Ultraviolet Light and Its Role in Predation in Fish

How Fool-a-Fish Was Discovered

By Milan Jeckle M. D.

Ultraviolet Light and Its Role in Predation in Fish

How Fool-a-Fish Was Discovered

By Milan Jeckle M. D.

A.  Darwin's Theory and the history of the invention of Fool-a-Fish.

When skin diving I noticed that at 40 feet of depth and beyond, there is no visible light, it is absolutely black. That always made me wonder, “Why do deep water fish have eyes?”  Darwin's theory states that if a biological function is not used, that function becomes a burden and will be lost.  A great example of this selection process is the cave dwelling fish of the USA Southwest deserts.  These cave fish live in underground pools of water devoid of sunlight.  The cave fish have completely lost their eye structures.  Their eyes have been replaced by fleshy membranes.  According to Darwin, this eye structure loss is natural selection, reducing the blind fish’s biological burden of possessing a function which is not useful for survival or reproduction.  Interestingly, the complete loss of their eye structures didn't take very long, probably occurring within a time period of several thousand years.  Natural selection is a powerful force with rapid consequences. Then I ask again, “Why do fish have eyes?”

B.  Visible light’s ability to travel through clear water.

The blue and violet wavelengths of light penetrate water only about 40 feet at which time those wavelengths are completely absorbed. Prior to the violet-blue wavelength absorption, water completely absorbs the red light in the first two feet and yellow-green light in the first 15-20 feet.  So why do fish that spend the majority of their lifetimes deeper than 40 feet have eyes?

Visible colors of red, yellow-green and blue are maximally transmitted only 2-40 feet

in clear water.  This 40 foot radius of transmission is in every direction, not just depth.

Only because of ultraviolet vision are fish able to see objects more than 40 feet away

either by reflection or silhouettes. 

C.  The answer to the question “Why do fish have eyes?” is found in recent scientific research articles.

The first part of the answer came in a scientific article published by Duke University researchers under the authority of Woods Hole Oceanographic Institute.  That article states, “it has been conservatively estimated that there is sufficient ultraviolet light for vision down to 200 meters (700 feet) in clear ocean water”.  Other scientific articles report there is sufficient ultraviolet light transmission to support ultraviolet vision for up to one half mile in clear water. So in summary, I was reading quality scientific research articles that were reporting that ultraviolet traveled through water at least 700 feet and maybe as much as 2,500 feet before it was absorbed, unlike visible light which is completely absorbed in the first 40 feet. 

The second part of the answer came in scientific articles discussing the recently recognized ultraviolet visual capabilities of birds, subsequently enlarged to include bony fish.  Many of these discoveries of ultraviolet visual capabilities depended upon the scientific advances in the late 1990s which made possible chemical analysis of the optically active Rodopsin proteins in the retinas of fish and birds.  The result was the scientific recognition that bony fish and birds have a Rodopsin protein in their retinas which reacts to the ultraviolet wavelengths around 360 nm, a wavelength totally invisible to humans.  We also discovered that insects, shrimp and crabs have similar keen ultraviolet vision.  Indeed, insects and birds have brilliant ultraviolet reflecting plumage, feathers and body parts clearly identifying species, sexual differences and state of health to each other, though to the human eye they may all look alike. 

D.  Ultraviolet light compared to visible light and x-rays.

Ultraviolet light has a shorter wavelength with higher energy than the wavelengths 400-700 nm visible to humans. By comparison, X-rays are even shorter than ultraviolet light with correspondingly higher energy than that possessed by ultraviolet light (prolonged exposure to x-rays can be lethal).  We all know that x-rays cannot be seen by the human eye. We also all know that x-rays can penetrate through the human body (humans tissues are largely transparent) except our denser bones.  Ultraviolet light can be thought of as similar to a long x-ray, invisible to the human eye but able to penetrate some solid objects much further than visible light, in this case-- water.

E.  Ultraviolet light is a spectrum with many wavelengths similar to the visible light spectrum

The spectrum of ultraviolet light is defined as electromagnetic radiation with wavelengths between 400 nm and 10 nm.  Biologists further divided ultraviolet light into UVA, 400 nm to 320 nm; UVB, 320 nm to 280 nm and UVC and UVD, 280 nm to 10 nm. Between 10 nm and 0.1 nm is the spectrum of x-rays. 

