Virtually every fly fisher loves to fish a hatch. It’s hard to beat the pleasure of targeting a rising trout, selecting the right fly, presenting it well, and watching the trout rise and suck in your proffered fly. But most of the time, there is no hatch. Therefore, trout mostly fill their gullets with foods found below the surface. In “Fly Fishing the Subsurface, Suspension Nymphing”, I’ll begin a review of subsurface techniques and how to choose among them to fish a variety of stream features.

The Water Column

Compared with the water’s surface, fishing the subsurface is much more complicated. Of course, it doesn’t help that we can’t always see what’s happening there unless we go diving. But in general terms, we divide the subsurface into 3 layers. The upper 1-2 inches is referred to as the film, and the lower several inches is referred to as the bottom layer. Between these two layers is the largest layer, the mid-layer.

The mid-layer is the most complex. Its depth and force changes seasonally and with any significant precipitation. In addition, similar to the surface, it is affected by stream structure, which creates pockets of slow and fast water. Unlike the other two layers, the mid-layer has no non-aqueous interface to create friction. Thus the mid-layer moves faster than the surface, and still faster than the bottom layer, which is the slowest layer.

Given such differences in the water column, it should come as no surprise that a variety of techniques have been developed to fish the subsurface. Seasoned anglers arrive streamside prepared to fish several techniques. They evaluate both the water’s surface and the subsurface before preparing to cast their first fly. If no hatch is present, the focus is upon the mid and bottom layers, as the film is an important layer primarily during a hatch (see Fly Fishing Emergers).

Nymphing

Nymphing is the most commonly used method to fish the subsurface. It is so effective, that fishing clubs in England banned its use on chalk streams in the early 1900’s. Even today, some clubs continue to ban nymph-fishing. Over the years, a number of techniques have been developed to fish nymphs. Let’s begin with the simplest, suspension nymphing.

Suspension Nymphing, the Set-Up

Most fly fishers begin nymphing with the suspension technique. Other names for this technique include “dry-dropper”, and in the summer-time, “hopper-dropper”.

With this technique, a nymph is suspended, or dropped, with a length of tippet, from a dry fly, or a bobber-like affair, referred to as a “strike indicator”. The nymph is most often weighted. Alternatively, shot is pinched onto the tippet. Either method of weighting must be sufficient to sink the nymph to the slowest moving water near the bottom of the stream. This is where trout most often find nymphs crawling about the stream-bottom, feeding upon detritus.

As a rule of thumb, a length of tippet approximately 1 1/2 times the estimated stream depth is attached from the nymph to the indicator or the bend of the dry fly hook. In slow water, this may be more than is needed, leaving too much slack. Conversely, in fast water it may not be enough, with elimination of slack almost immediately. Thus, while the “1 1/2 rule” is a good starting point much of the time, a study of the water is helpful before starting.

A proper length of tippet allows the angler to begin a drift with a bit of slack in the tippet. Due to the speed differential between the mid  and bottom layers, the slack will be taken out as the drift proceeds. Once the tippet has straightened, the nymph will be dragged unnaturally along the bottom layer, alerting fish to its fraudulence. It’s difficult for the angler to detect this, but the indicator may be slowed a bit by the dragging nymph.

If dragging is suspected, it is easy enough to re-introduce slack. Simply perform an upstream mend if the indicator is upstream, or stop the downstream drift if the indicator is downstream. Once corrected, continue the drift. On longer drifts, especially if not getting strikes, I automatically adjust the drift several times.

If the nymph is deep enough, it will catch on rocks or other bottom-structure “periodically”. Everyone has their own yardstick, but I think that if the nymph isn’t ticking the bottom every 3-4 drifts, it isn’t deep enough. In that case, I either lengthen the tippet or add weight until I am feeling the bottom with some regularity.

Suspension Nymphing, the Approach

Suspension nymphing is best done by casting upstream, and drifting the flies downstream. Sometimes a strike is self-evident. Either the fish is seen turning under the indicator, or the indicator is pulled under the surface. More often, however, strikes are more subtle. They may be detected by noting that the indicator briefly pauses, or shifts slightly from its course. In each instance, the hook should be set. If no fish is on the line, simply lower the rod, and allow the drift to continue.

Personally, I prefer to use a dry fly rather than a strike indicator. It is easier to cast, makes less disturbance on the water’s surface, and casts a smaller shadow. In addition, even in the absence of a hatch, some fish invariably take the dry fly.

In some states however, only two flies can be fished at a time. Hence, the use of a strike indicator allows two nymphs to be fished, while the dry-dropper method allows only one. Nonetheless, I still prefer to fish a dry-dropper most of the time.

During a hatch, a variation of this technique is to drop an unweighted nymph from a dry fly. This is a very productive method to fish a hatch, as there are more pupae and nymphs trapped in the film than hatched flies on the surface. I use a short length of tippet, 6-8 inches, to stay “in touch” with the nymph. Longer lengths leave slack, allowing fish to spit the hook before being detected.

Suspension Nymphing, Casting

Most authorities recommend casting with a large, open loop to avoid snagging indicators and flies on the trailing line. But I prefer to cast normally, with a tight loop, which gives me better control and accuracy. I do make certain to keep my line-speed fast. In addition, I tip my rod slightly to the side, and bring the forward cast over the back cast. Should the flies sag a bit, due to arm fatigue, there is no line below them to snag and tangle with. So it’s a fielder’s choice, most dependent on the caster’s style and skill.

To begin a drift with the desired slack in the tippet, one must either mend the line at the onset, or use a “tuck cast”. Mending at the onset of a drift is messy, and disturbs the water. Thus most anglers learn to use the tuck cast, as championed by the late Joe Humphreys. In essence, it requires the caster to overpower the last forward cast, and tip the rod back a bit just before the line fully unfolds. The resultant abrupt stop causes the weighted nymphs to swing backwards under the indicator, and enter the water vertically. Here’s a short video demonstrating the tuck cast-  https://www.youtube.com/watch?v=Yy4FptzL94A.

