Fishing with Nymphs - Getting it Down to the Trout by Forrest A. Young

During the entire month of January this year, I was lucky to be able to spend a month targeting large trout in New Zealand (NZ). The challenge of sight fishing in NZ is unmatched and much of it is targeted nymph fishing.  There simply are not enough fish for a prospecting approach. 

Ninety percent of what I did was casting at fish that we (as in the guide in most cases) had spotted.  Spotting fish in the ultra-clear waters of NZ streams can be very challenging and the skills of a guide to assist is extremely valuable. 

Applying this type of thinking to fishing in the U.S and Canada will yield improved results for any angler.  The much-discussed Czech nymphing is all about penetrating the water column, over-coming drag, and optimizing the presentation of the nymph to feeding trout.  Since 90% of a trout’s daily feeding pattern is dedicated to subsurface feeding, it stands to reason that fly fishermen should use these techniques to achieve a better catch rate.

The rigs that I saw for target nymphing in New Zealand are quite different from practices in the U.S. and Canada. 

The common plastic indicator used across North America makes far too much noise and has too much presence on the water to be useful in targeting wild adult trout. 

A bit of sheep’s wool attached 12”-24” above the fly with a form of riffle hitch and coated with floatant makes a far better strike indicator.  The wool lands softly and is quite inobtrusive as it passes over the fish.

Alternately, a larger dry fly can also be used as a strike indicator.  The “fly indicator” can have advantages since the trout may elect to strike it occasionally.  However, the reverse can be true if the fish recognizes the fly as something un-natural.  It may go “off feed” if it senses something is not right.  As a result, I prefer the bit of sheep’s wool as my indicator.  I suggest using the smallest amount of wool possible.

If the trout is carefully observed for a few minutes, the chances for a successful presentation are greatly increased.  While there are quite a few ways to present a nymph, I have observed two different forms of subsurface feeding. 

The most challenging is the take right below the surface. This take will masquerade as a dry fly rise since the fish typically breaks the surface with a splash and/or exposure of its back and tail.  This subsurface rise is quite different from the “ring” that is left after a typical sip of an insect floating on the surface film.  Reading the rise forms when watching feeding fish is essential to properly presentation.

First, we cast a small and light nymph just upstream of the fish so the nymph rides just below or in the surface film.  Accuracy here is paramount.  Inaccurate casts will often result in refusals or outright spooking the trout.  We are not penetrating the water with this presentation; we are looking to have the fly ride high in the water column. Here a light, unweighted fly with a small diameter wire hook is the obvious choice.

It is more common to find trout feeding deeper under the surface. A fish observed feeding on station and actively moving back and forth across the current it is most likely feeding actively well below the surface.  Taking time and observing the behaviour is really a critical part of sight fishing.

This presentation requires us to have the fly penetrate the water so that it drifts down into in the zone where the trout is feeding.  Depending upon the depth and current, nymph imitations may need to have metal beads or wire wrapped around the hook shank to give it enough density to sink. Again, we must consider the density of the water (800 times denser than air). 

A nymph will take several seconds to sink before it is deep enough to be in the feeding zone the trout prefers.  We can accomplish this first, by timing the cast so that the fly lands softly on the water upstream of the fish and has time to sink.  This takes practice.  To help you determine the sink rate of a particular fly, merely drop the fly in the water by your feet and count how many seconds it takes to sink 12-15”.  This test will give you a starting point for the lead-time in your casts.

Secondly, using a weighted nymph it is a good way to achieve water penetration.  

There are many ways to achieve this: copper wire wrapped around the hook shank; hooks with heavy gauge wire, or beadheads. You can combine these if it is necessary to go deep and achieve quick sink rates.

Learn How to Tie the Pheasant Tail Nymph

Another way to get a good sink rate is by adding weight to the leader ahead of the nymph.  In the days before lead was recognized to be harmful to wildlife, split shot was commonly used. Now, being aware of the environmental consequence of lead exposure in wildlife, I prefer a little dab of tungsten putty rolled into the tippet a foot ahead of the nymph.

