The following is how I would fish if I were anal retentive.
How Trout See
A trout’s vision is limited to a cone or window emanating at a 97 degree angle from its eyeballs. Objects outside of the cone and beneath its banked refraction in air are indistinct to trout, if not invisible. Objects within the cone are visible. The cone is more expansive the farther a trout is from the water surface and smaller if a fish is in shallow water. In other words, a deep-lying fish can see can see more above the water than a shallow one can. This is pertinent to the approach an angler must take and how on target a cast needs to be to present an imitation within a trout’s field of vision; a shallow-lying fish has a smaller field of vision, requiring a more accurate cast from the fly fisher.
Insects are near the bottom of the food chain and yet are some of nature’s most prolific survivors. They have accomplished this by unwittingly employing several strategies over the eons. One, insects produce huge numbers of offspring; they breed often and generate lots of progeny, which offsets extremely high mortality rates. Two, they migrate constantly towards more advantageous settings and frequently under optimal conditions. In a trout stream, insects engage in frequent searches for greener pastures, deliberately releasing themselves into the current so they will be brought to new habitat, hopefully habitat that can materially support them until they must move again. Since they are indeed so vulnerable to so many predators, insects stage much of this activity during low or no light conditions, when they are less likely to be seen. Ever wonder why the fishing is so good in the morning and evening? Or, in midday, how you see plenty of bugs on the bottoms of rocks but fish don’t seem to be eating them? Perhaps these bugs, being under rocks, are not so easily eaten.
Trout are ectotherms, cold-blooded creatures. Water temperature affects them greatly, especially at the extremes. You can run a fly right by the nose of a super cold or hot trout, it won’t eat, and there isn’t a dang thing you can do about it. Temperature causes trout to eat, not eat, eat certain things only, even migrate. Trout are happiest in water that is approximately 50 to 60 degrees. At least that’s the range they seem to eat the most. Over 70 degrees is approaching lethal; do not fish for trout when the water temperature is above this mark. Sharp temperature changes will trigger certain behaviors, especially in spring and fall, and in lakes.
You must know how to tie the improved clinch knot, the double surgeon’s knot, and the blood knot. You must know how to tie these knots well, very fast, and hopefully blind. If you aren’t comfortable with knots, you may subconsciously become unwilling to tie them. You will change flies less often and will be less likely to experiment with different rigs. Your creativity will suffer, and you will find you will catch fish only when conditions are just so. Your ability to adapt will be limited.
The reality of a cold blooded metabolism is that some or many fish will always be eating and, thus, will be caught and/or removed from a population. Nevertheless, some individual trout manage to reconcile their metabolic requirements with strong danger avoidance instincts. These fish are extremely cautious, and they’ll only eat when they are positive that doing so is a safe proposition. They are often large fish or, from habitual paranoia, are destined to be so. Anglers who dress, move, cast, or rig with careful intentions tend to catch lots of big fish.
Trout migrate large and short distances, on a seasonal or even daily basis, in response to certain environmental stimuli. Understanding trout migration is important, if only so the angler will place a reasonable amount of stock in theories about fish not being physically present at a certain location at a certain time (theories abound when fish aren’t being caught).
Mending and Casting
The difference between catching a fish or not can often be the six inches between where your fly lands and where it should have landed. It can be the drag that sets in right as your fly approaches your quarry. It is important to have control over your line while it’s in the air and on the water.
There Are No Rules
Period. Imposing rules on yourself can get in the way of your picking up on the lessons a day on the stream may be teaching you.