When spring temperatures begin to warm and runoff hasn’t yet taken over the rivers, fly anglers look for the first sign of surface activity. While midges dominate the late winter months, another insect starts to steal the spotlight as spring arrives: the blue-winged olive (BWO).
What Makes Blue-Winged Olives So Special
Blue-winged olives are small mayflies that hatch in cool, overcast, and often damp conditions—hallmark weather for early spring. Typically emerging when water temperatures reach the mid-40s, these insects are often the first major hatch of the season that triggers consistent dry fly action.
Their presence signals a turning point in seasonal fly fishing, offering both nymphing and dry fly opportunities for attentive anglers.
When to Watch for BWOs
• Late March through April – Depending on region, BWO hatches typically begin once ice is out and streams begin warming.
• Overcast Days – Blue-winged olives prefer cloudy conditions, often emerging during light drizzle or early afternoon when light is dimmed.
• Steady Flows – Avoid turbulent runoff conditions. BWOs thrive in stable water environments.
How to Identify a BWO Hatch
Look for small, olive-colored insects with bluish wings hovering low over the water. Trout will begin rising gently, sipping emergers just under the surface or freshly hatched duns resting in the film.
Key Fly Patterns for BWO Success
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BWO Comparadun – Rides low and mimics the vulnerable dun stage perfectly.
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RS2 Emerger – Deadly when trout are keying in on subsurface emergers.
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CDC Loop Wing Emerger – A great transitional pattern that bridges the nymph-to-dun stages.
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JuJu Baetis or BWO Nymph – Ideal for pre-hatch conditions when fish are feeding deep.
Tactics for Targeting BWO-Feeding Trout
Start the day with a small baetis nymph under an indicator or Euro-nymph setup. As fish begin to rise, switch to emergers fished in the surface film. When the hatch peaks, dry flies like a BWO Comparadun in sizes 18 to 22 will draw strikes.
Use long leaders with light tippet (5x to 6x) to reduce drag and improve presentation. Position downstream of rising fish and use reach casts to extend drift time.
Where to Fish During a Hatch
Look for slow-moving seams, foam lines, and the tails of pools. Trout tend to hold in softer water during hatches, especially when feeding near the surface.
The blue-winged olive hatch is a springtime rite of passage for fly anglers. It marks the return of dry fly action and gives fish—and anglers—a reason to look up again. Those who study the hatch and adapt their approach can turn these small insects into big spring success.
Image: thefeatherbender
