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  #21 (permalink)  
Old 11-24-2012, 11:11 AM
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Default Re: Does blue excite the trout?

Quote:
Originally Posted by overmywaders View Post
silver creek,

Where do you get that information? Most fisheries biologists acknowledge that the dorsal temporal zone of the trout retina still retains UV specific cones after smoltification. "THE MAIN SENSORS OF THE UV LIGHT WILL NOW BE THE BLUE CONES"
You asked the source of my information that trout lose their UV receptors after two years. It is from Trout University and Sexyloops. They both agree that UV vision in trout regresses in adulthood. Some scientist believe that it returns during the spawning and that somehow it helps returinging fish locate their native waters (see citations below).

Color Vision in Trout Eyes | Trout University

"The fourth is outside the band of wavelengths visible to humans and is referred to as "ultra-violet". However, the fourth class of cones disappears by the time a trout is two years old."

Salmonid Vision

"Most research indicates that salmonids have cones to detect UV light when small, but as the fish grow these cones gradually disappear. Their diet in their early period of life consists of zooplankton and other small creatures that reflect UV light, but as the fish get larger they can no longer filter such food with their gillrakers. This is given as the main reason why no UV receptors are found in fish above 2 years old.

Other studies, however, have shown that new temporary UV receptors are created annually to coincide with the spawning migration and that these are used to detect polarised light as a navigational aid.

This would mean that returning seatrout and salmon do have some ability to see UV but I have yet to see any evidence that would lead me to believe that this is used for prey detection. It would seem unlikely, both because this is the time when their appetite is suppressed and, if it was a useful tool for finding food, it is logical that they would retain it throughout their life."


Now I enter from science into philosophy and science. Let us assume that trout can see weakly into the ultraviolet via stimulation of the blue receptor at 440nm. A stimulation of the blue receptor is "interpreted" by the brain as indicating a specific color, in this case blue and not UV. So does the fish "see" blue or ultraviolet?

The fish does not "see" ultraviolet. The fish sees the color blue, because the blue receptor is what is stimulated as you quoted; "The main sensors of the UV light will be the blue cones." The trout does not see what it sees when the UV receptor at 355nm is stimulated. If that be so, then the blue appears slightly brighter due to the slightly extra stimulation from the UV.

Allow me to give an example of an analogous phenomena that we have all experienced, the doppler shift of a moving train whistle. The whistle sounds different approaching us and going away from us than it does when standing still. The true sound is when it is standing still. But when it is moving, there is a doppler shift to either a higher frequency (train moving toward us) or lower frequency (train moving away) Our brain can only tell us how our our ear drum has been stimulated and not the true frequency of the train whistle.
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Last edited by silver creek; 11-24-2012 at 11:58 AM.
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Old 11-24-2012, 12:43 PM
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Default Re: Does blue excite the trout?

silver creek,

I notice that neither you, nor the blogs you cite, have referred to any peer-reviewed scientific studies to prove your assertions.

You don't need to look far to find that biologists disagree with your premise and that trout do retain/regain UV vision.
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
Quote:
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 I stated in my last post, even if trout did not regenerate UV-specific cones, the other three types of cones also are sensitive to UV wavelengths. Further, rods are more sensitive to UV than to other wavelengths - which makes sense since the percentage of available light during dusk increases in the UV and decreases in 400-700nm (usual human visible) wavelengths.

Quote:
Stark et al. (1994) also
describe UVR cis absorption peaks for short-, medium and
long-wavelength cones in the rhesus monkey which
suggest a more dominant function for the detection of
UVR in this primate. The exact mechanism, however, of
this ocular UVR detection is not yet known. Specifically,
studies by Gouras (1984) and Chatrian et al. (1980) demonstrate
that rods are more sensitive than cones to short wavelengths.

