He's a question. Just how much colour does a trout see at depth?... lets presume we are talking clear water. According to Richard Walker, he says the spectrum ends at 6ft in particular 'red'.... I have invented many patterns where colour has been important on deep fished patterns albeit nymphs/buzzers and lures... I do understand that the certain original colour can be seen 'deep' in a different hue? maybe thats where it becomes important... discuss....

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Before you cast the fly, make sure you can handle the fish! Vuoi imbrogliare? Poi Non competere! (If you want to cheat, then dont compete)

I'm more inclined to believe it has more to do with contrast than colour. A red and black fly on the surface becomes grey and black at depth so the fish picks up on the movement caused by the contrast between the two.

I came across these a few yeas ago, it might be helpful.

Phytoplankton Lab: Hydrologic Optics Primer

How Fish See and use UV rays to find bait fish

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Don't worry, be happy.
Sandy
Carried it in full, then carry it out empty.

I cannot speak for trout of course, but I remember when I was a lot younger how some colours seemed to behave at depth when I did a little scuber diving.

Red turned to black very quickly. Green stayed green for much longer. Everything seemed to turn to shades of blue.

Fluorescent colours were certainly seen and stood out at greater depth than non-fluorescent colours.

A useful book to read on this subject is "What Fish See" by Dr Colin Kageyama who is a qualified optometrist as well as being a very keen fly and lure angler.

Have a look at this................

Colour Vision in Trout

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Sean


>>>>>>>MEMBER OF THE S.S.F.D.<<<<<<<<<

after certain depth does colour not dissapear and turn into a monochrome scale greys/blacks etc....

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WHEN YOU LEAVE THE RIVER, TAKE NOTHING, AND LEAVE ONLY FOOTPRINT'S!!!

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At about 10-15m red will appear to be dark green. I know this from the many times I have cut myself whilst wreck diving. Its quite good fun squeezing green blood out your finger

Interesting reading eh? Says this:

Consider a red object in the water. At a depth of more than 12 feet no long wavelengths remain so it can reflect no light. Therefore even at close quarters it appears black. Near the surface the full sun spectrum reaches it and it reflects the red portion. This is visible at close range and as already deduced is probably a brighter colour to a trout than it is to us but as distance increases the reflected light is absorbed and at some distance approaching 12 feet the object is no longer visible - only the blue scattered light remains. If the object were white, i.e. had the property of reflecting all incident wavelengths, then it would remain visible at longer distances.

Bang goes the theory of my Red Eric buzzer and Doodlebug which only seem to work fished deep....

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Before you cast the fly, make sure you can handle the fish! Vuoi imbrogliare? Poi Non competere! (If you want to cheat, then dont compete)

I read up a bit on this a while ago and was very interested in what came out. The effect of peaty water etc... also has a dramatic effect on what wavelengths of light penetrate and therefore which colours appear as they do above the surface.

I personally tie flies intended to be fished deep with fluorescent triggers (especially lures) if they are not imitative as I think i am right in saying that fluorescence is the absorbance of a non visible wavelength (UV) and the transmission of a visible wavelength (maybe well wrong on this though). As UV penetrates deeper than any visible light the fly should then appear the colour it was intended.

However I do not do this on "natural" flies such as buzzers as a red natural 20ft down will appear black and one that appeared red would look ou of place.

Just my thoughts and i am ready to stand corrected.

Dan

UV disappears in the surface layers of water matey.
It is all to do with absorption and scattering of light. It is the colour of the water which determines which colours "disappear" first.
The sky is blue because all the other colours of the spectrum are absorbed and scattered before the blue. Similarly the sea can be green or blue or even brown in estuarine water.

---------- Post added at 12:27 PM ---------- Previous post was at 12:21 PM ----------

Of course you also have to convolve the absorption of the colours of the water with the spectral sensitivity of the fishes eye!

It was my understanding that the longer wavelengths (red orange yellow) were the first to go (red is 700nm if i remember my A level physics) and the lower wavelengths have a much higher penetration which is why deep oceans appear blue (blue is about 400nm i think). Following this logic UV should penetrate even further as it has an even lower wavelength than blue light 200-400nm i think. Unless there is some lower limit to the wavelengths of light which will penetrate water below which all the light scatters?

Dan

Edit: just found a useful paper that explains the phenomenon and it suggests that UVb radiation should penetrate only as well as red-yellow across its wavelength range in pure water and even worse in coloured or algal water where particulates greatly increase the absorption of UV.

http://ies.jrc.ec.europa.eu/uploads/...R_22217_EN.pdf

Looks like i have to rethink my deepwater lures damn!!!!