This story was originally titled Trigger Nymphs: How to use “situational awareness” to increase your subsurface success. It appeared in the Aug-Sep 2018 issue of Fly Fisherman.
Trout have brains the size of a pea. They are capable of eating all available food sources, but sometimes they focus on specific triggers that suggest a specific emergence stage, size, shape, movement, or color. In other words, they become "selective." We all realize there are instances when trout develop this laser focus on some specific food sources. This is especially true on insect-rich streams where options for food are great, and trout can afford to be choosy about what they eat.
On the reverse side, on small mountain streams where less food is available, trout will chase down and eat anything resembling a possible food source. In these cases, variations of Pheasant Tails, Hare's Ears, and other suggestive patterns will catch fish all year. Suggestive patterns are the proverbial "killing two birds with one stone." Look at the how many possible mayfly species a Hare's Ear can imitate.
Most of the time, however, our trout fishing exists somewhere between these two extremes, and while the trout might not be completely selective, merely suggestive patterns aren't what the trout are looking for either. In most situations, fly fishers need to exhibit "situational awareness" and fish nymphs designed to trigger a strike when trout are keyed on a particular food item. It doesn't have to be an exact match, but you must be able to trigger a response.
If you've ever witnessed a great hatch on a legendary stream like the West Branch of the Delaware River, Henry's Fork, South Holston, or Silver Creek, you'll recall seeing surface-feeding trout keying in on specific insects. The same phenomenon occurs below the surface, but we can't always see what's happening. All we can do is look at possible variables and come up with a best guess approach. Situational awareness occurs when you are able to understand these critical clues about what's going on in a trout's world, and develop a strategy based on those observations.You should also know how to effectively tip the odds in your favor while nymphing. (Photo by Jay Nichols)
In the past I've been guilty of stubbornly trying to force feed trout what I want to tie on, but as a friend of mine once said to me years ago "You can't dictate to the trout what you want to feed them. Let the trout tell you what they want." He mentioned this after seeing my box full of only suggestive patterns. His rationale was that with good technique, any nymph pattern has the chance to catch a fish at given time. But to increase the odds of success, we need to show trout what they are looking for. We need situational awareness.
When Mother Nature is advertising a specific food item, we need to be good salespeople and give trout what they want. Don't try to sell trout a deep-drifting stonefly when they are eating sunken spinners less than a foot under the water. Give trout what they want, and you'll get what you want—more success on the stream. Take your time to read the water and in time, the stream will tell you what it's currently advertising.
My hope with this article is to provide you with several situations I see on my local waters, and provide you with examples to look for when fishing your home waters. Hopefully this will get you thinking about possible variables that can effect pattern selection during your own nymphing adventures.
My home state of Pennsylvania is known for its spring creeks and limestone streams, but these types of trout waters exist across the nation from California (Hat Creek and Hot Creek), to the Rockies (Paradise Valley spring creeks), and throughout the Driftless Region of the Midwest.
Freshwater shrimp (aka scuds) thrive in these types of waters, and provide trout a year-round food source. Scuds are also an important food source in major tailwater rivers like the Bighorn below Yellowtail Dam and the Colorado River below Glen Canyon Dam at Lees Ferry.
For many years I read about fly fishers using orange-colored patterns on the Bighorn to imitate dead or spawning scuds. Whether a trout knows an orange scud represents an easy, lifeless meal to pick off, or that it contains a belly full of extra protein in the form of eggs, is anyone's guess. Both are workable theories.
What we know is that trout see orange scuds on a regular basis, especially in specific locations. Scuds are killed when they flush through the dam turbines. They turn orange, and their corpses float through the upper reaches of many tailwaters. Bring a small section of orange scuds with you next time you fish near a dam release or any scud kill zone. You may find yourself with a few additional trout to net.
The methods of adding orange to scud patterns are endless. Some tiers use all orange, a hint of orange through the entire pattern, orange hot spots in specific locations, or an orange beadhead.
One of my favorite scud patterns is a "guide-style nymph," which means it takes only a couple minutes to tie. Guide-style flies are typically not pretty to look at, but very effective.
Trout Crack was created by John Wilson, who at the time was a guide on the White River in Arkansas. He's now the president of Cortland Line Company. Trout Crack is essentially a strip of orange V-rib pulled over the top of a tan or olive dubbed body, and ribbed with clear nylon monofilament or wire. A head of orange thread gives the impression of a dead or pregnant scud.
