Stop Changing Flies: How to Actually Choose the Right Trout Fly

Fly selection isn't a guessing game. It's an experiment. And you might be ruining the experiment.

There is a strange ritual that happens on trout rivers everywhere.

An angler makes three casts with a Pheasant Tail. Nothing. Off it comes.

Hare's Ear. Four casts. Nothing.

Copper John. Nope.

Perdigon. Nope.

San Juan Worm. Apparently the trout have also rejected worms.

Eleven minutes later, there are six perfectly good flies stuck in the angler's hat, the tippet is two feet shorter, and absolutely nothing has been learned.

Then comes the inevitable conclusion:

"I've tried everything."

No, you haven't.

You've changed everything.

And those are two very different things.

One of the most valuable skills in fly fishing isn't knowing thousands of fly patterns. It's learning how to systematically determine why a trout should eat the fly you're already fishing and, when it doesn't, knowing which variable to change next.

Stop treating your fly box like a slot machine.

We're conducting a science experiment.

Admittedly, it's a science experiment where the laboratory is moving, the test subject refuses to answer questions, the weather changes every fifteen minutes and occasionally somebody floats through your experiment in an inflatable unicorn.

But an experiment nonetheless.

Before You Choose a Fly, Don't Choose a Fly

This might sound ridiculous coming from a company that sells flies, but your first decision shouldn't be which fly to use.

Look at the river.

Where are the trout feeding?

Are they holding near the bottom? Moving through the water column? Bulging beneath the surface? Rising confidently? Chasing minnows along the bank?

Next, ask what food is available. Are mayflies hatching? Caddis bouncing around the river? Stoneflies crawling toward shore? Midges coming off? Grasshoppers getting blown into the water? Did yesterday's rain put worms into the system?

Then ask which stage of that food source the trout are actually eating.

This is where anglers get fooled constantly. Seeing mayflies flying around doesn't necessarily mean trout are eating mayfly adults. They may be crushing nymphs before they reach the surface. Rising trout may actually be eating emergers trapped an inch beneath it.

The insect you see isn't always the insect being eaten.

Only after answering those questions should you open the fly box.

A useful sequence is:

DEPTH → FOOD → STAGE → SIZE → PROFILE → FLY

Notice where "fly" appears?

Last.

Your Fly Box Is Not a Menu

Anglers tend to think about flies by name.

"Should I fish a Pheasant Tail or a Hare's Ear?"

The trout isn't participating in that conversation.

It doesn't know what a Pheasant Tail is.

Instead, think about what those patterns accomplish.

A Pheasant Tail provides a slender mayfly-like profile. A Hare's Ear creates a buggy, impressionistic profile. A Copper John provides weight, segmentation and flash. A Perdigon sinks quickly with a slim silhouette. A San Juan Worm represents something entirely different while offering tremendous visibility and movement.

Patterns are tools.

So instead of asking:

"What fly should I use?"

ask:

"What problem am I trying to solve?"

Now we're fishing.

The One-Variable Rule

Here's where fly selection becomes powerful.

Suppose you're fishing a #16 Pheasant Tail under an indicator.

Nothing happens.

What does that tell you?

Almost nothing.

Maybe the fly is wrong.

But maybe the trout are six inches deeper. Maybe they're eating #18 insects. Maybe they're feeding on caddis instead of mayflies. Maybe your drift has micro-drag. Maybe your indicator is too close to the fly. Maybe trout aren't feeding there at all.

If you simultaneously change the fly, depth, weight and location, then immediately catch a trout, congratulations.

You caught a trout.

But you learned almost nothing about why.

Instead, try changing one variable.

Add six inches of depth.

Fish it again.

Nothing?

Try another six.

Still nothing?

Change the size while maintaining approximately the same presentation.

Suddenly a trout eats.

Now we have information.

The smaller profile may have mattered.

That's enormously more useful than randomly rotating through your fly box until something eventually happens.

Except the River Is Cheating

Of course, this would be beautifully simple if rivers weren't rivers.

While you're conducting your carefully controlled experiment, the sun disappears behind a cloud. Water temperature rises half a degree. A hatch begins. Wind changes direction. Trout reposition. A pulse of slightly coloured water arrives from a tributary.

Your laboratory won't sit still.

That's part of what makes fly fishing so endlessly interesting.

You can never truly isolate every variable because you're fishing inside a living system. But that doesn't mean logic is useless. It means observation becomes even more important.

