SOUTHWEST MONTANA FISHING REPORTS OVERVIEW by Montana Angler 9.21.21
By angelamontana

Posted: September 22, 2021

Early Autumn is a transition time on rivers and streams across Montana and some exciting options present themselves as nights get longer and water temps begin cooling down. Fishing is generally very good but is also less predictable depending on the prevailing weather pattern. Indian summer and hot days can result in some of the best terrestrial fishing of the season. Early cold fronts can provide the potential for a low cloud ceiling overcast days bring a hint of late fall fishing. Browns are just starting to gain their autumn color and are moving out of their lairs in preparation for the spawning runs in October. Some of the lower elevation waters that produced poor fishing in the summer turn on as water temperatures cool and levels rebound with the demands of irrigation water ending. Many of these trout haven’t seen flies since the middle of June. Although the lower reaches of rivers like the Madison, Yellowstone and Gallatin along with the Upper Missouri and Jefferson do not have high trout counts compared to the more famous sections farther upstream (or in the case of the Mo downstream below the dam) they often hold some nice trout.  September also brings fewer anglers once vacation season winds down and the go to floats of the summer like the Upper Madison, Yellowstone and others see much less pressure and the trout start to drop their guard again.

Generalities
Water levels are still low but start to rise in mid September on many rivers that receive a lot of irrigation as the ditches are being turned off. In rivers above the irrigation they are mostly holding steady now at their base levels. Water temperatures are declining and even though some days are still very hot the nights are so much longer that the prolonged cooling effect when the sun goes down is bringing temperatures into the sweat spot. Almost all fisheries around the state are now an option from tiny meadow streams to low elevation waters. The lower reaches of rivers finally cool down again and the high mountain streams are still not so cold as to put trout in a deep freeze. The productive fishing hours are quickly transitioning to later in the day and getting out at the crack of dawn isn’t as important as it was just a few weeks ago. Fishing conditions are all over the place and vary by the day – some days they are looking for hoppers, other days small mayflies and nymphing is also productive. Streamer fishing is also getting better by the day as the big browns become unsettled before the spawn, but will get much better as we move later into the fall.

Hatches

Many of the aquatic hatches have run their course. There are still some late tricos on some waters and some mahogany duns and spinners are popping in the later afternoons and evenings. It is still a bit early for the baetis hatches but on some fisheries a few will start showing up soon on the infrequent cloudy and rainy days.

Terrestrials are still very important across Montana. Hoppers are mature and flying. The hopper fishing on the smaller meadow rivers continues to be very good and is day by day on the larger rivers depending on location and wind direction. On some rivers they aren’t quite looking for them and on others the bite is very good. I waded a small stream on a private ranch the other day and the hoppers were all over the place and trout were moving aggressively for them. The quality of the “catching” over hoppers depends on the amount of pressure trout receive. They get pretty smart after they see a dozen foam hoppers a day so look for waters that see less anglers for the best hopper fishing. If you are targeting more popular fisheries you may have more luck with “techy” terrestrials like small beetles and ants. In the mountains hoppers are less important but there will still be a few at higher elevations, especially in meadow reaches. Ants are a favorite early fall option as well.  Many species of ants produce large mating flights in the late summer and early fall and these can really get the trout moving for them.

For more by Montana Angler, click here.