Can A Fish See Color?

Fishing lures often boast great "attractive powers." Some lures rattle, some click, some fly. On balance, these "lures" are designed and built to hook fishermen, not fish. Why should fly fishers care about lures? The more I see fly tiers adding gimmicks to flies, the more their flies resemble lures. The more I see flies resembling lures, the more I realize their greatest value lies in fly-fisher "entertainment." Understanding how a fish sees will help you create flies designed, not to entertain, but to catch fish.

The fish's world
 A fish lives in water which, just like air, is a fluid. Being a much denser fluid, water greatly affects the properties of light. Like our eyes, fish eyes have a cornea, an iris, a lens, and a retina full of rods and cones, but many functions of the fish's eye are modified to deal with a water environment and produce excellent underwater vision.

The fish eye
Two major lens modifications affect the fish's vision profoundly-its lens is round, and it is much denser than a human lens. A fish lens can, therefore, focus heavily-refracted light onto the it’s retina, so it clearly sees objects underwater. To vary its focus, the fish moves It’s lens forward and backward. A freshwater fish is naturally farsighted, so when it wants to focus on close objects, it moves its lens back from the cornea and closeup focus is achieved. Fish enjoy a tremendous field of view, with 180 degrees of overlapping vision from both eyes. With their swimming motion and eye movements, fish generally don't have blind spots behind them and have good depth perception.

Light regulation
Fish don't need eyelids to keep their eyes moist, thus many fishers believe that fish cannot control the amount of light entering their eyes. They believe fish hide in low light areas to escape bright light. Wrong!

The fish eye controls light in a different way than a human eye. According to Dr. Bob Reinert, a professor at the University of Georgia, instead of an iris closing, or eyelids squinting, "The fish uses synchronized movement of the rods, cones, and pigment granules in the pigmented portion of the retina to control light entering the eye." While a fish can handle great variations in ambient light, one drawback to this method is that adjusting from low light to bright light may take a fish much longer than it takes us.

Can fish see color? 
In a word, yes. According to Dr. Reinert, "One of the best indicators that some fish see color is that they have cones, which are the color receptors in higher vertebrates. Another indicator is that many fishes are highly colored, and the most colorful fishes are found in shallow, well-lighted waters, where they are exposed to the full color spectrum."
Based on testing, the primary biological advantage of color vision for a fish is being able to contrast food targets against a variety of backgrounds. As a fly fisher, you should know that color can really impact a fly's effectiveness at times.
 
Effective flies
What are effective flies? According to Doug Hannon, the "BASS Professor," small flies emulating an abundant source of prey that glide quietly through the water with the least amount of ruckus are the most effective-because that's how real prey behaves underwater. Small, quiet, simple flies tied in natural colors don't give off negative cues which the fish see and sense.
Sized to match available food sources, they can be presented to imitate the actual motions of real prey. For example, crayfish may sink slowly, then dart off in short motions, settle to the bottom, and dart off again. Minnows will suspend, change directions, suspend, and slowly swim away.  All are small, quiet food organisms. Small crayfish, minnow, and leech patterns appear natural and are very effective.

Know the natural actions of the prey you're trying to imitate, then tie your flies with materials which imitate those actions. Keep the gimmickry out of your fly designs and keep your flies effective! 

By Bill Byrd is a freelance writer from Stone Mountain, GA.