1. Troutnut Forum
›
2. Fly Tying
›
3. UV Tying Materials - does this really make sense ?

Seeing all this UV material in the shops I got a little curious and started reading. I even got the book Scientific Angling and I even did that after reading multiple scientific findings that Salmonoid species loose their UV rods as they mature and only gain them back during spawning. These seemed like very credible sources.

Scientific Angling states that Trout have UV vision and therefore we need to understand how everything looks UV. I am skeptical but could not post a reply to overmywaders.com to get his comment.

So I asked some very accomplished fisherman here locally. These are guys that have spent the time researching trout behavior not just talking about it. His comment was that UV reflectance can generally affect the visibility of objects, more so at certain times of day than others. That means that some colors, blue for example are smart choices for nymphs mid-day in deeper water where UV penetrates and MAY contribute to the overall visibility of the pattern.

Personally I currently think I might have wasted 20 bucks on the book.

Any other thoughts on this UV mumbo jumbo ?? The adult fish we cast over "aint got no" UV Rods so what's the point really ?

Thing is I really like how the light catches some of this stuff and am using it ... but I think for its ability to scatter light..

More..

http://www.sciencedirect.com/science/article/pii/0042698987901246

" Microspectrophotometric analysis of the visual receptors of “yearling” brown trout, Salmo trutta, revealed three cone types, double cones with visual pigments absorbing maximally at about 600 and 535 nm, and two types of single cone withλmax at about 440 and 355 nm. Two-year-old fish did not possess the u.v. cone cells. Microscopical analysis of the cone mosaic in “yearling” trout showed a square pattern of double cones with a central single cone and corner single cones, but in two-year-old trout the corner cones were absent. It is concluded that u.v. sensitivity is derived from the corner cones of the mosaic, and that it is only present in young trout."

Hi Mikey,

There's a lot of confusion on this topic out there. We really went 'round and 'round on this a short while ago in a very long thread, including participation from the author himself. It covered both UV and fluorescence. Click on this link and get back to us with your thoughts.
http://www.troutnut.com/topic/7879/UV-spectrum-and-trout

Ah! I was posting when you were.... Thanks for the article! I'll make it a link for you.

Paul, it appears you are vindicated about the lack of UV vision in adult salmonids.

Mack,

Many came to the same conclusions years ago. Wished they were right, as it would certainly make things a lot simpler.:)

Read the same link I posted for Mikey. In the middle of it are a few posts traded between us addressing the issue of how visible color is perceived/responded to as well.

Entoman,

I did not see any reply I could identify as the author of Scientific Angling nor did anyone seem to address the question directly. Do adult trout see UV.
Further I am confused how the PH reference snuck in?

But... I do think it is probably useful to understand how our flies look to us under UV conditions as that is all that penetrates in deeper water and in low light conditions it may tell us something.

I found an srticle on SexyLoops that left me with the impression that contrast is important, perhaps more important than UV or VIS color. So my thinking is that one would need to make sure that they use contrasting colors in terms of UV for wet flies especially.

All those photos of materials under UV would be really useful if they were captured with normal vision equipment (no UV filter). That way we could see how they appear to the trouts normal VIS.

The results of the 1987 study above have been modified since that date as researchers found that mature salmonids have UV cones still present in the dorso-temporal region of the retina. One researcher in the field thinks these are blue cones, but even he admits that it is of no moment as all of the RGB cones have a secondary peak in the ultraviolet that gives them ultraviolet vision. Also, the rods at night are more sensitive to UV than to visible light.

