overmywaders

Behavioral studies have been conducted with trout trained to choose a particular color from among others of the same luminance.

See http://www.overmywaders.com/cblog/index.php?/archives/112-Ultraviolet-Vision-in-Trout.html for an article on UV vision in trout.

A 2013 study revealed that brown trout preferred stickleback minnows when they were able to see the sticklebacks' natural UV markings. See http://www.currentzoology.org/temp/%7B8FAC0D77-C93C-4CF9-94DF-757BF3A0F365%7D.pdf

Silver,

You missed the following in the Discussion paragraphs:

 

In the present study, the UV-reflecting sticklebacks

were attacked first significantly more often. Subsequent

attacks of trout only tended to be more frequently targeted

at the UV reflecting one. Assuming a similar success

of hunting by trout for both the UV-reflecting and

non-reflecting stickleback once attacked, the UV-reflecting

one will suffer a higher risk of being detected and

preyed upon. The matter of fact that trout were fed with

dead sticklebacks under UV+ holding conditions prior

to the experimental trials might have accounted for the

preference for UV+ prey because it looked similar to the

food previously experienced. Nevertheless, trout were fed

with dead stickleback only on very few occasions so that

some sort of learning effect can be virtually excluded.

You were very selective in your reading, or you have little regard for an honest discussion. You choose.

Of course, you will want studies for rainbow trout, all chars, Golden trout, cutthroat trout, Paiute trout, coelacanths, etc. I would expect no less from you...

and now, I expect no more as well.

Disillusioned again.

I agree. I said that in response to the statement "other strategies are used if the insect color was, for example, grey instead of light olive." I should have been more explicit, the same strategy is valid for all visible colors if the natural is of a type with that UVR. So, I would add some white Hareline rabbit dubbing for all mayfly dun bodies, and more for mayfly spinner bodies.

Did you have a chance to look at the study? The trout were of a size to have lost most of their UV-specific cones, yet they chose the sticklebacks where UV markings were visible over those with no UV visible markings. From the abstract:

 

The difference in attack probability corresponded

to the difference in chromatic contrasts between sticklebacks and the experimental background calculated for both the

UV+ and UV- conditions in a physiological model of trout colour vision. UV reflections seem to be costly by enhancing the risk

of predation due to an increased conspicuousness of prey. This is the first study in a vertebrate, to our knowledge, demonstrating

direct predation risk due to UV wavelengths

Regards,

Reed

Henry,

I'll take those questions in order.

 

 

Question 1 - How do we know that the specific band (wavelength) of UVR reflected by the mayfly will be the same wavelength of UVR in the white dubbing? (does the white reflect only the UV wavelength that the natural insect reflects and no other)

In photographing mayflies in the UV, I have found that the body reflectivity was generally 365nm to 400nm. Humans have similar cone pigments to trout and those humans who can see in the UV interpret the entire range as a bluish white, mainly varied by intensity. When we consider that blue is the range 455nm to 492nm and violet is the range 390nm to 455nm, it doesn't seem unusual for UV to have a 40nm span as gradations of one color. The intensity of the color UV may be most significant, that is, the percentage of reflected UV.

 

 

my question 2 is do all mayflies reflect proportionate UV to their shading and color that we can see?

Alas, I can only speak for the small set of mayflies that I photographed in the UV. From a scientific viewpoint, I lack the data to reply. However, if we extrapolate from the few known to the many unknown (a practice that is inherently wrong, though the conclusion may be correct) I would say that 40% UV reflectivity for the body of duns - with bars of lower reflectance - and 60%+ for spinners would be a safe bet.

 

 

The implication from your example is that we can mix the UV reflective white to any base non UV reflective color and end up the correct UV and visible color match. Or is this only one example of a specific UV matching strategy and other strategies are used if the insect color was, for example, grey instead of light olive. Or an olive caddis instead of a mayfly?

