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Old 08-16-2007, 09:14 PM
OSSCA OSSCA is offline
 
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Default Fish Vision Study

http://www.vims.edu/newsmedia/press_...ish_vision.htm
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Old 08-16-2007, 11:19 PM
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Default Re: Fish Vision Study

Very Cool study Osh

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Old 08-16-2007, 11:20 PM
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Default Re: Fish Vision Study

Quote:
Horodysky's research shows that striped bass are most sensitive during daylight hours to a wide range of colors from blue to red, with a peak at chartreuse. They have a "flicker fusion frequency" (essentially the "shutter speed" of an eye) of around 50, relatively fast for a fish, which allows them to track large, quick-moving prey like menhaden.
One intriguing aspect of Horodysky's research is the disparity he's found between the prey items that striped bass are adapted to see— large, fast-moving fish like menhaden—and the items that actually occur in their stomachs—mostly small crustaceans like juvenile blue crabs and mysid shrimp.
Horodysky and his faculty advisors hypothesize that striped bass are living in a visual world very different from the one evolution prepared them for. That's because human activities in the Bay watershed and the demise of the native oyster have dramatically reduced the clarity of Bay waters Chesapeake Bay used to be very clear,says Brill. Now we've made it mucky. So we see the visual ecology of the Bay changing. Our argument is that over evolutionary time these fish have made certain visual choices, then suddenly find themselves in a visual environment they didn't evolve in.
I would have expected the total opposite.
What is most interesting is that they could possibly be adapting to the changing environment of the bay.

Some other cool stuff for those who have the time to read it.
https://www.stripers247.com/phpBB2/showthread.php?t=6843

This is Power point presentation on fish vision from the Rochester Institute of Technology computer science dept.
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An article from sws can fish see colors. SWS article




Can Fish See Color?

Most scientists think so. Here's how it can work for you.

January 1, 1999
By George Poveromo



As any angler knows, artificial fishing lures come in a wide range of attractive colors and color combinations. Whether fish actually see color — and, more importantly, whether they react to it — has been an ongoing debate for quite some time. As one major manufacturer of offshore trolling lures once told me in confidence, "You can catch offshore fish on any lure color, since it's the action of the lure that attracts and provokes them into striking — not color."
At the opposite end of that spectrum, experts at inshore-lure companies believe fish can indeed distinguish colors. Their philosophy is that if their lures aren't ultra-realistic, they won't fool as many fish.
The Science of Vision
"A big factor is the color spectrum and what happens when light moves into the ocean," says Dr. Linda Farmer, director of the Undergraduate Program in Marine and Atmospheric Science for the University of Miami. "As light travels through the water, red, which is the longest wavelength, is absorbed first, followed by orange, yellow, green and blue and, eventually, indigo and violet [the shortest wavelength], leaving no sunlight below a certain depth. Red will appear as a faint black. The color violet will remain intact the longest." It should be noted that how far down these colors penetrate varies based on water clarity, the amount of light and other factors.
The complexity of vision in fish varies from species to species. Some experts believe that offshore fish such as billfish, tuna, wahoo and dolphin are colorblind and only distinguish objects that contrast with the background they see. These fish are thought to possess two visual pigments, sensitive to blue and yellow light. According to Farmer, some inshore fish have more than two pigments. Fish with four pigments can detect many colors and can distinguish bright and dark objects against any background. Armed with this knowledge, I discussed my approach with some successful anglers.
Offshore Evidence
"The purple-silver-black combo is the ticket," says Frank Johnson of Mold Craft. "If I had to choose just one lure color for billfish, it would be purple, hands down. We not only sell more lures in this primary color, but we've got guys using it all over the world, and saying it works. There has to be something to it."
Dissecting the idea that offshore fish see more shades than colors, it could be argued that purple may indeed offer a sharper contrast against a bright sky or blue ocean. One could also say that the purple hues closely resemble small tunas, on which billfish prey. Could it be the "match the hatch" theory at work? Or are fish more keyed in to the color patterns of their forage, rather than the type of forage?
I've long had confidence in trolling lures in colors that mimic the natural forage. My go-to colors are all-blue or blue-white, which I think mimic flying fish. When peanut dolphin are abundant, I'll add a few green-blue-yellow combinations to our spread to imitate dolphin.
The Inshore Spectrum
Eric Bachnik is chief operating officer of L & S Bait Company in Largo, Florida — makers of MirrOlure — and a light-tackle inshore angler.
"Our top-selling MirrOlure pattern for 65 years has been the red head-white body," says Bachnik. "Perhaps it appears like an injured baitfish. That's followed closely by our natural scaled sardine pattern.

Color By Number
General guide: percentage visible at depth.

