Troutnut Forum > Photography > Bug Bellies II
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©2004 Mike Speer
Underwater Cutthroat caught at Boxwood Gulch Ranch, on the north fork of the South Platte river near Bailey, Colorado. An Ex-streamly clear tail water, great for sub-surface photography.
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Underwater Cutthroat caught at Boxwood Gulch Ranch, on the north fork of the South Platte river near Bailey, Colorado. An Ex-streamly clear tail water, great for sub-surface photography.
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| Gripngrin | December 4th, 2006, 9:11 pm | |
| Front Range - Colorado Posts: 17 | Somewhat related to Bug Bellies, the topic started by Louis prompted a thought concerning trout vision. I once heard that trout have slight telephoto vision, allowing them to scrutinize bugs (bellies). Also wondering if they can see in color, low light (nocturnal), approximate field of vision, etc? After years of guiding and observing trout feed, take flies, etc, it seems that they may have a telephoto vision at times allowing them to see an upcoming bug at more than ten feet, as well as a macro vision able to distinguish between real bugs and the best tied imitations. Can anyone verify or comment on this. If you have any information it would be good reading for us trout nerds, uh, nuts. Mike | |
| Grip'n Grin Mike | ||
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| DMM | December 4th, 2006, 11:16 pm | |
| Posts: 141 | Trout are myopic (near-sighted) due to the structure of their eyes. Rather than flattening or becoming globular like our lenses do, trout lenses move in or out of the eye to focus. The resting position of the trout lens is away from the back of the eye, and toward the environment--thus myopic. Trout also have binocular vision. They can see in 3-D, but it can be a fair distance in front of the fish. The binocular vision is not at the very tip of the nose. Trout can also see in color. This kind of changes based on the time of day, though. Since they don't move their pupils, they can't control light intensity entering the eye very well. At times of high light levels, the cones (color-sensing cells) migrate to the front (retina), ahead of the rods (light--b&w vision). There is some pigment movement in the retina too (not rods/cones). At any rate, trout can see quite well at night or in the day. The eye (rods/cones) changes seasonally, too. The time of day trout see poorly is dawn and dusk--probably why they're easier to catch. This is the middle of cell migration. Color shouldn't be as important during dawn/dusk as a result. Something else to consider is the lateral line system. This allows them to feel vibrations in the water (the line of special scales you see on the side of the fish mid way down). They can navigate throughout the environment quite well even without eyes (sadistic former biological experiments show that). I have read (though I forgot the source, so I don't know how accurate this is, but it wouldn't surprise me) that trout can feel a swimming insect up to 10 feet away. I don't know how far a trout can actually see. They don't see behind them, though. If you're careful, you can sometimes sneak up to a trout from behind and grab its tail (probably only in moving water, though--to mask your movement from their lateral line). I hope this makes sense. I was trying to avoid technical terms for people not familiar with such things. | |
| David | ||
| GONZO | December 4th, 2006, 11:38 pm | |
| "Bear Swamp," PA Posts: 1079 | Hi Mike, There are some excellent discussions of trout vision in recent literature, though I'm at a loss to remember specific references off the top of my head. (Marinaro's In the Ring of the Rise and Goddard and Clarke's The Trout and the Fly are two classics on this topic, but there are more recent discussions. Perhaps someone else can help with those). The telephoto aspect is not one I can confirm (although the lens of the trout's eye is more spherical than ours), but I'll take a stab at your other questions. Because they possess both rods and cones, trout can see color and have low-light vision. It is sometimes assumed that the transition from one to the other (normal daylight vision to black-and-white "rod" vision) may produce a temporary visual handicap for the trout. I have even read some speculation that this might be a reason that many trout stream insects have evolved periods of regular behavioral drift that peak at dusk and again at dawn (to take advantage of the trout's temporary visual adjustment). Because trout eyes have more rods and human eyes have more cones, it is assumed that our perception of color and detail is superior (cone-enhanced qualities) and the trout has superior sensitivity to movement, contrast, and low light (rod-enhanced qualities). Trout have about 180 degrees of monocular vision with each eye and an approximately 30 degree overlapping field of binocular vision directly in front and a bit ahead of their nose (this also extends upward, but the calculations are more complex). When viewing through the water's surface, they have a 96-97 degree "cone of vision" which permits above-water objects to be seen through the trout's "window." Due to the refraction of light as it enters the water a larger above-water field is captured, but objects close to the edge of the circle (Snell's circle, where the effect of bending is the greatest) are subject to distortion. Outside of this cone, the underside of the water's surface appears as a mirror reflecting the underwater scene. Hope this basic info is helpful, but I'm sure someone here can add to it. (David, I'm counting on you, pal.) PS--Sorry, David, I guess we were in Louis's famous IM mode! Please feel free to correct any mistakes or misconceptions I may have offered. PPS--Very cool photo, Mike! | |
