Trout Feeding Modes

 Last week’s post was fairly lengthy and contained several new concepts that could benefit from further discussion. In this week’s post I will start by explaining the basic concept of the trout feeding mode continuum. Successive posts will build on this foundation, leading the fly angler to a more complete understanding of just what leads up to the moment when the fish takes your fly.

The feeding mode continuum is really quite simple. It starts with fish that are feeding opportunistically. In the opportunistic feeding mode a trout will essentially sample everything that appears to be even remotely edible. Buggy looking things and critters that move in a tantalizing way are at the top of the list but small bits of wood and bright, colorful objects are also tested to see if they might contain any nutritional value. In the opportunistic mode, trout feed without any concern of being caught and are usually found in seldom fished places where food is scarce and organized, heavy hatches are rare.

At the opposite end of the continuum are hyper-selective trout. When it comes to hyper-selective trout, there are two factors at play. The first one is that trout that are under heavy fishing pressure usually become more selective in the search image they respond to in order to avoid the unpleasant experience of being caught (sometimes a negative search image comes into play – more on this in a later post). The second factor is that in the presence of a heavy hatch, or several hatches taking place at the same time, it becomes more efficient to focus on a single life-stage of a single bug. This narrowing down of the search image allows a trout to feed without having to waste time inspecting each item in the drift and making a decision on each one – instead, the process becomes automated.

The trout feeding mode continuum then, encompasses the entire spectrum of possible feeding behaviors from opportunistic to hyper-selective. Most of the time trout are somewhere in the middle of the continuum – in what I call the non-hatch mode. Here, there are still elements of selectivity where the different search images a trout has been recently exposed to influences which flies they are most likely to take. 

In next week’s post I will super-impose a normal distribution on the feeding mode continuum and explain more fully what a search image is. Then you will start to see what drives an individual trout’s behavior when it is “deciding” whether or not to take your fly.