FLYMPH FORUM

Question: If the colors of most fly diminishes between 3-5', how deep does UV penetrate the water water and stay vital?

My understanding of fluorescent colors is that they contain brighteners which reflect all light to a higher degree. While they glow in UV blight they also reflect a larger amount of regular light as well. If this makes them appear more visible as they go deeper would take some experimentation, which may already be out there in cyberspace somewhere.

Many anglers believe in and use "hot spots" on their flies claiming they work better. I believe these spots are especially used on Czech. nymphs. http://www.flyfishohio.com/hot_spot_nymphs.htm

Mark

Most scientific research indicates that only juvenile trout have the ability to see in the ultra violet range, and lose this ability as they grow. No UV receptors have been found in fish over two years old. Assuming this is true, then the use of ultra violet reactive materials on flies is pointless anyway.

The "glow" which humans see on some materials under UV is fluorescence which is a result of UV light, and not UV light itself.

Some migratory fish achieve some temporary UV sensitivity when migrating, but as they do not feed while doing so, the sensitivity is not prey oriented.

UV-light is a whole range, and has a whole range of uses and effects. How far UV light penetrates water depends on the intensity of the light and the clarity of the water. It has been measured at levels strong enough to cause severe sunburn in divers at a depth of nine feet in the ocean with the sun overhead.

Some general info; http://en.wikipedia.org/wiki/Ultraviolet

TL
MC

The main difficulty here is deciding whether the UV induced fluorescence makes some things more attractive to trout. In most cases I think not. Trout main feeding times are at periods of extremely low UV light conditions, and fish also actively avoid bright sunlight. Some flies seem to work better with various additions of fluorescent materials, but there is no scientific basis for this.

TL
MC

Soft-hackle wrote:My understanding of fluorescent colors is that they contain brighteners which reflect all light to a higher degree. While they glow in UV blight they also reflect a larger amount of regular light as well. If this makes them appear more visible as they go deeper would take some experimentation, which may already be out there in cyberspace somewhere.

Many anglers believe in and use "hot spots" on their flies claiming they work better. I believe these spots are especially used on Czech. nymphs. http://www.flyfishohio.com/hot_spot_nymphs.htm

Mark

That is impossible, no object can reflect more light than it receives. Fluorescence is the result of some substances actively emitting light. This is what makes them glow when subjected to ultra violet radiation. The excitation of the material causes them to emit visible ( to humans) light. Presumably this is also visible to fish. Whether this is of much use on flies is moot, for a variety of reasons. It might make them better under some circumstances. Unfortunately there is no definitive way to know.

There are lots of articles about this on the web and elsewhere, but nobody has yet proven these things to work.

TL
MC

Doubtless trial and error is the only real option in this case Donald. Some people are absolutely convinced it works, but none have as yet been able to prove it. Believing something is not proof that it works!

Although it is well documented that birds and flowers use "colours" in the UV spectrum for various purposes none of these are prey oriented.

Also, natural selection would indicate that something which makes prey more attractive to a predator would be actively selected AGAINST!

Lighting up in such a manner, basically advertising "Here I am all bright and juicy, come and eat me" would go against all known prey behavioural models. That is not to say that using various bright colours might not be very effective at times, we all know this to be the case, but it is not normal prey behaviour. Possibly the main reason it is successful. Abnormal behaviour or appearance on the part of prey animals, or even other animals that look or behave "abnormally", will invariably result in them being targeted, although not necessarily as food.

A recent article demonstrating an example of this,

http://www.dailymail.co.uk/news/article ... ction.html

the same thing happens to albino birds, and other "abnormal" animals.

UV light is reflected by various things, notably shiny metals. This is not the same thing as fluorescence which causes the objects concerned to absorb ultra violet radiation and emit visible light. These things are often confused in discussions on this related to fish and flies.

Also, before such materials can fluoresce there has to be a source of UV light which will make them do so. As previously stated, at low light levels there is either very little or no UV radiation present, and so the materials will not fluoresce. Even at normal daylight levels, it is not generally possible for human eyes to discern the fluorescence produced, it is simply "drowned out" by normal visible light. There is no reason to assume that fish can see that any better than humans can, and although if they do it might make such materials more attractive to them, that would merely be an assumption.

Unfortunately, many people when writing on such things make various assumptions, and then go on to build whole theoretical edifices based on such assumptions. The whole of which is of course completely invalid if the assumption is false.

TL
MC

daringduffer wrote: What colour would you dye that dubbing material...?
dd
[/b]

I would not dye it at all, I would use it as it is or for blending. ( Although I might dye the tail). One of the major characteristics of hair from albinos like this is the lack of pigment, so although they look "white", they are actually very translucent. This can be of major advantage in some blends. A small amount of translucent ( Clear, not white), Antron can also improve some dubbing mixtures considerably. This is obviously because of the way they transmit light.

TL
MC