Here is one quote:

Ultraviolet visual sensitivity appears to be reduced and, possibly, lost during smoltification in anadromous populations of salmonid fishes. Similar changes occur in non-anadromous salmonids over a mass range that is associated with smoltification in their anadromous conspecifics. However, in sexually mature adult salmonids, ultraviolet-sensitive cones are present in the dorso-temporal retina, suggesting that ultraviolet sensitivity (i) may be regained with sexual maturity or (ii) might never be completely lost.
from Functional mapping of ultraviolet photosensitivity during metamorphic transitions in a salmonid fish, Oncorhynchus mykiss
Mark E. Deutschlander*, Danielle K. Greaves, Theodore J. Haimberger and Craig W. Hawryshyn 2001Functional mapping of ultraviolet photosensitivity during metamorphic transitions in a salmonid fish, Oncorhynchus mykiss

and another
The most parsimonious explanation for the data is that UVS cones degenerated and UVS cones were regenerated from intrinsic retinal progenitor cells. Regenerating UVS cones were functionally integrated such that they were able to elicit electrical responses from second-order neurons. This is the first report of cones regenerating during natural development. Both the death and regeneration of cones in retinae represent novel mechanisms for tuning visual systems to new visual tasks or environments.
from Degeneration and regeneration of ultraviolet cone photoreceptors during development in rainbow trout
W. Ted Allison†, Stephen G. Dann‡, Kathy M. Veldhoen, Craig W. Hawryshyn§*
Article first published online: 17 OCT 2006
Journal of Comparative Neurology Vol 499 Issue 5

As you can see in the image below, the secondary peaks of the cones provide plenty of UV input, especially at dawn and dusk, when the percentage of UV solar increases.


Personally, I don't think you wasted your money. :)

Regards,
Reed

Awesome... thanks... was looking for verification..

Mr GearTheory ;) in a couple weeks here we can show your UV experiment to some old sulky Brown and see what he thinks...We'll present it to him in low light :)...Real low light.

If we are lucky we may run into some Light Hennies...Maybe like that one year James and I were upstream of Daisey Bend and couldn't open our mouths without swallowing a half dozen of the little critters! On our caps, in our ears, on our rods, and all over the stick-boat...I would make a cast and my fraud would land between 6-8 naturals...Impossible competition. We waited it all out and then when it was petering out, went head hunting! Yahoo!!!

If you hear a loud scream, don't be alarmed...It's just Spence crossing the Crawford County line. ;)

I can't speak to this bc, as I said before, I'm just not up on the latest. I'd have a lot of reading and chatting with old friends to do before I could say much of use.

I read Mr's Curry's book and can only say that it's interesting. Whether it can be put to good practical use remains to be seen, or not (pun intended).

Just for clarity, the last graph provided above is for cichlids, not for rainbow trout. And apparently such cones are not ubiquitous in cichlids.

I've been aware that anadromous salmonids gain visual pigments annually upon sexual maturation. There are now company's producing UV reflective lures for bass. I was not aware that bass had such a capability, esp in light of the degradation of UV with dec water clarity. But, a very few anglers, myself included, have been aware of female LMB taking on a bluish "aura" (for lack of better) during the spawn. One angler/researcher has described female florida LMB as "lighting up" while in the throws of spawning. I've wondered if LMB also regenerate visual pigments annually, when they are in very shallow water to spawn. Visual cues during courtship are critical to spawning success for many fishes, bass too.

This might not help anglers any, if the bass, or trout, then lose those pigments.

Hi Mikey -


My apologies, Mikey. It is a very long thread and I should have identified the salient contributions and their authors. Reed (Overmywaders, who wrote the post with the graphs above) is the book's author. He made many excellent posts in the thread. Paul (PaulRoberts) addressed the question directly as well, with good counterpoints.


I was a bit confused by that as well. Mack (Brookyman) can speak for himself, but I believe he was referring to fluorescence/phosphorescence/UV reflection in a general acronym, not the chemical properties of water.


Ah! I struggled with this myself. The problem is how do you make something visible that is invisible without artifice? There's no way for us to know what reflected UV really "looks" like as we are blind to it. The problem with UV filters/infrared filters is that they distort the relationship with visible light as they would appear together in nature (if we could see it).

