Not much change in the last week with those low, warm water conditions. This applies to Chesterfield, Daniels, Treasureton, Sand Creek, and Twenty-Four Mile and even Island Park Reservoirs. Your best bet for action is for gulpers on Hebgen Lake. Or if you do not mind thick weeds, try the channels between them on Springfield Reservoir. Best bet is with dry damsel, speckled dun patterns or your favorite midge pupa pattern under an indicator.
Consider fishing around creek mouths now. Get to these locations as early as possible, because when word gets out about good fishing there, you will have company. Some will enjoy crowding your location if you are having luck. Small woolly bugger types, Mity mouse, bead head peacock leeches, olive or gold crystal patterns on an intermediate line will get action going for you.
The cool wet weather we have had for the last few days is just what is needed to sustain good fishing on many small streams. Any that do not have a healthy component of inflow from springs, or have lakes in their drainage are examples. Thus such as the Salt River tributaries, Robinson, Diamond,Beaver, Medicine Lodge, and Canyon Creeks will benefit. Don’t fish these streams right after a heavy or even moderate rainfall. Wait a day or two for flow to return to near normal, then because time of the year is right, consider presenting terrestrial patterns for the best dry fly fishing.
The river from Ashton Dam downstream is in the “summer doldrums” now. Go elsewhere unless you try at sunrise or sunset with streamers. The big mayfly hatches are pretty much over in the Pinehaven-Harriman-Last Chance section (except for a few places where springs enter the river) until speckled duns and trico emergences become important. Your best chances here are with terrestrial patterns. Patterns tied with traditional materials tend to have a more delicate imprint on the surface than those tied with foam or rubber. Thus, be a bit careful when choosing hopper patterns if you will be fishing slower waters. In sections with faster water and a more broken surface, such as in Cardiac Canyon or around Riverside Campground, this difference is not as significant.
Riffle fishing on the South Fork is about as good as it gets, especially on the upper river. The flow out of Palisades Dam has been a bit over 13000 cfs with water temperatures in the high 50s in deg. F. for weeks. This is the kind of stability that results in consistent insect activity needed for great fishing. Pink alberts and the remaining PMDs are the reasons. Begin in the AM with nymphs, switch to your favorite emerger pattern as the day advances and you see increased rises. Some folks prefer to stick with their favorite emerger pattern, but others later on switch to a dun pattern for the surface. Fishing the banks is also a good strategy. Hoppers are out and sure to increase, so your favorite pattern should be in that fly box.
Flow out of Mackay Dam has dropped from a little over 200 cfs to 160 cfs in the last few days. This means easier wading, warmer afternoon water temperatures, less overhead cover, and therefore a greater need for being stealthy and for playing fish quickly. Some western green drakes remain here, but terrestrial patterns are becoming more effective. Tricos are yet to be important, but should begin to be such any day now.
Terrestrial patterns are about the most important dry flies to have in the box these days for success on Park streams. This includes hoppers (of course), ants, craneflies, and beetles. So many flyfishers forget patterns for a terrestrial not in the above list of suggestions. That would be patterns to simulate deer flies and horseflies. If you enjoy fishing meadow streams such as Slough, Boundary, Duck, and Soda Butte Creeks or Bechler, Fall, Madison, or Gibbon Rivers, you know how annoying these pests can be. They seem most numerous on the brightly sunlit areas of these and other like waters, and their bite hurts like “——!” I have been accused of “chumming” when I swat one, then flick the crushed result into the water to wait for a downstream take. When I hear that rise take place, I put an imitation on and go for it. A big, juicy looking humpy is my favorite for this purpose, but choose your favorite, and with a downstream drift, you are sure to have action.
Overall fishing the South Fork has been good. There have been a couple of days where it has been slow but the cooler water temperatures this July has made the fishing better than recent summers.
Most days there is some good activity in the riffles with pale morning duns, both olive/yellow and pink. When fishing the riffles your best success will come by constantly changing your patterns from high silhouette duns to emergers and then maybe a nymph suspended in the surface film. Drift purple or gold bodied chernobyl stones against the slower grassy banks and over the riffle drop offs. There are some big hoppers out on the lower river below Byington and down to Menan. We are starting to see some golden(mutant) stone casings along the shore but we need to see some drops in the river flow to really get those bugs emerging. If you stay on the river late there has been a good caddis hatch. Finally we have still been relying on a brown rubber leg/small tungsten nymph combination when nothing is going on topside.
The next two to three days we are suppose to have some good cloud cover and that usually makes for better fishing. Good luck!