The Journal Answers: Scuds and Sowbugs are the staples of any White River fly box, alongside midges for one good reason. These food sources are always in the river and they always seem to work. But don’t worry about your question, you aren’t the first to ask in the past month.
So let’s start at the beginning. Turn any water-covered stone in the system and its a fair bet you’ll turn up one or the other. As you will see from the images below Sowbugs are deep bodied, kind of like little shrimp, though they aren’t a true freshwater shrimp. Colors can range from orange to tans, browns greys and olives
Sowbugs on the other hand are shaped more like those slaters, or roly-polys you find in the garden. A feature of these bugs is the darker centre and almost translucent edges. Most of the sowbugs Ive found tend to lean to subtle shades of gray, and olive.Pictures from Troutnut.com
Basically you can approach fishing either scuds or sowbugs as you would any other nymph pattern. Dead drift, with or without an indicator, works pretty well. This is a great approach on big fish too who find it hard to resist these tempting morsels.
But you do need to fish these flies down where they live, among the stones. Neither are regarded as Olympic class swimmers, though scuds can dart short distances, so they don’t roam far from the protection of home. So if you aren’t catching fish on these patterns try going deeper before changing flies.
I generally run these flies in low water conditions, (just on habit) though you can fish these patterns on higher water levels. I tend to rely on the built-in weight in Davy’s Sowbugs or McClellans’ Hunchback Scuds and V-Rib Woven Sowbugs or Kaufmann’s Scuds, in slower water.
But in the faster shoals, I’ll start adding weight depending on water speed and depth. Generally I’ll set the shot 6″ to 8″ above the fly, trying to get the shot bouncing over the tops of the gravel or bedrock and the fly swimming slightly above the bottom.As I mentioned earlier I fish these dead-drift, either searching likely water or sightfishing to individual trout holding in a feeding lie. However, and in fly fishing there is always a however, I recall watching a Gary Borger video a couple of years back in which he advocated swinging scuds through the faster riffles of Yellowstone Valley spring creeks, mised with jerky little strips or twitches of the rod tip. To some this might have been heretical but the titbit stayed with me.
Last fall the Journal was messing around at Wildcat, sightfishing to a health brown and in exasperation at missed take let the scud swing downstream through the tailout of the pool. Of course the scud was hammered. Remembering Borger I tried again and it was the same result.
One day does’t make a rule, but it was enough of a indicator that I’m going to keep it in my bag of tricks.
I hope this helps you out.