Ultraviolet vision in fish and birds occurs in the UVA range of 400 to 320 nm.  UVA causes sun-tanning of the skin in humans but is not humanly visible.  UVB is probably not seen by any living specie because its higher energy is too damaging to retinal proteins.  Humans can experience the deleterious effects of UVB radiation because its high energy causes progressive sun burning of the human skin. Lucky for humans and all other living species, the high energy, very damaging wavelengths of UVC, UVD and x-rays are rapidly absorbed in the environment or by the earth's protective ozone layer. 

F. Ultraviolet vision is present in most species except mammals.

Recent research articles report that UV vision appears to be fairly widespread in freshwater fish, turtles and most salt water marine species.  Other recent research articles report that UV vision appears to be a general property of diurnal birds. Scientists have further determined that insects and crustaceans possess UV vision capabilities even though they possess compound eyes which are structurally different from those of vertebrates. 

Surprisingly, it has been determined that mammals possess in their DNA the genes that enable UV vision but these genes have been disabled by mutation.  These mutation findings suggest that mammals lost UV vision (and also vision in the red spectrum) during that time period of evolution when mammals existed as underground, night functioning, shrew like organisms with no Darwinian benefit accruing for red or UV visual abilities.  Later in the evolution of mammals, the great apes of Africa and humans regained red vision but not UV vision.  All other mammals, except great apes and humans, see only two colors, namely yellow-green and blue.  For instance, like all other mammals, except old world apes and humans, deer and elk do not have active retinal proteins sensitive to red light. As a consequence, red and orange hunter colors can be worn without the hunter being color identified by the targeted deer or elk but are easily seen by other hunters, leading to greater safety in the woods.

G.  The ultraviolet light wavelengths used in fish vision.

Research suggests that most if not all UV vision occurs in the UVA wavelength of 400-320 nm with maximum perception at around 360 nm.  In accordance with quantum theory, which postulates that electromagnetic energy exists simultaneously as a wave and as a discrete packet of energy, the reactive retinal Rodopsin proteins have a very narrow range in which they will accept and react to a particular packet of wavelength energy. 

H.  How this information was used to invent Fool-a-Fish.

Upon striking an object, visible light is absorbed, transmitted or reflected or some combination thereof.  The same is true of ultraviolet light.  The problem then was to find a substance which would be nontoxic yet highly reflective of ultraviolet light.  Several crystalline compounds came to mind.  For years white pastes of Zink Oxide or Titanium Dioxide have been safely used by mountain climbers and a few beachgoers to protect their lips, ears and noses from sunburn.  These crystals do not absorb ultraviolet light rather protecting against sunburn by reflecting away the ultraviolet light. 

I rejected using Zink Oxide because it has been identified as a toxic waterway contaminate choosing instead to use the more expensive titanium dioxide.  I studied and then altered and made substitutions in chemical formulations likely to result in the product now known as Fool-a-Fish. 

I.  Worldwide Patent Search.

I employed a patent attorney who performed a worldwide patent search to determine the uniqueness of Fool-a-Fish.  The patent attorney subsequently reported that enhancing UV reflection in a fishing product was a unique, one-of-a-kind intellectual concept which had never been presented as a viable invention idea to any Patent Office in any country in the world.  I was understandably encouraged. 

J.  Dr. Cleary and Gonzaga University Chemistry Department.

I visited the Chemistry Department at Gonzaga University where I employed as a private consultant the Professor of Physical Chemistry, Dr. David Cleary.  I have a college degree in chemistry with a year of postgraduate studies in crystals and metals.  I am also a medical doctor, graduating from the University of Wisconsin-Milwaukee School of Medicine in 1964.  Nonetheless, I could not have proceeded developing the formulation and making the necessary measurements without the guidance and help of Dr. Cleary. 

K.  Titanium dioxide crystals, the ultraviolet light reflecting crystal in Fool-a-Fish.

Titanium dioxide exists naturally in two different crystalline forms, Rutile and Anatase.  The Rutile crystalline form of titanium dioxide is the second most refractive crystal known to science (Diamond crystals are the most).  It is the inherent nature of crystals that when they are broken into smaller crystals, they only become smaller remaining as identical clones of the original (much like Russian dolls), with all the same properties of their parent crystal.  The titanium dioxide crystals in Fool-a-Fish are machined to microscopic size yet retain their reflective abilities, “like thousands of tiny mirrors”.