Thus, to test for cone detection of shorter
wavelengths of the visible spectrum rod responses must be
eliminated by the use of a saturating steady adapting light.
Therefore, it is possible that UV-vision is maintained with
largely rod-dominated system under scotopic viewing
conditions and cone-dominated system under photopic
conditions.
[emphasis mine]
from Near ultraviolet radiation elicits visual evoked potentials in children
George C. Brainard, Sabrina Beacham, Britt E. Sanford, John P. Hanifin,
Leopold Streletz, David Sliney

(yes, young children are UV-sensitive, as are adults when the lens of the eye is removed in cataract surgery. So, if your four-year-old claims to see something you can't, perhaps it is his UV vision)

So, silver creek, in brief, the prevailing science (not the science of 1978) 1/ records UV-specific cones in the dorsal-temporal region of the adult trout retina, 2/ all the cones of the adult trout are sensitive to UV, and 3/ the rods are more sensitive to UV than to longer, lower energy, wavelengths.

---------- Post added at 11:43 AM ---------- Previous post was at 11:25 AM ----------

silver creek,

You said:
Quote:
Now I enter from science into philosophy and science.
You didn't start with science, but with a regurgitation of an old, disproven theory passed through other hands.

Quote:
Let us assume that trout can see weakly into the ultraviolet via stimulation of the blue receptor at 440nm. A stimulation of the blue receptor is "interpreted" by the brain as indicating a specific color, in this case blue and not UV. So does the fish "see" blue or ultraviolet?
Logic would tell us that it doesn't matter how the trout interprets the wavelength of light; it is sufficient that it receives the wavelength and that the wavelength is representative of a reflected wavelength from its prey. If the wings of a dragonfly have large, highly-UV-reflective spots, the trout will expect an artificial to have similar UV reflective patterns; no matter that it is translated as blue.

Quote:
The fish does not "see" ultraviolet. The fish sees the color blue, because the blue receptor is what is stimulated as you quoted; "The main sensors of the UV light will be the blue cones." The trout does not see what it sees when the UV receptor at 355nm is stimulated. If that be so, then the blue appears slightly brighter due to the slightly extra stimulation from the UV.
That is based upon the old theory that trout lose all their UV-specific cones; which, as noted in my second post, they do not - they retain the UV-specific cones in the dorsal-temporal region of the retina. The trout still "sees" pure UV on the UV-specific cones, as well as UV on all the others. At dawn and dusk, when much of the feeding takes place, the percentage of solar UV begins to exceed the percentage of solar RGB; and at night (scotopic period) the blues and UV dominate the rods.
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Old 11-24-2012, 02:54 PM
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Default Re: Does blue excite the trout?

It has worked for me, here is my favorite a Blue Assissan soft hackle
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I like red also
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Old 11-24-2012, 02:55 PM
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Default Re: Does blue excite the trout?

Thank you for referencing the paper below. I was not aware of it.

Functional mapping of ultraviolet photosensitivity during metamorphic transitions in a salmonid fish, Oncorhynchus mykiss

I have read the paper and my critique of the discussion, findings, and conclusions of the paper follows.

They reference previous papers that showed that UV receptors do disappear in adult trout but are present in parr. Therefore, these are the references that you wanted from Sexyloops and Trout University.

"Age-related loss, or reduction, of ultraviolet photoreception appears to occur in many species of fish, including salmonids (Bowmaker and Kunz, 1987; Whitmore and Bowmaker, 1989; Hawryshyn et al., 1989; Loew and Wahl, 1991). ……Parr are ultraviolet-sensitive, and possess ultraviolet-sensitive cones in the retinal mosaic (Bowmaker and Kunz, 1987; Browman and Hawryshyn, 1992; Browman and Hawryshyn, 1994; Beaudet et al., 1993; Novales Flamarique and Hawryshyn, 1996; Novales Flamarique, 2000; Parkyn and Hawryshyn, 2000). …….. As parr undergo smoltification, ultraviolet sensitivity appears to decrease and may disappear altogether in some species. In conjunction with this loss of ultraviolet sensitivity, ultraviolet-sensitive cones are no longer present in at least some portions of the retina of salmonid smolts (Bowmaker and Kunz, 1987; Hawryshyn et al., 1989; Beaudet et al., 1993; Novales Flamarique and Hawryshyn, 1996; Novales Flamarique, 2000; and see below)."

They then cite other research that shows some of the UV cones either persist or are regenerated in the dorsal temporal retina.

