10/25/2026
A discussion about trout vision and flies ……
The ideas about trout seeing colors and having vision that is very, very, good are well established. This is supported by those fishing, and catching, using flies as small as 30’s and 32’s. I have been with clients where trout would inspect and refuse 20’s, then readily take the same fly as a #26. It is pretty cool to watch.
It is also well established that the light striking the water at a low angle does not pe*****te the water surface, it bounces off the surface. This creates a situation where trout on the bottom can only see objects floating on the surface within a certain circle above them. This creates a cone shaped field of vision with the cone apex at the trout’s eye and a circle of vision at the surface. The closer the trout is to the surface, the smaller their circle of vision becomes. Everything outside this circle is a mirror image of the bottom. Everything subsurface, the trout see very well.
The mantra for wet fly selection for fishermen has always been “size, shape, color” regarding fly selection. I would add “movement” is also important. Movement of the materials makes flies like soft hackles and rubber legs so effective.
For the dryfly fisherman the problem is a bit different. The fish can’t see the fly floating in the surface film. But, so far the argument has been presented as if the surface is flat and calm. First, flat calm water doesn’t happen very often. Second, every point of contact the fly, or the bug, makes with the surface causes the surface to bend. This changes the light incidence with the surface and allows some light to pe*****te. The trout sees this as “sparkles of light” in the mirror surface. Any part of the fly, or bug, that pe*****tes the surface can also be seen by the trout. You can see this by sitting in the bottom if a swimming pool and looking at a floating object.
It is postulated that the trout can identify these “sparkle” patterns to food items, especially if part of the abdomen, or the nymphal shuck, has pe*****ted the surface. I would argue that this is why emerger flies, parachutes, and no hackle flies are so effective.
Now, I know that there have been a few fish caught on traditional hackled dry flies. However, most mayflies I’ve seen don’t just rest on their legs and tail ends. They rest on their bodies and fire parts of the body. I’m not the only one to advocate for flies that float in the surface film. Swisher and Richard’s, and Nastasi and Caucci wrote books on their no hackle flies. When you add the number of emerger patterns and the CDC dries, I’m thinking these flies are an advancement.
I’ve been tying my CDC dries now for 7-8 years. I’ve shown them to many, fished them with clients, and given away quite a few. The keys are getting the tail barbules to flair out as outriggers, and using enough CDC to float the hook. A dubbed body helps because it absorbs some floatant. Whether as a mayfly or a caddis, CDC dries floating in and on the surface film are here to stay.
