish. Nymphs with and without beads give best results around riffles.


Today at Jimmy’s March 9th, 2021

It’s Just Around the Corner

We bet you’ve heard the words in the above title a time or two recently! Also, it’s been a windy winter, both politically and seasonally.  But within a matter of days we will advance into springtime. Expect the usual transition weather period which varies yearly.  But with increasing daylight hours and warmth, fly fishing will come out of essential hibernation for most of us.  True, a few hearty souls braved winters extremes to be on the water, but “Just Around the Corner” is that for which most of us have been waiting.  If you are new to the area, here is an overview of what to expect as the season progresses, if you are a long-time resident, what you have been anticipating is about to arrive.

It begins with midge activity on streams that remain open year-round and those for which the catch and release season applies. It’s mainly limited to lowland water because most higher elevation waters remain snow bound or iced over and secondary roads are yet to open. As daytime lengthen and atmosphere warms, blue wing olive (BWO) and March brown mayflies begin to appear. Streamers become effective in fooling post spawning cutthroat and rainbow trout. Caddis at lower elevation waters begin working their maturing way up the rivers in increasing number to be important salmonid food through the season.  When mid-May arrives major fly fishing events begin. Back country roads begin to open to allow access to an expanded variety of waters including low land still waters.

Now happenings resembling a series of gold rushes begin.  First comes the Henry’s Fork giant and golden stone fly events. Waders and boaters converge to follow “the hatch” up the river from mid May into mid-June. But that is not the only premier angling event happening. Ice usually leaves Henry’s Lake in late May, but Old Man Winter not always cooperates. Cool springtime waters make for excellent fishing on lakes and reservoirs. In mid-May the Montana general season opens. The Yellowstone Park season opens to feature Firehole River fly fishing. So begins the “high season“ for area fly fishing retailers. As the Henry’s Fork stone fly event dwindles, another massive event, the Henry’s Fork mayfly emergence begins. From all corners of the earth fly-fishers converge on the middle river and Island Park to enjoy salmonid responses to drake mayflies, PMDs, BWOs, flavs and types of lesser renown.  Some visiting fly-fishers bring accents of and attempts at the English language that confound understanding. Run-off declines in such as the Teton River drainage, South Fork and Salt River tributaries and still waters attract fly-fishers with damselfly and the beginning of season-long speckled dun activity. Stone fly activity begins on these streams as waters clear and warm. It is the turn for the South Fork and Teton River stone fly events by early July, and the same on the Madison River works its way upstream extending the “high season.”  It continues into July as the South Fork drainage mayfly event expands to last into early autumn and terrestrial insects join caddis flies, mayflies and stone flies as a major salmonid food form on all streams. By now social turmoil on so many waters, much added by floating recreationists, drives many fly-fishers to seek solitude and tranquility. Some turn to lightweight equipment and seek small waters to find these conditions as all secondary roads are open. Fall River Basin in the SW corner of Yellowstone Park, Southwest Montana waters, Big Lost River Copper Basin waters, upper Blackfoot, and Teton River drainages offer relief from icon water crowds (Go to the Articles section of our website to find strategy and character details on many of these waters: so many of them offer more than solitude and tranquility). The August gulper phenomenon takes place on not just Hebgen Lake, but on many of our still waters, and fly fishing success on streams begins to dwindle if one is not equipped to present terrestrial insect patterns.

Late August and September are likely the most pleasant times to be on the water in our area. Insect pests have much diminished, air temperatures have mellowed, most visiting fly-fishers have departed for jobs, school, or family obligations.  Fall colors make carrying a camera a good idea. The fall peak of mayfly activity takes over with early-in-the-day tricos, BWOs, and on some waters the mahogany dun. Early September is a good time to enjoy quality Wyoming waters such as Flat Creek, the Grays, Gros Ventre, and Salt Rivers. By October frosts work their way down in elevation and begin the end of the dry fly season excepting for the hardy midge and BWO activity. Killing frosts will soon dampen terrestrial insect populations to further decrease dry fly fishing.  However, the cooling waters return streamer fishing to its early spring effectiveness as brown trout begin spawning migrations on all waters they occupy.  Presentation particulars  overwhelm pattern selection during these times. Low light and unsettled weather offer the best success opportunities whether the South Fork, Henry’s Fork, main stem Snake River, Lewis, Madison and Beaverhead Rivers and Silver Creek are targeted. But those cooling mornings and chilling breezes suggest that again Old Man Winter is arriving re-establish ice in the guides and reels and to push so many fly-fishers back inside to savor the season that was.

Idaho Falls is the Greater Yellowstone Area’s southwest fly-fishing hub. The town is surrounded by quality waters, still or moving, large or small, and the town offers all services in quality to fly-fishers.  We at Jimmy’s All Seasons Angler feel duty bound to capture information that impacts all forms of fly-fishing on area waters throughout the season and relate such to you to help choose which to enjoy at any time. We offer quality fly-fishing items, Idaho, Montana and Yellowstone Park fishing licenses, we maintain our web site fishing report as up to date as possible, and we offer instant information to those visiting Jimmy’s or making email or telecommunication inquiries.

