Can Trout See Colour?

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Mr Notherone

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Most of what we know about fish vision comes from chemical and biological study of the fish eye. We don't know what image is "seen" and interpreted by the fish brain. The evidence suggests that fish can distinguish colour but it is probably not as we do. Water clarity, light and depth are bound to be factors.

As anglers most of us would agree that we have direct experience of fish responding differently to different colours. Maybe we over exaggerate this with the huge variety of colours used to tie flies. I'm certainly convinced that colour matters, but maybe not as much as others may claim.
 

Cap'n Fishy

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We should be careful how we describe all of this . Can Trout see colours as we can then probably not , however I am sure they do detect changes and subtleties of colours that we dont . How they detect UV has always fascinated me . A few years ago I had a pack of UV shrimp ice dub I loved for Grayling bugs . When it was about finished I got another pack , same colour looked identical but i fished flies from it with ltd success . A few months later I was tying a fly and using a UV pen on the wing case , when the light touched the dubbing threads in the dubbing were very iridescent, brain cells started working and i dug out the old and new dubbing and shone the UV pen on it the difference was astonishing . I encourage all of you if you havent already to shine UV on your dubbing packs its amazing how they look completely different . Now if the fish can detect UV....

O M W

I think you are confusing UV with daylight fluorescence. Your eyes cannot see into the UV part of the spectrum, so whatever you saw coming from your dubbing was not in the UV. Fluorescent materials shift UV light into our visible spectrum. The jury is still out on fish seeing into the UV, I think.

However, a good point on the whole colour thing...

UV penetrates water well. Red light doesn't. If you take red daylight fluorescent material (eg Globrite shade 5) down into the water, at a depth when everything else is losing its ability to reflect light - and so colours - the red fluorescent (thanks to UV) will glow brightly, showing itself up. A hotspot of fluoro red on many patterns makes them more effective for me, I reckon.

Another couple of colours... hot orange and claret. Not particularly common in nature, but present in 100s of tried and trusted fly patterns that have persisted over many many decades - because they catch a lot of fish. There is surely something going on there with the way the fish are picking out those colours?

Col
 
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If it wasn't for colour male salmon in spawning time wouldn't go mad everytime a red fly passes by.
 

jerryrum

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I don't know if what holds true for stickleback can automatically be applied to trout, but.....

When I was at university we carried out an experiment with male stickleback during the breeding season. An oversimplified version of this was:

A single male was put in each of two tanks with a cardboard divider between them. They were both fairly placid until the cardboard was lifted and they could see each other. When that happened they both went mad trying to get to each other to fight.

The tanks were then separated and a variety of 'props' were placed next to each tank. We used things like cardboard sticklebacks in greyscale, a tank with a minnow in, a bit of blue wire, a bit of red wire, variety of lego bricks etc.

Unfortunately I don't have the results to hand, but the crux of it was the colour red caused much more of a reaction than the shape, movement or any other factor of the prop.

In short, a bit of red sewing wool sent them wild, a pretend fish on a stick did nothing.

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Cap'n Fishy

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I never said they did ....

As far as I can make out, the 'UV' in 'UV dubbing' is just marketing spiel. It has no connection with light in the UV range. It's just a trendy name and it has a purplish tinge to it. Some might be fluorescent and others not fluorescent - which I think explains the difference in your results under a UV torch. So, I was wondering, why the bit at the end about whether fish can see UV light... :confused:

Col
 

rabmax

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Sure they see colours.Maybe not in the same way we do perhaps.Everyone will remember struggling to catch.Then change to a fly same size say but different colour & start catching.Why are hot beads & hot spots so effective.
 
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I made a strange observation with a trout I had overeducated by catching it five or six times in three years. In spite of being caught it stayed in the waterbassin under the mill I lived in. One day I watched him hanging perpendicular in the water, his nose half an inch from a living Danica, it saw the animal move just as I did and just hung there, for ten maybe fifteen seconds. It did not make one attempt to eat it and sank to its lie. Till today, I'm still wondering what this trout was looking for. And yes, I caught it again afterwards with a replica.
 

Cap'n Fishy

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I made a strange observation with a trout I had overeducated by catching it five or six times in three years. In spite of being caught it stayed in the waterbassin under the mill I lived in. One day I watched him hanging perpendicular in the water, his nose half an inch from a living Danica, it saw the animal move just as I did and just hung there, for ten maybe fifteen seconds. It did not make one attempt to eat it and sank to its lie. Till today, I'm still wondering what this trout was looking for. And yes, I caught it again afterwards with a replica.

That is very similar to an experience Jimmy and I had on Menteith a good few years ago. We were in the boat, stalking fish that like to lie along the end of the Arnmach promontory, picking at stuff that comes round the corner in a food lane, but also on bits falling out the overhanging tree branches. The trees gave shade, allowing us to see through the water. Jimmy's dry fly was sitting on the surface, and a trout appeared, standing on its tail, bolt upright in the water, directly under his fly. It sat there for about 10 seconds, with its snout half an inch below the fly, seemingly staring at it. After what seemed an age, it quietly rose the extra half inch and gently sipped in Jimmy's fly and he hooked it.

You do wonder what their selection criteria are and what computations are going on during those seconds of pondering, eh? ;)

Col
 

Tangled

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Similar experience described earlier but in my case I felt the fish was smelling it - my trout was too close to even see it, his nose was virtually bumping into it inside his blind spot.

