Are Trout Color Blind?


The fact that we humans can perceive light and color makes us oblivious to how other creatures perceive the same. Believe it or not, some animals and even some human beings are not able to perceive light and color as we do. 

The most common condition that affects color perception is color blindness. Red and green color blindness is the most common form of color-blindness and it’s a condition in which an individual or animal isn’t able to tell a color as being either red or green and confuses it for another color. 

For us to get to know whether or not trout fish can perceive color, it’s first important to see how exactly the eyes can see in color. 

How Do Eyes Perceive Color?

The eye has a region known as the retina where all the light from the outside world lands on. The retina is then responsible for sending neural signals to the brain through the optic nerve. On the retina, there are numerous layers, each with a specific function but the most critical layer is the ‘Rods and Cons’ layer. The layer of rods and cones contains cells known as rods and cones. Rods and cones function as receptor types of cells meaning they are the cells that can ‘see’ light and color from the environment. 

The rods are responsible for all the black and white or monochrome colors, while the cones are the ones that tell the different colors. Essentially whenever we see color, it doesn’t mean that the rays of light arriving at the retina are retina are colored.  Instead the rays of light are of different wavelengths that are specific to each color. 

The cones are of three different types each for the three primary colors: Red, Blue and Green. All other colors that we can perceive are a combination of two of the colors or all three of them in a certain order. When we see a rainbow essentially, we are looking at a gradient of the three colors.

Everything in the world has characteristics that enable it to absorb visible light from the sun. The sun emits certain rays of light including visible light which is why we can see color. This is the reason why it is hard to see things in the dark because of the absence of visible light. Light bulbs have been made in such a way that they also emit visible light to some extent but not like the sun.

When visible light falls on objects, they absorb it and then emit as a narrow band. This is then perceived as color by the eye. So, when we see color, we do not see the color of the object, but what we are seeing is the narrow light band that is being emitted by the object. 

The three types of cones in the retina are the chlorolabe, cyanolabe and erythrolabe which perceive green, blue and red respectively. Each cone has a characteristic wavelength of light that can perceive.

How Trout Perceive Light and Color

Just like human beings, trouts also have rods and cones in their retinal layers. However, they have four different types of cones for color perception. Each cone perceives lights at four wavelengths: 600nm, 535nm, 439nm and 350nm. The 535nm and 439nm cones are easily comparable to the cones in humans that perceive the green and blue color. That is, the chlorolabe and cyanolabe cones. The 600nm cone is slightly similar to the erythrolabe cone is humans but it can perceive longer wavelengths. 

The 350nm cone is the additional cone that isn’t found in humans. This is because the wavelength of light that it perceives is slightly below the color range of the cones on humans, which is between 400nm and 700nm. The 4th cone can perceive ultraviolet light which is slightly below the range of visible light. It is speculated that this cone usually disappears as the trout matures.

During the early years of development, the 350nm cone allows the fish to see planktons and zooplankton on the surface of the water as they emit ultraviolet radiation. It has also been speculated that the ultraviolet cones usually reappear in larger fish especially during spawning for the purposes of navigation through the water.

It has also been discovered that whereas human beings will perceive color as dark red, trout see the same color as being bright red. This is because the lowest wavelength value of the color red in human beings coincides with the peak of perception of the color red in trout. This also means that trout can perceive color better than human beings even in conditions where there is low light. 

How the Aquatic Environment Influences Color Perception in Trout 

Even though we humans have almost the same retinal cells for the perception of light as the trout, we both perceive light and color differently. This is because the aquatic environment doesn’t receive light from the sun like we land animals do. The quality of light that reaches trout fish is said to be lower than the one that we perceive. 

When the water is clear, the blue rays of light upon striking the surface of the water disperse to different directions thus causing the fish to perceive the color blue. This is the same phenomenon that has been applied when describing why the sky is blue.

Red light rays from the sun usually strike the surface of the water and pass through it thus, and the fish can see the color red at an even brighter scale than it is when close to the surface. However, as the red light moves through the water most of it is also absorbed and converted into heat energy.

In the long run, the absorption of the red light and dispersion of blue light affects how the fish see and what they see in water especially at long distances. For the trout, a red object emitting red light rays on the surface of the water will be seen as a black object because of the absorption of the red light; the further down the fish is from the surface. If the fish is close to the surface, then it may be able to perceive the red color even brighter than it is because there is minimal absorption.

The color white is however visible to the fish no matter how deep it is. This is because white objects don’t absorb any form of visible light. For this reason, if you use a red-colored bait such as a fly that mostly has red pigmentation, the trout will choose the fish with whitish scales that are over 12 feet over your bait that is less than 10 feet away.

How Do Trout Perceive Color in Low Light Conditions? 

Low light conditions include conditions at night time and in places where the water is muddy or has a lot of impurities. The perception of red light is not really affected by low light as the distance from the surface to the fish already affects its perception in a big way. 

On normal occasions the rods and cones of the trout’s retina are usually arranged in such a way that the cones are on top of the rods. This ensures that color is perceived first and light after. However, during the night, the cones lie below the rods and thus color perception doesn’t occur first. Therefore, as nighttime approaches, trout respond less to color and more to light. Under these conditions when fishing for trout at night, using a lamp is the best way to attract fish.

Fluorescent light is of a different wavelength compared to visible light and thus is penetrates the water surface better than visible light. Therefore, it has been noted by fishers and divers that fluorescent colors of red and green are more visible at night compared to all other colors of visible light.

Final Word

Trout are not color blind in any way. They have the biological features and more that allows them to perceive light and color. However, the environment in which they live can be the limiting factor. Thus, color vision in trout is only of maximum value during fishing in water that is shallow and clear and where the fish are close to the bait. 

During fishing, one should do as much as they can to first attract the attention of the fish so that they are first attracted to the movement on the surface. After this they will move towards the bait which will allow them to see the color. This also shows that fishers who place the bait at the bottom of the water surface have an advantage over those who fish from the surface. 

Impurities in water also impact their ability to see color but not so much the perception of the color red. When fishing it is advisable to use fluorescent light, which is mostly white rays which the fish can see at all distances.

Fishing using bait at night may be unfruitful as color perception is minimal at night and thus using lamps and torches to illuminate the surface of the water is advised. This will go a long way in attracting the fish to the surface where they can then be captured using whatever bait.

Using the right type of light and looking for trout in the right environment is paramount when fishing under different light conditions to minimize the effects of environment on the trout’s ability to perceive light.

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