by | Sep 2, 2021

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And just like that, September has arrived. The grassy hillsides are turning golden yellow, brown trout are on the move, elk are bugling and yesterday, the upland bird hunting season opened here in Montana. Fall is here folks! Bring your waders and boots, that warm layer for the morning session and don’t forget that stocking hat for when the weather turns a bit dicey. Need to fix those waders? We got you covered with patch kits at the shop. Don’t worry though, summer returns each day about 12pm as long as the sun is shining. Daytime highs have been in the 70’s all week with mostly sunny skies and a little bit of wind. Morning temps are a bit chilly and sitting in the low 30’s. The weekend outlook is for sunshine and a solid dry fly bite in the afternoon.

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 – BY JOnathan heames

Henry’s Fork Streamflows

Island Park Dam:  330 cfs

Ashton Dam:  1060 cfs

St. Anthony:  910 cfs

Fall on the Fork is right around the corner and we are beginning to see some of the early fall insect activity with the cooler temperatures.  The warmer days are reminiscent of summer and summer bug selections are still in effect while the weather is fair.  These coming weeks are some of the most beautiful of the year.

In the Box Canyon, fishing remains consistently good, flows are low and getting lower, but at 330 cfs, it is still easily navigated and the fishing worthwhile.  Shorter leaders and lighter weight is the name of the game in much of the canyon, with dry/dropper rigs producing in runs that often require indicators and split shot.  We are generally nymphing in here with rubberlegs 6-10, perdigons 16-18, PT nymphs 16-18, and Zebra midges 16-18 in red and brown.  This is a great time of year to throw a streamer in here, either under and indicator or stripped with a floating line, we have been having success with white Bouface leeches, copper Zonkers, olive BFEs, and Sheila Sculpins.

The Ranch has been fishing pretty darn well, it seems the cooler weather we had in August pushed some of our hatches forward and we are seeing some mahogany duns and baetis on cooler days, warmer days are producing tricos, some callibaetis, and PMDs.  It’s a good idea to have ant patterns and small hoppers as well.  Weeds abound and are a force to contend with this time of year, be sure to keep a big bend in your rod when you’re hooked up with plenty of tension on the line to assist in not losing those big Ranch trout, they will use the weeds in their attempts to escape!

The canyon country below the Ranch is in great shape during these times of low flows, lots of the structure that is usually under heavy whitewater is now more easily accessed with flies.  Dry/Dropper rigs reign supreme here as nymphing rigs typically result in many lost flies.  Pretty hard to beat a Chubby Chernobyl to a rubberlegs stonefly nymph here.  If they are fussy with the stonefly, try a #14 mayfly nymph or caddis pupa.  Streamers are a great choice as well, the same patterns we use in the Box Canyon will work down here.  

Warm River to Ashton has been fishing quite well with some larger trout showing up here and there.  Brown trout are beginning to move around and get aggressive, be prepared for them to show up attached to your flies at times throughout the day.  Nymph rigs, dry/dropper rigs, and streamers will all produce down here.

The river below Ashton reservoir is showing signs of life, afternoons are still a wild card, especially with the fair weather we have in the next week’s forecast.  Look for an increase in the activity down there as the month progresses and during periods of fall weather.

Have fun out there!


September in Yellowstone is tough to beat.  
As we begin 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. 

Northeast Corner – Slough Cr, Lamar River, Soda Butte Cr
Stable 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. Be on the lookout for sparse hatches of fall baetis, flying ants, and small hoppers. As always, small soft hackles swung through the riffles and runs will produce well when fish aren’t looking up.


The flows at Hebgen Dam dropped a little bit over the past week, and we are now sitting at 778 CFS out of Hebgen Dam, 908 at Kirby and 972 CFS at Varney Bridge. Hopefully these flows don’t drop any more, we prefer to have a more water in the river. The long term 82 year median stat is 1050 cfs out of Hebgen Dam. River temps are cooling off and start at 54 degrees and fluctuate about ten degrees throughout the day. In general, the cooler morning 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.

Wade Stretch:Sparse caddis hatches can still be found skittering about in the upper river throughout the day, at any given time a fish just might eat one of those in a pocket behind a rock or the skinny water along the bank. Efficiently covering these lies 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. Nocturnal stones are skating around in the early mornings, so twitching your chubby or hopper pattern is a fabulous plan, just fish 2x so you don’t break off a very possible large trout willing to eat it. Nymphing with rubber legs, #14-18 BH pheasant tails, golden stone nymphs, perdigons, prince nymphs, 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 sunshine in the coming days should make for decent hopper and ant fishing all afternoon long.

Float Stretch:There are still some caddis hatching about, a quick look on the bow of your boat mid morning will show you just that. Fishing a single caddis pattern, tight to the banks or in the slicks will raise a few nice fish throughout the day. Early in the day rolling a hopper/noctural stone fly could produce a large strike or at least a few nicer fish willing to window shop more so than eat the fly; but be prepared for the eat! Try fishing a single dry fly and if you are dead set on fishing two dry flies; lengthen the distance between the two flies. There are times when it helps, but this that longer distance between the two flies can be a little tough to tun over if the north wind comes your way. When rolling the middle of the river, danglin’ a tungsten bead under the Hopper will produce. 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, 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. 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.
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!


With another stable week of weather in the forecast, look for stillwater fishing conditions to remain in the nice little late summer/early fall pattern we’ve had. Modest levels of aquatic insect activity, cool water conditions, and good but not red-hot action are what I’d expect. The callibaetis are tailing off every day and chironomids are becoming more important again. Spend some time on the depth transitions and deeper sides of dropoffs but keep an eye on the shallow flats for signs of feedign activity on or near the surface. At dawn and dusk, walter may find conditions comfortable enough to slide shallow to feed on leeches and baitfish. This is also a great time of year to cover alot of ground on foot or by boat looking (sight fishing) for cruising trout along the margins. Many of these fish will respond to a well presented terrestrial insect imitation like a flying ant, beetle, or hopper. For those folks who enjoy chipping away on the lake, moving around, and trying a variety of techniques over the course of a day, you should be able to find a few fish these days.


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