The Extraordinary Rainbow Trout

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The Extraordinary Rainbow Trout

by Ron Newman

Throughout the fishing season I frequently hear other fly fishers comment about the Rainbow Trout they have just caught. The comments usually follow the theme of; how beautiful, how amazing, how fantastic or how well it fought. But have you ever REALLY thought about the attributes of this incredible fish?

For example, consider that a moderate size Rainbow can accelerate from a standstill to about 23 mph (or 37 kilometers per hour) in about one second. A larger fish can get in an extra one or two mph. Almost instantly the fish is traveling more than 33 feet per second and can maintain that speed long enough to easily strip a hundred yards of line and backing off your reel. Its no wonder that if a fly fisher is going to loose a Rainbow, it usually happens within two or three seconds of being hooked. Can you think of another member of the animal kingdom that can reach that speed so quickly? Even those animals known for their speed, such as the Cheetah or Greyhound, cannot accelerate that fast.

And just how strong is that Rainbow Trout? A trout of three pounds can easily break a leader tested to six-pound strength. That's double its body weight. I defy you to break, rather than cut, monofilament tested to just your own body weight. Few members of the animal kingdom can accomplish this feat but some larger trout do this on a regular basis.

Rainbow Trout are also known for their jumping ability. A Rainbow can easily leap into the air three or four times its body length. In the animal kingdom, jumping to a height of more than two body lengths is uncommon even on dry land. The household Cat and a few other members of the animal kingdom can make similar leaps but that doesn't detract from this incredible ability. In human terms, the trout is jumping 18 to 24 feet into the air out of a swimming pool.

Have you ever thought about why the Rainbow is extremely agile, can stop on a dime, or has teeth but doesn't chew? How does it change color to match its surroundings or suck oxygen from water without clogging its gills in underwater debris or how can it remain suspended in the water column with virtually no fin movement? These can all be explained but will have to wait for a longer article. The main point is that even though all these physical attributes are amazing, the 'senses' of a Rainbow Trout are even more amazing.

Photo courtesy of Sheridan Lake Resort

The sensory input received by a Rainbow is estimated to be 500 to 800 times more acute than the sensory input received by a human. This fish can perceive its surrounds to a degree that we can only imagine. The fish's brain is entirely devoted to bodily functions and sensory input. It doesn't possess a Cerebrum and yet is quick to learn from experience. The Cerebrum is the center for thought and reasoning in humans.

The eyes of a Rainbow do not have eyelids. They are quite sensitive to bright sunlight. A trout is somewhat near sighted but can see quite well up to distances of about twenty feet. Sight is used to locate food at close distances while its other senses are used to locate food at further distances. The eyes of the Rainbow are well designed for seeing color. They see color in the red to blue wavelengths about the same as a human. However, in the yellow to green wavelengths the trout see color much better than we do. Part of the reason for this enhanced color perception is that the yellow to blue wavelengths of light travels better in water than in air.

Having the eyes on the side of the head also gives the Rainbow Trout a different perspective on the world. This placement of the eyes allows the fish to see to the front, sides and most of the way behind. The only blind spots are immediately behind and directly below the fish. Upward and directly in front, the fish has depth perception or binocular vision as both eyes come into play. Toward the rear and to either side, only the eye on that side is used and the trout has monocular vision without depth perception. Viewed from below, the water surface reflects light when viewed at an angle. So the trout can only see the upper world through a small round 'window' that is directly above and has a diameter that is about twice the depth of the fish. A trout cruising 10 feet down can only 'see' a dry fly presented within about 20 feet of its location. Ears? No, the Rainbow doesn't have an external ear yet it can hear sound better than almost all land animals. The trout's three-chambered 'internal' ear picks up sound very well. If you drop your glasses in the bottom of the boat, a trout across a large lake will easily hear that sound and the nearby trout will probably be spooked into a non-feeding phase by the noise. The ear also serves as an organ for balance. Land animals use fluid in the ear for balance. In a fluid environment, the trout uses calcified stone in each ear chamber to help it tell up from down and left from right.

The senses of taste and smell are particularly well developed in the Rainbow Trout. They are better developed than the legendary Bloodhound and about 500 times more sensitive than these senses in a human. It is believed that Rainbow Trout, steelhead and salmon (all of the scientific Order of Oncorhynchus) use taste and smell to help locate the waters of their original spawning streams.

