Back in the late 1960s, a new trend arose in fly fishing that was known as “matching the hatch.” A hatch is the specific point where the larval form of an aquatic insect rises to the water’s surface (referred to as “emerging”), shucks its outer shell and metamorphoses into a flying insect.

Check your fly: The art of fly-tying means watching what’s hatching—such as this female March brown, Rhithrogena morrisoni. Photo courtesy University of Oregon

Choosing flies resembling insects that are either in their larval form, about to hatch or newly hatched is nothing new. For hundreds of years, folks have been tying flies that were intended to duplicate, with reasonable accuracy, the insects that were hatching on the water they would be fishing. But this new trend was consciously different, because it took a more avowedly scientific approach. It required of the angler the kind of serious observation of the aquatic insect’s life cycle, appearance and action that one would expect of an entomologist. Matching the hatch also advocated extremely accurate duplication (sometimes at streamside with the aid of a portable fly-tying kit) of the specific insects that were actually hatching in real time.

As a sophomore in high school who tied a limited variety of flies, I read Doug Swisher’s pioneering Selective Trout, one of the first books on the subject. Actually, I read enough of it to be intimidated by the disciplined approach and then lost interest. I was catching plenty of cutthroat trout on little Western streams and mountain lakes that had lots of fish and not much angling pressure. Discipline in fishing was something that I, as a 16-year-old, pimply-faced kid who was already catching fish with easy-to-tie attractor patterns, just couldn’t relate to.

One of my fishing pals, Stephen Downey, consistently catches more fish than I do. True, he’s a better fisherman than I am, but as I’ve gotten older, I’ve become more interested in observing insect activity the same way I watch for and identify birds. These days, I tend to spend considerably more time sitting at streamside observing than fishing.

A couple of years ago, I began carrying two little books when I fish—Art Flick’s New Streamside Guide and Trout Stream Insects by Dick Pobst. I also started packing one of those little nets that’s used to catch goldfish in home aquariums, so I can catch flies for identification. The first insect that I conclusively identified was the little black caddis, a black wisp of a thing about the size of a No. 16 hook. According to Pobst, this insect “emerges from gentle riffles and runs” and “rides the water as an adult.” I had seen this insect randomly riding smooth water, but it’s too small and dark for me to have noticed where it was actually hatching until I caught one and looked it up to find out about it.

Knowing where a specific insect emerges—in this case, in gentle riffles and runs—changes things considerably, because it tells you where fish are most likely to be taking advantage of a feeding opportunity. Once I found out that the little black caddis was probably emerging in the riffles 30 feet upstream from where I was sitting, I tied on a black-ant imitation (the closest thing I could find at the time in my fly box), trimmed the top off the hackle to more closely mimic a caddis emerger, rigged a strike indicator, and cast it into the riffles upstream. I caught a fish on the second cast, and the experience made a big impression on me.

Concerning insects that will be emerging on Western North Carolina waters in April: The March brown, when preparing to metamorphose, will move from the floor of the rapids (where they’ve lived for 99 percent of their lives) to emerge in slower water. The Quill Gordon lives and finally emerges in fast water. Blue-wing olives, in the larval form, inhabit gentle riffles and runs containing vegetation.

So identifying aquatic insects tells you more than just which imitation to tie onto the tippet; once you know where that insect is emerging, it also tells you (in theory, at least) where you’ll find the fish—and where you should fish the larval imitations. If, for example, you see March browns emerging in slow water, you might choose to tie on their larval-form artificial—a buggy little traditional pattern called a gold-ribbed hare’s ear—and fish it through fast water that’s upstream from slower water, because that’s where the larvae are actively preparing to emerge.

Just as a birder looks for specific markings to identify birds, an angler can do the same with aquatic insects. Many of the upright-winged flies we imitate in WNC waters have two or three tails. I easily identify two-tailed insects with the help of a memorized letter sequence: “QMGCD.” If I see a flying insect with two tail segments, I know it’s either a Quill Gordon, March brown, Gray fox, Cahill light or Dun variant. That tells me which insects I’m not seeing while hinting at what I may be seeing. From there, all you need to do is remember a few reasonably easy rules. A March brown, for example, looks similar in color (especially in marginal light conditions) to a gray fox, except that the March brown has barred wings.

Of course, all this information doesn’t necessarily mean you’ll catch more fish—at least it hasn’t for me. But when I’m not catching fish, it gives me a satisfying activity that’s bound to yield valuable knowledge for the next time I’m out there watching what’s emerging.

[Jeff Ashton lives in Weaverville.]

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