To UV/Fluoro or not to UV/Fluoro?

[MCC]

Those extracts aren't all a hundred percent accurate but you get the general idea.

When UV is considered from a Trout's perspective it gets even more interesting......

Here is an extract from an e-mail discussion from a couple months ago.


Just copy and paste notes with a conclusion but this is pretty interesting stuff.

UV reflective materials do not react under a UV light. This means that particles of light in the UV spectrum that hit the material will be reflected and become more visible to predators that can see UV light. If no light is present, then there is no UV light either. If there is no UV light, then there is no UV reflection from the materials.




So, Trout can see UV being reflected off materials.

WOOOOPWOOOOOP!!!!!!!!!

But........



If you have spent any time scuba diving, you have probably noticed that some colours become less vibrant and eventually appear grey the deeper you go. This is because visible light can only penetrate so far in any direction, depending on the clarity of the water. This chart shows the estimated distance that visible and ultraviolet light can penetrate.


UV also penetrates deeper into water than any other colour which makes UV reflective materials more visible at greater depths.

WOOOPWOOOOOP!!!!!!!!!

So we can fish deeper and still be seen.

Cool

But........

Most research indicates that salmonids have cones to detect UV light when small, but as the fish grow these cones gradually disappear. Their diet in their early period of life consists of zooplankton and other small creatures that reflect UV light, but as the fish get larger they can no longer filter such food with their gillrakers. This is given as the main reason why no UV receptors are found in fish above 2 years old.

Research like this.....

Microspectrophotometric analysis of the visual receptors of "yearling" brown trout, Salmo trutta, revealed three cone types, double cones with visual pigments absorbing maximally at about 600 and 535 nm, and two types of single cone with lambda max at about 440 and 355 nm. Two-year-old fish did not possess the u.v. cone cells. Microscopical analysis of the cone mosaic in "yearling" trout showed a square pattern of double cones with a central single cone and corner single cones, but in two-year-old trout the corner cones were absent. It is concluded that u.v. sensitivity is derived from the corner cones of the mosaic, and that it is only present in young trout.

What does this add to the mix you may ask???

Well, a UV hotspot (#18) is only a hotspot to young fish that will be more likely to react to a trigger or any aggressive part of a fly.

The older, wiser and more selective fish will not see the “hotspot” and will therefore not be put off by it.




Trout Vision.jpgColour Depth.jpg

[dlampert]

Out of interest MC, are you now tying all of your nymphs with hotspots? In a dual nymph rig would you fish both nymphs with hotspots or an attractor and a more natural nymph without a hotspot?

[Andre]

Very interesting...I wonder how deep one can go with a fly before it loses any effect or colour in the water. Assuming clear water at a place like Lakensvlei for instance.

[MCC]

Daryll

I'm not sure whether the articles I copied also mentions that the same fading effect (at depth) also happens horizontally. Think about it..... if a fish sees a fly at a distance of say twenty feet it appears black and as it moves closer to investigate it starts lighting up. This could explain a lot of short takes....

Anyway, I really do like triggers in flies and a hotspot is just one example. Contrast in colour or ribbing also acts as a trigger or form of hotspot.

In discoloured water I will often fish two very different styles of fly and often both will have a hotspot of sorts but in clear water I will only use one attractor and combine it with something much smaller and more natural.

[dlampert]

Thanks, that is what I have been doing as well in clear water. As the season progresses I find the hotspots/triggers need to be more subtle, early season you can hit them with all the bells and whistles :-)

[Scythe]

At the end of the day all you need to remember is that you should never go shopping for fly tying materials without a UV torch and not all bright colours are fluo.

That's a valuable bit of info right there.

Lekker posts MCC, lots of good information.

[Andre]

Daryll, do you think that is because the fish become more educated and spooky due to fishing pressure as the season progresses, or would you think it is because of the water warming up, and the conditions changing as the summer sets in? I never fish hot spot flies on the Cape streams. Perhaps should try them.

Thanks, that is what I have been doing as well in clear water. As the season progresses I find the hotspots/triggers need to be more subtle, early season you can hit them with all the bells and whistles :-)

[dlampert]

Daryll, do you think that is because the fish become more educated and spooky due to fishing pressure as the season progresses, or would you think it is because of the water warming up, and the conditions changing as the summer sets in? I never fish hot spot flies on the Cape streams. Perhaps should try them.

Andre, my personal view is that fish get used to flies/hotspots/triggers. Several years ago I was one of the first people to start fishing orange tungsten beads on the rivers. At that stage you could catch fish almost at will on orange tungsten bead flies and they would outfish gold and other colours by a large margin. As more people started fishing them they became less effective. They now still work well early season or in high flows but from Dec/Jan I have found that they often put fish off (on our pressured rivers - non-cps rivers with less pressure they often still work well). I now tend to fish flies with much smaller hotspots/triggers but sometimes even these will put fish down. For example one of the nymphs I normally fish I tie with both CDL tails and black crystal flash tails. Later in the season the crystal flash tailed nymph will often be rejected - replace it with the CDL version and the fish eat it - the only difference in the tying of the fly is the tail. Considering that rainbows only live for 4 to 5 years are the fish teaching each other? :-) I approach fly tying as an arms race against the fish, you need to constantly evolve your patterns to stay ahead - that's my excuse anyway.

[Korrie]

I have posted this before, when Jiri Klima was here, and the previous day, he caught a fish on a Czech nymph.
The next day, he fished the same spot with the same fly and no fish, no take.
Sean Mills came around, and fished a diffferent fly and caught the fish in the exact same spot as Jiri's from the previous day.
And Jiri replied "the fish remembered the fly" Meaning his fly from the previous day.

So, if all the flies have a orange bead, or a hot spot of CdL tails that fish will remember this fly looking like that or having a special feature, caused him some major discomfort, he sure as hell will not take that fly again.
With all the Hotspots, fluoro and UV floating around in fly tying, I wondered how a good old fashioned wet fly, with a piece of silk thread, wrapped around the shank, one turn of hackle, and a tiny bit of dubbing, all in dull, drab colors, have managed to catch so many fish over so many years?

[Korrie]

Or Maybe it is a mind over matter.
If you don't mind about the UV and the Fluoro it does not matter, because you will still catch fish.