Fishing the Trico Hatch on the Bighorn River: Timing, Tactics, and Tips
Trico hatch season on the Bighorn River is a favorite for serious dry fly anglers. These tiny mayflies may look insignificant, but when they blanket the surface in late summer, they create some of the most technical and rewarding fly fishing of the year.
What Are Tricos?
Tricorythodes, or “tricos,” are small mayflies (size 20–24) that hatch in late summer. The females lay their eggs in the morning, followed by huge spinner falls that draw trout to the surface in a feeding frenzy—if you are ready.
When to Fish the Trico Hatch
- Peak Season: Late July through September
- Best Time: 6:30 AM to 10:00 AM
- Weather Factors: Calm, cool mornings produce the best spinner falls
Where to Fish on the Bighorn
Look for slow-moving slicks, foam lines, and side channels where trout can rise with minimal effort. Productive water includes long flats below riffles and seams near islands—especially between Afterbay and 3-Mile Access.
What Flies to Use
- Trico Spinner (Size 20–24)
- CDC Comparadun Trico
- Parachute Adams (for visibility)
- Griffith’s Gnat (as an emerger or cluster)
Pro tip: Keep your tippet fine (6X or 7X) and your presentation dead-drift perfect. These fish have seen it all.
How to Approach Trico Eaters
- Watch the rise forms carefully—sippers vs. splashy takes tell you everything
- Kneel or stay low to avoid skyline pressure
- Deliver short, clean casts with minimal false motion
- Be patient. These are chess matches, not shootouts.
Don’t Let the Size Fool You
Some of the biggest trout on the Bighorn will sip the smallest trico spinner with barely a ripple. If you land one, you’ll understand the obsession.