Ramblings of a Catskill fly fisher

Blue-winged olives are hatching in the Catskills

By TONY BONAVIST
Posted 9/22/21

With summer on the wane, and fall just a few short weeks, away, the little blue-winged olive mayfly hatches are beginning in earnest on most Catskill rivers.

I actually saw the first emergence in …

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Ramblings of a Catskill fly fisher

Blue-winged olives are hatching in the Catskills

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With summer on the wane, and fall just a few short weeks, away, the little blue-winged olive mayfly hatches are beginning in earnest on most Catskill rivers.

I actually saw the first emergence in late July this year, on the upper reaches of the East Branch of the Delaware River. The little flies were emerging in the midst of a very large sulphur mayfly hatch that ran well into August, which is an anomaly.

Of all Catskill mayflies, the olives hatch for the longest period of time. They begin in early spring, and extend well into fall, even November, for those anglers hardy enough to go fishing. Although the historical hatching record indicates it, I’ve never observed any significant olive activity on the river I fish until at least July. However, angling friends have noted that they have observed the flies on the Beaverkill during spring. That leads me to believe that olive hatches on the tailwaters are irregular, due to the releases of very cold bottom water. I’ve written about that before, and how that phenomenon appears to impact several different species of aquatic insects, with regard to the time of day and year they hatch.

Olive mayflies are members of the Baetidae family and the genus Baetis. There are several species of eastern olives, with all members so similar in appearance that it is not at all necessary to try to identify them to species, or imitate them with different fly patterns. Other than size, they look that much alike.

There are three other genera in the family Baetidae, with olives being the most important for eastern fly fishers. The various species of Baetis range in size from a large 18, down to 22, although I’ve observed individuals that appear to be as small as 24! For the most part, olives generally hatch during the afternoon, with emergence ending well before dusk. Cool, even cold, gray, rainy days produce the largest hatches of this species of mayflies.

There is another species of eastern mayflies, which anglers refer to as olives; it is Drunella cornuta. That fly is not a member of the Baetis olives. In fact, it is a member of the family Ephemerellidae, which include Hendricksons, red quills, pale evening duns and sulphur mayflies. The species cornuta, in comparison, is a much larger fly than the typical olive, with some individuals as big as a size 14. Unlike olives, cornutas hatch from May to August, with emergence from late morning into the afternoon. In addition to their larger size, cornutas can be distinguished from olives in that they have three tails, compared with two, and they have dark, olive-colored bodies.

An interesting fact about the biology and life cycle of some species of olive mayflies is that adult females lay their eggs underwater, like certain caddis! I do not know how that behavior affects spinner falls.

Over a period of many years, I have found rising trout, during olive hatches, to be very difficult. Like so many mayfly species, the trout, particularly wild trout, seem to prefer the nymphs and emerging flies to the fully developed, floating duns. Why that is the case, no one seems to know.

What I do know is that casting small dry flies to trout feeding everywhere, without a rise, can be very frustrating.

In one of my recent columns, I explained the success I achieved using a pheasant tail nymph, tied parachute style with a ginger hackle, during a sulphur mayfly hatch. Trout were taking emerging sulphurs and nymphs at the surface during that hatch. I was able to move half a dozen trout during that feeding spree—a first for me, after many years of trying a variety of techniques, like drifting small nymphs and swinging wet flies in front of feeding trout.

My idea, to try parachute-style floating nymphs, was actually spawned during August 2020, after a fruitless afternoon casting a variety of small flies to trout feeding on hatching olive mayflies, right at or just below the surface, while the duns floated along. After that outing, I tied some number 20 parachute, pheasant tail nymphs with a dun hackle. About a week later, during another olive hatch, with trout again taking emerging flies, I moved a few small brown trout with that nymph. While this parachute-style pheasant tail nymph is not foolproof, both the olive and sulphur versions have provided decent results, when all other techniques have failed. I’ll continue to research and fish these little imitations when trout are taking emerging flies, right at or just below the surface, when olives are hatching.

As fall approaches and the days shorten, other than a few caddis and Isonychia hatches, olives will be the only flies on the water. So make sure you have a supply of sizes 18 and 20, and even a few 22, dun imitations, along with a few parachute pheasant tails, in your fly box, along with plenty of 7x tippet. Then go forth and see if you can rise a few more trout before another season closes and the Catskill winter descends!

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