"Examination of the retina of four species of sexually mature salmonids, however, has revealed the presence of accessory corner (ultraviolet-sensitive) cones, in the dorso-temporal retina (Beaudet et al., 1997). These findings led to the hypothesis that ultraviolet-sensitive cones may regenerate into the retinal mosaic of adult salmonid fish (Beaudet et al., 1997) and, hence, that sexually mature fish may be ultraviolet-sensitive. Because the teleost retina grows throughout life and new photoreceptors are continually added to the retinal mosaic (Lyall, 1957; Johns and Fernald, 1981; Raymond and Hitchcock, 1997), this is certainly a plausible hypothesis. However, it is also possible that the accessory corner cones found in the retina of sexually mature fish are never completely lost. That is, loss of ultraviolet-sensitive cones at smoltification may not occur over the whole retina, and ultraviolet-sensitive cells may be retained in the dorsal retina throughout the life of the fish."

To investigate the UV cones in the dorsal temporal retinal of mature salmonids, they examined the Rainbow trout that they raised from wild eggs. They hormonally treated some Rainbow trout with thyroid hormone thyroxine to simulate the maturation process of the retina. They also raised a control group of non treated rainbow trout.

They use thyroxin to induce smoltification so they can study the retinal changes. However they admit that the issue of whether the changes are due to smolification or thyroxine has never been addressed and this is one goal of their experiment. That is, can thyroxin be use as a proxy for inducing adult changes? The difference between the thyroxine fish and the control fish noted later in this post, leads me to say no. They have not proven that thyroxine and natural maturation are the same. Nor do they cite any other references that show that thyroxine treatment is equal to the natural maturation process. Perhaps thyroxine is a true proxy, but they have not provided such evidence in the text of their paper or in the list of references.

"Exposure to exogenous thyroxine can (i) induce smoltification and photopigment changes in salmonids, including rainbow and brook trout (Allen, 1977; McFarland and Allen, 1977; Alexander et al., 1994; Alexander et al., 1998) and (ii) cause a precocial loss, or reduction, of ultraviolet photosensitivity and the number of ultraviolet-sensitive cones in the retina of rainbow trout parr (Browman and Hawryshyn, 1992; Browman and Hawryshyn, 1994). However, whether loss of ultraviolet sensitivity is complete during smoltification (or in response to thyroxine treatment) in O. mykiss has not been addressed."

They found a significant difference at week 6 between the control and the thyroxine treated group. Thyroxine treatment reduced the UV sensitivity in the ventral retina compared to the control fish. Dorsal UV sensitivity was equal to the control fish.

"At week 6, ultraviolet sensitivity was significantly reduced in all thyroxine-treated fish tested for ventral sensitivity (Fig.4). Ultraviolet sensitivity was significantly lower in the ventral retina of thyroxine-treated fish than in the ventral retina of control fish …. In addition, ultraviolet sensitivity was significantly lower in the ventral retina of thyroxine-treated fish than in the dorsal retina of thyroxine-treated fish …… When fitting absorptance curves to the thyroxine-treated, ventral week-6 data, we concluded that only the blue cone mechanism was necessary to explain the data."

They conclude that some UV cones persist after smoltification. Note that they say they persist and not that they stay at their original density. This is critical. Is the density the same as when they were parr or do some of the cones persist at a lower density? Note that their paper states in the bolded section above, "However, it is also possible that the accessory corner cones found in the retina of sexually mature fish are never completely lost." It is clear from this statement that the levels of UV cones are reduced, and that by using persist, they mean persist at a reduced level.

"Our finding implies that a population of ultraviolet-sensitive cones reside in the dorsal retina of O. mykiss after smoltification. Ultraviolet-sensitive cones (i.e. accessory corner cones) in the ventral retina disappear from the retinal mosaic during smoltification in O. mykiss (Browman and Hawryshyn, 1992; Browman and Hawryshyn, 1994; Beaudet et al., 1993). However, accessory corner cones have been observed in dorsal regions of the retina (H. I. Browman, personal communication), which apparently impart the regional ultraviolet sensitivity demonstrated here."

The problem with this conclusion is that it implies that the UV cones in the dorsal temporal retina do not later disappear and then regenerate during spawning. It is an inference and not proof that this is the case. They use thyroxine as a proxy for maturation, but can 6 weeks of thyroxine hormone treatment = 2 years of maturation in the wild? That is the fulcrum upon which this experiment rests.