You're not trying to create perfect science.

You're trying to become a better detective.

Before Changing Flies, Change Presentation

This rule will save you an enormous amount of time:

Before changing the pattern, make sure you've actually given that pattern a fair trial.

If you're nymphing, did the fly reach the feeding depth?

If you're dry-fly fishing, did it drift without drag?

If you're fishing an emerger, is it actually sitting in the film?

If you're swinging a soft hackle, did it move through the water trout are occupying?

A perfect fly presented incorrectly is still the wrong fly.

This is why experienced anglers can sometimes catch trout using remarkably ordinary patterns. They aren't necessarily carrying secret flies.

They're putting ordinary flies in extraordinary places.

Change Size Before You Obsess Over Colour

Fly fishing has convinced us that trout possess extraordinarily sophisticated opinions about shades of olive.

Sometimes colour absolutely matters.

But size and profile often matter more.

If trout are feeding on #18 mayflies and you're fishing something resembling a #12 Thanksgiving turkey, switching from olive to slightly darker olive probably isn't going to save you.

Go smaller.

Watch what happens.

If trout are inspecting your fly and refusing it, size should be one of the first variables you question.

A useful rule is:

Presentation before pattern. Size before colour. Stage before abandoning the hatch.

Put that one somewhere in your fly box.

Let Trout Give You Clues

A refusal isn't failure.

It's data.

A trout moves toward your fly but turns away? Excellent. At least the fish saw it.

A trout rises beside your dry but doesn't eat it? Perhaps it's feeding slightly below the surface.

Fish repeatedly inspect your fly? Consider size, profile or drag.

Nothing acknowledges your fly at all? Start questioning depth, location and whether you're imitating the correct food source.

The worst response is actually no response because it tells you the least.

A refusal is the trout saying:

"You're close. But something's wrong."

That's useful information.

When Should You Actually Change the Fly?

Change when you have a reason.

You identify a different insect.

Change.

The hatch progresses from nymphs to emergers.

Change.

Trout begin feeding at a different depth.

Adjust your presentation, then potentially change.

Fish repeatedly inspect but refuse your imitation.

Change size or profile.

Water suddenly becomes dirty.

Consider visibility, movement and contrast.

You notice trout chasing baitfish.

Please stop fishing the #18 Pheasant Tail.

The important word is because.

Whenever you change flies, you should be able to finish this sentence:

"I'm changing this fly because..."

If you can't finish the sentence, leave the fly on for another few drifts and keep watching.

You Probably Don't Need 400 Different Patterns

This is another mildly inconvenient statement for a company that sells flies.

A great fly box isn't necessarily one containing every fly ever invented.

It's one containing enough of the right tools to solve different problems.

You need different sizes.

Different stages.

Different profiles.

Different weights.

Different food categories.

And here's where buying flies by the dozen actually starts making sense. If #16 Pheasant Tails are working and you've got one left, you don't have a fly-selection problem anymore.

You have a procurement problem.

Conveniently, we know some people.

The point isn't to own twelve because twelve flies somehow catch more trout simultaneously. It's having enough confidence patterns that losing one to a tree, rock, trout or your fishing buddy's ear doesn't suddenly end the experiment.

Become a Trout Scientist

The best anglers I've fished with aren't necessarily the people who know the most fly names.

They're the people who notice things.

They ask questions.

Why did that fish move?

Why did it refuse?

Why did trout suddenly start rising?

Why did this fly work in that seam but not the slower water?

They develop theories, test them and adjust.

Sometimes they're completely wrong.

That's okay.

Being wrong and learning something is considerably more valuable than being accidentally right.

That's the real game of fly selection.

Not guessing correctly.

Deducing correctly.

So next time nothing eats your fly, resist the urge to immediately attack your fly box like you're trying to defuse a bomb.

Watch the river.

Think about depth.

Identify the food.

Determine the stage.

Match the size.

Consider the profile.

Evaluate your presentation.

Then, if the evidence points somewhere else, change the fly.

One variable.

One reason.

One new piece of information.

Because the river is already changing enough variables without your help.

And when everything finally lines up, the indicator disappears, the dry gets eaten or the line suddenly comes tight, you'll have gained something considerably more valuable than knowing which fly caught that trout.

You'll understand why it worked.

And once you understand why, you can do it again.

That's when fly selection stops being luck.

And starts becoming fishing.

FishFuel supplies the variables. Unfortunately, the trout still control the experiment.