Though I find Reed's work fascinating, and well worth the dough, I'm still on the fence about all this. Even assuming he is correct about salmonid vision, the only way to make sure our flies look like the naturals would be to use sensitive equipment to measure the wavelengths of light reflected/emitted from the critters and then match our flies with materials that match not only in frequency blend (color match), but location (pattern). Practically speaking, that's an impossible task. Lets say a nymph is found to have some UV reflection of various frequencies from various locations on it's body (a debatable assumption as well in normal conditions, BTW). To simply add a particular UV frequency matching material to a fly willy nilly without good location or blending is like putting a red wingcase on a brown nymph to match a natural that has some red & blue highlights at various locations. To add UV material without any frequency match at all would be like putting a yellow wingcase on it. To what point?

First a reply to Mr. Roberts. I used those graphs because they were easier to understand than most of the trout specific retinal absorbance graphs available. However, if you piece together the graphs of rainbow trout retinal sensitivity found at http://jeb.biologists.org/content/204/14/2431.full.pdf you will see they are similar.

I wrote about riverine trout, I'll leave largemouth bass to you.

Entoman, you said "Even assuming he is correct about salmonid vision..."

It is not up to me to be correct about salmonid vision. The many scientists who have studied trout vision since 1993 - with Flamarique as the exception - asset that there exist UV specific corner cones in adult trout. Flamarique thinks they are blue-specific, but admits that in terms of trout vision, the secondary peak in the UV inexorably provides UV input.

The manner in which I hoped fishermen would take advantage of the ultraviolet vision of riverine trout was through applying some cool logic to the choice of flies and fly tying materials. For example, since many mayflies having their mating swarms after dusk, those mayflies would require UV markings by gender and species. Therefore, some UV reflectance in the wings and body - but particularly wings - would not be amiss in the artificials. I feel that the effective fly patterns shown in the book supported that hypothesis.

Sorry about that, Reed. I did not mean to imply in any way that your reasoning regarding trout vision isn't backed by good science - just that that science (and the conclusions drawn from it) may or may not be eventually proved correct. Assuming it's correct, applying it to angling opens up even more puzzles to resolve. Fun stuff, to which you are greatly contributing.

Mack -

No, here. That's what I get for trying to interpret your use of PH. Sorry about that.:) Thanks for a further explanation of what you were trying to say. I wasn't aware PH had anything to do with UV penetration or perception.

Mack,

I've found that trout (as with all wildlife) are disturbed primarily by movement, no matter what we are wearing. It's important to keep in mind that we aren't hunting ducks or turkeys whose sharp vision is working in the atmosphere. Fish in shallow water have a pretty small window looking out on the terrestrial world. The vast majority of the underside of the water is mirror and unless you are wearing glowing solid colors (like solid white or Red) it's a pretty safe bet that you aren't being noticed through it unless you're doing jumping jacks. However, If you are moving around in the window you're a dead duck no matter what you're wearing. Staying low below the window's horizon, keeping movement to a minimum, dull clothing, and no shiny/flashy objects are the keys. Excepting poor casting, fly line color is perhaps the most important detection factor on larger streams were keeping distance is easier. You don't want it contrasting with the background moving in and out of the window or have flashing movement penetrating the mirror.

Soft, slow wading (in calm streams) - keeping low with everything but the fly and tippet out of the window - minimized movement and flash outside of the window in the mirror - competent casting and fly placement - delicate pick-up as far away from the "zone" as practical; these are the key components to trout angling stealth. Failing to observe these practices will usually prove fatal to one's chances, whether you paint your face and wear camo or not...

Scatter light...that's it. I started mixing SLF Prism I fibers in with my rabbit dubs awhile back...more fish. And more recently I started mixing in Ice Dub fibers (some UV, some not), more fish. It's the flash, not the light spectrum. Remember, all the manufacturers are trying to sell something to YOU. Brown trout don't buy books. Brown trout buy something that looks like supper...and a little pinch of flashy synthetic mixed in with your go-to dub may cause that bruiser to come up to the nymph...Scatter light...