They later go on to try to unify their findings with earlier findings that reported that all UV receptors recede in adults. They theorize that earlier studies examined primarily the ventral retina that does show disappearance of the the UV cones. One would have to go back to the original investigators to see if they agree.

"Earlier studies on ultraviolet sensitivity in both artificially induced O. mykiss smolts (i.e. rainbow trout parr treated with thyroxine) and larger, more developed, juvenile rainbow trout showed a reduction of ultraviolet sensitivity using stimulus presentations that may have illuminated primarily ventral retina (Browman and Hawryshyn, 1992; Browman and Hawryshyn, 1994; Beaudet et al., 1993). Given stimulus design considerations, however, it is unclear how well focused these stimuli were on the retina (see Introduction)."

They conclude is that some UV cones remain in the dorsal retina after smoltification. One would need to examine older wild fish at 2 years to see if that is true in 2 year old wild fish since they have not proven that thyroxin is equal to maturation in the wild.

Secondly, even if this were true in wild fish, the visual field of the dorsal retina is that area of vision below the horizontal midline of the field of vision. So if we are to be accurate and accept the persistence of direct UV vision in adult wild fish, it would be approximately 50% of the visual field at a reduced level of UV cones, and would exclude dry flies that are seen by the ventral retina.

Add your previous post that stated the even with the "persistence" of some of the UV cones in the dorsal retina, the blue cones were responsible for most of the UV sensitivity in adult salmonids, I think they perceive UV as more blue than UV.
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Old 11-24-2012, 08:32 PM
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Default Re: Does blue excite the trout?

silver creek,

Multiple studies done in recent years usually balance conjecture formed because of the results of any one study. Here for example, is another study:
Quote:
Abstract
The distribution of corner (putative ultraviolet-sensitive) cones in the retina of Atlantic salmon was examined from the small
juvenile (parr) stage to the adult stage (approaching sexual maturation). Small parr weighing 5 g lacked corner cones everywhere
except, mainly, near the dorsal periphery. Large fish (5 kg) approaching sexual maturation showed corner cones in other areas of
the dorsal retina besides the periphery. These areas, characterized by low resolving power, had similar corner cone densities to
analogous areas in the smolt retina, suggesting that corner cones are formed in the periphery and incorporated into the dorsal retina
of the Atlantic salmon sometime during the smolt stage. This incorporation is partial both in numbers of cones and in location (only
the dorsal retina is affected). These findings contrast with the situation in rainbow trout where corner cones from existing mosaics
are only partially lost from the ventral retina, if at all, and where production and incorporation of these cones into the dorsal retina
occurs throughout life. Thus, in salmonids, there are at least two different strategies that determine retinal corner cone distributions.
[emphasis mine]
from Partial re-incorporation of corner cones in the retina of the
Atlantic salmon (Salmo salar)

Inigo Novales Flamarique
2002
Vision Research 42 (2002) 2737–2745

also

Quote:
Recently, Martens (2000) has shown that smolt rainbow
trout retain corner cones throughout most of the dorso-temporal retina. This result challenges the notion of a functional loss in UV (corner cone-driven) sensitivity in smolt fish, as concluded from behavioural studies
(Hawryshyn et al., 1989; Browman & Hawryshyn,
1992). It also raises the question of whether the loss of
corner cones in this non-anadromous species is different
from that in anadromous (sea-going) salmonids where
corner cones seem to disappear almost entirely around
the time of smoltification (Kunz, 1987; Kunz, Wildenburg,
Goodrich, & Callaghan, 1994; Novales Flamarique,
2000)
Gradual and partial loss of corner cone-occupied area in the
retina of rainbow trout

Inigo Novales Flamarique
Vision Research 41 (2001) 3073–3082

You said:
Quote:
They conclude is that some UV cones remain in the dorsal retina after smoltification. One would need to examine older wild fish at 2 years to see if that is true in 2 year old wild fish since they have not proven that thyroxin is equal to maturation in the wild.
See other studies above.

