Peninsula Fly Fishers

Entomology And Trout

by Igor Doncov

March 2004

Fishing, in it's basic form, is really just a form of hunting. Unlike hunting, however, where the hunter actively pursues his quarry, the fisherman attracts the fish to the hook by preparing a food source which the fish finds so irresistible that it overcomes it's fears and takes the offering. You would think that this underlying principle of all fishing would motivate trout fly fishers to study a trout's diet more carefully. But apparently not!

Ask a fly fisher about entomology and you will often get a scowl and something like, "I can't be bothered counting the number of hairs on the abdomen of a mayfly". Well, guess what? That's not entomology! That's taxonomyundefineda branch of the life sciences dealing with identification. Entomology is a broader field that deals with all aspects of insect life. It covers life cycles, reproductive patterns, natural history, migratory behavior, feeding behavior, and population dynamics, to name just a few. An understanding of entomology is what permits a mediocre trout fisher to move up to the next level.

In order to see the importance of entomology to flyfishing, it is instructive to look at the history of the sport. In my opinion, there are two ways to gain flyfishing knowledge: (1) trial and error, and (2) investigative research. Up until about WWII, trout flies were designed through a system of trial and error. A pattern was constructed and offered to the trout. If it was not rejected, it was considered a good pattern. Attractor dry and wet flies dominated the sport. This period of history largely ignored entomology and generated primitive patterns by today's standards. The Royal Coachmen was considered by many to be the best all around dry fly. Despite the limitations of this methodology, a few superior patterns were developed: the "Adams" and the "Hare's Ear" come to mind.

A revolution in fly fishing started around the 1950's as the sport caught up to the science. Schwiebert wrote Match the Hatch and we started to look below the surface. Parachutes replaced hackled dries because they created more realistic profiles. Doug Swisher came out with no-hackle dries to represent emergers. Emergers now dominate fly patterns because it was shown that trout will usually ignore duns and feed on emergers during a hatch. What's an emerger? No one knew until they studied the entomology of a mayfly. La Fontaine wrote Caddisflies, and we finally moved on from religiously dead-drifting elk hair caddis flies. He showed that prior to emerging, caddis swim actively beneath the surface and that trout feed selectively on these pupal forms, rather than surface adults (which are more evasive). Enter Sylvester Nemes and his soft-hackled flies which cashed in on this very important behavior. The current state of flyfishing stands on the shoulders of these men and others who had the curiosity and intelligence to examine the entomology of the trout's food source. They revolutionized the sport and the revolution continues today in stillwaters, saltwater, and other mediums.

Most anglers undergo a similar maturation process during their careers. We all start out by wading freestone rivers, flicking our Royal Wulffs at likely pocket water. We end up covering a lot of holding water, catching fish that are not actively feeding, but are on the lookout for an infrequent bug. Eventually, we end up visiting a quality fishery, such as the Big Horn River. A trico spinner fall has just occurred and the fish are pigging out. We cast our Humpy and nothing happens. We have the worst fishing day of our lives. At this point in his career, the angler either takes a quantum leap forward or remains in mediocrity. If unwilling to accept defeat, he hits the flyshops and starts to read the books mentioned above. He learns what the major bugs are and the circumstances of their hatches, and targets them accordingly. He fishes the BWO hatch on the Green in April. He fishes the chironomid hatch in Kamloops in early May. He fishes the caddis hatch in the August evenings on the Missouri River. He fishes the summer sardine hatch in Baja (just kidding). And so on.

A lot of effort and literature at our club seems to be devoted to the relative importance of fly casting to a flyfisherman. I suppose there is a sense of achivement in being able to hit a twelve-inch target. But it is far more valuable to know (a) which twelve-inch target holds the feeding trout, (b) what time of day and year the target holds the feeding trout, and (c) what fly to deliver to the target. Entomology answers those questions. My philosophy is, if you can't hit the target, for gosh sakes, take a couple of steps closer and cast again. By the way, stealth is an undervalued skill in flyfishing. It too should be ranked above casting ability.

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