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  1. #1

    Default How trout see prey behind rocks

    I've described before how trout use the refraction and reflection of light from the water air interface to see behind objects. Trout use the mirror surface of the water outside of Snell's window to see prey.

    The illustration below is from pg 36 of Gary Borger's book Presentation.

    At 1 minute in the video below, largest trout goes behind the boulder but you can still see it reflected in the surface mirror. Trout use the mirror to hunt for prey.


    Last edited by silver creek; 11-19-2015 at 09:34 PM.


    "Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

  2. #2
    Join Date
    Mar 2008
    Pinedale, WY
    Blog Entries

    Default Re: How trout see prey behind rocks

    Silver: Excellent video. I've seen that reflection from the surface in underwater shots that we have done when fishing with Rod (aka rodneybo) using his GoPro, but never thought about how a trout could see predators behind rocks, very interesting.

  3. #3

    Default Re: How trout see prey behind rocks

    So it is not magic after all. Proof, it's done with mirrors


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  4. #4
    Join Date
    Jan 2012
    Rky. Mtn. West

    Default Re: How trout see prey behind rocks

    Thanks for that SC. Great video. Makes me think about what our flies on the surface really look like to the trout too. Its usually not what we think. I suppose they can see 'em coming better than we think too.

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  6. #5

    Default Re: How trout see prey behind rocks

    Seeing that video reminds me of why I got into fly fishing. The learning and the knowledge never stops. As always, thanks for the informative post silver.

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  8. #6
    Join Date
    Mar 2015
    Crowded Colorado

    Default Re: How trout see prey behind rocks

    Silver, that was awesome!! Watching that I was thinking, if I was a trout, how would I know if I was rightside up or upside down?

    Wish I knew if there was a trout in front of a rock when I'm sneaking up from behind it.

    I learn so much from you guys and I appreciate it.
    The only thing human kind ever learned through history, is that through history, human kind has learned nothing.

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  10. #7

    Default Re: How trout see prey behind rocks

    I posted a more complete discussion of the trout's window here:


    "Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

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  12. #8

    Default Re: How trout see prey behind rocks

    With most dry flies, because they are almost entirely resting above the mirror of the water surface, the mirror has little to do with how the fish sees them. But with bass lures and flies which rest partially under the surface, the mirror might actually allow the fish to see the reflection of the upper sides and back of the lure or fly. So although I've had a number of anglers say that the color of the back of a surface lure makes no difference because the fish can't see it from below, that is not always true--they see its reflection.

    Underwater flies, of course, are a different story. But it seems to me that, with the apparently lack of visual acuity of trout discussed in the other thread, a nymph drifting along behind a rock five feet away from the fish is probably not going to be noticed by the fish, since it has to see the reflection of that nymph from what to it is a long way off.

    I find this subject of vision in fish extremely interesting, and few anglers know much about it, though most THINK they know a lot about it. For instance...some subsurface bass lures were produced with a chrome finish that was highly reflective. Most anglers assumed that this shiny chrome would be highly visible to bass. But...most prey fish species like minnows have scaly sides that are almost as shiny when you hold them in your hand as that chrome lure. Why? Because their sides act as mirrors underwater. Picture a predator fish looking horizontally through the water at a "shiny" minnow. It is seeing that minnow against a background of the water behind it, and depending upon the amount of water without obstructions in the background and the clarity of the water, that background will mostly be a smooth green or olive color. But the minnow's sides are reflecting the water at that same level and angle. So those chrome silver sides will actually appear to be the color of the water behind the minnow, and it blends in almost perfectly. This explains why sparsely tied Clouser minnows and such are often more effective than more full ties. We cannot get that reflective quality very well with bucktail and flashabou, but as long as the tie is sparse, the fish sees partially THROUGH the materials the fly is made of, giving it an appearance much the same as if it was a minnow reflecting the water environment.

  13. #9
    Join Date
    Nov 2009
    White City (tad north of Medford) Oar-E-Gone

    Default Re: How trout see prey behind rocks

    Second time tonight I've gotten this message:

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    Being its just short of mid-night I'm doing a what the heck!!
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  15. Default Re: How trout see prey behind rocks

    I think that's really cool and all but this was shot in still water. The streams I fish the surface is usually so choppy that only in the stalest pools would the mirror be practical. I looked back through some of my underwater videos from eddies and the surface was too broken to see anything especially size 16 and smaller.

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