Suspension Nymphing, the Flies

For nymphs, I typically use generic patterns. Nymphs blend with the stream bottom for their own preservation. Thus shades of brown and olive usually suffice. I like a bit of flash, and use dubbing blends with crystal flash or similar materials for the thorax. For legs, I either pick out a bit of the dubbing, or wrap a small hackle between the head and thorax. For weight, I use a tungsten bead-head for my heavy nymphs and brass for my lighter nymphs. I prefer red, pink or black colored beads.

If fishing two nymphs, I put my heavy fly in the point position. I attach the second, nearly weightless fly, eye to eye with 6-10 inches of tippet. With this method, both nymphs remain in or near the bottom layer of water. If fishing my usual dry-dropper method, I use only one weighted nymph.

For the dry fly, I find that a #14 parachute pattern or a palmered pattern, like an elk hair caddis, readily float one nymph. If I can fish two nymphs, or the water is fast and pulling my dry fly under, I move up to a #10 or #12 size fly, usually a Kaufman stimulator. During the summer and early fall, grasshopper and other terrestrial patterns work very well.

Suspension Nymphing, Limitations

One of the limitations of suspension-nymphing is the fact that the nymph(s) drift at a fixed depth under the indicator. But as we move from one section of stream to another, the water depth varies, requiring adjustments to the tippet length. Some indicators are designed to facilitate this. For a full discussion, see https://news.orvis.com/fly-fishing/pro-tips-choose-right-strike-indicator . But if fishing a dry dropper, a bit more time is needed to make the necessary tippet adjustments.

Another limitation arises because most runs vary in depth, usually in the shape of a bowl or hammock. Thus on any drift, the nymph is sometimes too high in the water column, sometimes too low (constantly getting caught on the stream bottom), or just right. Ideally, it would be just right most of the time. Thus I usually settle on a tippet length that puts my nymph on the bottom of the mid-portion of the run. It will be a bit high at the head of the run, and a bit low at the tail, but just right for most of the run.

If the water is deep, the necessary length of tippet between indicator and nymphs is quite long. More weight is needed to sink the nymphs, and slack is increasingly difficult to judge and manage. In addition, it is more difficult to avoid tangles when casting. Thus for me, if the water is more than 2 1/2 – 3 feet deep, I prefer to use other techniques, which I’ll address in my next blog, “Tightline Nymphing”.

Strike detection is also less than ideal with suspension nymphing. Due to the intermittent presence of slack, fish have time to spit the hook before affecting the drift of the indicator. It’s hard to know how many strikes are missed because of this. But when I began experimenting with tightline nymphing about twenty years ago, my increased catch-rates convinced me that the number of misses is substantial. Nonetheless, suspension nymphing is a productive way to nymph in many situations.

Suspension Nymphing, Ideal Water Features

Long runs typically feature lengthy stretches of water at a nearly constant depth. They also slow down, allowing longer exposure of the nymphs to feeding fish. The picture below illustrates such a run. It’s fall time, and the water is fairly shallow. Thus this run is readily fished with the suspension technique. Due to the water’s clarity and shallow depth, it is better fished dry-dropper than with a bulky indicator.

subsurface fly fishing, suspension nymphing

A long run on the Ruby River, Montana

Another stream feature frequently encountered is bankside runs. Slow, outside bends with overhanging vegetation provide cover and shade for the trout. Water depth is typically uniform, and the water is slowed by friction with the bank. Thus these runs are ideal for suspension nymphing, as seen below.

fly fishing the subsurface

A bankside run on the Rio Corcovado, Patagonia

Riffles and pocket water typically hold many trout, but they are especially difficult to fish. The proximity of widely different water velocities makes it difficult to keep our flies in the seam, which is where trout hold. Suspension nymphing provides visual confirmation of where our nymphs are drifting. Ideally, they should drift along the quiet side of each seam.

fly fishing the subsurface, suspension nymphing

Rocks on the MadisonRiver, creating visible seams

Large rivers such as the Madison present another challenge as well. Due to their breadth and flow, it is sometimes difficult to get close enough to a “fishy” piece of water to effectively use other nymphing techniques which require proximity to the angler. Thus suspension nymphing, which can be used from greater distances, is a good option.

Stillwaters are also an excellent venue for suspension nymphing. Food is not delivered by a current to waiting fish. Rather, the trout must cruise about in search of their food. They typically do this at a nearly fixed depth. Thus the key is to find that depth, and use a length of tippet to match it.

All stillwaters have midges, which flourish in their mud bottoms. Many times, trout can be seen cruising just below the surface, looking for midge pupae. They leave a tell-tale riseform, as seen below.

fly fishing the subsurface, suspension nymphing

A small mountain lake with bulging trout

To present pupae, I use 6-8 inches of tippet dropped from an adult pattern or a terrestrial. I carefully watch the trout’s path, and cast my flies at least 10-12 feet ahead to avoid spooking them. The dry fly holds the pupa at the selected water level. When the trout is 4-6 feet away, I give my flies a slight twitch to get its attention.

Midges in stillwaters are usually larger than we are accustomed to seeing on streams, so I don’t hesitate to use larger patterns, size #18 or even #16.

In Closing-

I’ve commented before about my reputation for not caring to share water when I’m fishing, but on this small stillwater, it was a pleasure!

fly fishing the subsurface

“sharing the water”

fly fishing the subsurface

but 3’s a crowd!

Next month I’ll continue with tightline nymphing.

Written by Al Simpson, June, 2019.