Field & Stream Online Editors
Field & Stream Online Editors

What goes up must come down. This maxim applies as much to trout fishing as it does to the law of gravity. The mayfly hatches so ardently pursued by both anglers and trout in late spring and early summer return to the river as mayfly spinner falls.

After hatching, most mayflies wing to streamside vegetation where they molt once and then, within a few hours or days, return to the river in mating swarms. Females then lay eggs by dipping to the water’s surface, and both sexes fall spent and dying in large numbers. While many anglers follow the original hatches, a few also follow the falls, which can sometimes produce larger trout.

Mayfly spinners are generally uniform in shape: long, slender tails; a slim body; and wings outstretched and flat like those of an airplane as the spent insect floats on the surface. Imitative spent-wing patterns are generally simple, but your flies must be right on in terms of color, size, and shape. Trout become extremely selective as they feed on spinners, partly because the naturals aren’t about to escape and partly because such feeding often takes place in slower currents that allow fish a long look at your fly.

Matching the fall is an easy task thanks to the many first-class fly shops that have proliferated near major trout rivers. Just find out what mayflies are hatching and get some spinner patterns along with your regular emergers and duns. If there’s no fly shop near you, all major mail-order retailers of flies (such as Cabela’s and Orvis) sell spinner imitations.

Most spinner falls occur in the early morning, late afternoon, or evening. Because they usually happen only in specific weather conditions, they can be easy to predict. Clear days with little wind and moderate temperatures are ideal. Wind and rain tend to disperse mayfly mating swarms, which means the passage of a frontal weather system will postpone both a spinner fall and your fishing.

Don’t give up, however, if the weather isn’t quite right. If a gusting breeze seems to be pushing mayfly spinners away from the river, take a short walk along the riverbank. Somewhere among the river’s curves and bends you’ll find a stretch in the lee of the wind. In such protected areas, you may also find mayflies and rising trout.

If the evening spinner fall you anticipated gets blown out by a thunderstorm, you can try again the next night, but you may be better off if you check the following morning instead. Late-spring mornings often offer calm weather, and mayflies will mate and fall to the water as the air warms a couple of hours after sunrise.

Most mayfly spinner falls take place over and along riffles. The spent insects are then carried by the current into the pool below, where most of the trout are stacked up. There are usually large numbers of spinners spread along the surface, which means trout can feed from a variety of spots. Understanding this is a key to finding larger trout.

Deep, fast-water chutes at the heads of pools and bankside logjams are ideal hideouts for big trout, but they aren’t ideal feeding locations. In the fading light of evening, as growing numbers of spinners on the water lure big trout to the surface, the fish move into efficient feeding zones. The shallow gravel shelves adjacent to fast-water chutes are one example, where slower water allows larger fish to easily sip spinners brought down by the main current nearby.

The tailouts of large pools are my favorite spots because most other anglers ignore them. You’ll want to fish your dry spinner patterns across and downstream to the risers. The only danger is in having a truly big trout run out of the pool and downstream when hooked, in which case you’ll be left shaking and holding an empty reel.