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AfishinadoMarch 30th, 2013, 7:29 am
SE PA

Posts: 73
Yes, Goddard believes he has proved that when a fish drifts back with the floating object held at a certain angle, it is doing just that. This behavior is most noted in bright light when a critter in the middle of the window would be a black silhouette. Un-pressured fish will hold in the current and as the object hits the Snell, that brief look will trigger the response to take or reject. An educated (pressured) trout will do the "drift back" for a longer inspection in the hope of avoiding "sore mouth." :) The really smart ones will even turn to follow a little to verify further by changing the background or backlight. Those are the really tough bastards! :)LOL Pretty compelling evidence...


We've all seen educated trout drift back to inspect our fly. Many times I can attribute this behavior to the fish watching for drag in the drift of the fly. As soon as even a little drag is detected the fish turns away on goes back to it's original holding position. I've caught many really tough fish just by changing my tippet length or size and/or mending or introducing slack into my cast, or even changing my casting position to one more favorable to achieve a drag-free drift.
OvermywaderMarch 30th, 2013, 8:56 am
Posts: 31I have a theory, just a theory, that the reason trout drift backward inclined at a 70 degree angle observing the fly, is in order to use polarized light to see the surface fly clearly in fast broken water.

I recall an instance in which I observed two rainbow trout drifting ahead of my fly, preceding it by about 18", at a depth of 10", and tilted at a 70 degree angle. The sun was very bright and the water was broken - making observation based solely on Snell's circle of little use.

Why did they drift inclined at such a steep angle? Could it have offered some benefit visually? At that angle, the light reflected from the fly would have entered their retina in the dorsal-temporal region, the same area that retains UV corner cones. Studies of trout have shown that they can respond to polarized light at 0 degrees and 180 degrees in the UV spectrum.
" UV ON-response units showed polarization sensitivity for vertically (0° and 180°) polarized stimuli, while ON-response units of the short, middle and long cone mechanisms were not polarization sensitive." from A cellular basis for polarized-light vision in rainbow trout
D. J. Coughlin, C. W. Hawryshyn

"In the retina of salmonids and goldfish, the ultraviolet cone mechanism responds maximally to vertically polarized light, and the green and red cone mechanisms (which make up the two dissimilar pairs of the double cone) respond maximally to horizontally polarized light (Hawryshyn and McFarland, 1987; Parkyn and Hawryhsyn, 1993). Single-unit recordings from biphasic cells in the torus semicircularis demonstrate that the inputs from these two orthogonally sensitive mechanisms interact antagonistically, i.e. input from the ultraviolet mechanism produces an ON response, and input from the green and red mechanisms gives an OFF response (Coughlin and Hawryshyn, 1995)." from The role of extraocular photoreceptors in newt magnetic compass orientation: parallels between light-dependent magnetoreception and polarized light detection in vertebrates
John B. Phillips*, Mark E. Deutschlander‡, Michael J. Freake and S. Chris Borland

So, does polarized light provide better detail in broken water than un-polarized light? (It does for the fisherman, which is why he wears polarized sunglasses.)

What do you think?
Regards,
Reed

Overmywaders
GutcutterMarch 30th, 2013, 10:53 am
Pennsylvania

Posts: 470
Un-pressured fish will hold in the current and as the object hits the Snell, that brief look will trigger the response to take or reject.

An educated (pressured) trout will do the "drift back" for a longer inspection in the hope of avoiding "sore mouth."


The really smart ones will even turn to follow a little to verify further by changing the background or backlight.


I can attribute this behavior to the fish watching for drag in the drift of the fly


I wonder if the “discriminating” trout (educated) keeps the insect within Snell’s Circle as a means to study and verify?


Are we attempting to anthropomorphize our quarry?

Overmywader has done an excellent job of discussing and describing what a trout sees. Not what a trout thinks.
Do trout think?

I would bet everyone here has had a similar experience to what Afishionado has described.
Sometimes changing the casting angle and adding length to our leaders provides a better drag free drift.
So does the imitation's "behavior" trigger a take?

And how many times have we changed to a different stage imitation and were rewarded with a take on the first drift?
Does changing the fly's "attitude" -on, in or beneath the surface- trigger the take?