COLOR
Red 10 feet 6.5% - 30 feet 0.025%
Orange 10 feet 50% - 30 feet 12%
Yellow 10 feet 73% - 30 feet 40%
Green 10 feet 88% - 30 feet 69%
In clear water, fish can see a natural-forage-pattern lure better and it resembles what they're eating."

Of the vast colors and combinations offered by his company, Bachnik believes that in cloudy or tannic waters, fish can see gold and chartreuse patterns better. "In these conditions, fish rely heavily on vibrations," says Bachnik. "On dark nights, I like all-black, black-silver or purple. Even on moonless nights, there will be some light that helps fish see and dial in on the silhouette. On a bright night, I'll choose lures with holographic or mirror inserts."
When plugging inshore, I "match the hatch." If there's an abundance of a specific bait, chances are gamefish will be tuned into those colors. I often go with the red head-white body lure if there is a lack of bait. Two things are certain: Gamefish respond to lure color, and we'll still continue to fish our go-to lures. But experimenting with color in the quest to find a knockout lure is a challenge we seem to enjoy.
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Old 08-18-2007, 09:48 PM
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Default Re: Fish Vision Study

IS COLOR IMPORTANT? This is a serious question for fly tiers and fly fishermen to ask. Some anglers maintain that the choice of color is critical, while others say it is not important. Scientifically speaking, there is evidence to suggest that both points of view may be correct. There is good evidence that picking the appropriate color or colors will, under certain conditions, improve your chances of attracting fish, but science can also show that in other situations, the color of your fly is of limited value or no importance whatsoever.
Fish have been around for more than 450 million years and are remarkable creatures. Over the thousands of centuries, they have made many superb adaptations to survive in the marine environment. Living in the world of water is not easy, but it does present some environmental opportunities as well as serious challenges. Sound, for example, travels almost five times faster and much better in water than it does in air. The ocean is actually a very noisy place. Fish capitalize on this by having an excellent sense of hearing, using both their inner ears and lateral lines to detect prey or avoid enemies.
Water also contains unique chemical compounds that fish utilize to identify other members of their species, tell when reproduction time has arrived, find food, detect predators, and perform other functions. Fish have evolved a remarkable sense of smell that is thought to be about one million times better than that of humans.
Water, however, presents a serious challenge for fish and fishermen when it comes to vision and color. Many characteristics of light quickly change as it moves through water. The first thing to realize is that the color of your fly in the water is almost always different from what it is in the air. I have to be a little technical to explain this, but I think if you bear with me, you'll have a better understanding of how fish perceive color and how this impacts the flies we tie and use. And while I mostly refer to fish and fishing in salt water, these same principles apply to the freshwater environment.
Attenuation of Light

The light that humans see is just a small part of the total electromagnetic radiation that is received from the sun. We see what is called the visible spectrum. The actual colors within the visible spectrum are determined by the wavelengths of the light: the longer wavelengths are red and orange; the shorter wavelengths are green, blue, and violet. Many fish, however, can see colors that we do not, including ultraviolet.
When light enters water, its intensity quickly decreases and its color changes. These changes are called attenuation. Attenuation is the result of two processes: scattering and absorption. The scattering of light is caused by particles or other small objects suspended in the water — the more the particles, the more the scattering. The scattering of light in water is somewhat similar to the effect of smoke or fog in the atmosphere. Coastal waters generally have more suspended material due to river input, material stirred up from the bottom, and increased plankton. Because of this greater amount of suspended material, light usually penetrates to a lesser depth. In relatively clear offshore water, light penetrates to a greater depth.
Light absorption is caused by several things, such as the light being converted into heat or used in chemical reactions such as photosynthesis. The most important aspect for fishing is the influence of the water itself on the absorption of light. The amount of absorption is different for different wavelengths of light; in other words, various colors are absorbed differently. The longer wavelengths, such as red and orange, are absorbed very quickly and penetrate into the water to a much shallower depth than the shorter blue and violet wavelengths.
Feather Pup


Hook:
Regular saltwater hook, size 3/0.
Thread:
Brown Monocord (210 denier).
Wing: Brown bucktail with strands of gold Flashabou. Tie two brown grizzly hackles and one golden brown grizzly hackle on each side of the tail. Tie the hackles curving out.
Collar: Brown marabou.
Head: Brown Wool.
Eyes:
Yellow plastic doll eyes.