| Konchu | December 5th, 2006, 12:42 am | |
| Indiana Posts: 218 | What about UV-light and the ability to see polarized light? | |
| DMM | December 5th, 2006, 12:54 am | |
| Posts: 141 | No apologies necessary GONZO--my post seemed a bit incoherent anyway. It's a little difficult to adequately cover in a few paragraphs. Also, I don't know people's backgrounds in science. I thought I would just expand on the bit about Snell's circle. Snell's Law deals with the way light bends when moving from one medium to another. When light enters a medium that is more dense (like from air into water) the light bends toward the normal. Conversly, when light enters a less dense medium, it bends away from the normal. The "normal" is what physicists like to call an imaginary reference line that is perpendicular to the ground at 90 degress (in other words, straight up). This has a couple of relevant consequences. One, objects appear to be closer, bigger underwater (from your above-water perspective). The second is difficult to explain without pictures, but I'll try... Snell's Law is the following: n i * sin(theta i) = n t * sin (theta t) (the i's and t's are supposed to be subscripts for incident and transmitted rays) That's a very easy equation to use. Anyone with trig knowledge can use it. The n's are constants that can be looked up. For water at 20 degrees Celsius, n is 1.333. I don't know for air, but it's around 1.000. Anyway, this is important because a trout can see more than you'd think. Providing I didn't make any dumb mistakes, the following example should demonstrate this. Assume you are 6 feet tall and 3.6 feet back from the bank. Also assume the bank is a sheer drop into the water. If the trout is 7.8 feet away from you (4.2 feet from the bank toward the center of the river) it can see the top of your head as long as it is no deeper than 9.99999...feet. Draw that out...it's amazing people ever catch fish in pools! Maybe Jason could program a Snell's utility for everyone to play with. I'm sure the rest of the site isn't keeping him very busy... ;) | |
| David | ||
| DMM | December 5th, 2006, 12:56 am | |
| Posts: 141 | I agree with GONZO--cool photo. Trout can only see UV light as very young fry. It doesn't really matter though as UV light doesn't penetrate water very well. | |
| David | ||
| GONZO | December 5th, 2006, 1:17 am | |
| "Bear Swamp," PA Posts: 1079 | Thanks for the additional info, David--also very cool! As I understand it, the trout's focus would also come into play when considering the situation you describe. If it was close to the surface and focused on a bug, the surrounding images captured (say, of an angler on the bank) would be quite blurry. If it was deeper and the lentis muscle was retracted, the focus could extend to infinity and the image of the angler would now be clear. Am I correct in this understanding? If so, it may be another reason that trout can often be more closely approached when surface feeding on a hatch. | |
| DMM | December 5th, 2006, 10:58 am | |
| Posts: 141 | Oops! I did make a dumb mistake--I used the complement of theta! I fixed the prior post. Just be glad I don't design bridges... | |
| David | ||
| DMM | December 5th, 2006, 11:03 am | |
| Posts: 141 | Another oops...Some Salmonidae can see UV light as adults. I'm not sure which species can or cannot. But still, UV light only penetrates a few meters... | |
| David | ||
| DMM | December 5th, 2006, 11:12 am | |
| Posts: 141 | GONZO--you are correct about the focus issues. It's that way regardless of if your in/out of water. Focus on your thumb one foot from your face, and try to read something three feet away. It's a simple matter of focal point. The differing densities of the media just complicate the issue a bit. | |
| David | ||
| Martinlf | December 5th, 2006, 8:36 pm | |
| Palmyra PA Posts: 1049 | What a great series of posts, at least the parts I could understand. Much food for thought. Thanks, David, and Gonzo. | |
| "Their friendship was in the nature of a religious confraternity, bound not by the fish but by fishing, by the stony peaks, the shadowy hollers, the deep pools and the shallow white water, and the urge of the discipline." --Fred Chappell | ||
| Gripngrin | December 5th, 2006, 11:11 pm | |