Finally, another approach, demonstrated by several New Zealand guides, was to use a sparsely nymph tied with a heavy hook.  This fly was a version of the San Juan worm called an “ace in the hole,” and was a last choice when going after fussy or already struck fish. 

Since water is so dense, a fly with the smallest surface area will give you the quickest water penetration.  Merely getting through the surface tension - as is illustrated by how well our dry flies float - is the first step in sinking a nymph down to where trout are actively feeding.

There are a few difficult trout lies where the water is extremely difficult to penetrate.

The first of these are at the heads of pools where the water - right before the pool - is running very fast and is relatively shallow.  Actively feeding trout will lurk down in the safety of the pool and make short excursions into the last of the shallow run right ahead of the pool to grab a nymph before it drifts past. Drag free drifts that keep the fly deep in the target zone can be quite a challenge. 

Spending a few minutes of observation before you cast will give you the best chances to have a successful presentation.

Other difficult presentation water includes deep water in pools or in lakes. For example, I have seen some highly specialized rigs that use extremely long leaders when fishing Chironomid flies in lakes. The most difficult place to fish nymphs are in tail-outs of deep pools where there is quite a bit of current.  Being aware of the hydraulics is critical to catching a fish that is feeding here. 

As the water shallows at the tail of the pool, it is moving upwards at speed in addition to moving downstream.  Penetrating water that is rushing upwards and downstream simultaneously is very challenging.  This is even more difficult if there is a tree or other obstruction over the pool. 

Trout greatly prefer pools and runs that have overhead cover. That is why we experience so many situations where the casts are difficult.

I recall one stretch while fishing with guide Kevin Payne on a spring creek in sight of Mt. Cook, on the South Island NZ.  A pool that held several 5-7 pound trout was being fed by a fast run of water funneled through a narrow rocky chute.  As the water entered the pool, it pushed towards me off the bank at a 45-degree angle.

After the bend, the pool shallowed and there were at least three large trout feeding actively.  I watched, as occasionally one would leave the depths to chase nymphs that had slipped past them in the rush of the water.  The problem was, the trout were at least 36” deep and the water was rushing up and out of a 6’ deep pool into the shallows of a tailout.

Thus, I had to surmount three major challenges in getting a nymph down to where those trout could see it. 

First, I had to make an accurate cast far enough upstream to allow time for the fly to sink-while at the same time not allowing my heavier leader, or worse, the fly line to pass over the wary fish holding deeper in the gin-clear water.  For this reason, almost all fly-fishing in NZ is done with 15-17’ leader/tippet combinations. 

Secondly, my fly had to penetrate over 36” of water column against the flow of the water up and out of the pool.  Thus, the first choice was a tungsten-bodied nymph. 

If you have ever cast a heavy tungsten nymph with a 17’ leader and a short amount of fly line across a 20-foot wide river, you can imagine the challenges. Problem: 15’ leader + 9.5’ fly rod = 24.5’.  Looking for a 30’ total length presentation allows 5.5’ of fly line to help cast the fly and leader.  Add a 20-knot wind and you can understand the challenges of this situation.   

I made several fair casts with a very buggy looking nymph. 

I had one of the smaller 5 lb. fish follow the nymph for about two meters, but it did not eat the fly.  Once a fish leaves the pool, it is my opinion (and Kevin’s) the trout becomes more and more reluctant to feed as it gets further away from its original station.

Thus, after failing to get the necessary depth to our fly, we decided upon a different strategy.  Kev dug in his amazingly diverse fly box and found a sparkly tied worm fly on a very heavy wire hook.  On the first cast, this fly sank right into the zone and we were rewarded with a beautiful 7-pound Kiwi brown trout. 

This fly’s combination of very low water resistance, i.e., low drag, and heavyweight allowed for fast and quick water penetration and depth to get the fly into the optimum zone for the fish to eat it.

While this particular type of pool only represented one out of every ten pools that we fished, the time you devote to challenging water will amount to a significant portion of any trip.  Being prepared with the knowledge and skillset to surmount these challenges will account for a lot more fish caught and a lot more satisfaction in accomplishment.

- written by Forrest Young