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How to Fool Selective Trout During a Blue-Winged Olive Hatch

Lessons learned during the first mayfly hatch of the season.

How to Fool Selective Trout During a Blue-Winged Olive Hatch

There may still be snow on the ground (or snow in the air) when tailwater trout move from their deep, slow wintering holes and begin hunting Blue-winged Olives in the riffles. (Pat Dorsey photo)

This article was originally titled, "Spring Thing" in the April-May 2015 issue of Fly Fisherman magazine. 


Born and raised in the central Rockies, I grew up fishing on some of the most technical tailwaters in the country. Each journey into Trout Country became a problem-solving exercise where the river and trout determined the best solution for success.

I’ve spent hundreds of days on the South Platte River in Cheesman Canyon, where part of my curriculum involved learning how to fool selective trout during a Blue-winged Olive hatch. This included understanding all the facets of the emergence, from the complexities of catching trout on tiny nymphs (before the hatch), to dry-fly fishing under the most challenging of conditions.

The fish I fooled provided positive reinforcement on reading the water, matching the hatch, fly selection—and presentation. Most importantly, I was able to take the skills I learned in Cheesman Canyon and apply them to other rivers with similar success.


Success is always sweet, but strange as it might sound, some of my most valuable lessons on Western waters came as a result of failures.


I recall standing knee-deep in the Ice Box (a famous hole in Cheesman Canyon) at 1 P.M. casting to a pod of rising trout that were sipping Blue-winged Olives. Toward the head of the run there was an especially impressive rainbow that was surfacing every three to five seconds.

How to Fool Selective Trout During a Blue Winged Olive Hatch
The worst weather in March and April often results in the best Blue-winged Olive hatches, and you’ll often have the stream to yourself. (Pat Dorsey photo)

I knew from the head-to-tail rise forms that the trout was feeding on duns. I quietly moved into position, standing 20 feet downstream from where the fish was feeding just under the surface. I was confident that if I sneaked in from behind, I had a good chance of fooling the trout.

My first cast was 2 feet short. I immediately picked up my fly line and recast, but I overcompensated, and my next cast was too long. The disturbance from my fly line falling to the water over the trout sent it darting for cover.

While my failed attempt was disappointing, it taught me the importance of a down-and-across presentation combined with a reach mend. It didn’t take me much longer to figure out that a delivery where the fly precedes the tippet is the most effective strategy for difficult rising fish almost anywhere—from Silver Creek to the Henry’s Fork.




Trout Selectivity

By the first week of April (late March when conditions are favorable), trout that spent the winter in the slow runs and deep pools of Western rivers move back into the faster riffles, preparing for the first mayfly hatches of the season. Gone are the days of feeding opportunistically on intermittent hatches of midges; trout instead become more focused and feed selectively on Baetis nymphs. Fly fishers who fail to recognize these seasonal feeding transitions have extreme difficulty fooling fish.

How to Fool Selective Trout During a Blue Winged Olive Hatch
Baetis nymphs are active swimmers, and sometimes a swinging presentation with a Leisenring lift can entice selective trout into taking the fly. (Pat Dorsey photo)

Baetis nymphs are most active midday from 1 to 3 P.M., which provides some of the best nymph fishing of the spring season. Concentrate your efforts in the shallow riffles, runs, and transitional zones (mid-channel shelves and gravel bars), where you expect to find the heaviest concentration of feeding fish. In clear water, you should find opportunities to spot and stalk some impressive trout this time of year in 12 to 18 inches of water.

When the fish are especially picky, I use a tandem nymphing rig consisting of three Baetis nymphs. (Check your local fishing regulations with regard to the legality of multiple-fly rigs, each state varies.) I normally use a Juju Baetis as my attractor (because of the flashback), and drop a Stalcup’s Baetis, trailed by a chocolate Foam Wing Emerger on the bottom.

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Let Your Flies Swing

The majority of fly fishers are familiar with basic dead-drift nymphing techniques. In most situations, there’s no substitute for a precise dead-drift; it’s the difference between catching and not catching fish.

As a professional guide, I have ingrained this concept into my clients’ heads for over two decades. But I’ve also learned that it never hurts to experiment from time to time and closely observe what happens.

I remember one afternoon on the Williams Fork watching a rainbow feeding voraciously on Baetis nymphs. It was early afternoon, and there was already a smattering of Blue-winged Olives on the water. It was a bright and sunny day so the duns were escaping the water quickly, which eliminated the possibility of any dry-fly fishing.

The fish I was watching was clearly keying on Baetis nymphs. The trout frequently turned and chased its food downstream.

After the rainbow intercepted a Baetis nymph, it returned upstream to its original holding position. Every few seconds the trout repeated the process, eating a dozen or more Baetis nymphs in less than two minutes.

After the trout rejected my initial dead-drift offerings, it became evident to me that it was keying on the swimming behavior of the emerging Baetis nymphs. While I had the correct size, silhouette, and color of the naturals—it didn’t matter; it was the behavior of the emerging Baetis nymph that provided a trigger for this feeding fish.