What do you think is most important?

-Drift (drag free or active)
-Depth (on, in or below)
-Size
-Pattern style
-Color

Where does UV profile fit in?

Thoughts?


All men who fish may in turn be divided into two parts: those who fish for trout and those who don't. Trout fishermen are a race apart: they are a dedicated crew- indolent, improvident, and quietly mad.

-Robert Traver, Trout Madness
TroutnutMarch 30th, 2013, 4:42 pm
Administrator
Bellevue, WA

Posts: 2567
I have a theory, just a theory, that the reason trout drift backward inclined at a 70 degree angle observing the fly, is in order to use polarized light to see the surface fly clearly in fast broken water.


That whole idea sounds pretty interesting. I wonder if there's a way to set up a physical simulation of the fish visual system (as it pertains to that one experiment) with cameras and see how it works. It should be possible to figure out the problem mathematically, too, but that would take a lot of work.

Are we attempting to anthropomorphize our quarry?

Overmywader has done an excellent job of discussing and describing what a trout sees. Not what a trout thinks.
Do trout think?


They absolutely do. Their thinking is very different from ours, of course, and they don't have many of the complex, human-like thoughts some would assign to them. But "thinking" in some form is critical to any animal with a brain.

One of the things we know about the brain, even ours, is that it can only process a tiny portion of the information received from the eyes. That's why it's hard to find a needle in a haystack or Waldo in a "Where's Waldo" book. Yet it's easy to find a strobe light in either one, and it's easy to notice many important everyday things like stop signs. One of the functions of the brain (visual attention) is to determine which visual information gets prioritized, which includes tuning the visual system to be more sensitive to some types of colors, shapes, patterns, and motions than others. There's a constant, complex two-way flow of information, with the eyes telling the brain what's out there, and the brain telling the eyes how to prioritize it.

I think practically any characteristic of prey can potentially trigger a take, but some are much more likely than others. Reed pointed me to a nice chapter on perception in his book that outlines the various ways a mayfly might look to a trout, and suggests why flies that look unrealistic (to us) can look pretty good to a trout that sees mayflies in all different sorts of optical situations and physical conditions (classic mayfly floating pose, wings broken, laying flat with one wing stuck on the water, etc). If you have his book, check that one out.

The bottom line is that fish do think, and one of the things they probably have to think about the most is deciding what is or isn't food. One of my Ph.D. chapters ties into this -- I'm studying how fish react to all the other non-food junk floating down the river, besides our flies. If you've ever set a drift net to sample drifting insects, you've probably noticed that you mostly get little bits of leaves and twigs and such in your net, not bugs. Your net's catching the same stuff the fish are seeing, and it's amazing how much of that stuff there is, even in clear water. The fish have only a second or two to make a decision as these items drift by them, moving quickly and rotating at various angles. Under those circumstances, do you think you could reliably tell a cased caddis larva from a twig?

I think the difficulty of this job, of figuring out what is and isn't food under such tricky conditions, explains a lot more about trout behavior than most people (including most scientists) appreciate. That's why I'm studying it.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
EntomanMarch 30th, 2013, 4:59 pm
Northern CA & ID

Posts: 2604
We've all seen educated trout drift back to inspect our fly. Many times I can attribute this behavior to the fish watching for drag in the drift of the fly. As soon as even a little drag is detected the fish turns away on goes back to it's original holding position. I've caught many really tough fish just by changing my tippet length or size and/or mending or introducing slack into my cast, or even changing my casting position to one more favorable to achieve a drag-free drift.

I think we can all agree that drag at the wrong time will usually lead to rejection. I can't say they are looking for it though, just that they react when it occurs (usually negatively). If no drag occurs, they will often still continue to inspect and either accept or reject based on other criteria.

Are we attempting to anthropomorphize our quarry?

Yes, for the last five hundred years or so, but as a literary device in FF literature.

Do trout think?

Without getting too deep into the weeds on defining thinking, No. Again, complex stimulus responses are attributed to cognition as literary device.

What do you think is most important?

