For all plants and animals, nature has a rigid schedule, such as when fawns are born, flowers bloom and trees leaf out. The same can be said of aquatic insects, in that there is a specific time each year that these organisms emerge from their underwater habitats. This process is dependent on water temperature for the first species that begins this annual progression. If the water is too cold, the hatching process will be delayed until more favorable conditions occur. 

There are three species of mayflies in the family Ephemerellidae, the genus Ephemerella, that hatch in chronological order beginning the third week of April and ending in late June. That is under normal, freestone stream conditions. The tailwaters are excluded because cold bottom-release water has been shown to impact hatching times and duration.

The first fly of this group is the eagerly awaited Hendrickson/red quill hatch, Ephemerlla subvaria, which begins in late April under normal flow and temperature conditions—which is rarely the case. For example, the last two seasons began with flows that were way too high, so that the hatch was not fishable. When conditions are correct, the Hendrickson/red quill hatch begins between 2 p.m. and 3 p.m. Hendricksons and red quills are always preceded by a hatch of little blue-quill mayflies that, as funny as it may sound, never seem to be taken off the surface.

A few days into the Hendrickson/red quill hatch, spinners will appear and mate high over the river. After mating, the females will flit over the water with large yellow egg sacks attached to the end of their abdomens. Once mating and egg laying are complete, both spent males and females die and fall to the river’s surface. 

While the Hendrickson/red quill hatch is talked about a great deal in the off-season and anglers wait with a lot of anticipation, the fishing is seldom easy. Even when there are a lot of duns on the water, the trout don’t always rise, causing frustration. Early-season cold water temperatures are often the cause. In the seasons I’ve been fortunate enough to fish the Hendrickson/red quill hatch, I’ve learned that spinner falls should not be missed. Spinners begin to appear over the water right around 6 p.m., and anglers who stick around can often find some exceptional sport. Plus most anglers will have left the river by then, thinking the fishing is over and are anxious for dinner and a cocktail. The Hendrickson/Red Quill hatch can last into the second week of May, with a few spinners hanging around a week or so later.

The second mayfly in this progression of three is the pale evening dun, Ephemerella invaria. Duns are a pale yellow-green, with a large wing, a size 16. Emergence begins right at dusk on freestone rivers. Duns hatch in large numbers, leaving the water almost immediately, allowing little prospect for fishing. Emergence in the tailwaters is a completely different event. I first found this hatch one afternoon on the Upper East Branch about 5 p.m. I was in the meadow next to the river, taking photos, when pale evening duns began to hatch in large numbers; trout were rising everywhere. It didn’t take long for me to trade my camera for a fly rod and start fishing. I don’t know how many trout I landed that afternoon, but it was enough. Probably some of my best dry-fly fishing ever. 

Pale evening dun hatches begin around the second week of May, following and sometimes overlapping the Hendrickson/red quill hatch, although the two species hatch at different times. While the literature indicates that this species hatches between 3 p.m. and 4 pm, I have never seen it then. Five is the earliest; dusk the latest. The pale evening dun hatch can last well into June. But unlike the Hendrickson/red quill hatch, I’ve never found a spinner fall for this species.

Much to the consternation of my friend Bill Dorato, the little sulphur mayfly is the last of these three spring mayflies. It is classified by the taxonomists as Emphemerella dorothea. The males are smaller than the females, perhaps a size 20. They have big eyes. Females are a true size 18, with smaller eyes. On freestone rivers, sulphurs hatch late in the day and into the night. On the tailwaters, we’ve seen them much earlier in the day. In fact, for several years, sulphurs hatched in huge numbers around one afternoon along the Upper East Branch, a mile or so below Pepacton Reservoir, an anomaly due to the very cold water. Sulphurs do not appear to hatch at that time any longer. In fact, sulphur hatches appear in much smaller numbers than they once did on the Upper East Branch, if they appear at all. Sulphurs cause all kinds of aggravation for anglers, because trout often take the emergers instead of duns. Like pale evening duns, I’ve never found a sulphur spinner fall.

Of these three very important species of mayflies, pale evening duns offer the best fly fishing. Trout actually seem to prefer the duns to other forms. One evening, my friend Jamie and I landed 16 very nice browns between us during the pale evening dun hatch. That’s how good fishing can be when that fly is on! 

These three species provide the bulk of early-season fly fishing on Catskill rivers. When conditions are right, they should not be missed.