L.  Other chemical characteristics of Fool-a-Fish.

The multiple other chemicals along with the manufacturing process used to make Fool-a-Fish results in a transparent, flexible, odorless, water resistant, nontoxic  coating.  This imperceptible coating holds the microscopic crystals of titanium dioxide in position no matter if used on baits or lure while still wet or first allowed to dry.  Dried Fool-a-Fish looks similar to white dust. Wet Fool-a-Fish resembles skimmed milk. Fool-a-Fish is chemically very stable with a shelf life of at least five years.

M.  Example of reflectance studies done at Gonzaga University.

A graph of degree of reflectance at visible and ultraviolet wavelengths caused by a thin, translucent layer of Fool-a-Fish on a clear glass slide proves the power of Fool-A-Fish. Interestingly, the reflection is strongest at approximately 350 nm in the ultraviolet spectrum and 450 nm in the visible spectrum.  These are the wavelengths where the Rodopsin proteins in the retina of fish react most strongly to ultraviolet light and to blue light respectively.

N.  “Black Light” fluorescence does not measure ultraviolet light.

A Black Light is an optical device which is designed to emit visible violet and invisible long ultraviolet wavelengths.  This device will cause about 15% of materials to fluoresce.  Fluorescence is scientifically defined as the molecular absorption of a short high-energy wavelength followed by radiation of a portion of that energy at a longer wavelength.  This Black Light testing has no scientific relationship to UVA reflectance or to Fool-a-Fish.  The visible light seen coming from florescent materials is visible within a spectral range between 700-400 nm.  Florescent light is therefore just another humanly visible light and is limited by the laws of physics to the 40 foot water penetrating abilities of all visible light. 

O.  Anxiety and concerns prior to the first field tests of Fool-a-Fish .

In August, 2004 Dr. Cleary and I had prepared enough Fool-a-Fish for an initial fishing test.  All I knew at that time was Fool-a-Fish was a pleasant, odorless white liquid which efficiently reflected UVA and blue light.  The big three questions were, “Will Fool-a-Fish attract fish??  Will Fool-a-Fish make no difference at all?  Will Fool-a-Fish scare the fish away?” 

P.  Initial results.

I used it first aboard Captain Mark Sappington's Yakutat Charters out of Yakutat, Alaska on a combined halibut-silver salmon ocean fishing trip.  We started halibut fishing in 150 feet of water 10 miles out of Yakutat Harbor using large halibut hooks baited with silver salmon heads dropped down to the bottom.

Captain Mark stiffened his stance in skeptical disapproval when I applied Fool-a-Fish to my salmon head bait and dropped it over the side.  He asked me, “What is that white stuff?”  I answered, “Something I think might make the halibut bite better.” He shook his head in disgust.  Mark Sappington is a great charter fishing captain.  He tried to understand and made no move to interfere with my crazy behavior even though he obviously disapproved.  After 15 minutes my halibut rod bent over with the first strike of the day. A fitful struggle ensued as I used all my strength to bring this unexpectedly strong fish to the surface.  That first halibut was about 100 pounds, too large to safely take aboard the vessel when alive.  Captain Mark killed that first halibut with a 4-10 shotgun blast to the head.  Mark was busy pulling and lifting the first halibut onto the boat as I rebaited with another silver salmon head to which I again applied Fool-a-Fish.  Captain Mark was watching me out of the corner of his eye and it was obvious that he still did not like Fool-a-Fish. 

About one minute after my second Fool-a-Fish coated salmon head bait hit the bottom I got a second big strike.  The second halibut looked like a 100 pound twin of the first when I finally got it to the surface.

Jeff Johnson, who was fishing on the other side of the boat, asked me if he could use Fool-a-Fish on his bait during the time Captain Mark was shooting and muscling in the second halibut. Jeff applied Fool-a-Fish to his salmon head and dropped it over the side. Wide-eyed with surprise, Jeff was nearly pulled off the boat by a 130 pound halibut which took his bait immediately as it hit the bottom. Captain Mark Sappington was heard to say, “ Hey, that stuff really works”. We four halibut fishermen caught our individual limits of two halibut for a total of eight within two hours.  Seven were caught with Fool-a-Fish treated salmon head baits and all seven were at or over 100 pounds.  Scott Finley caught the eighth halibut, a 15 pounder, on an untreated salmon head bait. We threw Scott's 15 pounder back. We also caught about 10 large Ling Cod, all on Fool-a-Fish sprayed heads.

