Western Baetis range in size from #18 to #24. They live in most waters and hatch for much of the year. However, in the cooler months they begin to dominate the action, and eventually they become the main game. With midges as the lone exception, Baetis represent the only hatching activity when the days become short and low temperatures prohibit other insects from emerging. With little or no competition for attention, Baetis attract trout growing urgently aggressive before the lean days of winter.

Baetis dun.

Fish migrate to winter habitat when water levels begin to recede. These are usually areas where greater depth provides comfort and security. Feeding areas are frequently different, but always close by. Larger trout have a tendency to feed in surprisingly shallow water. Venturing into such hazardous territory is risky for the fish and they won't tolerate careless wading or errant casts.

Baetis CDC Hackled Quill

Hook: #18-22 Tiemco 100 BL. Thread: Olive 8/0. Tail: Coq de Leon or medium-dun hackle fibers. Abdomen: Olive goose biot. Thorax: Olive dubbing. Wing: Paired medium-dun CDC tied upright and divided. Hackle: Grizzly dyed medium dun.

On bright days, an autumn Baetis hatch usually begins in late morning and continues sporadically into the afternoon. Peak activity can occur just before dark during warm weather. When the hatch is relatively sparse, a breeze that collects the little mayflies against the bank or along the edges of exposed weedbeds is an advantage. The largest trout seek such areas where a concentration of insects serves to justify the effort of rising to such a small food source.

A question that may never be answered is why the best fishing so often occurs in some of the most raw weather that fall can deliver. Ideal hatching weather seems to be overcast with temperatures at or only a few degrees above freezing. Light rain or wet snow seems to help rather than hinder the action. For whatever reason, chilly, gray, and even damp days bring intensified hatching activity that can keep the fish up and eating steadily for as long as four or five hours. Hardy souls who understand the peculiarity of Baetis await such days with great anticipation. The sight of half an acre of rising trout may seem unbelievable to some, but I have experienced it many times on big rivers like the Snake, Yellowstone, Bighorn, Missouri, and Henry's Fork. Smaller waters like the Madison and Firehole also get their share of Baetis activity, as do many spring creeks throughout the Rocky Mountain West.

Emergence is most important, but anglers should not overlook Baetis spinner falls. Sight-nymphing is a productive way to fill the quiet times. A small Baetis nymph twitched close to the surface can work when a rising fish resists a floating imitation. Medium olive seems to be the dominant body color of Baetis duns, though some range in color from tan to gray. Duns have smoky-gray wings. Spinners have a body color similar to the duns, but the wings are transparent.

Casting to trout in thin water is a different game than many are accustomed to playing. A presentation made quartering downstream places the fly in the trout's view ahead of the leader. The downside to this strategy is the likelihood of bringing yourself or the motion of casting into the trout's window of vision. Working from behind the fish with an upstream presentation shortens the necessary casting distance by keeping the angler out of view, but it has limitations. Even at close range, delivering pinpoint accuracy with a slack leader is not easy. With no opportunity to manipulate the drift with mending techniques or rod-tip maneuvers, the cast must be perfect. The advantage of fooling the fish with the least number of casts possible can not be overstated. A light, flexible tippet of 6 or 7X helps the fly follow the subtle currents and prevents drag. A happy fish is one that feeds without knowing it is being fished to. Savvy trout recognize drag.

Baetis spinner.

Catching fish often depends on imitating the stage of the mayfly the fish is feeding on. This can vary from fish to fish, especially when the hatch is heavy. Carry an assortment of nymphs, emergers, duns, and spinners to suit the feeding preferences of each trout. During a hatch, trout have several choices from which to pick. Finding the right fly sometimes takes time, but patience usually prevails. I usually make certain the fish is large enough to justify my time and effort. Changing flies or adjusting tippets can be excruciatingly difficult when you are shivering and your hands are numbed by the cold. Fortunately, crowds are seldom a problem at Baetis time, which means you can often move to a different fish when the one you are casting to refuses to eat your fly.

Baetis CDC Biot Spinner

Hook: #18-22 Tiemco 100 BL. Thread: Olive 8/0. Tail: Coq de Leon or light-dun hackle fibers. Abdomen: Olive goose biot. Thorax: Olive dubbing. Wing: Paired light-dun CDC feathers tied spent.

Although I have enjoyed many successful days of Baetis fishing, they have never been easy. Trout in most Western waters spend six months or more trying to avoid artificial flies. By fall, they are keenly adept at identifying fraudulent food and quick to shy at the slightest disturbance of their territory. Shallow water flowing over dense weeds creates brutally complex currents that can instantly corrupt the drift of the most carefully presented fly. Thankfully, most of us are also at our best during this time. With nearly a full season of casting, wading, and observing under our belts, we are as well prepared for this kind of fishing as we will ever be.

There is a social aspect to autumn fishing that contrasts with the long days of the earlier season. It is a different pace when mornings become frosty and darkness arrives early. Gone are the crowds of summer, leaving only those of uncommon sensitivity to the rhythms of a season both hostile and hospitable. As a group, those who hunt the water at Baetis time are knowledgeable and accomplished anglers who relish a challenge. Many are river guides who devote their knowledge and skill to the enjoyment of others for much of the season. Others live in far-off places but are drawn here each year by forces they understand but cannot explain.

In autumn, time in fly shops and saloons often exceeds that spent on the water. Conversation in the hours between hatches is never more stimulating as old friendships are renewed and new ones are begun. There is always much to share and learn when the last hatch of the season brings such dedicated and obsessed anglers together. The memory of these special days gets us through the long winter to the time when it all begins again.