A Rainbow Trout can smell the difference between two aquatic plants of the same species that are side by side. It can even taste the difference between two species of Chironomid and thus will have a preference for one species over another. Rainbow Trout are very sensitive to differences in ph, salinity and the differences in amino acids as found in their food sources. It is thought that the Rainbow may even have taste and smell sensors on parts of its body other than in the nostrils and mouth and that these may actually help the trout in locating its food.

Would you believe that we have yet to come to the most astounding aspect of the trout's senses? Besides the normal touch sense that most animals have, the Rainbow Trout has what scientists are calling the "Distant Touch" sense. This is sort of like Extra-Sensory Perception or ESP. The scientists aren't exactly sure how this all works but here are a few of the known details.

Water is 800 times denser than air. In part, this is why the trout can hear, smell, taste and see color so well. As a denser medium, water carries the mechanisms for sensory input much better than air. The senses of touch and perception are no different. The Rainbow can feel and perceive distant objects or movements about 800 time's better than we can and may even have a form of echolocation.

Imagine that someone drops a ball of cheese at the other end of a football field. Other than the fact that you saw it drop, you probably wouldn't know that it had happened. At that distance, with its eyesight, a Rainbow Trout wouldn't see the cheese ball drop. However, underwater it could 'feel' the concussion of the cheese ball hitting the ground, hear the sound it makes when it hits and may even be able to smell and taste the cheese shortly after the hard outer cover breaks. It is even possible that, through echolocation, the trout could tell us exactly where the cheese ball hits in the end zone.

A person capable of doing the same would be considered to have ESP. The trout's primary receptor for this ability is the Lateral Line. It is also known that the Supra-Orbital and Sub-Orbital lines on the jaw and back on the trout's skull play a similar role. The trout may have other distant touch receptors of which we are yet unaware. The full sensory capabilities of the Rainbow are yet to be determined by the scientific community.

With its distant touch sense, a Rainbow can detect the slightest movement of an aquatic bug (or fly) at quite a distance and even on the darkest of nights. It can just as easily detect if the movement is wrong. For the fly fisher, the reward comes when the trout 'inhales' the fly very softly. That's a sure indication that the trout is feeding on the fly rather than taking it out of aggression or territorial protection. They will 'strike' a fly, sometimes very hard, for a number of reasons but they will only 'inhale' the fly when they are confident that it is their desired food source.

In human equivalents, we seem to have an animal that is faster than a speeding bullet, able to leap tall buildings in a single bound, is stronger than a charging locomotive and even has its own form of X-Ray vision or an equivalent there-of. Remind you of anyone? I'm not sure about you but I consider the Rainbow Trout to be the Superman of the animal kingdom. If we were handing out awards, I would certainly vote for Mother Nature and her creation of the Rainbow Trout.

A 'few' Fishing Tips related to this article:

  • Let a trout have as much line as it can take immediately after the strike.
  • Set any fly 'softly' as the fish may already be making a run.
  • Use a leader strength that is 'double' the weight of the fish you may expect to catch.
  • Let a jumping or running fish 'strip line' off the reel but be prepared to take up slack at any time.
  • Fish a sinking fly deeper in the water when there is bright sunlight.
  • Don't expect success to be too great on a dry fly on or near the surface when there is bright sunlight.
  • Fish dry flies fairly close to where you saw or 'expect' a rise but use a 'soft' presentation.
  • Ensure your retrieve represents the 'bug' being fished. Change retrieves if necessary.
  • Make the imitation of yellows and greens in a fly as close as possible to the actual bug.
  • During daylight and at close distances the fish will 'look' at your fly so make sure it will pass the 'close' inspection.
  • Don't make moderate to loud noises while fishing or anchoring as they may 'spook' the fish in that area of the lake.
  • Avoid getting any smells on your fly that the trout may consider 'foul'. Particularly those that are acidic, or basic, or salty, or taste like sun-tanning lotion.
  • Try some of the commercially available odors on your fly that supposedly attract fish. You may find one that actually works and improves your success.
  • Be prepared to fish a fly pattern, even small ones, after dark. Fish will 'find' and accept that fly if retrieved correctly. The larger fish actually feed at and after dark.
  • If fish are 'slamming' your fly, they are not taking it as a food source. You may improve your success by changing the fly or the retrieve. However, sometimes they will only take an attractor fly.
  • Feeding fish will come from more than a 100 feet away to take a properly presented food source.
  • Trout can perceive a fly from a considerable distance. Make sure their 'first' impressions are good.
  • If you are matching the "beginning of a hatch" without success, try some various colors or sizes as the fish may have specific species preferences.

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The Extraordinary Rainbow Trout