Seeing is Believing-Fish Senses

The answer is simple and complex at the same time. Have you ever wondered whether fish can really see color and, if so, what do they actually see? Scientists tell us that fish can and do see color, but there are countless variations to what they see depending on a host of factors. The color of light varies by shadings starting with blues at the short end of the spectrum, followed by greens, yellows, and oranges until red is reached at the long end of the spectrum.

White light is made up of all colors or wave lengths mixed together. We are familiar with seeing color through the medium of air, but other changes take place when the medium is a liquid. Water serves as a filtering process in which certain colors (wave lengths) are selectively removed at specific depths or horizontal distance. This alters the color characteristics of light.

Color is absorbed from the light as it passes through the water toward the object and then again when it is reflected by the object and passes back through the water to your eye. That means that when you look through the surface and see a lure underwater, it will have lost a great deal of color because the light has passed through the water twice. A fish at a particular depth, however, only has to deal with light loss from the surface to its depth and then for a short horizontal distance to the lure.

The deeper you go in a body of water, the more the light rays are scattered and the darker it becomes. Water absorbs the longer waves (the reds) fastest and even in clear water they are gone within 20 to 30 feet. In murky water, red disappears even sooner. Blues and greens are absorbed slowest, so a fish living in deeper water faces a monotonous blue-green aspect.

At dusk, when the underwater light begins to fall rapidly below the fish’s threshold of color vision, reds are the first to go and blues the last. When the total light level falls below one foot-candle, the fish have switched to sensitive rod vision and are unable to distinguish color even in bright moonlight. At dawn, the pattern is reversed when the fish begin to switch to color sensitive cone vision with the blues and greens appearing first and reds last.

All fish cannot see color equally well nor can they discern color with equal ability. While most species have color vision to a degree, some are much sharper at color discrimination than others. The presence of both rod and cone receptors in the retina of an eye is a strong indication of color vision. Not all fish see color. Sharks have only rod receptors and see everything in black and white, yet they have survived for eons of time. A deep-water fish such as the snapper would have little use for red sensitivity, since it lives where there is no red light. A red snapper would be gray or black in its home range.

After years of experimentation, I’ve come up with a couple of theories. My two favorite colors are light and dark. If one doesn’t work, I try the other. At night, if you are using surface lures or artificials running just under the surface, remember that the sky is lighter than the water which means a dark color will stand out. If all this fails, pick a color you believe will catch fish and try it. It will usually produce.

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