Another option is a version of Sexy Walt's Worm that contains a 50/50 blend of natural Hare's Ear dubbing and orange Ice Dub. Trout Crack and Sexy Walt's Worm are my two confidence patterns whenever I'm in scud country.
I once heard someone say that the best hatch in Pennsylvania isn't Sulphurs, Blue-winged Olives, or even Green Drakes . . . it's sucker spawn. It's hard to argue that point. This event not only influences the types of flies the trout will take, but where the trout locate themselves in the stream. When suckers are spawning, trout don't seem to care about much else.
I've heard many people say that egg imitations aren't "real" fly fishing. I disagree. Where I live, sucker spawn is part of the natural system just like mayflies, caddis, and stoneflies. If sucker spawn isn't a real fly, then neither is a baitfish imitation in saltwater or drifting sockeye egg imitations in Alaska. Refusing to switch over to sucker spawn at times is merely a failure to observe and react. I've seen situations where it seemed every trout in the stream was focused exclusively on sucker spawn, and acknowledging this situational variable was critical to catching fish.Flies that take advantage of situational feeding opportunities are important parts of your fly selection. Sunken terrestrials, sucker spawn, swimming nymphs, mayfly nymphs with pronounced budding wingcases, and flies that imitate dead or dying shrimp should be in your play book. (Photo by Jeff Simpson)
Many of the streams I fish contain white suckers, a species that begins to spawn in the spring when water temps reach 50 degrees F. Suckers seek out shallow riffles with pea-sized gravel, normally at the ends of larger pools. I've witnessed short sections of streams that appear to be devoid of trout, until I find a pod of 30 trout congregated into a small area fighting over displaced sucker eggs.
Because competition is fierce among these hungry trout, presentation is not as important as other times of the year. For example, when I began teaching my kids how to fly fish for trout, I realized I needed to provide them with immediate results. Our hard-fished local waters can be challenging for all angling skill levels during normal conditions, and sometimes it's downright difficult for kids to catch trout.
So whenever I located a pod of spawning suckers during a guide trip, I'd take both of my kids out that evening to the same sucker spot, and they were rarely disappointed. I rarely use the word "epic" but if you find a group of trout feeding immediately downstream of actively spawning suckers, you'll have an Homeric experience.
All Great Lakes tributaries have spawning runs of different types of suckers, which explains why steelhead there are so partial to egg and sucker spawn imitations. In Alaska, trout feed on eggs from spawning Pacific salmon, and in the fall, some rivers with Rocky Mountain whitefish have similar occurrences. It's always a good idea to carry flies that imitate eggs and spawn sacs from other fish.
Less than 10 years ago I was coaching the North Carolina Fly Fishing Team. I frequently drove to western North Carolina, coached for a few days, and then drove back to Pennsylvania. I always stopped at the South Holston River on my way back. I parked at the lot near the outflow grates, curled up, slept in the back seat of my Toyota Corolla, and woke up at first light to get on the water. It was a great opportunity to fish one of the more challenging East Coast streams.
On one occasion I stopped at the local fly shop, and the guys behind the counter suggested nymphing with split-back Sulphur nymphs. Up to that point, I never heard the term "split back" but the shop guys suggested that the highly educated South Holston River trout keyed in on the yellow budding wingcase of these mayflies during their emergence. As it turns out, the pattern fooled many wary trout on the South Holston, and I soon discovered how effective it was on my local waters as well.
The version I tie has a budding wingcase made of a tuft of yellow Holographic Tinsel. The key to any variation is building a budding wingcase to match the size and color of the natural you're imitating. For example, you can turn any Sulphur pattern into a budding wingcase pattern by merely adding yellow holographic flashback. Another good option is using Mike Mercer's Trigger Nymph concept and using a tuft of protruding dubbing to imitate a budding wingcase.
The concept doesn't just apply to Sulphurs. Budding wingcases trigger a feeding response in trout on highly pressured waters everywhere, and it's a great element to add to any Blue-winged Olive imitation.
Currently my favorite dubbing for a budding wingcase is Hareline's Laser Dub. Light yellow is a great color for Sulphurs and PMDs. I use gray for Blue-winged Olive nymphs. The options for creating mayfly imitations with budding wingcases are endless.
