Tactics for Fly Fishing a Hatch
After a bit of a hike, we reach our stream. As rods are being assembled, the first question is usually “What fly are you going to use?” But a better question is “How are you going to fish this hatch?”, or “What tactics are you going to use?”. Fly selection is an important part of the tactics decided upon, but there is much more to it than simply “matching the hatch”. Wild rainbow and brown trout are often choosey, or “selective” of their food choices. And during a hatch, they may progress through their meal much like we progress from salad to entree to dessert.
So let’s start over. We have reached the stream, and observe some bugs in the air and on the water’s surface. Noting their size and color is a good start. But even more important is noting what order of insect they are, mayflies, caddisflies, midges, or stoneflies. With this added information, we can consider both which flies to use and how to fish them.
Beginning with mayflies, the newly hatched dun must float on the water surface for 20-30 seconds in order to dry its wings before it is able to fly. Thus a dun pattern is usually an effective pattern for fishing a mayfly hatch. But we also know that many rising nymphs are unable to break through the surface film, and still more are unable to escape their split exoskeletons. These bugs, unable to take flight, are more vulnerable to feeding trout than the duns. Thus emerger and cripple patterns are more effective than dun patterns during a hatch. Even better is to fish a tandem of flies, a dun and an emerger or cripple pattern.
A mayfly hatch is often a mixed affair. That is, although fly fishers still refer to it as a “hatch”, aerial mating and ovipositing may take place along with some hatching activity. A female mayfly sitting on the water’s surface with a full egg sac is a very nutritious meal!
After ovipositing is completed, the spent female will lie prostrate on the water surface, unable to escape a feeding trout. Thus, as the “hatch” progresses, the available stage of a fly changes, and trout change their preferences. An observant fly fisher responds by changing tactics, and selecting fly patterns that imitate the preferred stages.
All of these vulnerable mayfly stages, trapped nymphs, crippled duns, hatched duns, ovipositing spinners, and spent spinners are carried in the stream current. Thus the imitative patterns are best fished with a floating line, and drifted in the current, just like the naturals.
Next, let’s consider a caddis hatch. Caddisflies undergo a complete metamorphosis, similar to butterflies, before attempting to leave their water world. Transformed from a larva into a pupa, they have legs that allow them to quickly swim to the water surface and blast through the film. Once on the surface, they swiftly split their exoskeletons. Unlike mayflies, their hydrophobic wings allow them to dry their wings with a few flaps, and take flight in a second or two. Thus they do not present the same mayfly-like vulnerable stages to the trout.
Caddis hatch throughout the day in small numbers, and usually attract little notice from the trout. Once hatched, they fly to streamside brush, where they mate. They return to the water a few days later at dusk to oviposit. Thus the evening caddis “hatch” is a mixed event, with hatching flies and ovipositing flies. Many caddis species dive into the water and attach their eggs to stream-bottom rocks. They then try to swim back to the surface. As a result, there are simultaneously rising pupae, diving egg-laden females, and spent females swimming about.
It should be very apparent that fishing a caddisfly hatch requires different tactics than those used to fish a mayfly hatch. Generally speaking, fewer fish are taken with dry flies. When I fish a dry fly, I like a pattern that is heavily hackled so that it can be skipped on the surface, imitating a newly hatched fly, flapping its wings to take flight. I cast them across or slightly downstream, so that they can be skipped upstream, just as the naturals do.
But most of the action is under the surface. Emergent pupae or soft-hackled wet flies are good patterns. Most important is how they are fished. Emerging pupae swim upstream. Therefore, I cast my flies across or slightly downstream, and pause the drift several times, which draws the flies toward the surface. This can be done with a dry-dropper rig, or a tightline rig. With the former, I drop the pupa pattern with 6-10″ of tippet, tying the tippet to the hook-bend of the dry fly, and the to the hook-eye of the pupa pattern. When tight-lining, I use two pupae patterns, tied hook-eye to hook-eye, roughly twelve inches apart. A really good tactic is to intermittently bring the upper fly all the way to the surface, and dap it there, like a hatched fly trying to take flight.
Although midges undergo complete metamorphosis, similar to caddis flies, they are severely handicapped due to their small size. As the pupae try to break through the surface film, they are victims of the equation E=MC squared, that is energy = MASS x speed squared. Thus, during a hatch, there are many pupae trapped in the film, hanging vertically, and unable to emerge from the water.
When fishing a midge hatch, I almost always use a tandem rig, consisting of a dry fly and an emerger. For the dry fly, a small Parachute Adams or a Griffiths Gnat work well. They will draw some strikes, but more importantly, they are visible to the fly fisher, and act like an indicator. For the emerger, I prefer a Quigley Cripple. It hangs vertically in the water, just like the trapped midge pupae, and its post is visible. I tie them hook-eye to hook-eye with 12-24 inches of tippet.
I cast my tandem of flies upstream, and let them drift naturally.
When mature, most stonefly nymphs crawl to the stream’s edge where the adults emerge. They mate in the streamside brush and return to the water several days later to lay their eggs. Thus, although adult stoneflies may be present, there is no “hatch”. Big and clumsy, they often fall or get blown from the riparian foliage onto the water. Otherwise, the females have come back to the stream to lay their eggs, dropping them onto the surface. In either event, they become trapped in the film, and wiggle about, similar to terrestrials that don’t belong on the water.
To fish them, I like a fly with some palmered hackle, similar to caddis patterns, which allows me to skip them about, imitating their helpless behavior. I cast them across or slightly downstream, so that I can best impart action to them during the drift.
Having already stipulated that a hatch is fished with a floating line, the remaining equipment to consider includes the leader and the rod. The selection of these is mostly driven by the stream and its conditions. So lets begin with a small stream, like the one seen below.
Leaders serve two purposes, to put space between the fish-spooking line and to allow the fly to move freely on the water, much like the natural bugs. In general, I use the shortest workable leader, to avoid excess slack and increase hook-set. On small mountain streams, 7 1/2 – 9 feet usually works well. My preference is fluorocarbon. It sinks just a bit, making it nearly invisible. Floating mono is highly visible from below the surface.
I generally prefer fishing with a 10 foot rod. But for small streams, I usually fish an 8’6″ rod. This allows me to more easily weave through all the streamside brush, and cast with a full stroke in limited space. I like a rod with medium-fast action and a soft tip. The soft tip loads easily with just 2-3 feet of line outside the tiptop, yet the rod readily casts 30-40 feet should I encounter a long run.
When fishing medium-sized, like the one above, or larger streams, I prefer a longer rod, generally 10 feet, with a medium-fast action and a soft tip. This provides greater reach over intervening currents, and easily casts longer distances that are often encountered on large streams. It also handles small dry flies, tandems, and streamers, all of which may come into play when fishing a large stream all day.
I usually fish with a 12′ leader, but if a stream is heavily fished, or low and crystal clear with spooky fish, like the stream below, I lengthen the leader to 15-20 feet.
So next time you fish a hatch, take a few moments to study the bugs and the stream, then select the tactics most likely to put some fish into your net.
Written by Al Simpson, February, 2021.
4 thoughts on “Tactics for Fly Fishing a Hatch”
Excellent article, as usual.
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