Nymph or Dry – A small stream decision.

Box of 6 Flies

Before the first cast comes the decision: which type of fly, nymph or dry? Logically, you could choose either, or both (and yes, I know there are also streamers, but it is a rare choice, so let’s not complicate things). This decision is often driven by the angler’s preference, predilection, fanaticism, or the latest magazine infomercial. I have tried to put my prejudices aside to give you an approach that will give you a choice that may improve your chance of success.

I consider the following questions:

  1. Are the trout rising?
  2. What food sources are available and abundant?
  3. Where is the trout likely to be holding?

Are the trout rising?

This is why it pays to stop and watch the water before you fish. If you can observe a trout rising, it gives away its location and a likely way to fool it.

When a fish is rising , it means the trout is looking up for a meal, and often means the trout is sitting mid water or higher. In this situation it is important that you fly be above the trout’s holding level, a dry, a lightly weighted nymph on a greased leader or a dry with a nymph on the dropper ( up to 60 cm) are all options.

A heavy nymph on a long leader is likely to drop below the level of this trout and therefore drift by unnoticed and untouched.

What food sources are available and abundant?

According to many reliable sources, most of a trout’s diet consists of sub-aquatic insects. Some say it is as high as 70%. In New Zealand rivers, this is often much higher. A nymph will generally take a trout all year round but may not be the best choice on a given day.

Certainly, the insects we imitate with dry flies are not abundant year-round, and typically early season and very late season there are very few species that are in sufficient abundance to suggest imitating them is the best option to fool a trout.

In the warmer months, November through to March, here in Victoria, terrestrial insects are abundant, as are hatches of sub aquatic insects. A single dry fly is great first choice at this time of year; however, you can also choose a lightly weighted nymph or a nymph dry dropper. Recent rain will lift the water levels, and releasing more nymphs, so as the water drops to a fishable level, the trout can be focussed on nymphs and reluctant to rise.

Very early season Sept/October and late season May/June, the cooler weather and higher flows means very terrestrial few insects about and little or no surface feeding. While catching a trout on a dry fly is not impossible it is highly improbable, and the weighted nymph will be your best choice.

Where is the trout likely to be holding?

Trout hold position , facing up stream, where the force of the current is low. This enables them to minimise their energy expenditure while watching for passing food.

Fast water

In sections of the stream where the water is flowing quickly, trout are likely to be found in the lee of a boulder or mid-stream obstruction, hard up against the bank or right on the bottom. All these positions will have protection from the main current.

Slow pools and runs

In the slower pools and runs the trout may hold position to feed or patrol a beat searching for food.

Deep Water

In deep (over 1 metre) fast flowing sections, the trout will often be on the bottom, and will be hard to tempt with a dry fly. It takes a lot of energy to swim up to the top, then back down again, so it needs to be worth it for the trout. A big hopper will sometimes pull a large trout up from the deep. However, a better option is to fish a weighted nymph under an indicator on a long dropper that drifts just above the riverbed.

where the bubble line flows hard against the bank, or a log, the trout will be holding and feeding there, and a fly drifted within a few inches of the bank will be pounced on. Trying to fish a weighted nymph, or a dry dropper hard up against the bank is supremely difficult, and usually end up either drifting too far from the bank , or snagged up. If it is a smooth rock wall it is possible to hit the wall with nymph and indicator and let it slide straight down. A successful technique I discovered by accident on a pool on the Crooked River. A better option is a single dry fly (if the time of year is right), as an accurate cast within six inches of the bank is easier to achieve.

Midstream boulders can be targeted by drifting or swinging a heavy nymph drifted close by. Another option is to land a dry fly in the dead point above or below the boulder with a slack line presentation, so it pauses a few precious seconds to entice a take.

In the deep slow pools, the trout could be anywhere: deep on the bottom, or up on the surface feeding. If the water is over a metre deep, unless the trout are visibly feeding, a nymph is most likely to be productive, however in the warmer months a dry fly drifted in the bubble line is a better first choice, and if unsuccessful, you can always try a deep nymph subsequently.

Mid Depth Water

Any water between fifty centimetres and a metre deep is good holding water that allows a trout to feed easily anywhere from the bottom to the surface, however in the quicker water, the trout will need some protection from the current. At the right time of year, the trout will rise from the bottom to take the dry. A good first choice for any time of the season, is a dry dropper combination. Early and late season the weighted nymph should be first choice, and in the warmer months a dry fly is often best.

Shallow Fast Water

Trout, especially rainbow trout, like to feed in fast shallow broken water: there is food, oxygen and cover. In warmer weather this is a good area to target with the dry, or a nymph on a short dropper under an indicator/dry fly. Within this water the trout are often able to hold in hollows and depressions, or between small boulders. the quieter pockets are worth targeting in the same manner.

Often overlooked, slow shallow water can hold some surprising fish, especially if there is nearby cover or bolt hole. Given a nymph is likely to get snagged on the bottom, your best choice here is a dry fly. An alternate option is an unweighted nymph on a greased leader.

Summary

Depending on the time of year, and water speed and depth, sometimes there is a superior choice, however often not so important, and your choice may boil down to your personal preference. I have included a table and a legend below to give you a guide. Note upper case means the choice should be a primary one, lower case , means it is a secondary option you might also consider.

MonthDeep > 1mMid (0.5 to 1m)Shallow (<0.5m)
SepNWNW,dnNU
OctNWNW,dn,d,nuNU,d
NovNW,D,DNNW,DN,D,NUNU,D
DecNW,D,dnDN,D,NUnu,D
JanNW,D,dnDN,D,NUnu,D
FebNW,D,dnDN,D,NUnu,D
MarNW,D,dnDN,D,NUnu,D
AprNW,dNW,DN,D,NUNU,D
MayNWNW,dn,d,nuNU,d
JunNWNW,dnNU
Fly Choice by Month and Water Depth

Weighted NymphNW,nw
Unweighted NymphNU,nu
Dry Nymph ComboDN,dn
DryD,d
Fly Type Legend

At one stage, I used to fish almost predominantly the nymph. In warmer months a dry with a nymph dropper, and only fish the dry, when the trout stopped taking the nymph. These days my first preference is to fish the dry, where the time of year and water allows it. Where there is good holding water and the nymph is a better choice, I will swap over. I prefer to fish a single fly for simplicity, trusting in my choice. To that end I carry two reels, one rigged with a line and leader for dry, and the other with a line and leader for nymphing. I find it easier to swap reels over than meddle with leaders, especially if I need to swap back and forth as I progress along the stream.

Feel free to share your thoughts in the comments.

Author: twigandstream

Fly fishing Guide and Casting Coach.

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