The authors collecting nymphs in April by using a screen to catch whatever they dislodge from the bottom. (Al Caucci and Bob Nastasi photo)
March 03, 2025
By Al Caucci and Bob Nastasi
Editor's note: Flyfisherman.com will periodically be posting articles written and published before the Internet, from the Fly Fisherman magazine print archives. The wit and wisdom from legendary fly-fishing writers like Ernest Schwiebert, Gary LaFontaine, Lefty Kreh, Robert Traver, Gary Borger, Joan & Lee Wulff, Vince Marinaro, Doug Swisher & Carl Richards, Nick Lyons, and many more deserve a second life. These articles are reprinted here exactly as published in their day and may contain information, philosophies, or language that reveals a different time and age. This should be used for historical purposes only.
This article originally appeared in the April 1976 issue of Fly Fisherman magazine. Click here for a PDF of the print version of "Collecting Nymphs."
Caucci and Nastasi have been scouring stream bottoms for so long it's rumored they're developing gills under their fishing vests. Developers of the Comparahatch system, these two author-anglers share their collecting techniques with you.
Much of the information about hatching and feeding activity on trout waters is hand-me-down "old angler's tales" which may have started with information taken out of context in the first place. Some of this information may be either wrong or, at best, misleading. Over the years, we both can recall an abundance of well-meant advice from friends and local experts. Although it was given sincerely, most of it never panned out and resulted in many less-than-successful fishing trips in our early days.
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When hot tips on hatching and feeding activity never materialized, it was still fun to fish the water blind with nymphs, wet flies and streamers. Nevertheless, if our guess is correct, most fly fishermen sooner or later get that itch to catch good hatches–the kinds that put trout on feeding sprees.
Our years of research on many streams around the country show that, if you really want to fish the hatches on your favorite streams, you probably need to know more about them than you do now. Correct information is necessary in order to anticipate impending feeding activity and to be there at the right time with the right fly. The chances are that not much is known about your particular stream, so you'll have to collect the information yourself.
It's important to realize that, to really know a stream, river or lake can be a lifetime project. But the making of new some simple observations in the course of a few trips to new water will greatly increase your chances of success.
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Using a Stream Net A few minutes of work with a screen or other netting device will quickly reveal what aquatic insects are most abundant. The procedure is simple-one person holds the screen upright in the current while the second kicks up the bottom a few feet upstream. If you're working by yourself, you can brace the screen against some rocks and do your own kicking-up.
What you kick up will be caught in the screen, which is then taken ashore for examination. At first glance the screen may appear lifeless–filled only with debris and vegetation. But focus on a few square inches of the screen and it will soon come alive with the movements of aquatic nymphs and larvae.
The Willowemoc at DeBruce, N.Y.; a typical location suited to stream collecting of nymphs. (Al Caucci and Bob Nastasi photo) If you've done some homework and can already recognize the major nymphal types found in your particular area from photographs in our book, Hatches
[We have included in this issue Jim Gilford's superb photos and commentary on major nymphal types as an aid in this type of work. THE EDITORS.]
You should estimate the relative abundance of the types of aquatic life collected in your screen before put ting samples in plastic bottles to take home and identify later. The nymphs are best examined alive, and if you're in for a long trip you should be carrying them in stream water in a relatively large (one gallon, for example) container that will keep them alive until you can work on them. Final examination can be made with an ordinary magnifying glass, but an 8X magnifier will be most helpful for identification.
It is possible that any individual sample may be damaged in some way which might hinder identification. Make your identifications on the basis of your examination of several examples of the same type of nymph.
At first the novice may find it hard to differentiate among individual types within the stonefly, caddis and mayfly orders, although differences between the orders themselves are very obvious. Often mayfly nymphs of various types will predominate, although caddis flies may run a close second, or even pass, mayflies in numbers on streams with varying degrees of pollution. As we pointed out in Hatches, the mayflies can be divided into four basic nymph types as a basis for identification: the flattened clingers, the more rounded, feeble-legged crawlers, the tusk-bearing burrowers and the swift swimmers.
You should remember in doing your collecting that not all nymphal types will be found in the same places. Fast shallow riffles will yield nymphs of some types while silt bottoms and backwaters will yield others. If you're really going to cover a stream, make sure you do some collecting in all the aquatic habitats present.
You'll find an ordinary kitchen strainer handy too. You can simply hold this small item below some rocks in the same manner used with the larger screen. You'll get smaller samples but you'll avoid disturbing other fishermen who may be in the same area and who would probably resent a couple of guys kicking up the bottom of their pool. The strainer also is best for sifting silt to look for burrowing nymphs. Dig into three to five inches of silt and swish it around in the strainer. The silt will wash away leaving the inhabitants, if any.
Stocking Your Own Nymph Aquarium Before we leave the stream, we fill plastic jugs with stream water and collect some rocks, plants and so on from the stream bottom which will be used to stock our aquariums. Our aquarium set-ups range from very elaborate to very simple, the latter being the case when we're using them in some motel or cabin near a stream.
We have raised most of our stream-collected, immature nymphs to adults by creating the required environment for each nymph type in our lab aquariums, ranging from three to twenty gallons in capacity. The controlled temperature of a small room (55-65 degrees) accelerates nymphal growth and can yield a basement hatch in mid-winter.
If you are stocking an aquarium this spring-and we urge that you do--you'll get some valuable lessons on nymph fishing just by watching your collection. You'll be able to see how they swim and you may reach some conclusions about working your own imitations on the stream. You may also be able to watch the emergence stage and get some information on just how an emerger pattern might be designed and fished.
This article originally appeared in the April 1976 issue of Fly Fisherman. The fast-water clingers–i.e., Stenonema and Epeorus (March Brown, Cahill, Quill Gordon) and similar nymphs–are the most difficult to raise because they prefer a turbulent fast-water habitat that's hard to duplicate in an aquarium. We have had good luck here by using a series of aquarium aerators, the bubbles from which produce turbulence in the aquarium. Most manifolds on aquarium air pumps have several outlets which can be hooked up to several "air stones" placed under rocks in the tank. These can be adjusted to produce the desired effect. This set-up can be achieved for less than $10, not including the cost of the tank.
It is not our intention to push everybody into an elaborate aquarium set-up–even a simple glass jar can be of big help this spring. Collect some mature nymphs from the stream-those with dark wingpads which indicate they're near hatching–and place them in quart jars. This is also a good way to segregate various species for identification.
A filtration system won't be needed if you don't put too many in one jar but you will need an aeration system and you should try to keep the water between 55 and 65 degrees by keeping the jars in an appropriate location. The best place might be near a window which will also provide the natural cycle of daylight and darkness. After doing all this, don't neglect to check them from time to time and observe their activity.
The whole project is only a little bit of work and a lot of fun. You will also be a better nymph fisherman because of it.
