UV in your flies - fact or fallacy.

[fdavis 0]

Exceptionally well written article discussing the the UV rage currently going around many fly tying circles...

 

UV Colours for Trout - Fact or Fallacy. by Leonard Fleming

[SilverCreek 0]

I like the article below but there is one error and one omission.

http://feathersandfluoro.com/?p=8862

Leonard confuses reflection and fluorescence in some parts of the article.

He also describes bioluminescence which has NOTHING to do with UV radiation, and he does not mention UV phosphorescence that does apply to UV active materials. To be very specific, there are three possible ways that UV light can interact with fly tying materials. There is reflectance, fluorescence, phosphorescence. I do agree that UV activated fluorescence is the primary method that is used in fly tying.

 

The simplest to understand is is UV reflectance. UV is a spectrum of "colors" just like the visible ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, and Violet) colors of the rainbow.

 

 

We can see the visible spectrum above but we cannot see the UV spectrum below 380 nM. The invisible UV spectrum is NOT just one color. Just like the visible spectrum, the UV spectrum are different "colors" according to their specific wavelength. Just like a red feather reflects the color red, a “UV color” can be reflected but we cannot see it.

We have been using UV reflective materials for years. A mirror reflects all the colors of the visible spectrum, so if you want something that will reflect UV, use a reflective tinsel and it will reflect the visible light and invisible UV. What the newer UV reflective materials makers would like you to think is that these materials selectively reflect a UV color that matches a natural. So just like we would use a yellowish dubbing for a sulphur mayfly, they would like you to think you can match a "UV" color by using a UV reflective color that matches the natural. But if we cannot see UV, how can we (1) see the UV color of the natural, and (2) pick out that UV color in a dubbing since we will not see that color in the tying material. So, from my perspective, matching UV reflectance is near impossible.

Fluorescence is the second way we can use UV "activated" materials. Leonard fleming writes:"There is only one true form of fluorescence; it can be defined as luminescence caused by electromagnetic radiation (such as UV light) – this is the fluorescence we observe when we shine a black light on hot orange and chartreuse fly tying materials. .....i.e., when UV light is reflected in the form of colour photons by an object in such a manner that it appears to be a specific colour, such as red, orange, or yellow. ..."

Fluorescence is NOT REFLECTANCE. The light is EMITTED and NOT REFLECTED. Fluorescence involves a conversion of energy. No energy conversion can be 100% efficient so a high energy photon of light is absorbed by an atom and then immediately emitted as a lower energy photon of light. That is why the UV light is converted into visible light. UV light has a shorter wavelength and is higher energy than visible light. So UV invisible light is converted into the lower wavelength visible spectrum. That is also why we don't have a visible fluorescence with red light because it would convert the red into invisible infrared radiation.

There is a difference between the two forms of light we see. The normal light is reflected so the amount of light reflected depends on the color of the item and the amount of that color in the incident light. The fluorescent light is not reflected as Leonard writes. It is emitted and it depends upon how much of the incident light is absorbed and transformed into the emitted light.

The last way UV light interacts with material is luminescence. Leonard fails to mention this form of UV light interaction. This is fluorescence that is delayed. We can activate a luminescent material with UV light. The atoms in these materials absorb the UV light and are in a higher energy state. Over time, the atoms return to the lower energy state and release the energy as visible light. These are the "glow in the dark" materials and the delay and length of luminescence depends on how the higher energy atoms decay over time. Think of luminescence as a form of “radioactive” decay with the light photons being released instead of the high energy gamma rays of radioactive decay.

The tying materials below a phosphorescent and will continue to glow in the absence of light.

Fire Fox Yarn

Yarn Material for Fly Tying (Fly Tying, Fly Tying Materials, Yarns at TCO Fly Fishing)

Phosphorescent Tinsel

Loon Phosphorescent Hard Head

Here are several discussions of UV tying materials on another BB and this BB including posts by Reed Curry (Over My Waders) who has written a book about UV in fly tying.

http://www.flytyingforum.com/index.php?showtopic=70101&st=0&gopid=524267&&do=findComment&comment=524267

http://www.theflyfishingforum.com/forums/flies/349432-ultra-violet-flies-2.html#post660685

http://www.theflyfishingforum.com/forums/general-discussion/359390-more-uv-vision-fly-tying-materials-trout.html#post707988

http://www.theflyfishingforum.com/forums/general-discussion/359295-interesting-read-myths-2.html#post707358

[Piker20 0]

Very thorough reply.

