Watching trout rise from a vantage point on the riverbank will tell you where to cast. But by taking an even closer look and noting how those trout are rising, you can also glean exactly what type of fly to throw at them—especially when there are many different bugs flying in the air. Here’s what to look for.

1 – The Sip
What you see: A very subtle dimple in the water, and only the nose of the trout appears.
What that means: The fish are either sipping midges or eating spent mayfly spinners.
What to fish: A Rusty Spinner—but no bigger than a size 18.

2 – The Slurp
What you see: More pronounced “beaks,” eating on the surface.
What that means: The fish are dialed in on a hatch—likely mayfly duns.
What to fish: A size 18 Parachute Adams. When the fish are really chopping, try a cripple variation.

3 – The Splash
What you see: A sudden, explosive pop with some splash.
What that means: Trout are on moving targets, like skittering caddisflies.
What to fish: Tie on a caddis pattern, such as a size 16 Lawson’s Caddis, and don’t be afraid to give it a twitch.

4 – The Boil
What you see: Disturbed water but no faces—only a dorsal fin and maybe a tail.
What that means: They’re eating emergers before they reach the surface.
What to fish: A size 20 Flashback Barr Emerger just beneath the film.

Illustration by Mike Sudal.