5 Tips For Late Summer Fishing In Yellowstone Park

Fighting a Cutthroat in the Yellowstone Backcountry

Late summer is one of the most popular times to visit and fish in Yellowstone Park.  According to the Park Service, August accounts for almost 25% of yearly visits to the park, and my guide calendar backs up that fact. Although it is the most convenient time to visit for many folks, August and early September fishing presents a special set of challenges, not only in Yellowstone Park but all of the Rocky Mountains. Low water levels, combined with fishing pressure in July can make fish rather spooky. Water temperatures creep up as well, which can lead to poor fishing, especially on hot afternoons. There is also the fact that Yellowstone Park is a very seasonal fishery. No single stream fishes well for the entire season. There is always somewhere good to fish, but each river is not fishing well in late summer. I have had my fair share of banner days in the park in August and early September, but there are some key things to know in order to make that happen.
August brings low, clear water to the Lamar Valley
1.  Center your trip around the northern part of the Park  
The epicenter of late summer fishing is the far northern reaches of the park in the Yellowstone and Lamar drainages. Here, the angler will find a mix of placid meadow streams and swift, canyon stretches. The meadow fisheries are ideal places to fish the terrestrial insects that make up most of the trout’s diet in late Summer. The canyon areas are great places to beat the heat as the cool, oxygenated water keeps fish active. The famous waters of the Madison Drainage are too warm for fishing, so anglers based in West Yellowstone face long drives to fishing each day.  Instead, base yourself out of either Gardiner, MT or Cooke City, MT or park facilities in between the two. This will put you right in the middle of the best late summer fishing and give you plenty of options.
Hiking is a great way to escape the crowds
2.  Get off the beaten path
This is important at all times of the year, but even more so in late summer when the fish have already seen so much fishing pressure in July. There are essentially two ways to get off the beaten path in Yellowstone: #1, hit the trail, or #2 choose to fish streams that are overlooked by anglers, usually due to their small size. If you want to fish one of the famous fisheries like the Lamar River, Slough Creek, or Soda Butte Creek, your best bet is to hike into areas that see less pressure. This is all relative, because that means a 6 mile walk at Slough, but it could mean just a couple hundred yards on Soda Butte to an area where the stream is out of view from the road.

Choosing to fish a small creek is a great option for anglers who want a more of a total Yellowstone experience than just the shot at a big trout. While you will probably not catch a 20” Cutthroat out of a small stream, you will also not see other anglers and will end up catching more fish because the fish in small creeks are typically very eager to feed and not spooky. Carry a selection of basic attractor dries and terrestrials and pack a 3wt or 4wt rod if possible. A 5wt will work just fine, but you will get a better fight from the fish on a lighter rod. While good small streams are closely guarded secrets and too sensitive to mention online, virtually every piece of moving water in Yellowstone holds fish, so a map and some imagination is all you need.  
A pack trip is an even better way to beat the crowds!
3.  Downsize Your Tackle
As trout experience fishing pressure throughout the season, they begin to learn their lessons to a certain extent and become more critical of what is being presented to them. The angler needs to adapt by choosing lighter tippet and smaller flies as the season progresses. There are no hard and fast rules for this, as it will be different for each fishery. On flat, heavily pressured water like the Lower Meadow of Slough Creek, you are going to want to have some 6x in your pack.  On more broken reaches of river, such as the Black Canyon of the Yellowstone or the Gardner, 4x will do the trick.  You will also want to lengthen your leaders as well on the meadow streams in order to lessen the impact of your fly line hitting water. On the Lamar and Soda Butte, a 10 ft leader should suffice, while I would probably go to 11ft on Slough.

Another important consideration in August is the size of the fly you choose to fish. The trout will have seen innumerable #6 or #8 hoppers, so smaller hoppers in a #12 or even #14 become very important. These micro hoppers are starting to become very popular and are bestsellers in fly shops around the region. For the wariest of trout, it is often best to forgo hoppers altogether and choose small beetle or ant patterns. While they might not be quite as fun to fish as a big foam hopper, these smaller terrestrials draw less suspicion from the trout, who see far fewer of these imitations over the course of the season.
August Cuttie on a hopper
4.  Don’t Forget about Streamers
While late Summer is generally thought of (with good reason) as a time to fish dry flies, make sure you arrive with a good selection of streamers as well. There are two situations that I look for in August and early September as good times to throw streamers. The first is during the early morning hours on the meadow streams. The dry fly fishing in the meadows can be very slow first thing in the morning because the hoppers and other terrestrials do not become active until the day warms a bit. That can put the trout in a bit of a funk in the early mornings as they wait out the bugs. This is a great time to strip streamers and try for a real trophy. When streamer fishing in the meadows the two types of water I look for are undercut banks and slow, deep pools. You will still want to approach from downstream so as to not spook the fish. Present your fly in an up and across manner and strip the fly back to you with the current. This mimics a small fish fleeing downstream, taking the path of least resistance.

The second situation in late Summer that I like to strip streamers is during mid-day on canyon fisheries like the Yellowstone. Oftentimes the high, bright sun overhead at mid-day will drive the fish down on the Yellowstone and Gardner. The fish seek respite around large boulders, under ledges, around logs and various other sources of shade and cover.  Fish with this mindset will be hesitant to move all the way to surface to take a dry, but will have no problem ambushing a streamer that darts past their hiding place. Since you will be equipped with a floating line, choose streamer patterns with some weight to them so you can get them down to the fish. I like a carry some split shot as well, but remember that lead is banned in Yellowstone, so make sure you purchase some tin split shot before your trip. If you are having a good day tossing drys and the fishing abruptly slows in the heat of a day, a streamer is a good choice until the sun starts to get off the water in the evening.
Brook Trout are plentiful in small streams throughout the Park
5.  Be on the Lookout for Spruce Moths
While it may not yet be a household name, the Spruce Moth is quickly becoming one of the best hatches in the Yellowstone area. While the exact reason for the explosion in Spruce Moth population is not known, and it might not be good for the ecosystem at large, if trout are rising to a bug I want to have a good imitation in my pack. The moths are present around all types of Evergreen trees, so it is easy to pick out locations to look for the hatch. Even the meadow streams of the Lamar Valley have plenty of wooded stretches, so you could run into the hatch on any stream. The bugs are active in both the morning and evening, although the hatch tends to be heaviest in the morning. Most anglers started off imitating the hatch with a medium/large Elk Hair Caddis, but these patterns tend to be too bulky and float too high, and now most fly shops stock more realistic Spruce Moth patterns. The number of Moths seems to vary greatly from year to year, so there are no guarantees that you will run into the hatch on your visit. However, if you do happen upon the hatch, you will be sorely disappointed if you are not armed with the proper pattern.  Make sure to stock up at a local shop just in case, and seek out timbered areas in the mornings and evenings to look for the bugs.

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