Montana Fishing Report Overview
Most rivers across Montana are hitting there late summer stride which means many of the aquatic hatches have subsided with a few exceptions (like tricos and callibaetis) and transitioning to terrestrials and other non hatch related food sources. Water levels will continue to drop as what is left of the snowpack trickles out so moving to smaller flies, longer leaders and finer tippet is often a successful tactic. Water temperatures are a huge driving force in late summer. Every fishery has a different temperature profile but it is an important factor to keep in mind. Some fisheries are still too warm for good fishing during the late (like the Jefferson and Lower Madison). Other fisheries are best in the early morning and still others fish great in the afternoon (like rivers closer to the mountains or spring creeks with colder water temps). As nights continue to get longer water temperatures are on a steady decline and some of the lower elevation fisheries will turn on. Already waters like the Lower Madison are beginning to fish well later into the day.
The Yellowstone river and tributaries remain closed due to the PKD oubreak that has infected whitefish and resulted in high mortality rates in the Paradise Valley section of the river. Fisheries biologists are working to gather data related to the outbreak. PKD has occurred in other fisheries in the west including the Snake River system in Idaho where it also resulted in a die off of white fish although trout populations were not noticeably impacted. Montana FWP has indicated that they will begin opening the tributaries when they gather more data and at some point the main river when they are confident that fish are no longer under stress. The outbreaks are a result of a small micro organism that requires water temperatures in the high 50s or warmer so as we head into fall the outbreak should wind down. In other fisheries the whitefish population began building resistance to the spores that cause the disease and stabilized after the initial infection year. We will keep everyone posted on situation as biologists gather more data. Other rivers in the region remain unaffected and continue to fish well.
Late summer days can still be warm and trout often lay up during the mid afternoon hours on the larger rivers. On big rivers like the Madison and Missouri the morning fishing has been better than the afternoon fishing. As nights continue to cool fish activity should extend longer into the afternoon. On smaller waters or on windy days afternoon hopper and terrestrial fishing can often be outstanding. Trout are becoming more opportunistic as aquatic hatches subside and are looking for a mixed bag and are not as selective as they were in the early summer period. For surface action terrestrials like grasshoppers, beetles and ants can be very effective. For subsurface try big patterns that imitate small bait fish like sculpins along with smaller attractor nymphs that are pretty general. There are still some late caddis hatches in the early mornings and on some fisheries the tiny trico mayflies are thick. Pay very close attention to water temps as this will drive the best fishing. On the big rivers water temps are best in the early morning but on small mountain streams and shaded mountain rivers the early morning can still be pretty cold so just pay attention to the fishery you are on. Some fisheries just get too warm for safe fishing and fighting a fish in 75 degree water can kill the trout so stay away from the lower elevation big river fisheries until they hit their stride again in September. Many of the individual reports on our page also have a temperature profile so you can watch these closely. On days when a cold front pushes in or we have good cloud cover some water temps will be lower than normal and you can fish waters later into the day or visit rivers that are normally spring and fall fisheries. Trout eat every day so just make sure you are on the river during their feeding window - when that is just depends on the fishery.
Summer is the busiest time of the year for fly fishing in Montana so trout on popular public waters have now seen some flies. Fishing pressure is dropping off fast now that kids are heading back to school but trout are still a bit on the sophisticated side at the moment. It pays to try to think outside the box and get off the beaten path. If you can find lightly pressured waters trout will aggressively slam big hopper patterns. If you are fishing waters that see a lot of pressure the hopper bight might only be so so. This is the time of year when we start working extra hard to find trout that have seen fewer flies. Sometimes that means a visit to a private ranch, a long hike or simply fishing water on the big waters that other guides are skipping past like the backside trough of a rock well on the Madison that can only be cast to from the bank and not from the boats float fishing past.
Many of the aquatic hatches have run their course. The main hatches this time of year are the tricorythode mayflies (tricos), a few late caddis, and callibaetis on the lakes. There is also a nocturnal hatch of large stoneflies (most of us call them nocturnal stones) that can get the trout keying in on large stonefly dries at dawn or stonefly nymphs subsurface. Tricos are not thick on all waters but where they occur in abundance they can bring a lot of trout to the surface. The gulper fishing on lakes like Hebgen and Ennis can bring large trout to the surface when the callibaetis mayflies hatch in the late morning.
Terrestrials now are very important across Montana. Hoppers are now mature and flying. The trout are just now beginning to key in on them. On some rivers they aren't quite looking for them and on others the bite is already on. 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 more technical terrestrials like small beetles and ants. In the mountains hoppers are less important but keep an eye out for spruce moths - they are flying in the mornings and trout love them.