Trout Behavior 

Trout are amazing creatures. Understanding trout behavior is perhaps the most difficult challenge for the dedicated trouter. Each aspect of trout behavior will be examined, in their order of importance to the trout.

Reproduction
As with all wild organisms, the basic behavioral trait that gives rise to all others is the urge to reproduce. All other behaviors are secondary. Thus, other behaviors fall by the wayside when trout are in the process of procreating. Wild steelhead feed very little or not at all when they enter rivers to spawn, and likewise spawning trout ignore predators and enter shallow water when spawning. Migrations against heavy current show how the reproductive imperative overrides the urge to conserve energy. Because of all these factors, fishing trout during the spawn is a very different game. Here we are concerned mainly with normal, everyday trout behavior, so the reproductive cycle will be excluded.

Predator Avoidance
Just below the importance of reproduction is the urge to avoid predators. Generally, when a trout senses danger, it will dart into the nearest deep water or hide in heavy cover. This is why it is so important to stalk trout carefully. Predator Avoidance takes precedance over feeding, so a spooked trout is more concerned with staying alive than eating. Of course, both the environment and the temperment of the individual trout have an effect on the expression of predator avoidance behaviors. In gin-clear, shallow water with no cover, trout are much more wary. Also, while some trout might begin feeding again only five minutes after the perceived danger has passed, others will refuse to resume feeding for up to an hour. In all cases, trout feed only when they feel secure. If they are able to feed from deep water or heavy cover, they may just ignore predators altogether, since the predators have no chance at catching them in their location.

Energy Conservation
This very important behavior is what makes trout fishing so much fun. A trout, when not avoiding predators or reproducing, will attempt to conserve energy as much as possible. The urge to conserve energy of course takes precedance over feeding; otherwise trout would be chasing down and eating everything in sight. A trout conserves energy by moving as little as possible. It takes more energy for a trout to hold in a fast riffle than in a slower run. However, predator avoidance takes precedance, so especially vulnerable areas, even if they have slow water that takes little energy to swim in, are avoided. Behind and in front of rocks in a stream are small areas where the current is less intense - these areas are perfect places for a trout to conserve energy. Also, the water right on the stream bottom moves more slowly than the water above it, so it follows that trout will generally hug the stream bottom. This behavior colors every other aspect of trout behavior, in that whenever a behavioral characteristic compels a trout to perform some action, it is always performed with maximum energy efficiency in mind, unless it involves predator evasion or reproduction. Since energy conservation takes precedence over feeding, it follows that the trout will not act on its feeding urge unless the percieved energy to be gained from the food exceeds the energy that the trout will need to expend in order to capture it. Therefore, a trout will waste more energy charging across a pool to catch a large sculpin, but might only move a few inches in order to eat a tiny insect. Otherwise there would be a net loss of energy and the trout would be losing the survival battle. In particular, selectivity in trout is an extension of energy conservation. With all the various objects floating on the stream, a trout could spend hours constantly eating non-nutritive items and spitting them out - a complete waste of energy. The more food of a single type that is on the water, the more selective trout become. Selectivity allows the trout to avoid losing energy by chasing after things that are not food.

Feeding - Overview
Of course all trout must eat. And even though they conserve energy as much as possible, they must eat almost constantly, since they are expending energy constantly by fighting current, building body mass and reproductive cells, and respiring. When the economics of energy conservation eventually end up in the red, so the trout must feed to keep going. Trout may go about feeding in so many different ways that it is impossible to describe them all here. We will, at first, just look at the principles of abundance, mass, and prey attitude.

Feeding - Abundance
The principle of abundance explains the tendancy for trout to heavily exploit food sources that are common versus hunting around for things they don't see every day. To do otherwise would violate the law of energy conservation, because until a trout eats a few of something, it doesn't know if it is edible or not. So when a great number of insects appear, trout will let hundreds, perhaps thousands, of insects drift by. Once it is obvious that these insects are abundant, they will sample one. If it turns out to edible, feeding will commence. The trout select the abundant insect because there is a guaranteed energy return. Of course, this rule has a few kinks in it which make things a bit more complicated. Trout may spontaneously sample something outlandish simply because it looks edible. This, however, is the exception, not the rule, so don't count on it happening very often. Trout also may reject the most abundant food if they have been habitually feeding on something that has been more abundant in the past. After five straight days of heavy morning caddis hatches, you go out on the sixth day and see blue-winged olives coming off, with a few caddis mixed in. The trout may prefer the less abundant caddis because they have already been habituated to feed on it. Also, what appears to be the most abundant food source to us, might not be the most abundant source to the trout.

Feeding - Mass
The size of the food affects the behavior exhibited by trout in response to it. A trout may pass up a small insect if it is more than a foot away, but a large insect might be taken from three feet out, and a huge prey item (like a mouse) might tempt the trout to move ten feet to catch it. As far as insects on the surface are concerned, the trout will rise is such a way as to take the insect with as little effort as possible, because the insect provides only a small amount of energy. The smaller the prey item, the shorter the trout will be willing to move to take it.

Feeding - Prey Attitude
Prey attitude refers to how the prey is behaving. For example, if equal numbers of insects of two varieties appeared, and one was an active flier, while the other remained motionless, the trout may select the one that is inactive, since the trout is more successful at catching them, because feeding on them may provide a better return on their energy investment. Likewise, insects that are emerging from the water's surface will eventually fly away, so it stands to reason that the chances of the prey escaping are less the lower in the water it is situated.