Halibut fishing can be a very slow and unsuccessful venture, even in Yakutat.  Halibut fishing had been slow in the previous weeks with only a few caught. We decided to keep the seven largest halibut and turned to trolling for 10-18 lb silver salmon.                                  

Scott Finley and Jim Finley with two of the seven 100+ pound halibut caught off Yakutat, Alaska in August, 2004 using salmon head baits sprayed with Fool-a-Fish. (Several fishermen from North Dakota claim that these are not halibut but are actually jumbo yellow perch caught in their Devils Lake.  These North Dakota fishermen are wrong---note the characteristic halibut placement of the eyes in the fish that Scott Finley is holding.)

Q.  Silver Salmon fishing with Captain Mark Sappington

Mark trolls for silver salmon using a single large hook in a 6 inch strip of salmon belly skin, an inexpensive effective technique he learned when he fished for salmon commercially.  While trolling we tossed these Sappington Special baits to the side of the boat allowing them to straighten out as we cruised forward.  I applied Fool-a-Fish to the salmon belly bait but the other three fishermen did not.  Seldom did my Fool-a-Fish coated bait go through its 45° straightening cycle before receiving a vicious strike from a silver salmon.  We all caught silver salmon but I caught seven or eight salmon for each caught by the other three fishermen. When the day of fishing finally ended, Captain Mark Sappington asked me if he could be the Yakutat distributor if ever my Fool-a-Fish invention became

R.  Field testing.

On a cold day in December, 2004 Fred Techel, Tom Finley and I fished for large walleyes near the trout rearing fish pens on Pothole Reservoir in Eastern Washington.  As a test I used Fool-a-Fish on my night crawler-leaded jig combination.  My two friends used identical baits without the Fool-a-Fish. Adding to the test, there were at least 25 other fishermen in a dozen boats fishing the same area.  10 minutes after starting I caught and landed a 6 pound walleye.  Within 15 minutes I caught another 6 pound walleye and  10 minutes later I caught a final large walleye which broke my 8 pound test line at the boat.  My two friends did not receive any bites or catch any fish.  We three carefully watched and listened but did not observe any of the other 25 fishermen in the area hooking into a fish of any kind. 

That cold morning of fishing was discouraging for everyone except me. My two friends were more impressed than I was.  Not only did Fool-a-Fish not scare away walleyes, every indication was that it was an effective and helpful addition to traditional bait.

S.   Marketing

Fool-a-Fish was first sold in early 2005 at the Sportsman's Shows in Puyallup, Washington, Portland, Oregon and the Internet. Only small numbers of fishermen used Fool-a-Fish in 2005.   

T.  Early Results

Carl Gowin won the 3/12/06 Bassmaster Tournament on Broken Bow Lake, Oklahoma using Fool-a-Fish.

Fishermen in Texas reported a surprising increase in their catches of large mouth bass when using Fool-a-Fish.

Fishermen in Wisconsin, Michigan, Minnesota and the Dakotas reported increased catches of walleyes, northern pike, perch, crappies and trout. Ice fishing for jumbo perch and northern pike in the northern states and Canada was dramatically improved when using Fool-a-Fish.

Fool-a-Fish received national and international attention in February, 2006 in an Associated Press article by Nick Geronias which appeared in newspapers all over the world.  Paul Harvey talked about Fool-a-Fish on his morning radio program.    I have been the guest speaker on numerous radio programs across the USA. Prominent sportswriters like John Beath, David Mull and Rich Landers have written fishing articles which appeared in prominent fishing magazines.  Many professional fishermen successfully tested and used Fool-a-Fish during 2005 in American fresh water and salt water under many different conditions.

Captain John Keizer, one of the founders of Salmon University Fishing Institute in Seattle, Washington has written on several occasions that cut herring sprayed with Fool-a-Fish caught 3-4 times as many salmon as unsprayed cut herring identically and simultaneously trolled behind his fishing boat. 