-Drift (drag free or active)
-Depth (on, in or below)
-Size
-Pattern style
-Color

I would say the top three collectively. The latter two are also significant in many circumstances. IMO - trying to put them in a strict hierarchy of importance is an old FF canard. It's like trying to decide what's most important to get you where you're going: the car body, the chassis or the motor.

Where does UV profile fit in?

Wished I knew...:)
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
EntomanMarch 30th, 2013, 5:08 pm
Northern CA & ID

Posts: 2604
Jason - I see we were writing posts at the same time. Just wanted to follow up by saying we don't disagree. The apparent dichotomy is just from working with a different definition of thinking/cognition. Mine was based on the common historical use of the words that was synonymous with sentient reasoning in order to address anthropomorphism. The flip side - do humans ever think like trout? Yes, when we react without thinking.... Seems like this kind of behavior in humans is fairly common...:)
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
OvermywaderMarch 30th, 2013, 6:24 pm
Posts: 31As A.J. McClane (the finest fishing writer of all time) said of trout fishermen (IIRC) "We pride ourselves on outwitting a creature with a brain the size of a pea... which is not sufficiently evolved to burp."

We can be proud, not in out-thinking a fish, but in deceiving a prey that has an elaborate sensory system tuned at all times to flight. In many ways fly fishing for wary fish is much like defusing a bomb. The likelihood of explosion is greater than the likelihood of success; someone will always tell you to cut the green wire; and each day (astream) is never long enough (even though the internal timer stops at 1 second the moment you see the first rise).

Regards,
Reed

Overmywaders
TroutnutMarch 30th, 2013, 6:58 pm
Administrator
Bellevue, WA

Posts: 2567
Just wanted to follow up by saying we don't disagree. The apparent dichotomy is just from working with a different definition of thinking/cognition. Mine was based on the common historical use of the words that was synonymous with sentient reasoning in order to address anthropomorphism. The flip side - do humans ever think like trout?


That's a good point. When you notice a stop sign while you're driving, the brain functions of visual attention and pattern recognition you perform aren't necessarily any more advanced than those trout use to detect prey. Same goes for sensing when you're hungry, and a whole bunch of other basic biological functions we have in common with other animals and that our brains perform without any of the conscious, language-based mental reasoning that sets us apart from most if not all other animals. These brain functions are all forms of thinking or cognition. (In fact, I have a book on my shelf titled "Fish Cognition.") Trout surely don't think sophisticated thoughts, but they do think.

As A.J. McClane (the finest fishing writer of all time) said of trout fishermen (IIRC) "We pride ourselves on outwitting a creature with a brain the size of a pea... which is not sufficiently evolved to burp."

We can be proud, not in out-thinking a fish, but in deceiving a prey that has an elaborate sensory system tuned at all times to flight. In many ways fly fishing for wary fish is much like defusing a bomb. The likelihood of explosion is greater than the likelihood of success; someone will always tell you to cut the green wire; and each day (astream) is never long enough (even though the internal timer stops at 1 second the moment you see the first rise).


That's a great quote and a great point, Reed. I've often said that we're not really matching wits against a fish -- we're solving a puzzle created by millions of years of evolution. The puzzle is embodied in a fish that evolved to be extraordinarily good at two things: sensing danger, and identifying food. Trout can be an especially good puzzle because they evolved in an environment that strongly favored the development of very specific prey search images under certain conditions. We can be proud of solving the hardest versions of that puzzle (catching the most selective fish), just like we can be proud of solving a Rubik's cube or something -- we aren't outwitting the object itself, but we're still meeting a worthy challenge.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
EntomanMarch 30th, 2013, 8:25 pm
Northern CA & ID

Posts: 2604
So, does polarized light provide better detail in broken water than un-polarized light? (It does for the fisherman, which is why he wears polarized sunglasses.)

What do you think?

Interesting theory, Reed. I guess the questions I have are:
a. What acts as the polarizer? If it's refraction, wouldn't the location of the object in the mirror (and how the fish holds it there) be the important factor? How effective a polarizer can refraction be with a heavily disturbed surface?
b. What difference does pitch make to perception (other than maximizing binocular ability)? To me it seems a change in pitch by the trout is the same as rotating a picture in front of a human. How are different performance aspects of various portions of the eye (fish or human) affected by this?
c. How about roll? Seems like more impact on perception would be due to this aspect of fish posture.