| Front Range - Colorado Posts: 17 | Great feedback Dave & Lloyd. Once on the Green River, just past the lower put-in at Little Hole, my boat mates & I witnessed a large brown trout move a huge distance for a imitation cicada. From downstream ahead of the boat, this brown started from from about eight feet deep water, at least twenty feet away from my fly. This slow motion rise was in in slower water below a long tongue just before the bend going into the canyon. After seeing this I was convinced that trout had telescopic vision. Of course, a # 6 Crystal Cicada could probably been seen from the moon in the right light. Never the less, seeing this long distance rise was awesome. Oh yeah, landed him! He was shaped more like a largemouth bass than a trout. Measured 22 inch's at about 2.5 pounds. Do larger trout have bigger eyes, cones / rods, hence better vision? Would love to learn more about the lateral lines. Also, what state region do you work in? Mike | |
| Grip'n Grin Mike | ||
| Troutnut | December 6th, 2006, 12:24 am | |
| Fairbanks, AK Posts: 1213 | Once on the Green River, just past the lower put-in at Little Hole, my boat mates & I witnessed a large brown trout move a huge distance for a imitation cicada. From downstream ahead of the boat, this brown started from from about eight feet deep water, at least twenty feet away from my fly. This slow motion rise was in in slower water below a long tongue just before the bend going into the canyon. I've had a very similar experience on the Brule. I watched an 18-inch brown turn around and shoot about 20 feet downstream to slam an Ausable Wulff as soon as it hit the water. At the time (it was my first summer learning to fly fish) I thought it was impressive vision, but in hindsight it's obvious the fish just picked up on the vibrations. One other important point is that we tend to overestimate how far it's possible to see underwater based on water clarity. What seems "crystal clear" to us in a shallow stream might not really be even close. We stand in a foot of water and can clearly see the bottom 20 feet away from us, and we just kind of subconsciously assume something underwater at our feet could see that far too. When you think about it, it's obvious that that doesn't make sense, but many people don't stop to think about it. Something underwater can only see as far to the side as we can see when looking straight down into the water. So if you can see the bottom below you pretty well in 6 feet of water but not 7 (that's fairly clear), then you or a fish could only see that far to the side, too. I've only been on one or two streams, both small, where the clarity let details show up pretty well at 15+ feet. Even think about lakes; in how many can you see bottom detail well in 15 feet of water? | |
| Jason Neuswanger The Troutnut | ||
| Troutnut | December 6th, 2006, 12:25 am | |
| Fairbanks, AK Posts: 1213 | By the way Mike, great trout photo! | |
| Jason Neuswanger The Troutnut | ||
| Martinlf | December 6th, 2006, 11:34 am | |
| Palmyra PA Posts: 1049 | Jason's comment is intriguing, and reminds me of David's observation that trout are extraordinarily sensitive to vibrations, even to those caused by insects. I'll try to keep this in mind when tying streamers and wet flies, and when wading. Also, though spiked boots give added confidence, especially in big water, I believe I'm going to use my spikeless boots more, expecially when spikes are not needed. The spikes certainly create more grinding and scraping vibrations, and most likely often suggest the presence of a predator more strongly than simple felts. | |
| "Their friendship was in the nature of a religious confraternity, bound not by the fish but by fishing, by the stony peaks, the shadowy hollers, the deep pools and the shallow white water, and the urge of the discipline." --Fred Chappell | ||
| GONZO | December 6th, 2006, 1:36 pm | |
| "Bear Swamp," PA Posts: 1079 | Louis, I usually try to avoid using spikes or chains unless serious safety issues are involved. It can be a bit of a trade-off though. Even a fairly tame wading situation (in terms of current and depth) can be complicated by snot-covered rocks or slick ledges. If leaving the spiked boots behind means more slipping and stumbling, the stealthy advantage of a quieter bootsole disappears pretty quickly. Artful wading is an underestimated skill. Keep in mind, however, that fast water hides a multitude of sins. Vibrations, whether attractive or alarming, are masked by the turbulence and white noise of fast water, and the directional influence of the current comes into play. As David points out, the physical laws governing vision through mixed media (water/air) can be a little complicated to explain. But, they are easy enough to experience. While we may not be able to view the underwater world through a trout's eyes, seeing it with our own is an invaluable experience. I've had the opportunity to do a fair amount of scuba diving in trout streams (and I'd love to do more). Jason's observations about clarity, David's explanation of the function of Snell's Law, the qualities of sound (vibration) underwater, and the responses of fish to all of these things become much easier to understand when you can experience them firsthand. That experience is something I would recommend to any angler. | |
| DMM | December 6th, 2006, 9:35 pm | |