Another important mayfly nymph trait is movement. Perhaps there's no better example than Isonychia nymphs. These long, sleek mayfly nymphs wiggle as they actively swim, and they have prominent gills located along their sides. These insects have such a prominent wiggling motion that I feel it's important to tie and fish these nymph patterns to mirror these movements.
While some mayflies drift helplessly to the surface to hatch, the majority of Iso nymphs swim actively toward the shoreline and then crawl onto nearby rocks or vegetation to hatch. You'll see the nymph shucks on the rocks and vegetation, as with stonefly nymphs earlier in the year.
A dead-drift presentation works for Iso nymphs through most of the year, but during an actual emergence when Iso nymphs are actively swimming toward the shore, swinging the nymph toward the bank produces greater results. You can also add short strips with your line hand as you would with a streamer. Use a no-slip loop knot to provide additional movement.
It's important to buy or tie patterns that breathe and wiggle. Gills made of ostrich or emu breathe in the water like the natural gills of the insects. Tails constructed of marabou, or a small pinch of Arctic fox, also wiggle during the swung presentation and give the impression of life.
Just as with the split-wing concept being adaptable to more than just Sulphurs, this swimming tail concept can be applied to other patterns as well. One of my favorite stonefly patterns is a Mega Prince variation with a marabou tail for extra movement. I swing it toward the bank during the early summer stonefly migration. When you swim your nymphs, the fly doesn't have to be an exact replica. It's the movement the trout tend to focus on.
It's no secret that trout love terrestrials, but fly fishers place most of their attention on dry-fly patterns. As the name suggests, terrestrials don't respond well when falling into the water. These helpless land-dwelling insects become easy meals for trout once they find themselves in an aquatic environment. In some instances, terrestrials remain in the surface film for a short duration, but even a small amount of turbulence pulls them under. Once they become submerged, they drift downstream for long distances, which makes them easy pickings for trout.
Trout find a steady supply of drifting terrestrials through the summer, but a strong breeze or a brief summer rainstorm often displaces terrestrial insects in greater numbers, causing trout to at least temporarily focus on this important food source.
Nymphing doesn't mean bouncing your rig on the stream bottom. Trout are inured to seeing drowned terrestrials, but unlike aquatic insects, terrestrials don't start their journey at the bottom of the river, they enter the water from above. As a result, I nymph with lightly weighted terrestrial patterns and fish them higher in the water column. This means I may fish a sunken terrestrial higher on the leader when fishing a tight-line nymphing rig. Or I use a dry/dropper rig with a lightly weighted terrestrial a foot below a high-vis dry fly.Flies like Trout Crack or Sexy Walt's Worm are tied to imitate dead or dying scuds, but almost any small nymph tied with a fluorescent orange thread head will also do the job. (Photo by Jay Nichols)
Because I favor keeping these sunken terrestrials immediately below the surface, tungsten beadhead patterns are usually not my first choice. Instead, epoxy-style bodies or fur-dubbed patterns are all you need. Keep the sunken patterns sparse, and often the hook weight alone achieves the correct depth.
One of the best lessons I got in sunken terrestrials occurred when central Pennsylvania had its last appearance of the 17-year periodical cicada. Some of the best dry-fly fishing I've seen occurred within the first week of their arrival, but angling pressure eventually slowed it down.
My friend Brian Keen watched the effectiveness of dry-fly imitations diminish while seeing a number of cicadas drifting below the water's surface. He thinned the wings of his dry flies and used split-shot to sink his patterns. While it was difficult for him to move away from watching trout smash his #6 cicada dry fly on the surface, he couldn't argue with excellent results of using a giant sunken terrestrial. Brian showed me photos of some of the biggest brown trout he caught during the cicada invasion, and they all came from his decision to use a drowned terrestrial as a "nymph."
Understanding these triggers isn't a complex physics formula. Instead, it's simple observation and understanding the seasonal ebb and flow of what trout are eating. This ability to observe the aquatic world, understand its behavior on trout, and make adjustments is the kind of situational awareness that makes you a far more successful fly fisher. Experience on the water, help from your local fly shop, and good literature can also help you better understand when you need to be more specific with how you choose your flies. This kind of informed intuition can lead to better days onstream.
George Daniel is the author of the new book Nymph Fishing: New Angles, Tactics, and Techniques (Stackpole Books, 2018). He owns and operates the company Livin on the Fly and presents schools, seminars, and private lessons across the country.