The Food vs. Energy Equation: understanding trout mentality

This post was born 26 Mar, 2016 No comments

In the first installment of this series on trout mentality, I described to you how to think like a fish by describing the underwater world and the many dangers a trout faces on a daily basis throughout his life and, in the second article, I described what both the underwater and surface worlds look like from a trout’s perspective and explained why precision casting is so very important. Then, in the third article, I described the anatomy of the water column and how it affect your fly as it drifts and, in turn, how it affects a trout’s feeding behavior. Therefore, in this last installment of the series, I will describe a concept called the Food vs. Energy Equation which, once again, is related from the trout’s point of view and describes what the conveyer belt of food drifting in a stream looks like to a trout and explains why is imperative that a trout gain more energy from the food that eats than he expends obtaining it.

So, once again, imagine that you are a trout living below the surface of a swiftly flowing stream and recall from the first article that there is something out there that wants to eat you twenty-four hours a day, seven days a week. However, you have to eat even though moving out from shelter to feed means exposing yourself any number of carnivorous animals who would like nothing better than to have fish for dinner. But, trout have very primitive brains and thus, they lack the cognitive ability to qualify degrees of danger and thus, their mentality is, if it moves, run! If it doesn’t move, run anyway! Now, imagine finding the perfect place in the current such as small cave beneath a shelf of rock with an opening that faces the current where you can lay in perfect safety, expending very little energy to maintain your position while watching all of the detritus and debris drift by as well as any aquatic or terrestrial insects. But, because there is an almost constant flow of plant matter of various sizes and shapes drifting in a trout stream as well, you  must become very adept at a very young age at indentifying the size, shape, and color of the various insects that drift in that particular stream if you are to lean what is edible and what is not. Also, it is important to note that trout do not reach sexual maturity until they reach approximately 10 inches and thus, because trout do have very primitive brains, the only thoughts they have from the day that they are born until they reach adulthood, is to avoid danger and to eat as much food as possible because a trout’s growth rate is entirely dependent on its caloric intake vs. expenditure and, there lies the heart of the Food vs. Energy Equation.

Fly Fisherman

So, once again imagine that you are laying in your perfect place closely examining everything that drifts by your lie and, also remember that the surface of the water from your point of view appears as a giant mirror with round hole in it directly above your eyes with a width that is 2 1/4 times the depth at which you are holding. Next, imagine that your lie is actually a seat in an underwater buffet restaurant and the menu is whatever happens to float by in one of the three zones of the water column. Thus, all you have to do is decide what you want to eat and then leave the safety of your perfect place to dart out into the current and seize whatever it is that strikes your fancy and then return to your seat in the restaurant without getting eaten yourself. However, if you are to grow larger in order to become sexually mature so that you can pass on your “survivor” genes to your offspring, then you must gain more energy from the food you dart out into the current to seize than you expend doing so which is called the Food Versus Energy Equation. Consequently, you must also become very adept at gauging how much energy you receive from each type and size of insect that you normally encounter in your particular stream. Therefore, not only do trout learn to recognize shape, size, and color, they also learn to look for signs of natural movement such as gills moving on nymphs, wings fluttering on duns and adults, and leg movement from terrestrials and, at the same time, they learn to ignore anything that does not look alive such as bits of decayed leaves or tree limbs. Therefore, if your fly appears to drift unnaturally in any way due to drag on the fly line caused by adverse currents in any of the three zones of the water column, then the trout are habituated to ignore it as detritus. Also, it is important to note that the larger the meal, the more energy gained per venture out into the current and thus, as a general rule, the larger the fly you use, the larger the trout you are likely to catch. After all, imagine that someone offered you your choice between a free McDonald’s cheeseburger a free 20 ounce steak dinner; which one would you choose? Personally, I would choose the steak dinner and trout usually feel the same way and thus, while tiny nymph patterns work well in the winter when the water is cold and the trout are sluggish, larger nymph, dry fly, and streamer patterns offer the trout more energy per meal and thus, tend to work better when the water temperature is optimum. Consequently, the largest trout in any given stream are usually caught with streamer patterns once the water temperature rises into the 50’s and their metabolism speeds up enough to enable them to effectively ambush baitfish since such species as Dace, Chubs, juvenile Trout, and Crayfish represent that 20 ounce steak dinner to a trout.

So, hopefully you now understand the concept of the Food vs. Energy Equation and how it affects a trout’s decision to feed or not to feed at any given time due to one or more of several different factors. For instance, possibly having seen movement on the edge of their cone of vision that triggers their flight instinct to not seeing your fly as it drifts over their lie to classifying it as debris due to an unnatural drift to simply being unwilling to rise through the various layers of the water column to take a fly that they deem is too small to make the effort worthwhile. Then, there is the issue of some trout populations becoming highly selective during a hatch. However, as long as you keep in mind the four keys to understanding trout mentality, then you will have a significant advantage in catching them and, if you are really good, then maybe you too will develop my father’s seemingly magical touch to catch fish when no one else could!


Written by,

Bill Bernhardt

Outdoor Professional

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