As weather cools and winter begins to whisper of its arrival, those in tune with the water will see a shift in daily river cycles that signal seasonal change. For the last few months, the pale morning dun (PMD) mayfly hatch has been a staple of the Provo River’s rhythm, providing abundant food on the river’s surface and enticing trout to rise into late afternoons. These days trout continue to rise and yet fewer of the yellow-green PMDs are seen floating through feeding lanes.
Recently, as the occasional PMD flops down the river drying its wings, I’ve observed these tasty trout treats drifting through and past gauntlets of rising trout. Noses protrude in and around the PMD highlights and the rises often appear where there is no apparent food. Perhaps trout are taking ghosts of mayflies past, but more likely there are difficult to observe food sources directing a switch of focus.
It is important to recognize these shifting patterns on the river because as seasons change so do the hatches that provide sustenance for river residents. Fish respond by turning their focus to the most abundant and available foods and anglers will need to adapt as well. As trout rise to unseen insects, some may be left pondering what fly to try as their favorite PMD pattern loses its mojo. Answers are found on the river and when the light is right, just before the sun falls below the mountainous backdrop of the river valley, you might catch a wink of sun reflecting off the wetted wings of a fall arrival.
Commonly known as ‘tiny blue winged olives’, Pseudocloeon mayflies are sized at half, of a half, of a grain of rice. These mayflies are best imitated with fly patterns size 24-26 in grey to olive colors, and although minute, trout feed aggressively on adults and emergers in the surface film. The arrival of the ‘pseudos’ indicates that fall is here and not far behind we will see additional fall insects appear including blue winged olives and October caddis.
So the next time you are out, closely inspect the water and gather some insects to help match the size, shape, and color of your fly pattern to the pseudos that have arrived to our rivers. Then, as the season moves forward, be ready to observe further shifts on the river. Additional insects will arrive and others will fade as winter continues moving in. These changes on the river will alter trout feeding behavior and by noticing these changes and adapting to them, your time spent fishing will become more enjoyable.