Practical and Useful

Practical and Useful

Fishing Under the Hatch

  • By: Dave Hughes
  • Photography by: Dave Hughes

Fishing Under the Hatch
There’s a lot going on under the surface, and the trout are paying attention.

THE LATE POLLY ROSBOROUGH, AUTHOR OF Tying and Fishing the Fuzzy Nymphs, always declared that the biggest trout remain beneath the surface throughout a hatch, no matter how heavy, feeding on immature insects staging along the bottom or on their way toward the top for emergence. It makes sense: Insects are more vulnerable to interception then, and trout are less exposed to predation from birds and beasts, including you and me.
I don’t know that this is always true. I’ve had some nice-size trout nip at size 20 Blue-Wing Olive dun dressings on Montana’s Bighorn River, and some others make mistakes about size 22 CDC midge dries on food-rich lakes. As an extended observation, however, on those waters and many others, during those hatches and most others, I’ve taken the largest trout—and very often the most trout—by fishing a pattern that imitates not the adult that is hatching, but the nymph or pupa that is just moments away from becoming that adult.
Rosborough’s own prescription for the Gray Drake mayfly (Siphlonurus occidentalis) is a prime example. Though he had his Black Drake Spinner for the final and fatal stage of the hatch, he had no dun dressing, and relied almost exclusively on his Near Enough Nymph during the hatch. It makes sense. Gray Drake spinnerfalls can be heavy enough to require attention, but the duns crawl out on protruding grasses and reed stems to emerge. While wind or accident might sprinkle enough duns on the water to interest a few trout, they’re almost certainly an indication of much more extensive feeding going on underneath. Many more nymphs are taken moving toward shore. Rosborough’s imitative Near Enough, fished on a slow swing with an occasional twitch of the rod tip to mimic the darting behavior of the natural, incites much more riot than a dry fly adrift on top.
The Blue-Wing Olive mayfly (Baetis) is another example in which the messages might be more mixed. It’s a mid-water hatch. The number of duns on the water can be incredible. The size of the noses poking out to accept them can be disconcerting. Every trout in a pod, including the largest of them, might be happy to take floating insects, and to accept your dry flies. When that is true, I’d never be the one to recommend you cease fishing on the surface and turn to something sunk. But be sure to take a close gander at the rise-rings over which you’re casting. If bubbles are left in a rise, that’s an indication the trout broke the surface during the take; either an adult or a surface-film emerger went down the gullet. If no bubbles show in the rise, then the trout took a BWO nymph so close to the top that it looked like a surface take, but the surface wasn’t broken. The preponderance of trout in a pod might feed sub-surface, or it can be an individual thing: this trout taking duns and that one so near it preferring nymphs. It’s tempting to say that the little fish take duns and the big ones feed on nymphs, but in my experience it’s far more random than that. I do know, however, that when many trout or a single trout feed just sub-surface, you can present a dry fly to them perfectly and catch nothing but frustration.
The standard solution is to drop a Pheasant Tail Nymph off the stern of the dry fly, thereby offering trout their choice so you’ll fool them all. It might work on the smoothest water, in the best light, if you’ve got eagle’s eyes, but a nymph suspended from a dry fly of the same size normally pulls the dry fly under. You’ll have no way to tell what’s happening out there. When you fish a nymph, you want to know about takes as soon as possible. To fish under a BWO hatch, replace the dry fly with the nymph and add a tiny yarn indicator at the upper end of the tippet. To fish both a dry and a nymph, add a tippet behind the dry fly, tie on a nymph, then slip-knot a small yarn indicator about four feet up the leader from the dry fly. When you see the indicator move, or see a rise anywhere near it, set the hook.
Mayflies are quite various, in both dun and nymph stages. The same principles apply to fishing all of them, but you need to know what nymph dressing to fish under which hatch. One way is to study books, learn that the nymph of a Gray Drake dun is imitated with a Near Enough, that the nymph of a BWO dun is matched with a Pheasant Tail, and so on through the most important hatches. Another way is to accomplish your own studies. When you get into a hatch of mayfly duns, and have reason to fish under them, get out a collecting net and discover for yourself which nymph leads to what dun. Certainly such study will be most useful in your own fishing.
With caddisflies, midges, stoneflies and damselflies you’ll follow a similar formula for fishing under the hatch. You observe the adult on the surface, whether or not it’s attended by feeding trout. You correlate the adult with the stage that leads to it. Then you fish an imitation of that stage according to the manner in which the natural might move.
In the caddis life cycle, the adult emerges from the pupal stage. Caddis pupae have a characteristic shape: bulbous bodies with no tails, dark wingpads tapering along each side, long legs and antennae that trail back along the body. Their size will be in keeping with the adult they predict. Their color will be somewhat unpredictable. Again, you’ll need to establish the connection—Spotted Sedge adult to olive pupa; Brown Summer Flyer Sedge to amber pupa—either from books or through your own collecting. Once you’ve selected the right pupa to fish under the hatch, you can fish it on a slow swing, suspend it under a floating imitation of the adult if the dry fly will support it, add an indicator and fish it alone, or fish it in combination with a dry behind a visible indicator.
I once took a search through all my photos of caddis pupae. It turned out that all but a very minor few were one of four colors: olive, tan, cream or amber. If you were to choose a pattern style, say Gary LaFontaine’s Deep Sparkle Pupa, and tie it in those colors, each in a range of sizes from 12 to 16, you would have about 90 percent of all caddis pupae covered. It’s a small fly box that would prepare you to fish under nearly any caddis hatch.
I have occasionally had success fishing a Little Yellow Stone dry fly during Yellow Sally stonefly hatches. But I learned long ago, in part through reading Ernest Schwiebert’s Nymphs, in larger part through my own experience, that a standard Light Cahill wet fly in size 12 or 14, fished on the swing under the sporadic rises with which trout usually seem to respond to Yellow Sally adults, results in far more trout led thrashing to my hand. It’s not an imitation of the nymph. Instead, it imitates drowned and submerged adults. Such adults, whether stonefly, mayfly or caddis, offer another reason to fish under the hatch.
I’ve also noticed, while fishing my home Deschutes River through many seasons of the famous salmonfly hatch, that trout continue to focus on nymphs for a few days after adults begin to appear. As with all stoneflies, these largest of them crawl out to emerge, usually in late evening or after dark. It seems that trout keep their focus downward until about half the hatch is over and the balance begins to tip from nymphs to adults. Until that tipping point, I’ve seen trout feeding visibly on salmonfly nymphs in shallow water but refuse a natural salmonfly adult that struggled right over their heads. Early in the hatch, you need to fish under it. Later, a dry fly draws detonations.
When midges hatch, whether on streams or stillwaters, it’s fairly common knowledge that a Thread Midge Pupa suspended a few inches to a foot beneath a small indicator takes far more trout than almost any dry fly. There are exceptions, of course, just as there are during any other hatch. Most often, however, you’ll catch more trout and—as Rosborough pointed out—usually larger ones by collecting the prevailing midge pupa, matching its size and color, and fishing that pattern under the hatch, than you ever will by matching the adult midge.
I’m not recommending that you give up matching hatches. I’m advising that you take the discipline one step further: Learn what the insect up top tells you about what is happening down below. Trout are down there, often the largest of them. Fish under the hatch when conditions call for it and you’ll make contact with many more of them.
Dave Hughes’ latest book is Pocketguide to Western Hatches.

Photographs by dave hughes