Quote:
Secondly, even if this were true in wild fish, the visual field of the dorsal retina is that area of vision below the horizontal midline of the field of vision. So if we are to be accurate and accept the persistence of direct UV vision in adult wild fish, it would be approximately 50% of the visual field at a reduced level of UV cones, and would exclude dry flies that are seen by the ventral retina.
No, your "direct UV vision" (what is "indirect vision") is a strawman. Photons in the range 340nm to 400nm striking any of the cones - red, green, blue, or UV - will be recorded. At dawn and dusk, most of the vision would be through UV photons; the same is true with the rods after dark. The higher energy of the UV photons vs. visible light, is also significant.

Your statement "and would exclude dry flies that are seen by the ventral retina" is a red herring. Fish are not inextricably held in a plane parallel to the stream bottom. Trout tip down to examine things on the bottom, and tilt backwards to examine floating curiosities. When we speak of rising trout we don't mean that they rise like a submarine blowing all its ballast. Trout rise at an angle and will often follow a floating fly for yards, drifting with their bodies at a 70+ degree angle to the streambed.

Quote:
Add your previous post that stated the even with the "persistence" of some of the UV cones in the dorsal retina, the blue cones were responsible for most of the UV sensitivity in adult salmonids, I think they perceive UV as more blue than UV.
Well, you think you know how trout perceive UV. That is interesting. However, as I stated in my last post, it doesn't matter how they perceive the UV, what is important is that they do perceive the UV; so it behooves us to dress our flies with the UV reflectances of the trout's prey.
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Old 11-24-2012, 11:42 PM
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Default Re: Does blue excite the trout?

Quote:
Originally Posted by nrp5087 View Post
On Thursday evening at my flyfishing club my professor told me that the color blue has been proven to excite the rainbow trout and other species. This was determined from placing a sensor into the optical lobe of the trout and presenting the color blue to the fish. I decided to test it out and tied a blue wolly bugger with red hackle and this is what i caught out of spring creek PA

[IMG]Click the image to open in full size.[/IMG]
In a word...YES

THIS:

Click the image to open in full size.

“MOO’s BLUE MIDGE” # 18…

HOOK: Gamakatsu C12B Scud Hook, #18-#20

THREAD: Tiemco 16/0, Black

ABDOMEN: Blue Krystal Flash

TAIL: Pearl Midge Flash

RIB: Wapsi wire, x-sm, silver

THORAX: Purple Iridescent Peacock Herl (Spirit River)

BEAD: Silver Tungsten, sized to hook

...led to THIS:

Click the image to open in full size.

...and THIS:

Click the image to open in full size.

PALINISTA – (apologies to EVA PERON)

HOOK: Mustad C49S, #18 -#20, Daiichii 1130, #18-#20…used above

THREAD: Gordon Griffith’s 14/0, Red, White

TAIL: 1 Strand Pearl Krystal Flash

ABDOMEN:White Thread

OVERABDOMEN: Hareline Stalcup’s Micro Tubing, Blue

RIB: Wapsi Silver Wire, X-SM

WING: Grizzly Krystal Flash Black and White, 3strands, cut short

THORAX: Arizona Diamond Hair Pearl Green or Blue

BEAD: Silver, 5/64 or 1/16


...led to a whole bunch of THESE:

Click the image to open in full size.

THIS will be used in the coming week:

Click the image to open in full size.

ICU MIDGE TUNGSTEN (Blue) – Maktima/Variant…

HOOK: TMC 2499 SPBL, #16 – #18

THREAD: Tiemco 16/0, Black

SHUCK: Short strand of UV Pearl, Krystal Flash

RIB: Blue Wapsi Wire, x-sm

ABDOMEN: Black Glimmer Thread – Cascade Crest

THORAX: UV Black Ice Dubbing

CHEEKS: 1 strand each side, Micro Flashabou, Pearl

BEAD: Plummeting Tungsten Bead, Blue, sized to hook


...as to that UV discussion, the kind folks at Spirit River sent me an entire load of the company's new UV 2 Materials to tie with, along with some proprietary information on the subject of UV and their materials. Suffice it to say - that I would not be spending a whole lot of time at the vise, tying with this stuff, if I did not believe it is effective...


PT/TB
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Last edited by planettrout; 11-25-2012 at 12:21 AM.
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Old 11-25-2012, 09:52 AM
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Default Re: Does blue excite the trout?

