Does Angler Pressure Make Trout Eat Smaller Flies?

I’ve had this hunch for many years now, but I don’t think there’s any “scientific” way to prove my theory. So I’m doing the next best thing: I’m tossing the topic up for debate on FlyTalk.

I think all species of trout are not, in fact, timid, tiny bug sippers by nature. I think the reason that many trout gravitate to itty-bitty RS2s, and Barr Emergers, and Black Beauty midge patterns in some places is because the trout have had the snot pounded out of them so hard by angler pressure that they’re almost afraid to eat at all, and they focus on the most consistent, readily-available sources of micro-protein.

Think about it: If you got the tar beat out of you every time you ate a T-Bone steak, but only every once in a while when you ate a handful of granola. Well, you’d be a nuts ‘n berries fan soon enough, wouldn’t you?

To back my theory, I offer the following: I once watched no fewer than 19, 20-inch-plus rainbow trout eat my mouse fly patterns off the surface on a sunny afternoon. Of course, I had to take a flight to Anchorage, Alaska, a regional hop to King Salmon, Alaska and a 30-minute bush plane ride to find a river where this would actually happen.

I see it where I live in Colorado all the time. What are they eating on a public stretch of the South Platte River? Size #20 RS2s. What are they eating on the private water (same flow, same temperature, same basic geology and topography)? Size #12 Yellow Sallies.

The thing of it is, there are times when the “naturals” in a river explode, and the trout cannot help themselves. The stonefly hatch in Colorado’s Gunnison Gorge is an example. When the stonefly hatch happens, that river gets pounded by anglers. But the trout just cannot help themselves from smashing size #8 Sofa Pillows. That’s why we love it when those epic hatches happen.

But I think in the context of using attractor flies, and finding the bite–the more fish see, the smaller things get. If we closed the South Platte to fishing (and by no means am I suggesting we do) for two years, is there any doubt that the first angler back in Cheesman Canyon could throw size #14 Humpies all day and catch more fish than he/she could handle?

And, to a degree, isn’t that why a three-pound brown trout caught on the Delaware on a size #14 Hendrickson is a far, far more impressive fish than a five-pounder dredged up on a Western tailwater with a latex midge?

It is what it is. Maybe that’s evolution in action. We make the bed, and we lie in it. I don’t know if if there’s a reason to try and make changes. But I wonder if you agree that the more artificial bugs trout see, the “smaller” the game gets, and whether or not that’s a good or bad thing.