Tied by Capt. Lenny Moffo, Big Pine Key, Florida

Absorption also restricts how far light penetrates into the water. At about three meters (about 10 feet), roughly 60 percent of the total light (sunlight or moonlight) and almost all the red light will be absorbed. At 10 meters (about 33 feet), about 85 percent of the total light and all the red, orange, and yellow light have been absorbed. This has a direct bearing on how a fish perceives a fly. At a depth of 10 feet, a red fly appears gray, and it eventually appears black as the depth increases. With the increasing depth, the now dimming light becomes bluish and eventually black when all the other colors are absorbed.
The absorption or filtering out of color also works in a horizontal direction. So again, a red fly that is only a few feet from a fish appears gray. Similarly, other colors also change with distance. For a color to be seen, it must be hit by light of the same color and then reflected in the direction of the fish. If the water has already attenuated or filtered out) a color, that color will appear gray or black. (Fluorescent colors, which I will come to shortly, behave a little differently.)
It should now be clear how the depth of the water or distance from a fish affects the visibility of your fly. In extremely shallow and very clear water, colors may look similar to their appearance in the air; as your fly gets just three feet deep or three feet away from a fish — or less if the water has limited clarity — the colors will start to change, often with surprising results.
What Do Fish See?

Scientists really do not know exactly what fish see, or in other words, what images reach their brains. Most research on the vision of fish is done either by physical or chemical examination of different parts of their eyes or by determining how laboratory fish respond to various images or stimuli. Making broad generalizations about a fish's vision is complicated by the fact that different species may have different vision capabilities and that laboratory results may not represent what happens in the real world of an ocean, lake, or river.
Physical studies of the eyes and retinas of fish show that the majority can obtain a clearly focused image, detect motion, and have good contrast-detection ability. A limited number of experiments have shown that a minimum level of light is necessary before a fish can recognize colors. Another finding, but one that needs more study, is that some fish favor a specific color. This point may contradict or affirm your own fishing experiences, but remember that the attractiveness of your fly is a combination of many things, including its motion, shape, and color, as well as the scents in and depth of the water.
Most fish have an adequate sense of vision, but this is usually not so impressive as their sense of smell and ability to detect vibrations through their lateral lines. Fish usually use their sense of hearing or smell to initially perceive their prey, and then use their vision only in the final attack. Most fish can see in low-light conditions or dirty water, and a few can see objects over moderately long distances. Fish such as tuna have especially good vision; others less so. Fish are usually nearsighted, although it is believed that sharks are farsighted.
The majority of fish have developed eyes that will detect the type of colors typical of their environment. For example, inshore fish have good color vision, whereas offshore pelagic fish have limited color vision and detect only a few if any colors other than black and white. This is not surprising from an evolutionary point of view, because nearshore waters are lit with many colors; offshore waters, on the other hand, are mainly blue or green and contain few other colors.
The actual ability of a specific color to attract or even repel fish has fascinated both anglers and scientists. While there are no uniform answers, scientists have conducted experiments on this interesting question. For example, studies of sticklebacks during their spawning season have shown that males, which then have bright red coloring on their bellies, become very aggressive to decoys that also have bright red bellies. Similarly, decoys with extended bellies, which look like females carrying eggs, attract the males. But it isn't that simple: it wasn't just the case of a perfect decoy imitation, but rather the color or shape of the decoy. In addition, it was noted that a passing red car, seen from the fish tank, also excited male sticklebacks
Color Suggestions

Glimmer Herring


Hook:
Eagle Claw 254SS, size 3/0.
Thread:
White Flat Waxed Nylon (140 denier).
Tail: Silver holographic Flashabou.
Wing: Silver Glimmer, pearl Glimmer, olive Comes Alive, silver Bozo Hair, and olive Bozo Hair. To help the fly maintain its shape, lightly coat the base of the wing and throat with Softex or Soft Body.
Throat: Silver Bozo Hair.
Eyes:
Medium gold dome eyes.

Tied by Capt. John Haag, Brookhaven, New York

This is perhaps the most important point to remember: Most gamefish detect their prey by seeing the contrast of the forage against various colored backgrounds. The level or type of contrast depends upon many factors: time of day, type of bottom, transparency of the water, whether it is cloudy or sunny, and perhaps even the time of year. I wish I could be more specific, but such scientific information is not available. The best I can do is provide some general suggestions and information; determining the right color or color combinations will take a lot of fishing and experimenting under various conditions. Keep these ideas in mind the next time you tie or select flies.
  • Try to consider what the colors in your fly will look like at the depth you are fishing, and chose appropriately. For example, since red is the first and blue is the last color absorbed, it makes more sense to use a blue fly when fishing deep.
  • If you are trying to match a particular bait, the color of your fly should match the color of the bait for the depth you are fishing. In other words, try to match the underwater color rather than the color of the bait in air.
  • Many fish feed by looking up toward the surface of the water. In doing so, however, they have difficulty distinguishing specific colors, and the contrast of the prey against the surface becomes more important. When a feeding fish is looking up, a dark silhouette, even against a dark night sky, provides the maximum contrast and is attractive to predators. Selecting a fly based on contrast, rather than on specific colors, is often the key to enticing a fish to strike.
  • Black is the least transparent color and gives the best silhouette at night. Black is probably the most visible color under most conditions.
  • If your fly has two or more colors, the darker color should be over the lighter colors. Almost all baitfish have this color arrangement, and dark over light usually produces good contrast.
  • Different colored flies may be equally effective or ineffective simply because they are similar in color at the depth the fish see them.
  • If you are fishing your fly in deep water, the motion and any noise or disturbance it makes might be much more important than its color.
  • Increase the contrast of the fly if the water is dirty; decrease the contrast if it is clear.
  • A good profile is important when vision conditions are low (nighttime or dirty water). Black and red flies offer good profiles.
  • Some colors, such as chartreuse, always seem to work better than other colors. Yellow-and-white and chartreuse-and-white are also favorite pairings. Red and white, which provide good contrast under many conditions, is a popular combination for many anglers.
Understanding Polarized Light

