Guest Blogger: Michael Vorhis, author of ARCHANGEL suspense thriller, OPEN DISTANCE adventure thriller & more to come

What quality or instinct saves an organism from danger, when the organism cannot comprehend the concept of risk management? Is it the ability to reason–to analyze, conclude and decide? That process generally requires a computational engine larger than most organisms possess…not to mention time to think it through…not to mention the intellectual capacity to decide correctly. In an ecosystem that coughs up dangers which require near-instantaneous action to avoid, relying on such a scheme would doom most individuals of a species–even most humans.

What quality or instinct saves an organism from danger is Aversion. It is a born-in dislike of something in nature, something in the environment, that brings with it inherent risks. Heat. Wind. Noises, especially noises that match some born-in audio pattern, such as the sound of dogs barking or a predator’s hiss or low growl. Aversions born into each individual since the era in which those adaptations were naturally selected in the species can save enough numbers of the species to live and procreate another day.

Aversions can take numerous forms:

— Aversion to cold or heat–this kind of aversion “herds” organisms into eco-zones that match their physical limitations; long before they get into potentially deadly conditions, their discomfort turns them back toward zones in which they’re more likely to thrive and in which their prey thrives. They don’t have to think about it–they simple don’t like it too hot or too cold, and that’s enough to keep them in conditions that appeal to their physiology.

— Shyness–the aversion to companionship–pine martens, bears, some species of sharks, and other solitary creatures have a life strategy that leverages solitude to the individual’s benefit, for foraging, for breeding territories and for minimizing both large target populations that could be tempting to enemies and also individual impact on the rest of the ecosystem on which the entire species relies.

— Loneliness–aversion to solitude–the opposite of shyness–wolves, dolphins, mahi mahi, picas and marmots, etc. all leverage a life strategy that adopts the safety or collective intelligence or hunting effectiveness of numbers.

— Aversion to chemical conditions–slugs hate salty soil, certain worms eschew alkaline soil, etc. Many organisms migrate out of acidic conditions (or never enter those conditions to begin with), which instinct serves to keep them out of pine forests–either to save them from acidity or to save the forests from their upset of its balance, thereby helping them indirectly in the larger system balance.

— Lots of other kinds of aversions

Back to fly fishing: In trout (also many other fish species), in my opinion neither shyness for their own kind nor longing for them (except as an instinct exhibited by fingerlings) is seriously in evidence. I believe trout live where other trout live because food and conditions are plentiful, not because they seek each others’ company or the safety of a school. They’re quite willing to exist relatively alone if they find an excellent place to hole up and still feed. They have their dislikes–water too warm, water too acidic (because it reduces the hatch rate of their eggs), etc. But within physical “thrive” zones, in my opinion the primary aversion that saves trout from most dangers–at least the aversion that best serves my angling understanding–is an aversion to Light.

Aversion to light.

They don’t have to think about it–they don’t have to reason that “since I can see things on the bank clearly in good light, that means I can be seen from above, but if the surface is choppy it’s a lot safer because lines of sight are seriously disrupted.” They don’t have to tally up the various threats that must rely on visual acuity to get them. They just hate light the way they hate high acidity or oxygen-poor water, and it saves them–even the stupid ones–from most things.

It has long been known that fishing in early morning or late evening yields better results…in most venues and for most species. People say “fish don’t bite in the daytime,” but that’s not precisely true; it’s more a matter of where they are when the sun is high. They’re quite willing to feed, since feeding is about the only non-spawning game they play, it’s just that they’re generally not within bait-casting distance of a lake’s shore so much of humanity has concluded over the years that they only “bite” around dawn and dusk. In truth they venture into shallows in times of day when safety is better, or at least less poor–the low-light times.

That’s the daily cycle. And seasonally there’s a cycle too. Numerous studies have borne strong witness that as spring turns to summer, trout become increasingly nocturnal, to the point that they’re virtually 100% nocturnal by the heat of the summer. The species most studied to date has been the brown trout, but there’s evidence that most of the fish we pursue behave similarly as a general rule. Their aversion to light keeps them hidden from danger when the water is low and clear, compelling them to do their feeding largely at night. The specimens who remain active in bright daylight hours are the small fry–the ones who are terrified of being out at night when the big boys are prowling.

That can differ for some habitats of course, for example in flowing water that maintains riffles and rapids even in late summer months. Light, and therefore vision through its surface, is wholly disrupted by choppy conditions, so feeding activity can continue in midday. The same can be true of lakes in regions that develop overcast atmospheric conditions, or lakes that experience high winds in late summer–surface disruption is safety to fish, and again they need not reason it out–they feel safe because the light that penetrates through to them is weak.

Light and dark water.

As summer turns to fall and heads toward winter, trout behavior shifts toward diurnal feeding, beginning with feeding activity later in the morning and earlier in the evening, and eventually turning to an all-day thing. Insect life takes advantage of warmer daylight hours in winter, and the trout’s acceptance of the reduced light of a lower sun naturally aligns with that. It doesn’t mean they won’t feed at night; it simply means they have less of a daily ‘lay low’ period, and so they do what they do, which is feed, over more hours. In autumn they have a need to pack in the sustenance before the withering hand of winter comes down upon them anyway, so going more diurnal also aligns with that need. Again their aversion to light has a threshold, and when the light doesn’t approach that threshold the instinct allows them to take advantage of the insect life which is responding to what’s left of the year’s warmth.

So as the sun climbs during the day, trout tend to recede, deeper and under logs and banks and overhanging trees. As the summer wears on and stream flows clarify and recede, the depths are no longer there to attenuate the sun’s rays like before, and the riffles slow to where those rays aren’t chopped up quite as much. Do trout reason that these changes in their environment let birds of prey and other predators see them more easily? Based on our assumptions that brain size determines cognizant powers, we say they don’t. Yet still they change their behavior. We call it ‘instinct,’ and it saves them, just as a pre-programmed aversion to the unseen and unknown saves humans from predators of the night, whether we think about it consciously in terms of predation or not.

Now, realize that I’m talking about a general trend, shaped and modified by many other factors. There are other forces that sculpt a trout’s behavior, including water temperature (a separate discussion and one that also influences macro-behavior spanning weeks and months, hand in hand with light.) Motivating factors such as fresh rainfall, water quality degradation, influx of more aggressive species, and repeated alarm certainly can be dominating disruption factors too.

Dangerously clear water.

The primary factor that can challenge the “light” theory is a factor I call Opportunity. That topic covers temptation to feed on a cornucopia served up by some binging species of prey, and light be damned. I would like to explore that topic in a separate article.

Suffice it to say that trout behavior can be thought of in any framework of analysis a person likes–in terms of migration and spawining, in terms of invasive species movement, even in terms of trout-to-trout social behavior. I present the above discussion of “aversion” as one valid analytical structure, one valid partitioning of thought, that I believe can aid an angler in decisions on the water. I know it has helped me.

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