Hi Reed,

You said:

Quote:
Originally Posted by overmywaders View Post
silver creek,


No, your "direct UV vision" (what is "indirect vision") is a strawman. Photons in the range 340nm to 400nm striking any of the cones - red, green, blue, or UV - will be recorded. At dawn and dusk, most of the vision would be through UV photons; the same is true with the rods after dark. The higher energy of the UV photons vs. visible light, is also significant.

I am enjoying this discussion with you. I would like your take on the following which addresses the "strawman" allegation.

Let us exclude the UV cone for a moment since they perceive UV as UV. Let us consider the other cones (red, green, blue), which also respond to UV.

The brain interprets the signals from these cones as red, green, and blue respectively regardless of the presence of the UV cone. In other words, the presence or absence of a UV cone does not affect the intensity of the UV stimulus to these cones.

Therefore, the statement that the red, green and blue cones respond to UV should not be take to mean that they take the place of the UV cone or that as the UV cones regress, that the UV light stimulation of these cones increases to compensate. So the fish cannot separate what is UV and not UV light stimulating the red, green and blue cones.

The same is true of the rods at dusk. They perceive light intensity and not color so if shades of grey on a fly reproduce the light reflectivity of an insect, it would match the insect, regardless of the color.

If by strawman, you mean that my statement that the fish cannot separate UV from non UV stimulation of the red, green and blue cones is a strawman fallacy, I believe you are incorrect.

In my statement that trout see UV primarily as blue, you also said:

Quote:
Originally Posted by overmywaders View Post
silver creek,


Well, you think you know how trout perceive UV. That is interesting. However, as I stated in my last post, it doesn't matter how they perceive the UV, what is important is that they do perceive the UV; so it behooves us to dress our flies with the UV reflectances of the trout's prey.


I took the information that trout perceive UV as blue directly from your post. You wrote:

Quote:
Originally Posted by overmywaders View Post

Further, as Inigo Flamarique, who believes that trout lose all but a small percentage of their UV-specific cones at smoltification, wrote:

Quote:

MAIN SENSORS OF THE UV LIGHT WILL NOW BE THE BLUE CONES (WHICH HAVE THE PEAK ABSORBANCE-LAMBDA MAX- NEAR THE UV PART OF THE SPECTRUM).

Therefore, your allegation that I think I know how trout perceive blue should be directed at Inigo Flamarique, whom you quoted.

Regarding the dressing of flies with UV reflective materials, I agree that it would be useful if we knew what materials matched the UC spectrum of the natural we are imitating. That is the conundrum.

Since we do not see into the UV, we cannot tell if the natural has UV reflectivity, much less the intensity and shade of UV to use. I believe some insects such a beetles do reflect UV, but until there is some type of color system of UV material to match specific insects, I cannot see the benefit of using UV for UV sake except as an attractant strategy rather than a color matching strategy.
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Last edited by silver creek; 11-25-2012 at 10:36 AM.
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  #28 (permalink)  
Old 11-25-2012, 02:17 PM
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Default Re: Does blue excite the trout?

silver creek,

you said:
Quote:
Therefore, the statement that the red, green and blue cones respond to UV should not be take to mean that they take the place of the UV cone or that as the UV cones regress, that the UV light stimulation of these cones increases to compensate. So the fish cannot separate what is UV and not UV light stimulating the red, green and blue cones.

The same is true of the rods at dusk. They perceive light intensity and not color so if shades of grey on a fly reproduce the light reflectivity of an insect, it would match the insect, regardless of the color.
It is a strawman because it does not relate to the real issues. I don't disagree with what you wrote above, but, it is irrelevant. The fish doesn't need to know what is UV or not UV, it simply needs to receive the same general visual impression from a possible food item that it did from the last similar food item it successfully harvested. You may have colors on your fly that produce the same shades of gray as the natural; but if the natural has UV markings (as many insects do), the absence of those markings will be clearly evident to the fish. This is why one dressing of an Adams dry might beat another when fishing the same water, same hatch. Both artificials may appear the same to our eyes, but the difference in dubbed body, for example, in the UV may be great.