To swing your flies you’ll need to remove your strike indicator (if you have one) and position yourself upstream of the trout. Experiment with the length of your line so that when the leader tightens, the flies gently rise in front of the trout, simulating an emerging (swimming) Baetis. I have found that patterns like a chocolate Foam Wing Emerger (with a squared-off 2 mm craft foam wing) swing and rise to the surface with an irregular swimming motion that closely mimics the natural.

How to Fool Selective Trout During a Blue Winged Olive Hatch
A stomach pump quickly reveals the importance of carrying a thorough selection of Baetis nymphs during the spring season. Choose a pattern that is close in size, has a similar silhouette, and has approximately the same color. It’s important to note that spring Baetis are one to two sizes larger than the autumn generation. (Pat Dorsey photo)

Special lifting techniques like the Leisenring lift (named after James Leisenring) use a dead-drift at first to help sink the flies, and then use a swing-and-lift with the rod tip to simulate an emerging insect. Soft-hackles like Charlie Craven’s Soft Hackle Emerger are also good options if you plan on imparting some subtle motion with your rod tip.

Inclement Weather

March and April are two of the snowiest months in the Rockies and also two of the best fishing months, as gnarly spring blizzards can produce epic Blue-winged Olive hatches. If you are strictly a fair-weather fly fisher, you might want to consider the Green Drake hatch in July?

Fishing in extreme weather is really only as difficult as you make it. With all the modern-day advancements in cold-weather apparel, it’s easy to keep warm and dry in adverse conditions.

I plan many of my personal outings around snowy or rainy conditions because I have had some of my best dry-fly experiences when it’s nasty out.

I made it to the South Platte near Deckers last April when Colorado Highway 67 was barely passable, and the visibility was down to a couple car lengths. More than once, my buddy and I thought about turning around, but hope for a blanket hatch, solitude, and dry-fly fishing kept us on track. We eventually made it to the hamlet of Deckers around 11 A.M., and had the place to ourselves.

It was a classic Blue-winged Olive day, the skies were dark and gloomy and snow was falling. In conditions like this, BWOs begin hatching earlier in the day, and continue until early evening. Cool weather combined with moisture stalls the emergence process of the newly hatched duns, keeping them on the water longer, making them extremely vulnerable.

It seemed the trout anticipated these conditions as much as we did, and as suspected, scores of rising fish were already sipping Blue-winged Olives in the slower pools and tailouts. We hopped out of the truck and headed straight to the Bend Pool, where we spent the afternoon catching trout on dry flies.

Low-Riding Bugs

When I first began targeting Blue-winged Olive hatches, I fished a lot of conventional dry flies like Blue Duns and Blue Quills, which are traditional Catskill-style dry flies. I fooled some trout with these patterns, but I had a fair number of refusals, and some trout just wouldn’t take traditional hackled dry flies.

I tried all the common fixes—downsizing my tippet, fishing with smaller flies, using specialty casts and reach mends to perfect the drift—but the end result was often still a refusal.

I knew it had something to do with the way my artificial was sitting on the water. That’s when I began experimenting with Parachute and Compara-dun imitations. I immediately noticed a difference in the way trout were taking my fly—they were sipping it with confidence because my fly was sitting lower in the surface film, giving it a much more realistic impression to the fish. With these mayflies it’s important that the fly body sits down in the water, and that the fly doesn’t ride up high on its hackle tips.

Compara-dun-style flies meet all these requirements, and Mathews’s Sparkle Dun, Cannon’s Snowshoe Dun, and Barr’s Vis-A-Dun have fooled selective trout all over the country. They are must-have patterns for any serious Blue-winged Olive fly fishers—but they can sometimes be difficult to see.

Parachute posts provide the perfect wing silhouette, but also make your fly easier to see. I tie my Parachutes with a McFlyon wing instead of calf hair, which simplifies the tying process. By swapping the white wing with cerise, you have a hi-vis variation, which becomes much easier to see in harsh glare and foam lines.

Approach and Delivery

The primary goal of any dry-fly fisher is to get as close to a rising trout as possible without spooking it. I know this sounds obvious, but it’s more difficult than it seems. Getting close often means crouching, crawling on your hands and knees, and bushwhacking until you get to the best casting spot.

And what is the best location? Before you crawl, you need to determine if your delivery is upstream, downstream, or up-and-across. Which side of the river should you be on, based on the surface glare and visibility of your fly? Where can you best maximize your accuracy and line control? Is there adequate casting room for your backcast? Which direction will you set the hook? And finally, where do you land the trout after you hook it? Carefully consider these variables before you make your first cast.

I have found that an upstream delivery—casting from directly behind the trout—greatly reduces the chances of spooking fish because (in theory) you are casting from the trout’s blind spot. However, excessive false casting tends to spook fish, as surface feeders are extremely sensitive to overhead threats. Keep your false casting to a minimum, and learn to “shoot” line accurately so you don’t measure the line distance right over the trout’s head. Whatever you do, don’t overshoot your target and line the trout. Only the fly and a few feet of tippet should land in the trout’s field of vision.

