The Blue Wing Olive: An Angler’s Guide
The Blue Wing Olive, or BWO, a.k.a. Baetis, is a mayfly of critical importance to fly fishers. They hatch year-round, making them a consistent target for anglers.
Understanding the BWO lifecycle is essential to knowing when and how to fish them most effectively. This guide will walk you through the identification of BWOs, each stage of their lifecycle, the most effective fishing techniques, and the best fly patterns to use.
Identifying the BWO: More Than Just One Bug
When anglers talk about “Blue Winged Olives,” it’s easy to assume they’re talking about one specific insect. However, the term “BWO” actually refers to a broad category of mayflies in the Baetidae family.
The Baetidae family is incredibly diverse, with around 20 species of BWOs found in Colorado, 140 in North America, and almost 1000 worldwide.
In fact, if you’re fishing the South Platte River drainage, you might encounter all 20 of Colorado’s BWO species!
So, how can you identify a BWO?
These grayish to olive aquatic insects typically range in size from #16 to #22. Keep an eye out for these key characteristics when you’re on the water.
The BWO Lifecycle: A Fly Fisher’s Guide
Blue-winged olives go through several stages of life, and each stage presents a slightly different opportunity for fly fishers.
Nymph Stage
BWO nymphs tend to hide under rocks and in submerged vegetation. As they mature, they move toward the water’s surface.
To catch trout that are feeding on nymphs, fish in riffles and in back eddies, taking care to adjust your depth so that the fly is running where the fish are feeding.
Emerger Stage
Emergers are insects that are rising to the surface to hatch into adults. They’re especially vulnerable at this point, and some may get stuck in the surface film or foam.
One technique to catch fish that are feeding on emergers is to fish an emerger pattern behind a dry fly.
Adult Stage
Adult BWOs float on the surface of the water until their wings dry. If the day is overcast, this stage can last longer than on a sunny day.
To choose the best BWO pattern, observe what’s hatching on your local streams and rivers. Collect data on size, shape, and color to help you choose the right fly.
When do BWOs hatch?
Blue-winged olives are unusual because they hatch throughout the year, with peak hatches in March and October. This means they’re essentially the bookends of the fly fishing season.
Even more unusual is their preference for bad weather. Unlike some other mayflies, BWOs thrive in rain, snow, clouds, and wind. In fact, they seem to prefer the kind of days that keep most anglers indoors.
Finally, conventional wisdom says that BWOs won’t hatch when the temperature drops below 40°F. But I’ve found that just isn’t true. You can find them hatching even when it’s colder than you’d expect.
Selecting the right fly patterns: Matching the hatch
To be successful with BWO flies, it’s important to choose flies that match the insect’s current stage of development. You’ll want to have patterns that mimic the nymph, the emerger, and the adult stages.
Size and color are also important. Most BWO flies are quite small, in the size range of 18-26.
Recommended fly patterns
- Nymph patterns: The Pheasant Tail and Hare’s Ear are classic nymph patterns. The RS2 nymph in olive and gray (sizes 16-20) and the Micro Mayfly nymph (olive and brown) are also good choices.
- Emerger patterns: Try Barr’s Emerger (bead-head and standard) or a WD40.
- Adult patterns: The CDC Spinner Dry Fly, Parachute BWO, and Klinkhammer BWO are all worth a shot.
With a little experimentation, you’ll soon learn which flies the fish in your area prefer.
Frequently Asked Questions
What is a BWO?
Okay, let’s get this straight. “BWO” stands for Blue Winged Olive. It’s a type of mayfly that’s super important in the fly fishing world, especially because they hatch at times when other insects aren’t as active. Think of them as a reliable food source that trout just can’t resist, especially during the cooler months or when the water’s a bit off-color. Matching the hatch with a BWO imitation can be the key to success when other flies aren’t working.
What does a BWO look like?
Alright, so you know what to look for. BWOs are on the smaller side, mayfly-wise. We’re talking sizes ranging from about a size 16 to a size 22 hook. Their bodies are usually a dark olive to brownish-olive color, which is where the “Olive” part comes from. They get their name from their wings. The wings are typically a smoky, bluish-gray color, sometimes almost translucent. The nymphs are slender, often a darker olive or brown. Knowing these characteristics is critical to selecting the right fly.
Putting It All Together
When blue-winged olives start to emerge, pay close attention to their size, color, and profile. Every day on the water is a chance to learn something new, so keep experimenting with different flies and adapting to changes in water temperature.
The more you understand BWOs, the more rewarding your time on the water will be.