by | Sep 9, 2021 | 0 comments

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September is one of those months that we really love around here. How can you not love migratory trout, BWOs, Mahogany mayflies on the Ranch, Hoppers on the Madison, flying ants on Hebgen, Aspen leaves changing colors, the sound of flushing grouse and the smell of a spent shotgun shell? Over the next five weeks all of these wonderful things only get better! Daytime highs have been in the high 70’s all week with mostly sunny skies, summer even return for a could days this past week. Morning temps are a bit chilly and sitting in the low 30’s. The weekend outlook is for overcast skies, a solid chance of rain, rising fish and streamer eaters.

Swing season is right on our doorstep, and for those who enjoy the Spey game or want to learn more about this fun way to fish, we still have some spots available at our West Yellowstone Trout Spey Days event in the evening of Friday Sept. 24 and all day on the water on Saturday Sept. 25th. We have an awesome lineup of presenters this year that includes legends like Simon Gawesworth, Ed Ward, Eric Neufeld, and our own Matt Klara. Head on over to the EVENT WEBSITE for all the details and give us a call at the shop to get signed up for this limited access event.
If you’re coming through the area and would a like tour of the Golden Stone Inn, please stop by the shop and let us know. The fire pits are glowing and waiting for you and your buddies to settle in and reminisce.

Big Sky Anglers is OPEN from 7am to 9pm seven days a week. Remember, the freshest fishing report is found at the counter of our fly shop. Our shop staff and guides are out daily all across the Greater Yellowstone Area. Our fly shop remains a clean and healthy environment for both our customers and staff members. Stop on by, say hello, and we’ll get you taken care of. Most importantly, stay safe, stay healthy, and enjoy your time outside.

Take care and fish on,
~ Joe, Justin, Jonathan, and the BSA Crew


Henry’s Fork Streamflows

Island Park Dam:  375 cfs

Ashton Dam:  1070 cfs

St Anthony:  974 cfs

Indian summer days are ahead of us on the Henry’s Fork for the next week, it seems.  These are truly some of the most beautiful days to be on this river, leaves are beginning to change and the angle of the afternoon seems to enhance the visuals.  Crisp mornings and warm afternoons make up a mid-September day around here.  Fall is in the air, reminding us to enjoy these summery days while we still have them, colder temps will be here sooner than you think!  This is a great time of year on the Henry’s Fork, lots of good fishing to be had.

On the upper river, the Box Canyon is as pleasurable a place to spend the day as anywhere, flows are low enough that a variety of rigs can be used with success and the water more easily read.  At 375 it is a little bumpy in places for floating, but nothing that can’t be navigated with some care.  Small beadheads:  perdigons, zebra midges (red, brown and black), PT nymphs, and micro mayflies in 16-18.  The BSA Olive caddis pupa in a 14 is a solid choice any day.  Now is a good time to try a rubberlegs nymph or a streamer as well, we like black for the rubberlegs and olive, black or natural streamers like the BFE, Sheila Sculpin, BSA Bouface and zonkers.

The Railroad Ranch section in Harriman State Park has been fishing well lately, with good hatches of a variety of insects.  It seems each day has a different flavor, but you’ll want to make sure you have along a variety of the following bugs:  tricos, callibaetis, PMDs, baetis, mahoganies, and flying ants.  A few hoppers for a windy afternoon are a must, you’ll see the odd explosion in the distance that you should cover with a long drift.  Good fishing can be found at the moment from top to bottom of this section.

The canyon country below the Ranch has had some great and entertaining fishing lately.  These are incredible days to enjoy floats below Riverside CG and below Mesa Falls.  The scenery is stunning and the dry/dropper fishing active and fun for a variety of sizes of trout.  Streamer fishing is an excellent option in here on any day this month and always worth a try.  Hard to beat a chubby Chernobyl to a rubberlegs dropper in here…

The river below the confluence of the Warm River has lots of great opportunity as well, dry/dropper and streamer rigs are the main event here, but running a hopper as a single fly on a warm afternoon is a great way to poke around for the odd brown trout.  

