9/10/09
Insects and other foods the trout may be eating:
1.   Blue-winged Olives - mostly Little BWO - Isolated hatches
2.   Mahogany Duns
3.   Midges - hatching in isolated locations
4.   Little Yellow Stoneflies - hatching
5.   Slate Drakes - hatching
6.   Cream Cahills - hatching in Isolated locations
7.   Little Yellow Quills
8.   Needle Stoneflies
9.   Beetles
10. Grasshoppers
11. Ants
12. Inch Worms
13. Crane Flies
14. Helligramite
15. Streamers - matching sculpin, baitfish and small crawfish

The Learning Process - Part 48
There are a few things that are important that have to do with the way a trout sees
a fly that I have not yet mentioned. From what I have written in the last few articles,
one might easily get the impression that trout basically cannot see well. That is true
in a sense and completely untrue in another. Also, I know from email I receive, that
some of you, don't understand how anyone could possible know how well a trout
could and could not see. In some ways, I suppose no one really does, but in other
ways it is very clear what they can and cannot see.

When anyone refers to Snell's Window of Vision, they are referring to a guy that
determined that the refraction of light passing through water is different that air. If
you stick the end of your fly rod down into the water at an angle, you will see it
appears to bend at the point it enters the water. This optical effect is caused by the
change in speed of light as it goes from one transparent medium to another or air
to water. There is a point above a trout whereas their line of sight will not pass
through the surface of the water. It is exactly 48.5 degrees from a point at which a
vertical line extends from a trout’s eyes to the surface of the water.  This means that
they can see through the surface of the water in an area formed by a 97 degrees
cone. In other words, this isn't someone's guess as to what the trout can and
cannot see. It is a scientific fact.

As mentioned before, the areas of the surface that the trout can see through varies
according to the depth of the fish. Again, the diameter of the circle the trout can see
through (provided the water is smooth and not rippled) is roughly just over twice its
depth.  A trout located four feet deep will be looking through a circle with a diameter
of about four and a half feet. That sounds rather simple, except for one fact. Trout
cannot see well at a distance.

When a trout is viewing a fly, for example, four feet from it, the fish cannot discern
much detail. To put this in pure layman terms, he would have to get much closer to
tell much about it. When the trout is within three inches of the fly, for example, the
trout can probably see the fly even better than a human. We have trouble focusing
on objects real close to our eyes. A trout can focus clear at the distance of less
than an inch. What this amounts to is that is why trout will often approach objects
they take for food and then reject it when they get close. The facts are, the trout
can't see the fly well from a distance of two or three feet away. However, it is
thought by many scientist, that the trout can see better than the human when they
are close to something. It has been suggested they can see more shades of colors
than humans.

We have deal with object trout see on the surface and above the surface. If the
trout is in water with a rough surface, or not slick, flat and smooth, it would see
objects outside the window as a blur. It would probably be like me going through
one of these Halloween crazy minnow places.

We also haven't discussed the effects of sunlight on the water. That can vary what
the trout sees outside the water also. The thing we haven't dealt with at all is how
well they can see objects underwater.

When a trout is viewing an object in the drift below the surface of the water, it
cannot see it in clear focus at a distance either. They will approach and look at your
fly drifting along near the bottom just like they do the dry fly. When they get close to
it in clear water, they can see it in great detail. In other words, give the trout some
time to examine the fly below the surface, and it will be able to see it very clearly. If
the fly is cruising by at a fast speed, the trout isn't afforded that opportunity. They
will still get a clear quick glimpse of it when they get close to it, but they have
fractions of seconds to either take it or reject it. If it drifts by slowly, in slow to
moderate water, the trout has time enough to reject or accept it for something
natural.  

Also, keep in mind if the surface is rough, and the water is moving fast, the trout
want even be able to see the part of the fly that is above the surface of the water. I
can only see what breaks the surface skim. That may be a few legs (hackle on
some dry flies), the bottom of the hook, all depending on high the fly is floating in
the water and the type of fly it is.

Trout get a much better look at a fly that is under the water than they do a fly above
the water under the same conditions. That is what has always amazed me about the
way anglers look at flies. There are thousands of dry fly patterns and just a small
portion of that many for nymphs. It is even less than trout for larvae (which are
stupidly still called nymphs by most fly shops and even part of the fly industry).
Many Anglers seem to think how well the nymphs or larvae match the natural isn't
that important. They show much more concern for exact details of the dry flies, even
though it is a fact the trout cannot see most of the dry fly near as well as they can
see flies below the surface. These misconceptions have developed over the years
because anglers for the most part, haven't a clue of what a fish sees and don't see.
During the time man has learned enough to be able to travel to outer space, fly
anglers are still operating in the dark ages. I guess there is really nothing wrong
with that as long as its fun.


Copyright 2009 James Marsh