Sounds like your two fish had the fly right at its binocular focus.

trout-vision-fly-fishing-for-trout-in-streams1.png
 

bokbok59

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As a little boy my father use to say, gud the first trout you catch and choose a fly related to the dominant color in the fishes's stomach. I do not think fish see colors as we do, but relate it to the food source available to them at that time i.e. yellow or red, most insects tend to have some red as that is a kind of defence, indicating poisonous.
I'm not even sure how my own eyes work, but if you look at a group of people in a crowd, red seems to be dominant even if red is worn by less in the crowd, maybe its the same with fish.
 

Cap'n Fishy

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Similar experience described earlier but in my case I felt the fish was smelling it - my trout was too close to even see it, his nose was virtually bumping into it inside his blind spot.

Sounds like your two fish had the fly right at its binocular focus.

I'm sure our one was looking at it, not trying to smell it. When I say 'half an inch', it's more a figurative half inch, as we were not able to make an exact measurement for practical reasons. :whistle: It was very close, though... probably as you say, at its closest point of focus. Same as me when I am trying to tie a fly on. :p
 
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That is very similar to an experience Jimmy and I had on Menteith a good few years ago. We were in the boat, stalking fish that like to lie along the end of the Arnmach promontory, picking at stuff that comes round the corner in a food lane, but also on bits falling out the overhanging tree branches. The trees gave shade, allowing us to see through the water. Jimmy's dry fly was sitting on the surface, and a trout appeared, standing on its tail, bolt upright in the water, directly under his fly. It sat there for about 10 seconds, with its snout half an inch below the fly, seemingly staring at it. After what seemed an age, it quietly rose the extra half inch and gently sipped in Jimmy's fly and he hooked it.

You do wonder what their selection criteria are and what computations are going on during those seconds of pondering, eh? ;)

Col

Yep, I've been lucky to observe fish observing our imitations over a long period, I've seen things I couldn't believe trout could do before they decided to take or refuse an offering. What startled me with this particular trout was the fact it didn't even have a go at a live insect, it refused it for some reason, although it kept on feeding long afterwards. It was totally unaware of me, I could observe it unseen and saw it chasing insects all over the place without hesitation, yet on this one occasion it behaved completely different. When I presented it my imitation later that day it took instinctively. Maybe I just f*cked up its mind. :eek:mg:
 

Cap'n Fishy

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As a little boy my father use to say, gud the first trout you catch and choose a fly related to the dominant color in the fishes's stomach. I do not think fish see colors as we do, but relate it to the food source available to them at that time i.e. yellow or red, most insects tend to have some red as that is a kind of defence, indicating poisonous.
I'm not even sure how my own eyes work, but if you look at a group of people in a crowd, red seems to be dominant even if red is worn by less in the crowd, maybe its the same with fish.

Old saying among colourists...

"Warm colours advance, while cool colours recede." Red is the warmest of all colours.

How Colors Advance and Recede in Art - science of colour

Col
 

jack58

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In regard to UV I heard an American biologist talking about how young trout can see UV, however they lose the ability as they age but interestingly they regain the ability if they go out to sea and return.
 

Cap'n Fishy

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Yep, I've been lucky to observe fish observing our imitations over a long period, I've seen things I couldn't believe trout could do before they decided to take or refuse an offering. What startled me with this particular trout was the fact it didn't even have a go at a live insect, it refused it for some reason, although it kept on feeding long afterwards. It was totally unaware of me, I could observe it unseen and saw it chasing insects all over the place without hesitation, yet on this one occasion it behaved completely different. When I presented it my imitation later that day it took instinctively. Maybe I just f*cked up its mind. :eek:mg:

There must have been something about that insect that was over-riding the fish's feeding drive with its survival instinct... something that was ringing an alarm bell - even if it was a false alarm... Total guess, like... :noidea:

Col
 
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There must have been something about that insect that was over-riding the fish's feeding drive with its survival instinct... something that was ringing an alarm bell - even if it was a false alarm... Total guess, like... :noidea:

Col

I guess it was me :eek:, I shouldn't have caught the b*gger again so soon. It must have felt totally lost for clues after that.;)
 

Cap'n Fishy

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In regard to UV I heard an American biologist talking about how young trout can see UV, however they lose the ability as they age but interestingly they regain the ability if they go out to sea and return.

Yep - I've heard that one from various sources. Dunno if there is some evolutionary advantage to being able to detect UV when at sea, or when migrating their way home? Not that it is UV, but it is the first band of the visible (for us) next to UV... as mentioned upthread, I find that flies with a bit of blue in them are good for loch sea trout and salmon.

Our eyes have a UV filter in the lens - which is why we can't detect UV. Claude Monet had one lens removed at the age of 82, and then started painting white things as pale blue. It was hypothesised this was due to him being able to 'see' into the UV. Of course, our brains don't have any colour assigned to tag light in the UV wavelengths, so Monet's brain had to pick one to represent it... but it's interesting it picked blue. Might be a connection there... :noidea:

Col

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I guess it was me :eek:, I shouldn't have caught the b*gger again so soon. It must have felt totally lost for clues after that.;)

Your flies were too good an imitation! ;)
 

Cap'n Fishy

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One thing that always makes my head hurt when I try to get it round the subject...

Colours do not exist.

They are all illusions.

If you killed every animal with colour vision, the world would be nothing but black, white, and shades of grey.

All colours are the inventions of the brains of animals with colour vision, in order to tag separated-out bands of wavelengths of the visible (to our eyes) part of the electromagnetic spectrum.

It has evolved several times in several lines. Our own line gave it up back in the days when we were nocturnal animals, and we had to re-invent it when we became daytime creatures again.

As has been said upthread, there is absolutely no guarantee that we see colours the way fish do, because of the break and re-invention that took place in our lineages.

It's a whole fascinating subject. :thumbs:

Col
 
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