Below Ashton Reservoir will liven up as the month progresses.  Decent fishing can be found in the mornings, afternoons will be a wild card until the weather turns.  

Good luck out there!


Forecasts show a chance of showers and thunderstorms from Friday through Monday of this upcoming week. A change in weather is always welcome this time of year, as it pushes the dial from late summer to the beginning of Autumn, and jump starts fall fishing.
Expect to see hatches of small (size #22) fall baetis on any overcast or stormy afternoon. If we are especially lucky, we might even get a small bump of fresh migratory fish out of Hebgen Lake into the Madison River in YNP.

As we continue the slow transition from summer to fall in Yellowstone Country it’s important to be prepared for a wide range of hatches and fishing situations. There is still plenty of terrestrial season left ahead. So, be sure to have a good supply of hoppers and flying ants. But, the first fall hatches of baetis, drake, and heptagenia mayflies have begun, and no one fishing the park should be without some or all of their dun and emerger imitations – especially on overcast or stormy days. 

Northeast Corner – Slough Cr, Lamar River, Soda Butte Cr
Any significant rain will undoubtedly bring some color to Soda Butte Cr and the Lamar River this weekend. Keep a close eye on the flow charts, and check with the shop for the latest report on conditions.

Flying ant flights, and fall hatches of baetis and drake mayflies have produced some fun dry fly fishing on Slough, Lamar and Soda Butte.
Anyone heading to the Cutthroat Corner should not go without a good supply of JoJo’s Royal Ant, and JoJo’s Drake Mackerel.

Yellowstone River
As we have experienced all summer, flows on the upper-caldera stretch remain quite low. Many fish have returned back to Yellowstone Lake earlier than usual, but there are still a few quality Yellowstone Cutthroat remaining in the river. If you go, expect to cover a lot of ground hunting for these choice fish, and don’t waste your time fishing without a target. This is a spot-and-stalk situation requiring plenty of stealth and a good presentation. 

Late-August and early-September are an interesting time on this water as several mayfly hatches can be found, and they can be quite heavy at times, especially in the sections from Sulphur Caldron upstream to Cascade Picnic Area. Light olive-colored mayflies in size 16-18 can be found here from late-morning to early-afternoon. Of note with these particular hatches is the fondness that fish have for the nymphs near or at the water’s surface.

Gallatin River
Don’t be in a hurry to get to the Gallatin in the park as the mornings have been downright cold. But, by late morning, and through the afternoon expect to see consistent nymph fishing, and the occasional fish looking up for a flying ant, or small mayfly. 

Firehole River
It’s time to add the “strangest trout stream on earth” back to the Yellowstone fishing roster. Water temps have improved, and are consistently cool above Midway Geyser Basin.

If we see some scuzzy weather this weekend, the Firehole will produce the first significant hatches of fall baetis. In lieu of scuzzy weather, flying ants, small hoppers, and small soft hackles swung through the riffles and runs will produce well.


The flows at Hebgen Dam bumped this past week and we are now sitting at 844 CFS out of Hebgen Dam, 930 at Kirby and 983 CFS at Varney Bridge. River temps have cooled off and start at 54 degrees and fluctuate about ten degrees throughout the day. In general, the cooler mornings will offer a slower start to the day for dry fly fishing but nymphing or streamer fishing is a great option out of the gates. Longer floats are getting more difficult as the river is low and if the north wind gets to blowing, it really slows you down.

Wade Stretch: Small dark caddis are skittering around the upper river, a peacock PMX is a great fly to poke around with. Efficiently covering the skinny water and slicks and moving on after a handful of cast should yield a rise here and there. BWO’s have been seen on the cloudy overcast days, but don’t over look them on the sunny days either. You really shouldn’t go to the river without hoppers and ants! Jojo’s Royal Ant is the ant of choice (there are two other colors as well) but we also carry Arrick’s Flying Ant and Hoovie’s Ant in our boxes. Our Lighting Legs Hopper is proving to be a winner behind the Morrish Hopper in all sizes and colors. Rhyacophila caddis are in the drift most days right now. Check your boots for these little olive larva as they like to cling. Nymphing with rubber legs, #14-18 BH pheasant tails, golden stone nymphs, perdigons, prince nymphs, Cheeky fella(caddis larva), olive serendipities, zebras, and crystal dips have been effective in the deeper runs or fish them shallow around the bars and drop off near the banks. The over cast weather over the weekend should make for happy trout!

