young
Posts: 89
Joined: 9/23/2009 Status: offline
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"Color vision is a well-defined trait in shallow-water fishes of both oceanic and fresh water systems. It evolved, as it did in other animals, as a mechanism to allow the fish to better separate potential food items from the background. In the watery environment, the background may be either the bottom (normally a tarnish olive to green color) or the background may be the water itself. When looking horizontally through clear water, the background appears pale, silvery blue. This phenomenon is known as background space light and is caused by the scattering of blue light as it passes through the water. In water with a lot of suspended algae, the background space light is greenish yellow, and in tea-colored bog water, the background space light appears reddish brown.... Thus, for opportunistically feeding trout and salmon, flies or lures with strong coloration and/or a lot of flash--which makes them stand out strongly against the background spacelight--are great fish attractors.... Fluorescent colors stand out strongly against background spacelight of any color, and fluorescent shades of reds, oranges, purples, and chartreuse are highly attractive to salmon and trout.... For selectively feeding trout, color not only serves to separate the food organisms from the background, but also serves as one of the four major characteristics that triggers feeding (the others are size, shape, and behavior of the food item)...The question then becomes, how accurate does the color match have to be? It was a question that started me on a twenty-year experiment into the color preferences of selectively feeding trout. First I assured myself that selective trout are definitely sensitive to colors. They can and do distinguish between brown and olive, for instance... In response to the obvious question raised by this result, I found that even though trout can distinguish colors, they do not discriminate between very fine shades of any one color for selective feeding purposes. The reason for this lack of color hyper-sensitivity is simple: the food organisms vary slightly in color. If the fish were too color sensitive, much food would be lost. For selective feeding purposes, trout will normally discriminate between about four or five shades of a color, from the palest shade to the darkest. I also discovered that when matching some insects, a shade of a color different from the shade of the natural can be more attractive to selective trout; usually the more attractive shade has more chroma (the color appears more intense than the color of the natural)." Borger, Gary. Color Vision in Trout and Salmon. Still waiting for the pics of the wild brown trout caught on marshmallows and processed cheese.
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