Recent research shows that many fish sense polarized light. Humans do not have the ability to separate polarized from regular light. Regular light vibrates in all directions perpendicular to its direction of travel; polarized light, however, vibrates only in one plane. When light is reflected off many nonmetallic surfaces, including the ocean surface, it is polarized to some degree. This explains how polarizing sunglasses work: they block out the horizontally reflected polarized component of light from the ocean surface which causes most of the glare but permit the vertically reflected component to pass through.
Selecting a fly based on contrast, rather than on specific colors, is often the key to enticing a fish to strike.

It is not fully understood why some fish have the ability to sense polarized light, but there are interesting possibilities. Being able to detect polarized light might help fish in their migrations and ability to swim closely with others of the same species. The ability to sense polarized light must certainly be related to the fact that when light is reflected off surfaces, like the scales on a baitfish, it is polarized. Fish that can detect polarized light have an advantage in finding food. Polarizing vision can also enhance the contrast between almost transparent prey and the background, making the prey easier to see. Another conjecture is that having polarizing vision can let fish see objects that are farther away — perhaps three times the distance — as fish without this ability. If this speculation is correct, it may answer the question why some fish can feed under very low-light conditions. And there is more polarized light at dawn and dusk, which might explain why some fish, such as striped bass, seem to feed more aggressively at these times of the day.
If the ability to sense polarized light helps fish to find food, then it follows that flies that reflect polarized light should be more attractive to such fish. Some natural fly-tying materials, such as polar bear fur, are especially good reflectors of polarized light. Bucktail, on the other hand, is a relatively poor reflector of polarized light. There are artificial materials that simulate fish scales and various tinsels that claim to be excellent reflectors of polarized light. Flies with irregular surfaces may reflect more polarized light than smooth flies. I suspect that in the coming years, as we learn more, there will be an increased use of polarizing materials in flies and lures.
Fluorescent Colors Increase Visibility

Fluorescent colors, especially chartreuse, are very popular with saltwater fly fishermen. I almost always start fishing with a chartreuse Half & Half, even if it's just to see if there are any fish in the area. Under the right conditions, fluorescent colors, which are not naturally found in nature, can be very visible under water and seen for considerable distances. A fluorescent color is one that will be bright when exposed to light having a shorter wavelength. For example, fluorescent yellow appears as bright yellow when exposed to ultra-violet, blue, or green light. Alternatively, fluorescent yellow does not appear yellow when struck by red light that has a longer wavelength. Because of this unique characteristic of fluorescent colors, they do not have as dramatic a change of color when they are fished deeper.
The fluorescence of fluorescent colors is mainly due to ultraviolet (UV) light, a color that is invisible to us. Humans cannot see UV light, but we can see how it brings out the fluorescence in certain colors. Ultraviolet light is especially dominant on cloudy or gray days, and when UV light hits something having fluorescent material, its color becomes especially visible and vibrant. On bright sunlit days, the fluorescent effect is considerably less, and of course if there is no light, there will be no fluorescence.
Research shows that fluorescent colors are visible and distinct for longer distances than regular colors, and that a fly with fluorescent materials often attracts fish. To be more precise, a fluorescent color having a slightly longer wavelength than the color of the water has better long-distance visibility. For example, in greenish waters, the brightest colors would be fluorescent green or chartreuse. As good as fluorescent colors may be, they will usually not work if the fish are actively feeding on a specific bait, since it is highly improbable that the fluorescent color will resemble any color in that bait.
As you can see, light and color can get pretty complicated. But let's not forget what we are trying to do: have our flies imitate pieces of fish food. Fish are not very clever, and they attack prey — or flies — as an instinctive behavior motivated (or so we think) by one or more stimuli. These stimuli include movement, shape, sound, contrast, smell, color, presentation, and certainly other things unknown to us. Successful flies should probably include some of these stimuli, and then we need to consider other variables such as the time of day, the tide, and the presence of other fish or fishermen. This is a complicated venture, of which color can sometimes be an important aspect, but only if the fish can see the color.



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