Have any of you ever had any unexpected, eye-opening experiences when fly fishing?

I have had several fine learning experiences in my lifetime of fishing, one of which was particularly interesting and helpful, and one which truly opened my eyes to the unexpected. It happened several years ago on the Yellowstone River in Yellowstone National Park, when I was fishing with my teenage daughter, Lisa.

We were fishing along our favorite section of river one early afternoon when Lisa asked if there was any way we could get across the river to fish the opposite bank. There were few anglers who ventured over there, and we could always see plenty of fish working along the other bank.

The river is fairly wide there, but we found a spot below the big island were we were able to make our way across the current. The flat-looking current is deceptive here, and the unsuspecting angler can wade into some pretty strong, pulling currents if he isn't careful. We took our time, wading arm-in-arm until we made our way safely across the steady waist-deep flow. Once across, we worked our way up to a nice-looking sand bar that extended down from the bend for 50 yards or so, with good looking riffles on both sides. There was a good number of fish working on and just under the surface, so we anxiously waded out into casting position.

With no insects showing on the surface, we both opted for our most productive fly on past excursions, our little Red Spinner. The fly is a simple mayfly spinner patter, size #20, tied with split tails, mahogany (dark reddish) brown body and thorax, and palmered grizzly hackle wrapped over the thorax, then clipped on top and bottom so it rides flush in the surface film. We fish it like a standard dry fly.

We immediately started hooking some nice cutthroat, and continued to do so for a good half-hour or more. I was curious as to why the fish were taking this fly, because another careful study of the water revealed no mayfly spinners on the surface. In fact, we couldn't find any insects of any kind on the water, yet the fish were bulging steadily in the current, proposing one after another. And almost every time we presented our spinner pattern over a fish, it would rise up and take it purposely, without hesitation. It was a mysterious situation to be sure, but who cares about WHY fish take your flies, as long as they take them, right?

Well, the mystery was soon solved when I knelt down in the slow, shin-deep riffle and worked a nice 17-incher in against my waders for release. I handled the fish carefully as I softly forced its mouth open to where I could get my hemostat down to its tongue to grasp and back-out the tiny hook.

To my surprise, there were a dozen or more small dark-brown mayfly nymphs stuck to the inside of cutthroat's mouth and gullet! The naturals were almost identical in size, shape, and color to my little spinner pattern.

Then it hit me. The fish were feeding on the drifting nymphs just under the surface as they were getting ready to emerge, and our flies were representing them almost perfectly. It wasn't more than 20-30 minutes after my discovery, that adult Pale Morning Duns began appearing on the surface, and the trout started to rise to them without hesitation. Rather than change to adult dun patterns, we stayed without our spinner imitations and continued to take fish until the hatch finally subsided about two hours later.

I considered this one of my most meaningful learning experiences on the river. It all occurred by accident, but when I finally discovered what was actually happening, many past experiences of a similar nature on the river began to make more sense. And ever since that eventful day, I have never been without a few of my old Red Spinner patterns when fishing the Yellowstone and other streams that hold good populations of Pale Morning Duns.
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Now, a question: How many of you have had unexpected learning experiences that have helped to increase your ability to take your favorite fish?

Emerger