[JSzymczyk 0]

Can UV reflectance help? Maybe. Can it be proven, on any given day or hour or minute to be the deciding factor, among the other billion-and-a-half (rough estimate) variables in fishing that caused a fish to hit? If it is proven to your satisfaction, then good on you! If it builds confidence, then you will fish better and catch more fish.

 

Can fish see UV? Let's just say sure, ok. How do their brains interpret what those UV sensitive receptors in their retinas detect? No matter how much the hundred-pound heads THINK they know, there will always be a bit of guesswork.

 

Fluorescence and reflectance are seeming ALWAYS confused when this subject is written about. I see this (ha ha , pun intended) as another indicator that about 90 percent of fishing, and about 95 percent of fly fishing, is made up bullsh*t of which NOBODY has a complete understanding.

[JSzymczyk 0]

In fact, the absolute most noteworthy thing I took from that article was this:

 

[oldtrout58 0]

In fact, the absolute most noteworthy thing I took from that article was this:

 

Are you complaining? I like freckles.

[wschmitt3 0]

Freckles? That's what you noticed?

[JSzymczyk 0]

complaining? what gave you that idea??? freckles RULE!!!

[SilverCreek 0]

Can UV reflectance help? Maybe. Can it be proven, on any given day or hour or minute to be the deciding factor, among the other billion-and-a-half (rough estimate) variables in fishing that caused a fish to hit? If it is proven to your satisfaction, then good on you! If it builds confidence, then you will fish better and catch more fish.

 

Can fish see UV? Let's just say sure, ok. How do their brains interpret what those UV sensitive receptors in their retinas detect? No matter how much the hundred-pound heads THINK they know, there will always be a bit of guesswork.

 

Fluorescence and reflectance are seeming ALWAYS confused when this subject is written about. I see this (ha ha , pun intended) as another indicator that about 90 percent of fishing, and about 95 percent of fly fishing, is made up bullsh*t of which NOBODY has a complete understanding.

 

If fish see UV, they see it as a color. It is a color that we cannot see. The presumption, without evidence to the contrary, is that UV is no more or no less important than any other color.

 

You asked, "How do their brains interpret what those UV sensitive receptors in their retinas detect? How do their brains interpret what those UV sensitive receptors in their retinas detect? No matter how much the hundred-pound heads THINK they know, there will always be a bit of guesswork."

 

Fish have virtually the same 3 color cones that humans have plus a 4th UV cone that may or may not be present in the adult trout. So we do know how they work.

 

With all due respect, it would be an amazing coincidence of evolution if the eyes in fish evolved independently from the eyes in humans. You need to show that their rods and cones, which we also have; and a lens, which we also have; and a retina, which we also have; and an optic nerve, which we also have; and a visual cortex in the brain; which we also have; were totally independent of each other so that their vision system did not work like ours did. In fact the eyes of fish and the eyes of humans are so alike that it is one of the strongest pieces of evidence that we are related and can be traced back along the same evolutionary path. Their visual cone even have the same biochemical receptors that we humans do so, yes we do know how fish see.

 

In fact, have you considered the consequences if fish "eyes" did NOT work like human eyes? If humans and fish did not see in the same fashion, have you asked yourself how we could "match the hatch" at all. What if "fish eyes" detected and sensed their prey by the heat signal they gave off. How would we match the hatch then? The very basis of human fly tiers and fly fishers tying imitations that look like the naturals is based on the fact that the fish's vision and human vision is nearly identical.

 

http://www.ncbi.nlm.nih.gov/pubmed/18025012

 

http://www.sexyloops.com/articles/whatsalmonidssee.shtml

 

http://books.google.com/books?id=sQBnAQAAQBAJ&pg=PA8&lpg=PA8&dq=color+vision+in+trout&source=bl&ots=Y3N2ak-LVA&sig=laLdAW8UYJ7wbKaDa953DQEX0MI&hl=en&sa=X&ei=8Fx5VOzbII_GsQSNyYDwAw&ved=0CDcQ6AEwBDgU#v=onepage&q=color%20vision%20in%20trout&f=false

Furthermore, do you know how your retina detects the color red, and if you don't know, is the rose still red and would it look any different if you knew how the cones in your retina worked? The question has no relevance to how the fish sees. It's brain does not need to know how it sees UV any more than your brain needs to know how it sees red to appreciate the color red.

 

The thing about color is that if you remove a wavelength of color from a color spectrum that a fish sees, the "color" that is left is not longer the same color that the fish sees. In other words, the color of the fly that the fish sees is not longer the color of the natural. So it is really important whether the fish sees in UV or not. If it does, we are really not matching the color of any food item that reflects UV by matching the color we see to the flies we tie.

