A Little Known Two-Fer-One

By Scott Richmond

Most Oregon fly anglers know that the blue-winged olives (affectionately called "BWOs") fuel much of their winter trout fishing. But few fly fishers are aware that the BWOs can provide excellent sport in September. Here's how.

First, BWOs are many species that are lumped into three mayfly genera: Baetis (the most largest and most important), Pseudocloeon, and Diphetor. The latter genus used to be called Baetis parvus, then Baetis hageni, and now Diphetor hageni. But only an entomologist really cares about that. All a trout angler needs to know is that mature nymphs of this BWO genus like riffly water and are present in large numbers in September. If you kick up some rocks in a Deschutes' riffle in September, you will find two primary insects--Diphetors and stoneflies. And the trout are scarfing down both of them.

Hmmm. Two kinds of insects that live in the same kind of water and that trout eat all day long, even if there's no hatch. Hmmm.

By now you've figured out that you should tie on a large stonefly nymph, such as a Kaufmann's Stone or a Rubber Legs, then tie a small nymph on a dropper. Affix an indicator to your leader and cast away. Look for places where the water deepens and slows just below a riffle.

I think the best nymph to use on the dropper is a size 18 Gold Ribbed Hares Ear. The natural insect has two light bands on its abdomen, which the fly's gold ribs imitate. In fact, if you're tying this fly, use wider tinsel than usual and only wrap it twice.

In my experience, trout will take the stonefly about 2/3 of the time, and the Hares Ear about 1/3. I figure that means I catch 50% more trout than I would if I only cast the stonefly.

Scott Richmond is Westfly's creator and Executive Director. He is the author of eight books on Oregon fly fishing, including Fishing Oregon's Deschutes River (second edition).