08/26/11
Insects and other foods the trout may be eating:
1.    Blue-winged Olives (Little Eastern BWOs)
2.    Mahogany Duns
3.    Little Yellow Quills (
Heptagenia Group)
4.    Little Yellow Stoneflies (Little Summer Stones)
5.    Needle Stoneflies
6.    Slate Drakes
7.    Sculpin, Minnows (Streamers)
8.    Grasshoppers
9.    Ants (includes Flying Ants)
10.  Beetles
11.  Craneflies


Yesterday's Problems:
I had some major computer problems yesterday. I was later than normal getting
started posting the daily article and when I did, I discovered that I had lost enough of
my files that it would require downloading the entire Great Smoky Mountains website.
That takes about three hours at the fastest speed I'm able to acquire in Pigeon Forge.
There are thousands of pictures and over 2,000 articles and pages of info. Of course,
I have backups but I had my other computers tied up on other projects and that would
have taken just about as much time.

When Trout Can and Can't See You
Remember that trout see everything above the surface of the water through a circular
window that is directly overhead of their eyes. Everything else on the surface is seen
by the trout as a mirrored image of the bottom and structure in the water.

The following is a down and dirty analysis of how a trout sees objects, including
anglers, outside of the water, but I hope it's enough explanation to get the important
points across. I have written about this window (Snell's circle) before.

The diameter of the window is 2.26 times the depth of the trout. The deeper the fish,
the larger the window. Objects outside the water that appear near the edge of this
circular window are distorted, or much shorter and wider than they normally are.
Objects directly overhead in the center of the window are in focus and not distorted. If
the surface of the water is riffled, or rough, the window is still there, but the view the
trout's gets of objects outside the water that appear near the outside edge of the
window are blurred by the tiny waves of rough water. If an angler appears near the
edge of the window, his or her movements are blurred and greatly distorted.

There's another factor that affects the trout's vision of an angler. When light waves
strike the surface of water below a ten degrees angle above the horizon, about eighty-
five percent of them skip or bounce off the water.
This is called glare. This reflected
light or glare, doesn't get to the trout’s eyes and doesn't affect the trout’s vision. It
bothers anglers that are outside looking in the water. It does have the following effect
on the trout's view through the window.

An object outside of the water that’s below the ten degrees angle (ten degrees above
horizontal or 180 degrees) appears very dim and not well lit like other objects within
the trout’s window of vision and is hardly noticeable.
In other words, an angler that’
s below this ten degrees angle is not visible to the trout.

If an angler is thirty feet from the fish’s window of vision, this ten degrees angle will be
five feet, three and one-half inches above the surface of the water. If a person is
standing level with the water is only five feet tall, he or she won’t be visible to a fish. If
you want to get closer to the fish, you can do so by staying below this ten degrees
angle by kneeling down or to get real close, by crawling closer to the fish.

If you’re wading, only the part of your body that’s above the water counts. This means
you can get much closer to the fish wading, provided you don’t spook it otherwise. At
fifteen feet from the fish, this distance becomes two feet, seven and three-quarters
inches. A five-foot tall person wading in waist deep water, fifteen feet away from a
trout would be hidden from the its view.

There’s another factor. An angler that’s thirty feet from a trout holding near the
surface, located at a twenty to thirty degree angle above the horizon, would appear
very short and fat to the trout. This is because objects near the edge of the window of
vision are greatly distorted. Never the less, the fish could see the flattened out image
of the angler. If the angler suddenly moved, it would most likely spook the trout.
However, if the water is rough or riffled,
the fat and short angler would be
blurred
. His or her movements couldn't be distinguished from the movements of the
edge of the window of vision caused by the rough water. In other words, if the water is
rough, you can get even closer to a trout without it detecting your presence.

There's one more factor of great importance. Although a trout can see (peripheral
vision) almost all the way around its body, there is a 30 degree angle of area directly
behind the fish that cannot be seen by the trout. This is called the blind zone. If the
trout is not swaying its head back and forth, an angler in the blind zone isn't visible to
the trout. That's why it's important to approach the trout fishing in an upstream
direction.

There's other factors, such as the amount of available light, how well you blend in with
the background, movements like casting, sound and ripples of the water made
wading, and etc., but I hope this gives you a better idea of what a trout can and can't
see that's outside of the water.  

There's one thing for certain. If you are going to fish the streams of Great Smoky
Mountains anytime soon, you better understand this or you will find yourself
"spooking" instead of "catching". Well, maybe today's 30 percent chance of rain will
help this but there's a 70 percent chance it won't.

Copyright 2011 James Marsh