As noted in my reply above, I am extrapolating from a small sample. However, I can say authoritatively that visible color bears no relation to UV "color". See the Brown-eye Susan below in visible light and UV:

BTW, I noticed a new - 2013 - study on yearling brown trout using UV in predation of sticklebacks. See http://www.currentzoology.org/temp/%7B8FAC0D77-C93C-4CF9-94DF-757BF3A0F365%7D.pdf

Kind regards,

Reed

Silver,

Why do you constantly reference the irrelevant UV-specific cone controversy? As in

 

 

There is disagreement among experts as to whether adult non spawning trout can see UV. Lets put that disagreement aside and assume that trout see UV just fine.

That is a strawman and quite beneath your intelligence and dignity. There is no "disagreement among experts as to whether adult non spawning trout can see UV" through the use of their SW, MW, and LW cones and their rods.

Okay, to the quandary which you encapsulated in the statement: "It is not enough to know that trout food reflects UV. To actually make practical use of that knowledge, there must be a system that can match the UV color spectrum as we do with colors we can see."

I concur. I have already photographed a large selection of natural fly-tying materials and presented them in my book - http://www.amazon.com/New-Scientific-Angling-Ultraviolet-Vision/dp/0984086307/ Did you have a chance to look through it for hints on materials and their UV reflectivity?

I really need to do a rewrite and include tables of references by UV reflectivity and material type. Unfortunately, the UVR of one supplier's products may differ from that of another supplier.

Let us say that you wish to imitate the body of an artificial PMD with the UVR of the natural dun, which is, for the sake of this example, a pale olive. You know that the Hareline natural rabbit dubbin' looks like the image on the left in visible light and the right in UVR.

As the light-bodied Ephemera have, based upon my observations, a fairly high UVR (60%+), you could mix the light olive in the second row left, with the white in the second row, third from left.That would give you the light olive dubbing withe the appropriate UVR.

I wholeheartedly agree with your statement - "I think the current "UV" materials are for the most part UV fluorescent materials that have nothing to do with matching the UV reflectance of natural trout food."

Kind regards,

Reed

I'm not sure Silver is representing my view of UV sensitivity properly. Rather than write it all yet again, I refer any interested to http://www.overmywaders.com/cblog/index.php?/archives/112-Ultraviolet-Vision-in-Trout.html

You will note that not only do the cones of mature trout respond to UV, but the rods, which are used at dusk and nighttime, do as well. As for what "color" the ultraviolet wavelengths represent to trout, we cannot know for certain. We do know from our experience with aphakic humans (those people lacking the protective yellow pigment in the lens or lacking the lens itself) that humans "see" (interpret or perceive) ultraviolet as shades of pale blue. The opsins of trout and man are similar in their transmissions - trout have peaks at 434, 531, and 576nm, while humans have peaks at 420, 530, and 560nm.

However, it is not relevant what color UV appears to trout -- if the natural insect is seen with UV markings, the artificial should have similar markings. We treat all the colors we can see the same way: if an insect has sulphur yellow wings, we don't ask what color the trout sees, we replicate the sulphur color in our flies. The same should apply to UV.

Regards,

Reed

A type of fly that isn't used much any more is the Bivisible. The Bivisible in all its color combinations is still an effective dry fly for trout. Does it imitate anything specific? I don't know. However, the highly UV reflective white hackle (must be natural white or cream) seems to get the trout's attention.

Alas, it is hard to get the proper materials for Bivisibles. When properly tied, the hackle tip is tied in at the tail - or as the tail - and the hackle gets gradually longer as it spirals up the the hook, causing the finished fly to sit high at the head and low at the tail. However, modern genetic hackles don't have the spade shape of the old gamecock hackles; the lengths of the barbs are consistent throughout the length of the feather. So, to get a Bivisible to sit properly on the water, you now must trim the finished fly to shape.