 

We can use the example of color blindness to simulate the absence of UV vision. The color chart below shows the normal color spectrum in the upper left compared to the three forms of color blindness.

 

 

Protanopia which is just below the normal color vision chart is red color blindness. You can see that the entire color spectrum is shifted and NONE of the colors look the same so a person with protanopia could not pick dubbing to match a green fly because they cannot see green or match nay color that has green. Even though they are blind to red, you can see that this red blindness affects other colors such as green.

 

Now you know why we cannot match the colors that reflect UV light.

 

I disagree that reflectance and fluorescence are always confused. They should never be confused when an author is writing about the subject. One reflects color and the other glows a color. Things that reflect light can only reflect the color that is actually IN the light. Fluorescence creates light out of energy by exciting atoms.

 

If any UV mediated visible spectrum light should be confused it is fluorescence and phosphorescence, since both are due to excitation of atoms which later release the absorbed energy as light.

[crazy4oldcars 0]

Thanks Silver. That is such a palm to forehead (THOCK!) moment. What I had read, from both sides of the argument, led me to believe that it was mostly a marketing ploy. Being able to identify a UV "color" was never in any of my previous reading. My stance was more of the "We didn't need it to catch fish before, why do we need it now?" mentality. Not real progressive, huh? LOL

As you say, "Let's assume trout do see in the UV Spectrum." (paraphrased) Sometimes off-the-wall visible colors catch fish. Adding UV colors from any part of the spectrum could accomplish the same thing. But I've never had that work consistently enough to tie ALL of my flies that way.

 

Kirk

[SilverCreek 0]

Think of UV fluorescent materials as fly "brighteners" that can be used as attractor ingredients in fly tying. They make flies more visible in two ways, by emitting light and by creating contrast that is enhanced by the lateral inhibition feed back loop of visual receptors in fish retinas.

 

Here is the light absorption graph for distilled water. The higher the curve line, the greater the absorption of that light spectrum. You can see the minimum absorption is at violet, just before UV begins at 400 nm.

A very easy way to remember this curve it to visualize water as a “blue filter”. Just correlate water with the color of a blue ocean, and that water lets the color blue penetrate the deepest. You will be very close to the actual light absorption curve of water that is below.

This means that as the fly sinks, colors drop out from red to violet. Ultraviolet light penetrates as deeply as blue light. It continues to exist when the ROY G wavelengths are gone. In the case of fluorescent materials, the remaining UV is converted to visible light and this means the flies are brighter and more visible since fluorescent flies emit visible light. The fluorescent materials emit light which is added to the reflected light, and the fly is brighter than a fly that has no UV fluorescent materials.

So fluorescent UV materials are a tool to make flies more visible.

When mixed with non fluorescent materials, this creates a contrast that makes the fly stand out. For example, a white and red striped barber pole stands out more than an all red or all white pole.

 

Both fish and human retinas have evolved to see the edges between darker and brighter objects, because edges define objects. This is an evolutionary advantage. If we can pick out edges, we are better able to detect threats earlier than an animal that does not have this evolutionary adaptation. This phenomena is called lateral inhibition

 

Here's an example of the negative feedback loop of lateral inhibition.

Note that the lighter gray side seems to have lighter strip next to the darker gray, and simultaneously the darker side has a darker strip. This is edge enhancement caused by the photo receptors of our retina inhibiting the output of the photoreceptors next to it.

http://en.wikipedia.org/wiki/Lateral_inhibition

http://webvision.med.utah.edu/book/part-iii-retinal-circuits/feedback-loops/

http://www.nature.com/neuro/journal/v17/n2/full/nn.3627.html

What does this have to do with fluorescent UV fly tying materials? Besides being brighter under water than non fluorescent materials, when mixed with regular materials, they create contrast, and contrast make the flies more visible.

What does this have to do with fluorescent UV fly tying materials? Besides being brighter under water than non fluorescent materials, when mixed with regular materials, they create contrast, and contrast make the flies more visible.

 

[JSzymczyk 0]

 

Can UV reflectance help? Maybe. Can it be proven, on any given day or hour or minute to be the deciding factor, among the other billion-and-a-half (rough estimate) variables in fishing that caused a fish to hit? If it is proven to your satisfaction, then good on you! If it builds confidence, then you will fish better and catch more fish.

 

Can fish see UV? Let's just say sure, ok. How do their brains interpret what those UV sensitive receptors in their retinas detect? No matter how much the hundred-pound heads THINK they know, there will always be a bit of guesswork.

 

Fluorescence and reflectance are seeming ALWAYS confused when this subject is written about. I see this (ha ha , pun intended) as another indicator that about 90 percent of fishing, and about 95 percent of fly fishing, is made up bullsh*t of which NOBODY has a complete understanding.

