What Can Bass See - Part 1

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Bass are proficient sight hunters and once they are locked onto their prey, chances of escape are slim.  Combined with a highly developed lateral line, lightning-fast speed and exceptional vision, it is easy to see why bass rank high on the food chain; it is the visual system that provides bass its’ most lethal hunting tool.

Bait manufactures know that bass are primarily sight hunters and provide a multitude of realistic colors, styles, materials and actions to tempt bass.  With all of these baits on the market, it can be confusing when determining which lures to buy - especially which color.  We have all heard the old adage that most baits are designed to catch fisherman versus catch bass.  Do we really need every color of our favorite bait?  What colors can bass really see and at what depths does color become non-existent?  In this article I will focus on light, the properties of absorption and scattering, how water clarity and depth effects color, bass’ sense of sight, the anatomy of a bass’eye, and what a bass can and can't see based on published research.

Light is electromagnetic energy that travels in waves called frequencies.  A frequency’s range is called a spectrum and frequencies are measured in nanometers (nm).   Humans see frequencies ranging from 390 nanometers (violet) to 750 nanometers (red) which is known as the visible light spectrum.  Bass can see frequencies ranging from 400nm to 700nm.  Frequencies outside the visible light spectrum include high-frequency ultraviolet light, X-rays, gamma rays, and low-frequency radio waves, microwaves, and infrared waves.  A light wave contains all of the colors of the visible light spectrum (white light) and once it hits an object, certain wavelengths are either reflected or absorbed.  The reflected light is the color we see while all other colors get absorbed.  For example, a red crankbait reflects red light frequencies while every other frequency gets absorbed into the pigment.  White reflects most or all light off an object, while black does the exact opposite by absorbing most or all light.

The physical properties of water cause it to absorb light and the intensity of this effect depends on its purity and light strength.  The condition of the water surface, whether flat or wave action, has a minimal effect on the amount of light entering a body of water. According to retired Professor of Oceanography of Texas A&M University Robert Stewart, only two percent is lost in reflection.  In clearer water, light will reach greater depths versus water that is stained, muddy or has high levels of suspended phytoplankton and zooplankton.

As light travels through the water column (depending on its depth) eventually it will be completely absorbed leaving only darkness.  The depth at which 99 percent of all light is absorbed in a lake is known as the photic zone and conversely the depth at which there is no light is the aphotic zone.  Absorption is important to anglers when choosing lure color because water also acts as a color filter.  Pure water absorbs red and orange first, followed by yellow, green, purple and lastly blue. Some line companies have developed their products with this in mind like that of Cajun Line which features red line that uses the property of color absorption to help make their lines virtually invisible at certain depths.  The depth at which colors are absorbed depends on the level of water clarity and that level can change throughout the year and even daily with boat traffic, wind, algae blooms, flooding or lake turn-over.

Listing all the variations for every lake would be impossible.  Here are the absorption rates of absolute loss of color in the ocean based on a chart created by the NOAA (National Oceanic and Atmospheric Administration).  The rate is not what is visible to the eye but the total loss of a particular wavelength due to absorption:

  • red 65-ft
  • orange 82-ft
  • yellow 213-ft
  • purple 328-ft
  • green 393-ft
  • blue 688-ft

Clear lakes with a slight algae bloom filter out both blues and reds, primarily leaving the greens and yellows.  Muddy rivers, while allowing little light to penetrate at all, appear reddish because the blue and green colors are absorbed more than the reds.  It is important to note that all colors will appear as black or some shade of grey once reaching the depth in which complete absorption of that color occurs.  At that point, having a lure with the correct profile, action and/or sound of the forage you are trying to mimic is more important.  The exception to this rule is fluorescent colors.

Fluorescence occurs when a pigment absorbs high-frequency and short wavelength light, storing the energy momentarily (0.00000001 second) and then releasing it as light with a longer wavelength, which produces a warmer color.  This effect extends the depth at which color is visible in water as long as there are higher-frequency light waves present.

Depending on water clarity, anglers can use florescence to make their baits visible at greater depths compared to baits without florescence.  For example, in ultra clear water where red is normally absorbed in the upper 20 to 30-feet, fluorescent red continues to be visible as long as deeper penetrating higher frequency light waves are present. Fluorescent colors can be advantageous in heavily stained waters by giving bass a brighter and easier target to pinpoint.

