Fly fishing the Northern Rockies in September is an extremely enjoyable experience. With the heat of summer mostly behind us, the shorter days and cooler temperatures bring out new hatches and a return to larger insects such as the Western Red Quill, the Mahogany Dun and October Caddis. The Fall Baetis, although diminutive in size, becomes a behemoth in the feeding selection of local trout, not only on Silver Creek but on our local freestones as well. Tricos, though dwindling on Silver Creek, become more numerous on the Big Lost River and the lower Big Wood as well. September may mean the beginning of hunting season and back to school for the kids, but it also signifies a change in local entomology toward one of the most productive periods of the calendar year.
The Creek continues to fish well, especially in the mornings, with a continuation of the Trico spinner fall and Baetis emergence (both in size 20). Later in the morning, good numbers of PMDs (size 16) have been seen eliciting aggressive attacks. The Callibaetis (size 16) will continue to create great opportunities especially on breezy days creating a slight wind chop on the water and eliminating the sunlight-refracting effect of tippet. Often on these windy days, casting and stripping Callibaetis nymphs can lead to some impressive strikes sub-surface. Hoppers are still an option midday at the Creek, both on the preserve waters as well as on the north side of the highway. Look for the eventual emergence of the Mahogany Dun (size 14-16), a prime food source for the trout as they stock up for winter.
Big Wood River
The Wood has continued to fish well in the latter half of summer…perhaps the best summer fishing in years. However, September will open a new chapter for the Wood, as we see a return to large insects, particularly the Western Red Quill and the October Caddis. The Red Quill (size 12-14) is a true harbinger of autumn and presents itself very much like the Green Drake of July. In fact, Green Drake patterns left over from earlier in the summer will work wonderfully as an imitation for this sizable mayfly. In addition, especially on the lower Big Wood, look for a continuation of Tricos (size 20) and potential blanket hatches of the Fall Baetis (size 20) in the mornings and a significant Grasshopper presence in the midday and afternoon.
Big Lost River
The Lost is flowing at a very fishable 318 cfs and will continue to improve over the next few weeks. September is a great time to fish this conglomerate of spring creeks, alpine tributaries and tailwater as the September Trico spinner fall can be as prolific as any in the region. When the petite black and white mayflies are not present in the air, try nymphing with large mayfly nymphs such as Prince Nymphs (size 12-16) or Flashback Pheasant Tails (size 12-16) with a black, red, or brown Zebra Midge trailing behind (size 20). With the large brown Cranefly still present in good numbers, try the standard quartering-down presentation and skate the fly back across the river with the help of the current. Above the reservoir, the Kokanee are running in strong numbers making for added excitement and gorgeous photographs!
East, West, and North Forks of the Big Lost
The Upper Big Lost is still fishing well although the freezing nighttime temperatures will soon begin to chase fish downstream as their food sources diminish. Attractor patterns will continue to work well here, especially cream Elk Hair Caddis (size 14), Parachute Adams (size 16-18), Adams Irresistibles (size 14-18) and foam hoppers in a number of sizes.
South Fork of the Boise
The South Fork of the Boise is fishing well with Fall Baetis (size 20) in addition to the remaining Pink Alberts (size 16). Now that the river is at a prime walk and wade level, the increased access should amount to some superb fly fishing. Grasshoppers are still pulling fish up from the depths and can be fished on 3X and 4X tippet. As always, nymphing can be effective especially when imitating the Baetis and Pink Albert nymphs. Also, Woolly Bugger and Streamer fishing can pull some of the more picky fish out from behind boulders or from the deeper holes.
The Salmon is truly a spectacle right now, not just for the Trout and Whitefish angling, but also due to the return of the Chinook salmon. These King salmon, some of which tip the scales at over 40 pounds, are now appearing in the shallow gravelly runs as they complete their life cycle, laying eggs in the same locations where they were once conceived. Currently, floating is closed on the bulk of the river above the SNRA, so trade in your 10 weight for a pair of binoculars and revel in the beauty of these well-traveled fish.