Hmm.I can't say with any certainty that metallic "colours" are triggers for fish. They may be in some instances. The following may be of interest in this regard.
With regard to good generic flies, a good generic fly will work most of the time in most places. This of course is heavily dependent on presentation as well as the fly itself.
Usually, the vast majority of fish feeding on some insect or other will take something similar which is behaving correctly. They are NOT generally anywhere near as selective as is often proposed. This is indeed precisely what makes good generic flies like hare's ear nymphs, pheasant tail nymphs, and similar flies so universally successful. Given the correct dressings, they can be presented in a number of lifelike and attractive ways to feeding fish, and practically any fish is likely to take them when they are correctly presented.
With regard to "triggers" I have some specific theories on this which run contrary to many other people's theories. They work for me. I corresponded with Gary LaFontaine, among many others, about this over a period of time, and although we did not always agree, we had some interesting discussions! :)
My specific core theory on this matter is basically quite simple. Many people go looking for "positive triggers", etc etc , in order to make their flies successful. ( Gary liked the "positive trigger theory" for a lot of things, and I agree to an extent, but basically only in terms of insect behaviour).
For most of my flies, I do exactly the opposite! I try to avoid any "negative triggers" ( for instance by concealing the hook). If the fish does not suspect anything, then it will take the fly confidently. Normally a fish will only suspect something if a fly looks or behaves incorrectly, and it does so instinctively, not consciously.
Here is an extract from an article I wrote a long time ago on some of this;
With regard to the cave fish, and their "loss" of sight, as mentioned in various posts, it is more likely that the development of more efficient mechanisms caused their sensory organs to evolve in some other way. They have not "lost" their eyes, they have replaced them with something more efficient for their environment, perhaps more sensitive lateral lines? The capacity which they previously used to see with, is still used to "see" with, but in a different manner. Also, I remember reading that these fish lose pigmentation control, or even pigmentation itself. Some becoming almost transparent. These phenomena must be linked, as pigmentation/protective colouration in fish is also a visually controlled survival trait, which is of course useless in the dark.
With regard to the sensory perceptions of fish, and what they "think" when targeting food. It seems reasonable to assume that the fish would be more likely to select the majority of its food instinctively, not consciously. This implies that it would be more likely to avoid negative stimuli, than to actively seek positive stimuli.
This also seems a reasonable working theory to explain why fish will sometimes take more or less anything, and at other times be more (
apparently) "selective". Regardless of any theories about their intelligence, capacity for learning and so on. These are for the most part imponderables, and therefore basically useless to an angler seeking to catch more fish.
Actually they are no more "selective", in terms of consciously seeking particular items, but their focus on a particular item, after some
conditioning to it, is such that negative stimuli have a greater effect. Or they simply ignore items outside their present target schemata, unless these things have other overriding stimuli which trigger a response. A fleeing wounded bait fish for instance, or even a nymph suddenly rising rapidly to the surface within easy range, may "trigger" a sudden "involuntary" predatory response to capture it. The "trigger" is "in the fish", not "in the fly", and the response in this case is to a great extent directly the result of how the fly behaves in the fishes vicinity. "Induced takes", Leisenring Lifts" and similar techniques operate on this principle.
Practically all manipulative techniques rely heavily on this principle, but good flies enhance them even more.
It should also be remembered that "lifelike" in some cases means "dead"!!! Drag is a negative stimulus for many fish!
Regarding the colour question. Some colours under certain circumstances obviously do have an effect on the fish. If they are actually taking some insect which glows orange under certain light conditions, then an insect which has the same shape and size, but no orange glow, is likely to be rejected. Not because the fish are "selecting" for it, but simply because it does not fit their present target pattern.
How the fish actually perceive the orange glow, is ( for anglers) basically immaterial, and at the present time un-knowable in any case, that they obviously can do so is not immaterial.
The Orange Quill which was originally mentioned, is indeed usually only effective under certain light conditions, and in a spinner fall. There are pictures in some book or other, taken from below under such conditions, and it is more or less impossible to see any difference between the naturals and the artificials. In this case at least, it seems the same applies to the fish, as they take the artificial just as readily as they take the natural under such circumstances.
Some flies work on different principles to others. In some cases, ( I believe the majority), the lack of negative stimuli is obviously more important than the presence of "positive" stimuli.
A case in point;
I wished to design a generic dry fly, easy to dress, and as effective as possible under a very wide range of circumstances.
My thoughts were primarily on the design of a no hackle dun. and I wanted to conceal the hook as well. I had tried various other designs, and for one reason or another they either did not work very well, or were too fragile, etc.
In my opinion many ( conventional) dry flies have always been taken as emergers, or trapped and crippled duns, and similar, and not the high floating duns many people seem to think. ( body on or in the film). ( This is often the case with many other flies anyway, as most do not float as high on their tails and hackles as people like to imagine! ) This gives you at least two shots at a specific hatch though, and precisely those stages most vulnerable to fish, which they are likely to concentrate on.
It certainly works exceedingly well as a generic pattern, when dressed with hare fur, in various sizes, but it is not a "one fly solution" by any means.
I am happy that the basic design works, is easy to dress, is very robust, and up to now has proven very effective for a range of things, but I can not tell you precisely that it imitates some particular stage specifically.
One can alter some aspects to make it do certain things. If one uses a quill or thread body for instance, the abdomen sinks, ( on a degreased tippet),and one has a classic emerger. Normally I would however prefer a klinkhammer or similar for this.
If one uses a well defined guard hair bunch ( dubbed and brushed out) for the thorax, then it sits like a classic dun, except for the "wing forward" attitude, but the fish don't seem to care much about that. It also seems to offer a better footprint than standard hackled flies. At least I have had very few refusals to it, when casting to rising fish. Very many fewer than with "standard" hackled dry flies.
Varying the wing shape ( and bulk) also affects how the fly behaves. If one fans the fibres more in "Comparadun" style, and uses either a very lightly dubbed or smooth abdomen, the fly sits like a dun with a slightly sunk bum! The wings are then more upright,and the fibres at the bottom sides work like "outriggers" to stabilise the fly.
There is obviously still potential for a lot of experimentation here. One can make the basic design do a lot of things, but I have only tried a few up to now, so I can?t really give you any precise information.
My original objectives were to remove negative triggers. Where I think the objective is largely resolved, I have simply put "OK" after it.I can explain why as well if you wish. To whit;
Conceal the hook. OK
Either severely reduce, or remove the hackle entirely. No fly has a hundred legs sticking out of its head, and this has always bugged me. OK
Conceal or make the tippet less conspicuous. OK
Secondary ( but still important!) objectives were;
Must float well. OK
Robust. OK
Easy to dress. OK
Easy to dry!!!! OK
Must not twist leaders. OK
The final objectives were.
Be a good imitation ( Of?) OK but unexplained!
Be adaptable to suit various stages and circumstances. Not yet resolved.
The last two objectives are only partially resolved. The fly catches fish well, but I don't really know EXACTLY why it does so in any given circumstance. Although I can say that about many other flies as well. All I know is that I strove to avoid negative triggers, and it worked! :)
cont'd