I recall an instance in which I observed two rainbow trout drifting ahead of my fly, preceding it by about 18", at a depth of 10", and tilted at a 70 degree angle. The sun was very bright and the water was broken - making observation based solely on Snell's circle of little use.

Assuming the accuracy of your measurements, the fish were using the mirror a little ways out instead of the window, which is common fast water behavior. The window distorts images to the degree of its disturbed surface. In heavily disturbed windows as exist in fast water the fish is making it's mind up based upon what it sees of the critter indenting or poking through the mirror and doesn't depend on the window too much. In fact, the window only confuses things and may allow the critter to be "lost in the shuffle." This explains their reduced or even lack of selectivity (at least to silhouette and color above the surface) and our ability to approach them much closer. As for the fishes posture, I believe the angle of pitch had more to do with hydrodynamic efficiency than viewing from a different angle. Drifting back while maintaining a horizontal posture would require much more difficulty and energy to achieve, hold, and return to the original location.

I understand the following about fish posture in relation to the window and mirror:
Depth - controls the size of the window; the shallower the smaller
Yaw - moves the location of the window in its direction
Pitch - makes the window larger or smaller depending on direction
Roll - effects the window or mirror only as it relates to monocular or binocular perception with peripheral influences (assuming trout even have any) and how the brain interprets/sorts the data; no change to its size or location.
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
OvermywaderMarch 30th, 2013, 9:48 pm
Posts: 31One point I would like to make about the retina of vertebrates (fish and humans included) -- the retina is part of the brain. In fact, "The retina is actually an extension of the brain, formed embryonically from neural tissue and connected to the brain proper by the optic nerve." (Encyclopedia Brittanica)

So, two weeks ago when I had a retinal branch artery occlusion (blood clot), I lost part of my brain (horrors!). And there was so little to begin with. :(
Regards,
Reed

Overmywaders
MartinlfMarch 31st, 2013, 1:49 am
Moderator
Palmyra PA

Posts: 3002
Reed, any thoughts on the comments below gleaned from various posts in this thread?

Most of us have had a trout hit a fluorescent strike indicator.

. . .

One of them (dubbings) was a dark maroon/purple. I tied a hares ear with that and had such good luck with it that for years my friends and I used nothing else when we fished nymphs. Even bought several more vials of just that color. Since I often was standing around a blacklight with my fishing jacket on it wasn't long til I noticed that the purple hares ear fluoresced. Always wondered if that is why the trout loved the thing.

. . .

But back to fluorescence and fish. A now defunct shop, Cold Spring Angler, used to sell fluorescent orange dubbing to tie an ant pattern. . . . I've had exceptional luck with these ants, sometimes when nothing else would work. Comments above lead me to doubt that any ants fluoresce, though I hope to do some checking in the future, so my guess is that the fish are responding to something odd that just "might" taste good, much the way they probably respond to fluorescent strike indicators. The same might go for Creno's purple hare's ear that fluoresced, and caught so many fish. Anyway, I'll continue to use such dubbings, and perhaps mix up a few others to try, checking with my black light. And let's not forget those hot spots on flies that have become so popular.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
OvermywaderMarch 31st, 2013, 9:54 am
Posts: 31Martin,

I didn't study fluorescence in insects. However, "Resilin is a structural protein in insects that fluoresces in ultraviolet (UV) light." Here is a pertinent study - UV-Excited Fluorescence on Riparian Insects except Hymenoptera Is Associated with Nitrogen Content

and also Native Fluorescence from Juvenile Stages of Common Food Storage Insects

So, it would appear that some measure of fluorescence in the blue range of wavelengths, excited by UV in the 350nm range, would be appropriate in almost all artificial flies. In moderation, of course.

Many fluorescent dyes used in fly tying are also highly UV reflective. I show photos in the book of many such.
Regards,
Reed

Overmywaders
MartinlfJune 11th, 2020, 1:06 pm
Moderator
Palmyra PA

Posts: 3002
Here's one thread on UV. I think there's another.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
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