David Mull, editor of the Great Lakes Angler Magazine, wrote in the April, 2006 edition that he participated in a fishing tournament on Lake Michigan.  Using Fool-a-Fish, David Mull caught six lake trout and one brown trout when no fish of these species were caught by anyone else.  Mr. Mull then wrote in his last paragraph, “The next day, half of our spread had lures with Fool-a-Fish; the other half of the lures were untreated.  The half with the UV enhancer caught seven of our eight fish, including all three of our biggest kings (King Salmon)….”

Sports Writer, Doug Hubbard, wrote in the Wild Idaho News, “Researchers at the Woods Hole Oceanographic Institute have discovered vision may be the Sportsman's key to harvesting more fish.  The vision key is ultraviolet light (UVA)….   Researchers think that the fish see ultraviolet light as a white glow.  Humans cannot see ultraviolet light because humans lack a certain protein in their retina. Fish possess that protein so fish are able to see up to one half mile in clear water.”

U.  Flashers and other reflective terminal fishing gear.

I think that flashers and shiny lures reflect ultraviolet light as they wobble and twist through the water, just like they reflect visible light, and that is why they powerfully improve catch rates, particularly in deep water.  From the standpoint of physics, flashers do not reflect UVA as efficiently as the crystals of titanium dioxide, but the mechanism is different, with Fool-a-Fish continuously reflecting UVA in every direction and flashers intermittently reflecting UVA in a focused band.  In my opinion, the UV attracting power of flashers or shiny lures is enhanced by a coating of Fool-a-Fish.  I recommend applying Fool-a-Fish to flashers.  You will get a “double whammy” effect. 

V.  Fool-a-Fish with scents.

Yes, scent preparations are a proven, effective way to improve catches by appealing to fish’s sense of smell.  If you are a scent user, I think you should keep using scents but add Fool-a-Fish.  Since Fool-a-Fish is designed to stay on a lure and scents are designed to leach off, apply the Fool-a-Fish first and the scent preparation second.  You will have created your own personal “double whammy”, much more effective than using scents alone. 

W.  What we don’t know.  What we do not claim.                                                                                                                                     

Fool-a-Fish is advertised as a helpful addition to any bait or lure resulting in more fish and usually the largest fish caught for the same effort.  But, Fool-a-Fish is not magic. Fool-a-Fish is helpful in the hands of a capable fisherman fishing in the right spot with the right bait with much depending on good luck. Fool-a-Fish is a new product reported to be effective in the fish species against which it has been used but there are many kinds of fish where there no reports or limited reports.

Compare the exquisite visual acuity of a whitetail deer to the limited visual acuity of a black bear. I believe that different fish species will similarly have wide ranges of perceptive abilities in their ultraviolet visual acuity. Each fish species probably will be attracted to ultraviolet reflections in widely different degrees for different reasons. Sportscaster Sky Drysdale won the Rock River Hawg Hunters’ annual Rock River Open on April 30, 2006 using Fool-a-Fish. Sky reported that he also caught numerous white bass, two walleye, a few drum, a blue gill and a very large carp. Carp rarely take artificial bass bait so that was a first report on Fool-a-Fish v.s. carp, maybe an accident, maybe not. We wonder if it will be effective against those large eyed, shallow feeding exotics like marlin, tarpon and sailfish but there are no reports either way yet-- Fool-a-Fish is too new and exotics are hard to catch.  A vexing problem in 2005 for Fool-a-Fish sales was successful fishermen who discovered that Fool-a-Fish significantly improved their catch rates but they kept it under their hats as their secret weapon.

Just as humans will never be able to hear the high-pitched whistles perceptible to dogs, humans can never know what fish actually see. 

The perceptive Sports writers, Tom Pollock and John Beath, have analyzed and described the scientific reasoning behind the Fool-a-Fish invention. Their conclusion was, “This just makes good sense”.

X.  Some of the reasons inventing Fool-a-Fish has been so much fun.

Connecting the information contained in recent chemistry, physics and biological research articles to come up with Fool-a-Fish was my enormous stroke of luck.  On a sunny day in 2004 when I was driving down the freeway the whole idea of Fool-a-Fish just popped into my head. 

Inventing Fool-a-Fish has been as exhilarating as going fishing and hooking into the biggest fish in the lake.  The experience is even more exhilarating when you do the same thing in the company of friends, meeting a whole lot of really interesting people along the way.