March Hatch Guide – Everything You Need to Know About Colorado Hatches in March
- brianchilbert
- Mar 3
- 4 min read
Updated: Mar 3
March in Colorado is one of the most exciting months of the year for trout anglers. As winter thaws and the rivers begin to swell with snowmelt, fish start to key in on emerging hatches. While conditions can still be variable, March offers incredible opportunities for targeting a variety of hatches, particularly spring midges and blue wing olives, alongside opportunistic feeders like leeches, cranefly larvae, and trout eggs. Whether you’re fishing the Roaring Fork, Eagle, or Colorado River, understanding the hatches, water conditions, and trout behavior is key to dialing in your March fishing.
Below, we’ll break down the main hatches you can expect this month and offer pro tips from our seasoned Colorado River Outfitters guides, so you can make the most of your March on the water.
Spring Midge
Overview:
Spring midges are one of the first hatches of the season, and in March they are showing up strong across Colorado rivers. These are relatively large midges, usually black or gray in color, with long flat wings. Trout target them in all three stages: larvae, pupa, and adult, so having patterns that imitate each stage is critical.
Stages and Patterns:
Larvae: Typically yellow or pale olive and on the larger side. Trout key in on these early in March, especially in slower runs and deep pools before the hatch begins.
Favorite pattern: Juan’s Pale Ale Larvae
Pupa: Colors vary from brown to pale olive or black, sizes 18–14. Pupa patterns are essential when midges are hatching.
Favorite patterns: Size 16 Zebra Midge (black bead), Daysaver Midge (brown, size 18–16)
Adult: Usually black or dark gray, sizes 18–14. Look for trout sipping the surface in pockets and along the bank.
Favorite patterns: Goober Midge
Pro Tip from CRO Guides: Paul Killino notes that midges in March are often bigger than any other time of the year. Matching size is key, but don’t underestimate presentation. Slow, delicate drifts make a huge difference.
Blue Wing Olive (BWO)
Overview:
BWOs are small, slender mayflies, light to dark olive in body color with gray upright wings. They typically range in size 22–18, with size 20 being average. March is prime time to target BWOs in all three stages: nymph, emerger, and adult.
Stages and Patterns:
Nymph: Small, dark olive nymphs with dark wing cases. Trout are actively feeding subsurface in runs and slow riffles.
Favorite patterns: Daysaver Baetis (pictured above)
Emerger: As nymphs ascend to the surface, patterns that simulate emerging wings trigger strikes.
Favorite patterns: Barrs Emerger, Sexi Top BWO (size 18–22)
Adult: Classic parachute Adams works well, especially in slow pools and pocket water.
Cripple Stage: Fish sometimes sip partially emerged BWOs or those struggling in the surface film. The Ms. Tickle Cripple from Montana Fly Company is excellent for this picky presentation.
Pro Tip: Brian Hilbert emphasizes the importance of observation. “The river and fish will tell you exactly what you need to be fishing if you pay attention.” Look for insects on the surface, in the air, fish in the water, flashes, spend 5 minutes watching before you start fishing.
Bonus Opportunistic Imitations
Trout Eggs: Many rainbow and cutbow trout begin spawning in March, making eggs a key target.
Favorite pattern: Hans Sunny Side Up
Leech: Always a reliable option, especially in slower water or deep runs.
Favorite pattern: Mayers Mini Leech
Cranefly Larvae: Opportunistic feeders, often found after flows increase.
Favorite pattern: Philly Cheese Cranefly
March Water Conditions and Fishing Tips
March rivers in Colorado can be low and clear early in the month, transitioning to more variable flows as snowmelt begins. Fish tend to hold in deeper winter water pools where they can conserve energy and ambush emerging insects. As the month progresses and water levels increase, trout will begin to spread out throughout the river.
Key Tips:
Stealth is everything: Trout are sensitive to shadow and disturbance in clear water. Approach slowly, fish from downstream when possible, and use long leaders.
Match the stage: Trout are often keyed in on a specific hatch stage, whether larvae, nymph, pupa, or adult. Observing insects on the water and trout feeding behavior can clue you in.
Experiment with depth and weight: Slow, thorough drifts often outperform fast casting. March fish can be picky, so changing depth, weight, or insect stages can make the difference.
Pro Tip from Matt Weldon: “March is a great month to focus on perfecting your drift. Cast less, mend often and focus on getting a perfect drag free drift. Often times, takes are subtle! Set the hook on every twitch, hesitation or wiggle of your indicator.”
Why Hire a CRO Guide in March
Want to really dial in your March fishing? Hiring a Colorado River Outfitters guide is the fastest way to success. Our guides aren’t just experts at putting you on fish, they’re fantastic teachers. A day on the water with our team of seasoned professionals can accelerate your learning curve, help you read water, and fine-tune your hatch matching skills. The average length of full time guide experience on our staff is 18.5 years.
Fishing in March is incredible, the rivers are waking up, hatches are starting, and trout are hungry. With the right guidance, you can catch more fish, learn faster, and leave with a better understanding of Colorado’s winter-to-spring transition.
Follow Us!
For daily hatch updates, tips, and inspiration, follow us on Instagram and Facebook. Don’t miss your chance to book a March trip, slots fill fast!
📞 Call or text us at 970-236-1937
Understanding the timing, stages, and favorite patterns of these insects can transform your fishing experience and put more fish in the net. Whether you’re targeting rising trout on calm afternoons or nymphing emergers in faster runs, March offers some of the most dynamic and rewarding fishing of the year. Get out on the water, match the hatch, and make the most of this incredible early-season opportunity.
— The CRO Team
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