I recently read something on UV in mature trout eyes and apparently UV ability is present in fry, then lost. It is then regained at "maturity". Some speculation was that its role may be for navigation coupled with polarized light use. When I heard "maturation" I remembered research I'd read pertaining to the gain of red visual pigments at "maturation" in anadromuous salmon and steelhead, for use in shallow water and nuptial behavior. (I was interested in this research bc it explained the short wave length nuptial coloring in steelhead and all other salmonids.

Made me wonder if the reference to UV sensitivity in “mature” rainbow trout has a purpose other than feeding, and whether it is an annual event with “annual maturation” –associated with nuptial coloring, kype development, and nuptial behaviors. Would resident rainbow populations maintain this year round?

Mack's question of whether UV vision is useful is a valid question not just for fisherman but for fish too. Evolution tends to prune less than useful functions due of energy allocation pressures.

Interestingly, female largemouth bass have been described by some anglers as “lighting up” –taking on a very UV lavender “aura”. Doug Hannon talked about this in his writing. And I’ve actually seen this too, but so infrequently (despite looking at spawning bass closer than most) that I could say it’s always present. Maybe in situ lighting was involved?

Also, I’ve always noticed that post-spawn brown trout, in particular females as they recuperate (and a get “metallic” sheen again), have lots of bright UV-ish looking blue pigment on their bodies, especially on the gill plates and forward parts of the sides of the body.

And, come to think of it… is the very pretty pale blue pigment in resident stream brown trout –usually there’s a spot behind the eye (often associated with a black spot), and the blue halo’s around the black spots on the sides (esp fore)– UV reflective? If so, this would suggest social visual cues in the UV range amongst trout. Is this maintained year round? Is it more prominent in clear water, turbid water, shade, sun?

This one is lacking the black spot behind the eye, or maybe it's obscured. Anyway, it shows a lot of the blue pigment:


Anyway, all purely speculative. The simplest speculation is that UV vision and red vision in resident trout is permanent and applicable for visual cues and for feeding. Since UV reflectance is common in the terrestrial insect world it would make sense that rout might retain UV sensitivity. But I doubt seasonal changes in trout vision has been pursued very far.

Paul,

I put together a short paper on the issue of ultraviolet vision in trout. It may be found at http://overmywaders.com/cblog/index.php?/archives/112-Ultraviolet-Vision-in-Trout.html. I would appreciate your criticism, perhaps finding holes in my logic.
Thanks.
Reed

Very nice article, Reed. Well articulated and certainly reasonable. Perhaps you are right.

However, it seems to me the bigger question is what to do about it. As I've asked before, how do we address it? Your photos filtered for UV show a much different picture (pardon the pun) than what the fish see, assuming they "see" UV. For example, lets further assume we can't see green. If we filter for the entire band we would associate with green and then converted it to a visible color - say red - we'd be off the mark in terms of what the trout actually see. Your photos, while interesting, present this very problem. Similarly, to simply tie with a broad spectrum reflecting uv material may be like fishing with a Kelly green fly to match the dusky olive of so many of our hatches. How do we detect the subtle shading and blending with other colors that can often be important?

I think I understand your question. Let us say that there is a dusky olive fly hatching. I would choose a fly with colors of body, wings, and tail that were nearest to the colors of the original. That is what we do now. However, if it is a mayfly, I would know that the wings would have some bright marks in the UV, so I would add some transparent, in visible light, highly UV reflective spots on the wings of the artificial. If it was a caddis I was imitating, I would use a low UV-reflective - say 25% - coating to the wings. That way, if the underlying feather wing was highly UV-reflective, I would overcome that with my topical application. So, I don't need to know what the artificial looks like in UV, so long as I know some common attributes of the insects and other trout food and have a means of adding appropriate UV highlights.

Yeah, that's what I was getting at. Very good info, Reed. Makes sense... Thanks for sharing it!