Trout Vision - How Does a Trout catch a Fly?

ts47

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Silver,

I finally made it through the entire thread and many of the linked articles. Ard is correct... Very helpful information. Thank you for taking the time to share it.
 

ts47

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Silver,

You say that trout can see color. Also, In the first link you posted as a reference (http://www.flyfishingdevon.co.uk/how-does-a-trout-catch-a-fly02.shtml) about a quarter of the way down, which mentions the following;

"Therefore a trout has two cues that an approaching object may be edible:
1. body parts that break through the 'mirror'
2. wings appearing in the window
The next diagram shows what part of an insect are visible as it drift downstream towards a waiting trout.
At first only the legs are visible beneath the mirror ( ^ ^ in the diagram)
then as the insect gets nearer, the trout can see more and more of the fly's wings in its window ( 1 and 2 in the diagram below)
finally, when the insect reaches the edge of the trout's window, all of its body can be seen (3 in the diagram below)

Wings maintain the trout's attention on the fly as the fish rises towards the surface to intercept the fly."

Should we pay attention to the color of the post on say a parachute dry fly? Is it appropriate to assume that a colored post may not posses one of the cues a trout uses to determine if the fly is edible?

I would appreciate your thoughts on this. I also get that for some of us and for the small size of some of the flies we fish, our ability to see the fly may override the need to make that fly look more edible and that a smaller size may eliminate a trout's ability to see the post.

Thanks!
 

silver creek

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Silver,

You say that trout can see color. Also, In the first link you posted as a reference (How does a trout catch a fly?) about a quarter of the way down, which mentions the following;

"Therefore a trout has two cues that an approaching object may be edible:
1. body parts that break through the 'mirror'
2. wings appearing in the window
The next diagram shows what part of an insect are visible as it drift downstream towards a waiting trout.
At first only the legs are visible beneath the mirror ( ^ ^ in the diagram)
then as the insect gets nearer, the trout can see more and more of the fly's wings in its window ( 1 and 2 in the diagram below)
finally, when the insect reaches the edge of the trout's window, all of its body can be seen (3 in the diagram below)

Wings maintain the trout's attention on the fly as the fish rises towards the surface to intercept the fly."

Should we pay attention to the color of the post on say a parachute dry fly? Is it appropriate to assume that a colored post may not posses one of the cues a trout uses to determine if the fly is edible?

I would appreciate your thoughts on this. I also get that for some of us and for the small size of some of the flies we fish, our ability to see the fly may override the need to make that fly look more edible and that a smaller size may eliminate a trout's ability to see the post.

Thanks!
Clarke and Goddard explain how the parts of the fly that are seen in the window merge with the parts that are on the film as naturals and artificials approach and enter the window. To illustrate the concept, they use an up-wing pattern, specifically the mayfly because the mayfly wing being an up-wing is visible earlier in the window.

Before we can even discuss whether wings are important, we need to back up one step and decide whether shape is important. Since the wing profile of a mayfly is a major part of the shape of a mayfly, if shape is important, then the upright wings of a mayfly must be important. So for an adult pattern (subimago or imago), I believe that the wing is a necessary part of any imitation.

To address the specific question about the color of a post on a parachute fly, I believe that a parachute fly is NOT an imitation of an adult mayfly. The hackle being above the body means the body of a parachute is in the film. Also the post of a parachute is not the shape of a mayfly wing. I believe a parachute fly is a emerger imitation.

What the post represents is the emerging wing and body before the wing expands by being having their wings pumped full of liquid. The post represents the amorphous shape of the emerging body and folded wings.

I am not sure what the actual color of the emerger is at each mini stage of emergence. Emergence is a continuum and I would be surprised if the color of the emerging body/wing complex was the same color as the adult mayfly wing at all times.

So my practical way of dealing with this conundrum was to either use a white post, or a light grey post, or a post that is the about the color of the adult mayfly body. Quite frankly, I don't know that it has made much difference. Now I use a white post since it is easy to see but I have seen optic yellow and optic pink posts on some patterns. I don't use these colors myself.

As for the wing of an adult pattern, I do try to match those for color. When I do not have the color close to the natural, my strategy has been to use grey about the same shade as the natural wing. My theory here is that if the color is not right, at least the shade (the amount of grey reflected) is about the same as the amount of color reflected from the real insect wing.

When fishing small flies or flies that sit low in the water such as ant patterns, I use a bit of strike putty (Biostrike) that is place about 18" from the fly. That is my proxy for the fly. When it drags, I pick up and recast. When there is a rise that could be to my fly, I strike.

 

ts47

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Clarke and Goddard explain how the parts of the fly that are seen in the window merge with the parts that are on the film as naturals and artificials approach and enter the window. To illustrate the concept, they use an up-wing pattern, specifically the mayfly because the mayfly wing being an up-wing is visible earlier in the window.

Before we can even discuss whether wings are important, we need to back up one step and decide whether shape is important. Since the wing profile of a mayfly is a major part of the shape of a mayfly, if shape is important, then the upright wings of a mayfly must be important. So for an adult pattern (subimago or imago), I believe that the wing is a necessary part of any imitation.

To address the specific question about the color of a post on a parachute fly, I believe that a parachute fly is NOT an imitation of an adult mayfly. The hackle being above the body means the body of a parachute is in the film. Also the post of a parachute is not the shape of a mayfly wing. I believe a parachute fly is a emerger imitation.

What the post represents is the emerging wing and body before the wing expands by being having their wings pumped full of liquid. The post represents the amorphous shape of the emerging body and folded wings.

