When many fly fishermen think of mayfly spinners they envision a run full of rising fish feeding on the lifeless floating spinners as they float downriver. For many of us fishing for rising fish is our favorite technique but fishing spinner falls can be very challenging, especially the predictable and months long Trico spinner fall. The traditional approach has always been to fish a spinner pattern flush in the surface film. This can be effective but also is very challenging. If the lighting isn't perfect seeing your fly is difficult. If you can't see your fly you cannot see a fish take it, you are not sure if the cast is accurate and you cannot see if little micro currents are creating drag. The natural spinners are motionless and any drag on your fly guarantees a fish will not take it.
I eliminated all three of the inherent problems when fishing a floating spinner with a technique I developed on the Missouri River when fishing a Trico spinner fall. I used a drowned spinner pattern on about 8 inches of 6x fluorocarbon tied to the hook bend of a black bodied Vis A Dun. With the highly visible dry fly, I could monitor the cast for accuracy and drag and it served as an indicator when a fish took the drowned spinner and some fish took the dry fly. The technique proved to be extremely effective for any spinner fall including rusty spinners and I have successfully used the technique on rivers throughout the West. If spinners falls have been occurring but not while you are fishing, a drowned spinners is a good choice when setting up a nymph or hopper-copper-dropper rig. The spinners are a familiar forage for the trout and they won't hesitate to eat one subsurface. Baetis mayflies do not have a true spinner fall because the female accompanied by the male crawl under the water to lay their eggs, then they die and are carried downriver. . No doubt trout eat countless drowned Baetis spinners and a drowned rusty spinner is an excellent choice when Baetis have been hatching.