Float Stretch: Nymphing from the boat, especially in the cooler morning hours or throughout the day when the weather is nasty, is a great option with fish eating rubber legs, scuplins, zonkers, olive hare’s ears, cheeky fella, PT’s, Shop Vacs, guide dips and various Perdigons. As for the dry flies – Purple Chubbies, Lightning Legs Hopper, M’s hopper or a #12 Jojo’s Ant, Jojo’s Chubinator are great choices. When rolling the middle of the river, danglin’ a tungsten bead under the Hopper will produce. Let your drift roll and keep the fly on the river where it can get eaten. The streamer bite in the morning hours is always a good idea and if it stays cloudy, keep stripping. We love olive and black this time of the year and white is always a solid choice. Everyone has their favorites, that for sure. We like fishing a 150 grain line with various scuplin patterns like Ivan’s Dirty Dumpster and the Olive Peanut Envy. KG’s Mini Sex Dungeon in purple/black or the olive are solid choices as well. Pinch those barbs!

Please be respectful to those fish that do eat your fly. Land them quickly and take care to revive each fish with your anchor on the bank. Trout pics are something we all enjoy, but if you can avoid it in the afternoons please do so. Get creative with your pics and keep those fish wet. Celebrate the trout in the net and enjoy watching them swim away. We find that a slow mo video is the best way to capture the moment!


Autumn is here in the high country. It may not feel like it today, but this shot of heat will be gone tomorrow into Saturday as a cold front arrives in our region. It is a special time for all anglers, but especially so for those who concentrate their efforts on stillwaters. It may not be the easiest time of year to catch a pile of fish, but it is arguably the best time of year to target, hook, land, and release that one fish you dream of the other 10 months of the year. Larry. Walter. Hawgzilla. El Uno Grande. You know the fish. The biggest, fattest, healthiest, strongest, smartest, butt-kickingest brute in the lake!

As we get farther into the Autumn, insect hatches decrease, and with that, the important food sources change. In Autumn, chironomids are probably the main hatch/insect emergence to look for. Food sources also shift to leeches, scuds, and baitfish. These foods will be available more and more as weed beds die off and the trout slide back into the shallows to feed. Impressionistic patterns like Rickards’ Seal Buggers, Stillwater Nymphs, and Balanced Leeches in various colors are staples at this time of year. If you tie your own, this is the time of year to break out the Simi-Seal Dubbing again, or swing by the shop to pick up a few bags. While rare around here, don’t rule out the possibility of a water boatman fall, or feeding event. Justin, Dan, and I got our butts kicked last fall when every fish in the lake was feeding – on an insect we didn’t have an appropriate match for! Lastly, there are still chances at terrestrial insects bringing fish to the surface, so don’t leave your hoppers, ants, and beetles at home quite yet.

With all this hype, why doesn’t everyone fish lakes in the fall? Well, as I mentioned earlier, it’s not necessarily easy! The water is as low and clear as it will get before ice up, and with that, trout can be rather spooky. Up your stealth game with smooth casts and long leaders of 12-18ft! Weather conditions are not as stable as they are through summer and fishing conditions may not be as comfortable as we’d like. Low light periods linger longer, but the periods of intense feeding activity are often short, making success often a matter of fighting through long periods of “Type 2 fun” in order to experience an hour or two of angling glory.

Whether it is a roadside reservoir, a favorite natural lake, or a final hike into the high alpine that suits your fancy, keep after it as long as you are having fun!


Below are links to the flows in Montana and Idaho as well as. This time of the year flows and the weather are changing daily, if not by the hour. Click the links below for the most up to date information.

Montana River Flows
Idaho River Flows
West Yellowstone Weather Forecast