Bruce and the All Seasons Angler Crew


South Fork, March 6th, 2021


March South Fork

It’s been a long cold winter on the river, but here are a few things worth some words. First, the flow from Palisades Dam has been near consistent at around 900 cfs all winter. Downstream because of tributary contribution flow increases to around 1300 cfs near Heise.  Flow decreases somewhat downstream to the Henry’s Fork confluence. Midge activity seems to be increasing and will continue to do so as we warm up.  Activity can be particularly good were spring water enters.  Rubber legs patterns have been the best “go to” fly. Try them in traditional black , brown, olive, or tan (#4-8, all colors). Present these to run deep at the top of holes and runs drifting deep with an end-of-the-drift swing upward through the water column.  The best access is around the Heise bridge and there are some such points on downstream.

Stay warm, and wade carefully. The water is awfully cold!


Main Stem Snake River, March 2nd, 2021

Before flows increase, consider a trip to fish the Snake River below American Falls Dam where streamer presentation (cast and retrieve or drift under an indicator) is producing. Currently the reservoir is about 85 % full. The flow in the river below is somewhat under 400 cfs. This makes it easy to see all sub-surface features that can be dangerous to wading and it concentrates resident fish. However when irrigation begins in the Magic Valley, flows out of the dam will increase many times to satisfy water demands.  Now that we are in March, the increased flow could happen any time. We will keep track of how flows change here and give such information on this report to help you decide if a visit below the dam to fish is more or less an option.


Small Streams ( Blackfoot River in particular), February 16th, 2021

Remember the  song “The Old Gray Mare, She Ain’t What She To Be?” Sadly, that title applies to fly fishing on the upper Blackfoot River.  Go back six to seven decades, and the run-up of Yellowstone cutthroat trout from the reservoir to spawn in and to inhabit the river was unbelievable in number and size of fish.  The fishing was phenomenal! But the accumulated effects of several happenings have reduced fishing in the upper river to a state that could be described as OK.  Mining, grazing, each a legitimate form of human activity, reservoir water management, creel rates being too liberal, and an influx of birds of preys all contributed to make the demise.  Nevertheless the river remains a major Yellowstone cutthroat trout stronghold. Fisheries managers, land owners, concerned fly fishers, and private individuals observed this decline and began an effort to bring back a good share of the river’s ability to host more cutthroat trout.  As a result an exemplary piece of cooperation from land owners, mining companies, agency folks, Trout Unlimited, Idaho Conservation League and other organizations are combining to turn things around.

Check out the video link below to observe what is going on and who is involved to bring back a good share of the mid twentieth century quality to the upper river and to show what people who care can combine to accomplish.  In this case it is to retain and improve the habitat for a unique part of the Rocky Mountain fauna, the Yellowstone cutthroat trout.


Henry’s Fork, February 9th, 2021

Are you interested in doing a trip to fish the upper Henry’s Fork and drainage during the upcoming season? Would seeing how snow and water conditions appear to be stacking up to help in planning? The information Dr. Rob VanKirk compiles may help. Rob’s analyses, and reports on water and snow conditions is as good as it gets.   Below is Rob’s latest update.

Henry’s Fork Water Supply, Feb 09 2021


  • After a dry day, water-year precipitation is 84% of average, and SWE is 85% of average.
  • Island Park Reservoir gained 112 ac-ft yesterday, typical of fill on recent dry days.
  • The reservoir is 87% full, compared with 75% full on average.
  • Weather forecasts continue to lean more toward wetter, warmer conditions and away from the extreme cold forecast last week.


At 6 degrees F below average, yesterday was the coldest in 13 days. Only a trace of precipitation was recorded, leaving the water-year total at 84% of average. Snow water equivalent (SWE) dropped a percentage point to 85% of average. After declining steadily since last July, the three-year average watershed precipitation appears to have bottomed out in the past two weeks and should increase a bit over the next few weeks, if precipitation forecasts prove to be accurate. This index of long-term watershed conditions is just a hair above average right now.


Forecasts are still uncertain about the details of weather over the next week but continue to gain confidence in warmer, wetter conditions than were forecast last week. Very cold air is expected to stay just on the other side of the Continental Divide, leaving us on the warm, wet side. “Warm” is relative, as temperatures are likely to be near average for the next week, a few degrees colder than last week. Regardless of temperature, snow is certain on Thursday and Friday and likely again early next week. The 7-day forecast calls for 0.25 inch across the lower elevations and up to 3 inches at the southern end of the Teton Range. As was the case last week, precipitation will favor the southeastern corner of the watershed. If forecast amounts materialize, SWE in Fall River and Teton River subwatersheds will improve to 90-92% of average by this time next week. SWE in the upper Henry’s Fork will remain at or below 80% of average.


Island Park Reservoir gained 112 ac-ft yesterday, typical of fill rate on dry days. The reservoir is 87% full, compared with 75% full on average. The reservoir will reach the April-1 target of 120,000 ac-ft around March 1.



  • Watershed three-year precipitation average
  • Island Park Reservoir inflow/outflow: 15-minute data
  • Island Park Reservoir volume: 15-minute data
  • Island Park Reservoir volume: predicted vs. observed


Station guide and disclaimer

Glossary of Terms


Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-652-3567 OFFICE

208-881-3407 CELL

208-652-3568 FAX


[email protected]

Rob’s blog