By the way, we don't need to buy special materials to add high-UV reflective highlights to our flies. We just need to use the existing natural materials knowledgeably. There are several caveats:

• Don't use unnaturally white feathers, they have probably been treated with TiO2 as a whitener. Titanium dioxide absorbs UV and fluoresces blue, making the feather look whiter in visible light, but dark in UV. (TiO2 was added to skim milk to make it look richer as well.)
• Don't use real silver plated tinsel. Silver absorbs most UV light. Aluminum reflects most UV.

There are more caveats, of course.

Best regards,

Reed

http://www.overmywaders.com

Mike,

That is why I wrote this about the images:

 

 

Underwater flies even in shallow water on an overcast day or at night, seem to benefit from the scattering of UV which provides a bright background. The old adage, "Dark Day, Dark Fly" makes some sense, IMO. The photos below (by Professor Thomas Cronin) show the contrast.

Using a streamer that reflects little UV makes sense if you want it to stand out against the UV background at night. And, black streamers do perform well at night, as do UV-dark wet flies like a dark Montreal.

OTOH, a chartreuse fly sometimes works well at night, and most chartreuse pigments are highly UV reflective. Go figure.

Fly fishermen have a long history of bullheaded opinions over the best fly line, fly floatant, floss, you name it. That just adds to the sport. Fortunately, I know from personal experience that they are all wrong.

I use lure techniques - attempting to stimulate curiosity, anger, territorial behavior - with flies often. When doing so, I am not using strict imitation. I am, if you will, luring the trout rather than depending upon their feeding behavior.

It is none of my business what type of object is at the end of your tippet. The only time it becomes controversial is when someone tries to present a case for the state declaring a stretch of water Fly-Fishing-Only. Then, I will want a clear definition of a fly, fly-fishing, etc., because it affects everyone. That is a subject for another thread.

I am an old fart, too. Some of the old ways, flies, lines, rods, still make sense. I love silk lines. See http://www.overmywaders.com/index.php?silk I don't resist change, but I like to be certain of its benefits.

I responded to the article presented in the original post of this thread. The article's author was in error on most counts. That aside, some interesting issues that Silver knows but hasn't mentioned are the periods of dusk and night. During dusk the trout has mesopic vision, both the rods and cones of the retina are in use, while at night the tour has scotopic vision, only the rods are available. The rods of the trout retina are up to 1000x more sensitive to photons than the cones, but the opsins (pigments) process the information on a grayscale, from black, no input, to white, maximum input. So color in flies is not relevant on a dark night. But... during dusk the percentage of solar light in the UV wavelengths increases and starlight and galactic light also provides UV. It is this UV light that the mayflies use for finding their river and illuminating the species and gender of their prospective mate. Naturally, one would suppose that if mayflies have these UV markings, astute fishermen would copy the markings. And they did. Below is an Adams dry fly in reflected UV light (special camera and filter required):

The wing, hackle, and body resemble the barred UV signatures of many mayflies. And so it is with many of our most popular and enduring fly patterns.

The use of fluorescent materials may not "trigger" a take because of the visible color. Many fluorescent artificial pigments are also very bright in the UV, that may indeed be what helps with the take. BTW, the notion that a trout "wants to eat our fly" may be demeaning to the trout. Having no hands, if a trout wants to inspect a curious bit of flotsam, e.g., a cigarette butt, he uses his mouth.

Among fly anglers there once was a distinction between flies and lures. One fished lures, e.g., a small Colorado spinner with trailing fly, to excite the trout and encourage a strike (not a "take"). Flies, OTOH, were designed to closely imitate a natural prey item, e.g., a grasshopper or mayfly. Today we don't distinguish between lures and flies - mores the pity - which means we think we are encouraging a feeding response when it might be a curiosity or anger response. So, fly flingers chuck-n-ducking their Clousers or other jigs may be using the excitation concept of lures, rather than the imitation of food. The same might apply to the use of gaudy colors or rubber legs.

Underwater flies even in shallow water on an overcast day or at night, seem to benefit from the scattering of UV which provides a bright background. The old adage, "Dark Day, Dark Fly" makes some sense, IMO. The photos below (by Professor Thomas Cronin) show the contrast.