 

If fish see UV, they see it as a color. It is a color that we cannot see. The presumption, without evidence to the contrary, is that UV is no more or no less important than any other color.

 

You asked, "How do their brains interpret what those UV sensitive receptors in their retinas detect? How do their brains interpret what those UV sensitive receptors in their retinas detect? No matter how much the hundred-pound heads THINK they know, there will always be a bit of guesswork."

 

Fish have virtually the same 3 color cones that humans have plus a 4th UV cone that may or may not be present in the adult trout. So we do know how they work.

 

With all due respect, it would be an amazing coincidence of evolution if the eyes in fish evolved independently from the eyes in humans. You need to show that their rods and cones, which we also have; and a lens, which we also have; and a retina, which we also have; and an optic nerve, which we also have; and a visual cortex in the brain; which we also have; were totally independent of each other so that their vision system did not work like ours did. In fact the eyes of fish and the eyes of humans are so alike that it is one of the strongest pieces of evidence that we are related and can be traced back along the same evolutionary path. Their visual cone even have the same biochemical receptors that we humans do so, yes we do know how fish see.

 

In fact, have you considered the consequences if fish "eyes" did NOT work like human eyes? If humans and fish did not see in the same fashion, have you asked yourself how we could "match the hatch" at all. What if "fish eyes" detected and sensed their prey by the heat signal they gave off. How would we match the hatch then? The very basis of human fly tiers and fly fishers tying imitations that look like the naturals is based on the fact that the fish's vision and human vision is nearly identical.

 

I do not possess the technical ability to argue your statement... The fact remains that NO MATTER what color or other characteristics a tied fly has, there is a giant steel hook protruding from it... and SURELY the fish SEES that as well as all the other details, yet it wants to eat the fly. Perhaps my previous post was not quite accurate enough, or well thought out enough (hoo boy, I am guilty, just ask my wife) to correctly make my point..... OK, you can satisfactorily make the argument that "we" understand WHAT a fish sees, but no on can yet, with any certainty, say what a fish sees THAT MAKE IT STRIKE A FLY.

 

Bottom line, I really like the pic of the girl.

[salmobytes 0]

It has been suggested the visual appearance of most aquatic prey critters has gradually evolved as a natural camouflage of sorts. Nymphs typically have mottled gray brown or olive coloring so they essentially disappear visually. Many minnows have mirror like sides that occasionally flash brightly, but more often reflect what ever background is present, which also tends to make them visually disappear.

 

Predators, on the other hand, tend to combat that camouflage war by gradually developing shape and outline detection systems that largely overlook mottled background mimicking prey coloring. Those piscatorial predator outline detection systems--it has been suggested--often rely on reflected UV light which tends to differ greatly between living tissues and inanimate backgrounds. That's a bit of a mouthful without any official citations in the fisheries literature. But I've seen it discussed. It seems to be a growing theme.

 

In that context matching the hatch can be seen as counter productive. Matching the hatch might mean making flies most likely to not be noticed. The best strategy, it might turn out to be, would be to match outlines sizes and shapes. But to ignore natural coloring, using super-natural colors and striping more likely to be detected by predator outline recognition systems.

[SilverCreek 0]

I wrote a piece on selectivity and how it develops in trout that might be of interest.

 

http://www.theflyfishingforum.com/forums/general-discussion/334575-selectivity-why-how-do-trout-become-selective-feeders.html

[salmobytes 0]

Cool post above. MSU (Montana State) is in the middle of a snow bowl with North Dakota State. So I didn't read as carefully as I might have. Not yet anyway. But I thought I noticed you saying selectivity happens sometimes. And like Newton's slightly flawed reasoning about the causes of gravity, most of what he said about predicting gravitation forces remains useful. As does the concept of selective feeding and therefore matching the hatch.

 

But what is most important to match? If predators are largely ignoring visual spectrum coloring because it's too hard to use, in favor of outline and size detection, then matching the hatch means matching the size and shape. But not the coloring. The late Al Troth and his still kicking and smart as a whip son Eric have an interesting video out there on the net somewhere, where Eric talks about switching patterns on tricky, hard-to-catch dimpling fish on the Beaverhead. Where Al had equal success with wildly different color combinations. And still caught fish. As long as the size was right. I'm not sure what I believe about coloring. I do think all color bets are still on the table.

 

I am a firm believer in matching size and profile............but not necessarily about color. I'll have to find some references. Reflected UV light is starting to look like an evolutionary important tool for outline and pattern recognition among aquatic predators of all kinds.