Dry, nymph, or streamer? A decision tree for the riverbank

You walk down to the river, open your box, and the first question you ask is the wrong one. Most beginners ask "which fly?" before they have any reason to pick one. The right first question is shorter, where are the fish feeding, and once you know that, the fly almost picks itself. This piece is the field card a guide would walk you through in your first ten minutes on the water.

The two things to read before you tie anything on

Stand on the bank for two minutes before you do anything else. Look at the water, not the box. Two inputs decide most of it.

What the water is doing. Cold or warm, high or low, clear or murky. You can read all three in a glance, and the combinations tell you a lot: cold-high-murky points one direction, warm-low-clear points the other.

What you can see. Whether bugs are in the air or on the water, whether fish are breaking the surface, and whether you can actually spot a trout holding in a clear run. Each of these signals points to a different fly, and a clean look at the water for two minutes will hand you most of them.

The decision tree

Read top to bottom. Stop at the first branch that fits what you see.

Are trout breaking the surface?
│
├── YES, and I see bugs in the air or on the water
│   │
│   ├── Bugs are upright and delicate (mayflies)
│   │   → Parachute Adams (size 14)
│   │
│   ├── Bugs are tent-winged and skittering (caddis)
│   │   → Elk Hair Caddis (size 12)
│   │
│   └── Bugs are big, loud, or hard to identify;
│       or the water is fast and broken
│       → Stimulator (size 12)
│
├── YES, but I don't see what they're eating
│   → Start with the Parachute Adams.
│     If three drifts produce nothing,
│     switch to the Elk Hair Caddis.
│
└── NO surface activity
    │
    ├── Water is cold, high, or murky;
    │   or you cannot see a fish to target
    │   → Olive Woolly Bugger (size 8)
    │
    └── Water is normal, fish are likely
        feeding on the bottom
        │
        ├── Clear, slow-to-medium water
        │   → Pheasant Tail Nymph (size 16)
        │
        └── Mixed or unknown conditions;
            "I don't know what to try"
            → Hare's Ear (size 14)

Six leaves, six flies. Every fly in your box has a job and a trigger, and the leaf-by-leaf explanation of each pattern lives in How to use your Hatch Theory box.

When the tree disagrees with itself

The river is not tidy. The tree will sometimes give you two answers at once, and the rule across all of them is to trust what you actually see over what the conditions suggest.

Fish are rising but the water is high and murky. Trust your eyes. If they are looking up, start with a Stimulator because it is easier for them to see in stained water than a delicate mayfly pattern, and switch to the streamer if it does not produce in ten minutes.

Bugs are everywhere, but no fish are breaking the surface. Trout often eat emerging nymphs just below the surface during a hatch without showing themselves, so tie on a Pheasant Tail and fish it shallow, near the top of the water column.

Cold water but a visible fish holding in a clear run. The streamer is the default for cold water, but a fish you can actually see is worth a deliberate nymph drift first. Run a Hare's Ear past it, and if it ignores you twice, strip a Woolly Bugger through the same lane.

Late summer, low water, no visible activity. Hot afternoons shut down a lot of trout, but the banks can still produce on terrestrials and big attractors. Walk slowly, cast a Stimulator tight to grass and overhanging trees, and watch for an opportunistic hit.

How to use this

Read the tree once now and save the page on your phone. The first time you stand on the bank with it open, watch the water for two minutes and follow the tree top to bottom. By the tenth time it will feel automatic, and you will look at the water and know, before you ever open the box, which fly is about to come out of it. Six of the seven slots in your box correspond to a leaf on the tree. The seventh is for a specific kind of day, and you will know it when it arrives.