I'll take your presentations in order:
Well, only one "scientist" has stated in recent years that trout permanently lose their UV cones; the rest, including the recognized authority on the subject - Dr. Craig Hawryshyn state that the dorsal temporal region of the retina retains UV cones. See "Beaudet et al 1997 ; Deutschlander et al 2001; Allison et al 2006; Raine and Hawryshyn 2009; Raine et al in press. Note that at smoltification, the dorsotemporal field is retained and is functional. This is a observation that runs through all of our publications."The newest studies indicate that adult trout can not perceive UV light. Also, even assuming these are wrong and trout can in fact perceive UV light ( although it would be better to call it "radiation", in my opinion, I think "light" is a rather unfortunate term in this respect), you need special equipment to detect UV radiation and you would have to test the natural flies you want to imitate under varying conditions of UV light, AND match what you found using artificials under the same circumstances. Even if possible this is difficult.
As for the single holdout, Dr. Inigo Flamarique, he stated in an email to me, after re-affirming his belief that the cones sensitive optimally to UV light are lost in smoltification:
[Emphasis his]DOES THIS MEAN THAT THE TROUT THAT IS A SMOLT AND OLDER DOES NOT SEE UV LIGHT? NO, EVERY VISUAL PIGMENT ABSORBS IN THE UV REGION OF THE SPECTRUM BUT ITS PEAK ABSORBANCE MAY NOT BE IN THE UV REGION OF THE SPECTRUM (SEE TYPICAL CURVES IN CHENG ET AL. 2006. J COMP NEUROL). BECAUSE THE LENS OF SALMONID FISHES TRANSMITS WAVELENGTHS IN THE RANGE 320-800 NM, ANY WAVELENGTH IN THE UV (320-400 NM) WILL BE SENSED BY THE BLUE, GREEN AND RED VISUAL PIGMENTS, ALBEIT THE SENSITIVITY OF THESE PIGMENTS TO UV PHOTONS WILL BE LESS THAN THAT OF A UV VISUAL PIGMENT. SO THE OVERALL SENSITIVITY OF THE SMOLT TO UV LIGHT (<400 NM) DECREASES DRAMATICALLY BUT IT DOES NOT MEAN THAT THE ANIMAL CANNOT SEE UV LIGHT. THE 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).
You said:
So, that is what I did. I took what may have been the first UV reflectance photos of some mayfly species (and caddis, terrestrials, etc.) and took UV reflectance photos of the "Best dry fly patterns of 1984" as determined by Dave Whitlock. It was remarkable, and I was quick to remark upon it, that the artificials had the appropriate UV reflectance.you need special equipment to detect UV radiation and you would have to test the natural flies you want to imitate under varying conditions of UV light, AND match what you found using artificials under the same circumstances. Even if possible this is difficult.
You said:
Ah, not so. Actually, the 320-400nm wavelengths (UVA) diminish more slowly, percentage-wise, than visible light at dusk. As well, both moonlight and starlight provide UV. Since UV wavelengths penetrate water deeper than visible light, they create the ambient light underwater against which objects lower in UV reflectivity stand out.Also, in low light conditions, when fish primarily feed, there is very little UV light at all, if any. At such times you can not even measure any appreciable effects on various things, much less flies. So even assuming that the fish can see UV light, they can't see it if it is not there. Again a dead end.
Think about this - most mayflies perform their mating at night. Since this is their one and only chance for a "good time" it behooves them to find a mate of the proper species and sex. Most insects have UV vision, and mayflies have species and sex specific UV markings; just perfect for those lanquid moonlit nights above the river. : )
So, if mayflies have these UV markings, and trout can see in the UV, won't trout choose those flies that conform to the UV markings they expect?
My book, which is on Amazon, contains all those arguments, backed by proper citations. I'm not plugging it, Mike, but OTOH, I don't want to write it all again in this post.
Best regards,
Reed
But as you quite rightly say, "'splainin' takes a lot of time" and effort, and in that regard one is often bound to assume certain things, one of which is that parameters are either known or agreed upon. This is extremely difficult I know.