Neil Travis - Sep 19, 2017

Are fish intelligent and do they think? If you listen to many fly fishers, especially those that fish for trout, the answer would be yes. However, is that really true? Let’s look at some definitions.

Intelligence – the ability to acquire ability and skills; one’s capacity for logic, abstract thought, understanding, self-awareness, communication, memory, planning, creativity and problem solving. It can generally be described as the ability to perceive information and retain it as knowledge to be applied towards adaptive behaviors within an environment.

Thinking – The action of using the mind to produce ideas, decisions, memories, etc., the capacity of the mind to reason or reflect.

Instinct – an inborn pattern of activity or tendency to action common to a given biological species.

With these three definitions before us it is obvious that fish, including those “smart” trout, are not intelligent and their thinking capacity is restricted to instinctual behavior. They do process information but not in a way that denotes intelligence or abstract reasoning. If they did we would never catch one except accidentally. Why then do anglers believe that fish are intelligent? I submit to you it’s an ego thing.

Fish typically have small brains relative to the size of their body when compared to other vertebrates. The fish’s brain is approximately one-fifteenth the mass of a correspondingly sized bird or mammal. In a fish like the trout the optic lobes of the brain are the most developed giving the trout excellent visual abilities and next is the cerebellum which is responsible for coordination, balance and movement. Areas of the brain normally associated with memory, problem solving and abstract thinking are noticeable absent. So what makes fish so difficult to catch?

What fish have on their side isn’t intelligence. They have a superbly tuned wariness that is tuned for avoiding predators. They have instincts that communicate what appears to be natural and what doesn’t within the environment in which they live. If you try to think like a fish you will not be doing any real thinking; the real challenge is your intelligence versus the fish’s instinct.

Getting back to the ego thing, if a creature with the brain smaller than our thumb nail makes a fool out of us with our big brain we have to find some logical excuse for our failure. If we believe that a fish is intelligent then we can excuse our failure. We do this in a variety of ways.

Many fly fishers believe that it is necessary to use a very fine leader to catch trout. They reason that the trout can see the leader and if they see the leader they will not take the fly. While they don’t necessarily say they believe the trout knows what a leader is it’s inferred by what they do in attempting to make the leader invisible. In truth the trout does see the leader, but since they are unable to perform abstract reasoning they have no objective way of connecting the leader to anything that is dangerous. The water is filled with a variety of objects; pieces of weed, leaves, and other organic material which is completely ignored by the trout. A piece of monofilament drifting along in the water is also completely ignored by the trout. You can prove this by casting just a leader tippet over a feeding fish. Unless you smack the fish on the head or make a significant disturbance on the water with your leader the trout will totally ignore it. It’s just another floating piece of matter nothing more. Now if your leader when it’s attached to an artificial fly makes the artificial act unnaturally the fish may well reject it instinctively but not logically. You reason that the fish rejected your fly because they saw the leader tippet; the fish rejected your fly because it did not act naturally or for some other reason we cannot understand. A finer tippet may be more supple allowing the artificial that is attached to it to behave more naturally – move without drag – but it will not prove more effective because the fish can’t detect it. If the trout is put off by your tippet why are they not put off by the hook? It is obviously more noticeable than the leader.

Another idea that we have accepted as truth is that fish, especially trout, become able to identify various artificial flies and thus we need to continually create new flies in order to fool the fish. Since fish lack the ability to form memories the idea that fish can remember that a certain fly is an artificial and thus to be avoided is not true. How many trout do you think have been caught on the Adams dry fly or the Pheasant Tail nymph? Why have the trout not been able to remember them and thus not eat them? We create new flies because we think we can improve upon the older patterns and then the older patterns fall out of favor and disappear. However, if they worked before they will still work today.

Part of what makes fishing in general and fly fishing in particular challenging is that we will never have all the answers to why fish do what they do. However, we can be certain that when we fail to fool them with our flies, lures or bait it’s not because they are too intelligent. The fish that are living in the water where you are fishing are the offspring of survivors. Their parents survived to become old enough and large enough to spawn and they passed those traits on to their offspring through their genetic material. If you understand that fish have only limited intelligence but that they have eons of survival skills passed down genetically you are on your way toward a greater and more truthful understanding of fish behavior. Properly understood that will make you a more successful angler.

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