During September mornings a Trico hatch on the Upper Teton River is predictable and consistent. Once the ambient air temperature reaches the mid-sixties the hatch turns on.
The river water is crystal clear with September flow rates around 200 cfs. When casting to trout under these conditions the presentation has to be perfect. The fish have ample time to study the imitation for an appropriate drag-free drift, size, and shape. Do not let the slow flow rate fool you, these conditions require much more technical prowess than fishing in faster water such as the South Fork of the Snake River.
Until this summer when I saw tricos in the air or on the water, I limited myself to dun and spinner patterns for rising fish. Recently, my experienced fly fishing partner suggested that prior to a predictable hatch, this is the perfect time to consider a trico emerger. Using a size 22-24 emerger on 6x tippet proved to be an effective pattern. I put on a second larger dry fly as an indicator about 18 inches proximal to the trico with 5x tippet.
Once spent spinners are seen on the water and you see the characteristic surface feeding frenzy, switch to a spinner pattern.
Too often, we dry fly enthusiasts become enamored with parachutes and spinners. If you are not seeing a lot of surface action consider an appropriate emerger pattern.
Doc Frangos, MCI
Victor, ID
September 2025