Nymph rigs, and why yours is not getting deep enough

Trout do the large majority of their feeding below the surface. That is not a controversial claim, and yet most people start out fishing a dry fly, because watching a fish eat something off the top is the reason many of us wanted to do this at all.

Nymphing is how you catch fish on the days when nothing is happening up there, which is most days. It has a reputation for being fiddly and unglamorous, and the reputation is partly earned. But the core of it is simple: get an imitation of a subsurface insect to drift past a fish at the depth it is sitting, moving at the speed the current is moving, and notice when something eats it.

Almost every problem in nymphing is one of those three things going wrong. Usually depth.

What the rig is made of

The standard indicator rig, working from the rod down, is roughly this:

• Fly line and leader. A tapered leader, commonly nine feet, transmitting the cast and getting you away from the thick fly line.
• An indicator. A float of some kind, attached to the leader. It suspends the rig, tells you how deep you are fishing and shows you the take.
• Tippet. A length of thinner level line from the end of the leader down to the flies. This is the part you replace as it gets shorter through the day.
• Weight. Either on the line, or built into a fly with a bead or a tungsten body, or both. This is what gets you down.
• One or two flies. If two, the second tied on behind the first, usually from the bend of the hook or from a tag of line.

That is the whole thing. There are dozens of variations and plenty of people with firm opinions about them, but none of the variations matter until the basic version is working.

Depth is the whole game

Here is the mistake nearly everybody makes for their first season, and plenty of people make for years: the flies are not deep enough.

The reason is not laziness, it is geometry. Your indicator sits on the surface, moving at surface speed. Your flies hang below it in slower water near the bed, dragged along behind. The line between them is not vertical, it slopes downstream. So the distance from your indicator to your fly, measured along the line, is longer than the depth you are actually fishing.

The rough rule that follows from this is to set the indicator at something like one and a half to two times the depth of the water. In a four-foot run, that means six to eight feet from indicator to fly. That feels like a lot the first time you rig it. It is usually still not enough in faster water.

The practical test is unglamorous and completely reliable: if you are not occasionally ticking the bottom, you are not deep enough. You want to feel or see the odd hesitation as a fly brushes gravel. If you never touch bottom, add weight or lengthen. If you are hanging up constantly, take some off. Most people never find the bottom at all, and conclude the fish are not there.

Then drift, which is the other half

A nymph dragging across the current at an angle looks like nothing that has ever lived. Fish ignore it, and you go home having covered a lot of water with an unconvincing fly.

The thing working against you is that the current is not one speed. It is faster at the surface than near the bed, and faster in the middle than at the edges. Your fly line lands across several of those speeds at once, the fast water grabs the middle of it, pushes a curve into it, and that curve starts pulling your flies along faster than the water they are in.

The fix is a mend: after the cast lands, you flip the middle of the line upstream without moving the flies, buying yourself a few more feet of honest drift. You will need to do it repeatedly through a single drift, and learning to do it without yanking the rig out of position is most of what improves in your first year of nymphing.

The other fix is to stand closer. A short line across one current speed is far easier to control than a long line across four. Nymphing is close-range fishing, and the instinct to cast further is almost always working against you.

Watching the indicator

Takes are usually not dramatic. What you are watching for is your indicator doing anything other than exactly what the current is doing: a pause, a dip, a small twitch, a sideways move, a hesitation that is out of rhythm.

The correct response to all of it is to set the hook. It will frequently be a rock, and that is fine. The cost of setting on a rock is a second of your time. The cost of not setting on a fish is the fish. New nymph anglers miss a great many takes they never knew about, and the fastest improvement available is simply to set on everything suspicious.

Set by lifting the rod smoothly and firmly downstream, not by heaving it skyward. A sharp upward yank with a heavy rig sends weight and flies flying at your head, which you will do once and then stop doing.

Two flies, and why

Fishing a pair of nymphs does two useful things at once. It doubles the number of imitations passing the fish, and, more usefully, it lets you ask two questions on the same drift: a heavier attractor-style fly and a smaller more realistic one, or two different insect stages, or two sizes of the same thing.

When one of the pair accounts for most of the fish, you have learned something concrete about the day, and you can put a version of it on both droppers. That is a genuine information-gathering method rather than a superstition, and it is the fastest way to work out what is going on in water you do not know.

Check the local rules on how many flies you may fish, because that varies by state and sometimes by individual stretch of river. Colorado Parks and Wildlife publishes the current Colorado regulations, and some sections carry their own tackle restrictions that differ from the statewide rule.

Where to put it

All of the above assumes you are drifting through water that holds fish. If you are not sure how to find that, read reading water first, because a perfect nymph rig drifting through empty water is a perfectly executed waste of an afternoon.

The short version: seams, the slower side of the current edge, the front and back of boulders, the lip at the head of a pool, and the shelf where a riffle drops into a run.

A short list of things that fix most bad days

1. Add weight. Then add more. This is the answer far more often than a fly change.
2. Move the indicator up. Deeper water and faster water both need more than you think.
3. Get closer and shorten the cast. Control beats reach.
4. Mend earlier and more often. The drift is decided in the first second after the line lands.
5. Set on anything odd. Free, and it costs you nothing to be wrong.
6. Change the fly last, not first. It is the most satisfying thing to change and the least likely to be the problem.

Which specific patterns and sizes to carry depends on the river and the month, and that is exactly the kind of thing that changes through a season, so it is not something to take from a web page written at one point in time. What a particular water demands of your kit is covered in our gear guides, and the fly-by-month detail for individual Colorado rivers is in the Colorado Playbook, which carries an edition date so you know how current it is.