I am not sure what the actual color of the emerger is at each mini stage of emergence. Emergence is a continuum and I would be surprised if the color of the emerging body/wing complex was the same color as the adult mayfly wing at all times.

So my practical way of dealing with this conundrum was to either use a white post, or a light grey post, or a post that is the about the color of the adult mayfly body. Quite frankly, I don't know that it has made much difference. Now I use a white post since it is easy to see but I have seen optic yellow and optic pink posts on some patterns. I don't use these colors myself.

As for the wing of an adult pattern, I do try to match those for color. When I do not have the color close to the natural, my strategy has been to use grey about the same shade as the natural wing. My theory here is that if the color is not right, at least the shade (the amount of grey reflected) is about the same as the amount of color reflected from the real insect wing.

When fishing small flies or flies that sit low in the water such as ant patterns, I use a bit of strike putty (Biostrike) that is place about 18" from the fly. That is my proxy for the fly. When it drags, I pick up and recast. When there is a rise that could be to my fly, I strike.

Thanks Silver!

I don't want to overthink things. Reading through that article led me to believe that posts on parachute patterns ARE visible to trout and may be looked at as upright (or as you say emerging) wings. Prior to reading your post, I was under the impression they were NOT visible. Putting this together with your statements about color and matching the hatch led me to pose the question.
 

silver creek

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I do think the post on parachutes are visible in the window before the body enters the window. Trout have poor vision so I suppose they could take them as wings early on before the entire fly enters the window. I am convinced that when the fish sees the complete parachute fly lying in the film and the post above, it takes it for an emerger rather than as a completely emerged dun.
 

ts47

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I do think the post on parachutes are visible in the window before the body enters the window. Trout have poor vision so I suppose they could take them as wings early on before the entire fly enters the window. I am convinced that when the fish sees the complete parachute fly lying in the film and the post above, it takes it for an emerger rather than as a completely emerged dun.
Understood... a still somewhat immature adult yet to sprout full wings and fly away. Thank you for your insight Silver! :)
 

silver creek

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Your question about the rise, the trout's window, and what he trout sees brought to mind another phenomena that may be helpful to some of the newbies who are reading this thread. Although this post is not about how a trout catches a fly but rather why does a trout refuse a fly, I think it is a lesson that is important enough to present it here.

That lesson is what we can learn from a refusal.

As the fish rises up to meet the natural or an artificial fly, the fish can at any time decide to refuse the fly. As the fish rises, the view of the fly gets clearer and clearer. So when it takes or refuses the fly it has the best view of the fly that it will every have.

That is why we can get "late refusals". This is when the fish gets close enough to the fly to see micro-drag or something that does not match its search image. Beginners will say that the fish "missed" the fly. Fish make their living by not missing food. The fish have learned to keep the food item at a set location relative to the edge of the window so that when it opens its mouth, the fish will take the item in. Rarely does a fish miss the fly. More likely than a miss is that the fish simple closed its mouth and the momentum of the rise carries the fish up and it bumps the fly.

We have all been in situations where we have seen a trout come up partially for a dry fly and then go back down. This is the fish seeing something that looks like food and it rises until it gets close enough to see that it is not food so it returns to its holding position.

My rule for refusals is that the longer a fish examines the fly before refusing the closer the fly and presentation is to the natural. You will find yourself in situations when a fish will rise and refuse just at the last moment. You cast again and it will rise almost to the fly before it refuses. On the third cast it comes up just a bit before refusing. On the 4th cast, you get no reaction. It has learned that you fly is not the real thing.

So a late refusal is not a bad thing because:

(1) You know there is a fish in that location that will take a proper fly with a proper presentation.

(2) You know the fly and presentation were very close to the natural.

Drag is #1 cause for late refusals. So counter drag:

(1) Examine your casting position. Is there a better location from which to cast that would cross fewer currents, make of fewer mends, and longer drag free drifts.

(2) Lengthen your tippet. If you have 2 feet of 5 X, put on 3-4 feet of 5 x.

(3) If lengthening the tippet does not work go down in tippet diameter. Try 3-4 feet of 6X when 5X doesn't work.

If reducing drag does NOT work, then you must assume it is the fly.

(1) Put on an earlier stage of the pattern you have on. If you have on dun pattern, try an emerger. If you have an emerger, try a "floating" nymph in or just under the film.

(2) If an earlier stage down not work, then consider that you may have a masking hatch. Look for smaller flies on the water.

Look for a smaller insect hatch that may be masked by the larger insect that is more obvious to you. The smaller insect hatch is more prolific than the larger hatch and so the fish feed on the smaller insects because there are more of them on the water.

When fish are feeding selectively, I always look for a masking hatch before I decide to put on a fly. One clue is that there are many more rises than the number of larger insects would indicate. So if you see a lot of rises but only a few large insects on the water and in the air, look for a smaller hatch that the fish are feeding on.

All the suggestions above ASSUME that you are skilled enough to rise forms so when you are fishing with surface flies, you are NOT confusing a head and shoulder's rise for a dry fly rise.

Rise forms are an entirely separate subject. I describe rise forms on this thread:

http://www.theflyfishingforum.com/forums/general-discussion/323665-real-predicament.html#post568445

In summary:

The order in which you make changes depends on the situation. For example, if the fish are actually rising and refusing the fly, the most likely cause is micro drag. So if you get a refusal the most likely causes in the order of likelihood are:

A. Microdrag

B. Wrong stage of insect

C. A masking hatch.
 
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