You said:
Quote:
I took the information that trout perceive UV as blue directly from your post. You wrote:

Quote:
Originally Posted by overmywaders

Further, as Inigo Flamarique, who believes that trout lose all but a small percentage of their UV-specific cones at smoltification, wrote:

Quote:

MAIN SENSORS OF THE UV LIGHT WILL NOW BE THE BLUE CONES (WHICH HAVE THE PEAK ABSORBANCE-LAMBDA MAX- NEAR THE UV PART OF THE SPECTRUM).

Therefore, your allegation that I think I know how trout perceive blue should be directed at Inigo Flamarique, whom you quoted.
silver, Flamarique never used the term "perceive", nor was he writing about perception, but sight. You were the one who said "I think they perceive UV as more blue than UV." Perception and sight should not be confused.

You said:
Quote:
Regarding the dressing of flies with UV reflective materials, I agree that it would be useful if we knew what materials matched the UC spectrum of the natural we are imitating. That is the conundrum.
Well, we agree on that. That is why I spent so much time and energy photographing natural and artificial flies and fly tying materials in UV light.

You said:
Quote:
Since we do not see into the UV, we cannot tell if the natural has UV reflectivity, much less the intensity and shade of UV to use. I believe some insects such a beetles do reflect UV, but until there is some type of color system of UV material to match specific insects, I cannot see the benefit of using UV for UV sake except as an attractant strategy rather than a color matching strategy.
Again, a reason why I wrote the book. BTW, the beetles I photographed had no UV reflective markings (of course, one might say that almost zero reflection is marking in itself). However, that doesn't mean that no beetles wear interesting UV markings.

For $120.00 or less you can buy a used Sony camcorder, then another $145.00 for a UV bandpass filter, and you will have a system to view and record any insect or tying material in the UV.
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  #29 (permalink)  
Old 11-25-2012, 03:52 PM
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Default Re: Does blue excite the trout?

Thanks for your reply.

Regarding perception and sight, you quoted Inigo Flamarique who "believes that trout lose all but a small percentage of their UV-specific cones at smoltification" and therefore "MAIN SENSORS OF THE UV LIGHT WILL NOW BE THE BLUE CONES".

You will recall that I discussed earlier that UV light stimulating a receptor other than a UV receptor is not perceived as UV by the fish. In this case, the stimulation of blue receptor will be perceived by the fish as blue, which is different than the trout's perception of UV via UV receptors. And I also pointed out that this is so, whether the UV receptors are active or not. The presence or absence of UV receptors has no bearing on the activity and stimulation of the blue receptors; and therefore, the fish sees the same degree of blue from the reflected UV regardless of the activity of the UV receptor. So as the UV receptors are diminished, the amount of blue stimulation does not change. The corrolary would be that the UV color seen by the fish diminishes as the UV receptors diminish, but the UV perceived as blue, green, red do not.

If the main stimulus of UV in the adult trout is indeed the blue receptor as the researcher you quoted states, then does not the trout "perceive" the UV as mainly blue? It seems to me that the conclusion follows from the inference, and the inference was from the researcher you quoted. If not why not?

Why does not the conclusion that the fish perceive blue as the main color of UV stimulus follow from "MAIN SENSORS OF THE UV LIGHT WILL NOW BE THE BLUE CONES"?

We seem to be plowing the same ground but at cross purposes to each other. I do not understand where "sight" and "perception" deviate in this case. Are you saying that UV light is not seen mainly as blue in adult trout? If that is so, how can the statement of Inigo Flamarique be true?

Addendum:

After reading some more, I find references that instead of receding, the UV receptors turn into blue receptors.

Cheng, C. L. & Flamarique, I. N. (2007). Chromatic organization of cone photoreceptors in the retina of rainbow trout: single cones irreversibly switch from UV (SWS1) to blue (SWS2) light sensitive opsin during natural development. Journal of Experimental Biology, 210, 4123-4135.

Reed, is this what occurs and is the information I am lacking ? If so then the addition of blue receptors would increase the perception of blue.
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Last edited by silver creek; 11-25-2012 at 04:30 PM.
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  #30 (permalink)  
Old 11-25-2012, 04:12 PM
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Default Re: Does blue excite the trout?

For me, Blue is the least color I use. Rather use purple then blue.
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