I enjoy this subject. Thanks.

Regards,

Reed

http://www.overmywaders.com

The UV curing adhesives that I am familiar with are transparent to UV light. When you think about it, if they were highly reflective or absorbent, they would cure on the surface, but not to any depth. Being transparent, they do not alter the UV signature.

P.S. - Norland sells the optical adhesives used by many of us who make lenses and/or filters. See https://www.norlandprod.com/adhchart.html for their products, most of which cure by UV and may be a good sub for your present adhesive. Click on the individual NOA number and it will show the transmission spectra.

The bright fishing vest lead me to test camouflage clothing, both hunting and military. Then I applied for a patent on camouflage in near-ultraviolet wavelengths using nanoparticles and thin films so that the product - UVRC (patented) - could be applied over existing visible and NIR camouflage without altering the Vis and NIR characteristics.

Ever since I released the book I have been developing UV camouflage and related items. See http://uvrdefensetech.com/index.php?home Try the video on the home page. The videos and images in Gallery are very interesting as well, IMO.

I can't sell you UVRC, sorry.

Best regards,

Reed

Actually, UV reflective fly tying materials are as old as fly tying. Think of how many patterns among the "Catskill style" dries use wings of pintail, wood duck, or teal white and black striped breast and flank feathers. Wings of these feathers show bright and dark in the UV; just as the markings on mayfly wings in the UV. One of the most popular flies -- the Adams -- also has very bright and varied wings in the UV.

Adams in visible light

Adams in reflected UV

Just like the other wavelengths we can't see, ultraviolet is operative in our fly tying whether we know it or not.

Good fishing.

Regards,

Reed

Cheech,

Thanks for the kind words.

Best regards,

Reed

Piker,

The book is http://www.amazon.com/New-Scientific-Angling-Ultraviolet-Vision/dp/0984086307/

regards,

Reed

I have never found any peacock eyes that are more than a few percent UV reflective. Nor have I have discovered any iridescent feathers that are UV reflective. Since the UV reflection is a factor of the construction of the feather, not a matter of pigmentation, in natural feathers, it would seem that iridescence and UV reflectance are antithetical. The popular and effective flies that use peacock herl - Coachman, Royal Coachman, Prince Nymph, Zug Bug, etc. - also have a highly UV reflective patch of duck feather, turkey biot, or natural white bucktail (Note: some white feathers and hairs are treated with TiO2 to make them appear a brighter white; this reduces their UV reflectance markedly).

As Silver is aware, the majority of the fishery biologists studying trout vision have concluded that mature trout either do not lose all their UV-specific cones or regrow some. What is also true is that there is a secondary peak for each of the red, green, and blue cones in the trout's retina, and that peak is in the UV... so all of the cones register UVA wavelengths. Of equal interest is the fact that the rods of the trout retina, which are used for night vision, are more sensitive to UV light than blue light. The UV percentage of solar light increases at dusk, the mayflies navigate by UV vision and find their mate based upon UV markings, so it is not unreasonable to approximate such UV markings when fishing mayfly patterns at night.

Humans start with UV vision, but lose it as the lens of the eye accumulates yellow pigments which block the harmful UV. Those people who have a clear lens or have their lenses removed in cataract surgery, can see in the UV -- the artist Monet is one example. Trout don't need protection from UV because they have stem cells in their retina capable of regrowing cones.

We already use many natural UV reflective materials in our flies. Most of us need not look for more materials. In my book I detail the UV aspects of twenty-four of the most popular (hence, I hope, effective) dry flies of 1980. In each case, the use of UV reflective material is in proportion to the naturals represented. For example, the common cricket reflects very little UV and the popular artificial cricket also reflects little.

Best regards,

Reed

Unfortunately, the Pisscalator Mark IV gave me some problems as well -- see Inventor's Notes on Pisscalator Mark IV