The physical properties of light scattering result in less direct light reaching a bass’ eye and giving a body of water its color.  Light is scattered in water when it collides with suspended materials such as soil particles, algae and dead or decaying organic matter (detritus).  The scattering effect creates a haze in which bass see weakened images and limits the distance they can see.  Light scatters more as it travels deeper eventually reaching a point in which all light is randomly scattered and at this depth, objects do not cast shadows and highly reflective objects no longer flash.  This is important for anglers to note when deciding whether to use a chrome bait versus a colored bait when targeting deeper fish.  The depth this occurs depends on clarity, so the muddier or more stained (turbid) the water, the shallower this effect will occur.

Bodies of water differ in color due to the suspension of light scattering particles and aquatic plant life.  For example, green algae in lakes or rivers causes the water to appear to be blue-green, the red sea has occasional blooms of red algae and Clear Lake in California looks pea soup green when the annoying algae bloom is at its peak.  A delta gets its varying colors from finely suspended silt and plant particles, while some mountain lakes look turquoise from finely ground rock known as glacial flour.

With that brief overview on light and color, let’s talk about the anatomy of the bass’ eye and its function.  Bass use their eyes to monitor ambient light, pinpoint motion and determine shape, size, form and color.  A bass’ eye is similar to ours with a cornea, lens and retina. Once light hits the retina, the signal is sent to the brain via the optic nerve and then interpreted.  The brain sees while the eyes gather the information.  The back of the eye contains the retina, which contains rod and cone cells, which are responsible for the sensory conversion of light.  Cone cells are utilized during the day while the more sensitive rod cells are used during low light conditions.

Some differences between a bass’ eye and our own: A bass eye is slightly oblong and ours is round. Their lens is round and ours is oblong. They do not posses eyelids or tear ducts, as neither would be much use underwater.

Humans have three photosensitive pigments (red, green and blue) in the retina compared to bass, which only have red and green.  Without the blue pigment, bass do not have the ability to see blues or violets.  This is important to note when choosing a lure that contains these colors as they will be viewed as shades of grey or black.  A visual study conducted by Kawamura and Kishimoto of Kagoshima University conclusively determined that bass possess color vision and the ability to discriminate colors.

So how does an angler use this information to their advantage?  When choosing lure color, use ultra clear water as your baseline and work from there.   In ultra clear water with bright conditions, a red crankbait will lose its color anywhere from 20 to 30-ft.  If the water is stained or muddy, the depth that red crankbait can be seen is even less.  Then add in factors like cloud cover, wave action and light intensity.  You will not be able to determine the exact depth of color absorption but at least you will have a good idea of what is going on.

When choosing lures on bright days go with brighter colors if you want your lure to be seen at greater depths; the more light available, the deeper your bait will be visible.  When choosing lure color during low light conditions or cloud cover, go with darker colored baits (or fluorescent) as there won’t be enough light for color to be visible at greater depths, the contrast of the darker bait will be more effective.  This is also when action, profile and sound become very important.

It is important for anglers to have an understanding of all aspects of bass fishing if we want to be successful.  Light, color and bass vision are just a small piece of the fishing puzzle.  Choosing the right color, action, profile and sound based on the information in this article should help you put a few more fish in the boat and give you a better chance of doing so.

In part two, we will discuss the properties of ultra violet light and if a bass can see UV light.  I will also share information via my discussions with a Professor of Visual Neurobiology, an owner of a bait company banking on baits that contain UV properties and the VP of Product Development of a well-known bait company.  Until next time stay focused, fish hard and I’ll see you on the water.

To read more great articles like this one, get a copy of Bass Angler Magazine at your local tackle shop or  bassmag.com

References:

Charles L. Braun and Sergei N. Smirnov.  (8/1993).  Why is Water Blue?  Inside Mines.  Retrieved on 7/22/2011 from http://inside.mines.edu/fs_home/dwu/classes/CH353/study/Why%20is%20Water%20Blue.pdf

Dr. Keith Jones.  (2002).  “Knowing Bass- The Scientific Approach to Catching More Fish.”  Gilford, CT: The Lyons Press

Unknown author.  (1/31/2011).  Light.  Water on the Web.  Retrieved on 8/9/2011 from http://www.waterontheweb.org/under/lakeecology/04_light.html 

Gregory Houtteman. (12/31/2006).  Effects of Water Depth on Color Visibility.  Educated Angler.  Retrieved on 8/9/2011 from http://www.educatedangler.com/index.php?option=com_content&view=article&id=921 

Robert H. Stewart. (9/15/2006).  Light in the Ocean and Absorption of Light.  Ocean World.  Retrieved on 8/15/2011 from http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_10.htm 

Gunzo Kawamura and Toshihisa Kishimoto (2002).
Color vision, accommodation and visual acuity in largemouth bass.  Fisheries Science 2002; 68: 1041-1046