How to Fool Selective Trout During a Blue Winged Olive Hatch
My favorite Baetis nymphs include: #20-22 Stalcup’s Baetis (shown here), Juju Baetis, Mercury Baetis, and chocolate Foam-wing Emergers. If you tie your own Baetis nymphs, make sure you tie them thin and sparse—bulky imitations do not fool nearly as many trout. (Pat Dorsey photo)

Drag is much easier to eliminate with an upstream presentation because your fly line and leader drift toward you, constantly creating slack. All you need to do is pay attention to line management and strip the fly line in as it drifts toward you and keep the line under your finger so you can set the hook. Perhaps the greatest benefit of this position is the angle of the hook-set, which almost always pulls the hook back toward the trout for a positive hook-up.

When you cast across and downstream to a rising fish, you’ll use a slack line cast such as a reach cast, S-cast, or parachute cast to offset the effects of the current.

If I have a choice, I prefer a downstream delivery because the first thing the fish sees is your fly—not the tippet, leader, or fly line—which in many cases results in a refusal or spooked trout.

Be careful with your approach, because the fish are facing you and are easily spooked by sloppy casting or aggressive wading. Wear drab clothes, keep your profile low, move carefully, and quietly.

One of the biggest challenges with a downstream delivery is getting a good hook-set because you’re pulling the fly away from the trout’s jaw, which naturally decreases your odds of a good hook-up. The solution is to be patient—allow the fish to engulf the fly, then watch for its head to dip below the surface. Then set the hook. Your odds of a good hook-set increase exponentially if the fish’s mouth is closed—it’s better yet if the fish turns to one side or another to resume a position. If possible, use a sidearm or sweeping motion to gently set the hook. If you set the hook straight upstream by merely lifting, chances are good you’ll miss the fish.

Up-and-Across Delivery

The up-and-across presentation is nothing more than a combination of the two previously mentioned tactics. It gives you the advantages of a downstream hook-set (sweep the rod downstream to heighten this effect), and by angling your cast accurately with an upstream reach cast you can show the fish your fly and nothing else.

Tips on Accuracy

I cannot overemphasize the importance of a precise delivery. Getting as close as possible to the rising fish increases your effective accuracy, and allows you to better control drag. Too many fly fishers feel the need to cast several feet or even several yards above a rising fish. Excessive line on the water requires mending, which often pulls the fly out of the feeding lane or causes movement that ends in a refusal.

Your landing zone should be a foot or 2 feet above the rising fish—less distance in shallow water, a little more distance in deeper water. The less time your fly sits on the water, the less likely it is to drag. In most cases, you only need a second or two (1 to 2 feet of drag-free float) to fool trout on the surface.

These are just a few of the lessons I’ve learned (or had reinforced) while fishing spring Blue-winged Olive hatches. Hopefully they’ll help you find some answers for the next difficult trout you find quietly nosing the surface, and asking you to play the game.

Eddies & Foam Mats

Eddies form where protruding logs, large boulders, and other structures along the bank deflect the current, causing it to slow and flow in a clockwise or counterclockwise pattern. These merry-go-rounds trap huge quantities of food and foam, making them prime feeding locations during the height of a Blue-winged Olive hatch, particularly on tailwaters and spring creeks where even the “leftovers” can present irresistible feeding opportunities.

How to Fool Selective Trout During a Blue Winged Olive Hatch
In foam mats and bubble lines, the author uses a #18-20 Hi-Vis Baetis trailed by a #20 Mathews’s Sparkle Dun. (Pat Dorsey photo)

Surface bubbles are also trapped by these back eddies and in some cases form to join opaque mats which are filled with food items, and at the same time provide excellent cover from overhead threats and other predators. I have fooled some of my biggest trout on dry flies in eddies.

In foam mats and bubble lines, I use a #18-20 Hi-Vis Baetis trailed by a #20 Mathews’s Sparkle Dun. The Hi-Vis Baetis is easy to see in foam and acts as a locator for your Sparkle Dun. If you are having difficulty seeing your flies, try casting them into the small spaces that open and close as a result of the conflicting currents. The trout also focus on these moving windows because they can better see the duns on the water. These windows open and close quickly, so precise, quick casting becomes paramount.

You may also see bulging riseforms, which means the trout are taking emergers just underneath the foam. This is the perfect opportunity to fish a dry-and-dropper rig. When I see this, I cut off the Sparkle Dun and tie on a Juju Baetis instead. The weight of the epoxy wingpad on the Juju Baetis is sufficient enough to get the fly just below the surface.


Pat Dorsey is the southwest field editor of Fly Fisherman and author of three books. His latest is Tying & Fishing Tailwater Flies: 500 Step-by-Step Photos for 24 Proven Patterns (Stackpole Books, Headwater Books, 2010).

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