| Posts: 141 | In response to Mike's questions: Larger trout have bigger eyes and therefore a different focal distance. Bigger eyes let in more light which is needed to see farther away. As an aside, that would require a little explaining, so I'm not going to address it. If anything is unclear or lacking in my posts, just let me know. Back on topic. As trout grow, their world just gets a little bigger. Rods and cones don't function based on size. They are cell types. The actual light absorption is dependent on certain proteins called rhodopsins. Protein function is dependent on protein structure. So, to see better, you would need a favorable mutation. Color-blindness in humans results from mutations in rhodopsin proteins, so mutations are not usually good. However, fish are vertebrates, and yet we call young fish "larvae." This is because fish often go through a lot of development between hatch/birth and adulthood; much more than us, for example. Very young (within a couple months of hatching)trout don't have calcified bones or scales, for instance. My point is that their eyes do change as they grow. Do they get better? That's hard to say, as they live under different conditions as they mature. Adult eyes may not help young fish. Walleye (Sander vitreum or Stizostedion vitreum depending on who you talk to) are a good example of this. Hope the walleye reference doesn't offend any of you salmonophiles, but get used to it because there are more non-salmon examples to come. Now for an easy answer...I live in Northwest CA right now. And now for the main feature...The Lateral Line! The lateral line is kind of part of a fish's hearing. This has to do with the properties of sound waves as they travel through water, so I'm just going to say vibrations from now on, as opposed to saying something like "near-field molecular compression." Basically, their "ears" and lateral line (I'll say LL) "hear" different parts of a sound wave. Now that I've confused you more... The LL is a canal that runs the length of the fish in an anterior to posterior direction. Realize I am generalizing here, though, as some fish have 5 LLs per side, for instance. Anyway, it is an actual tube/canal that opens to the outside environment via LL pores. If you look at a trout, you can see a line on each side of the fish. This is the LL. If you look carefully or with a dissection microscope, you will be able to see tiny holes along the LLs. These holes allow water into the LL main canal. It's like the drains from all the houses on your block draining into the main sewer line. Inside the LL canal are "hairy" cells with a little jelly-like cap. These structures are called neuromasts. Each neuromast sends a signal to the fish when one or more "hairs" are displaced. This is not a binary signal; the direction of vibration (direction hair is pushed) is conveyed as well. Also, the fish can sense different intensities of vibration along the LL. That is, a fish can tell if the signal is stronger ahead or behind it. So, if there is vibration in the environment, this travels through the water and into the LL canal via the pores, and stimulates one or more neuromasts. These in turn are associated with nerves, and send signals to the trout's brain. Another thing to note, is that the LL often branches into sometimes complex patterns, in the "face" of the fish. You can sometimes see these canals or some pores on fish faces. Lateral lines give fish a lot of information. Studies have been done where they took measurements of distances between schooling fish (herring I think). They then gouged out the eyes of the fish and observed schooling behavior. There was only one difference: the fish swam slightly further apart. Another example of the usefulness of the LL is in blind cave fish (Astyanax fasciatus mexicanus). These fish live in total darkness in underground cave waters in Mexico. Sometimes evolutionists like to say cute little things about evolution like, "use it or lose it." This applies to the eyes of this fish...well, lack of eyes anyway. They can live in total darkness and be completely fuctional using their LL. You can often buy these fish at the pet store, and they'll do fine mixed in with your average, eyed fish. The swim bladder of a fish can be used by a fish as an amplifier too, but that's enough typing. One other thing though...I notice my name has been in a number of posts of late. This isn't some secret code or something, is it? Are my pets going to start vanishing? I changed my mind, I live in Arkansas... | |
| David | ||
| GONZO | December 6th, 2006, 10:17 pm | |
| "Bear Swamp," PA Posts: 1079 | I notice my name has been in a number of posts of late. This isn't some secret code or something, is it? Are my pets going to start vanishing? I see I'm not the only one who suffers from occasional "posting paranoia." I think you're pretty safe here, David (or should I use DMM?). From one paranoid to another, however, I'd still keep an eye on those pets--you never know who's watching on the Internet! :) | |
| DMM | December 6th, 2006, 11:44 pm | |
| Posts: 141 | I forgot to mention that this adds another plus to fishing broken water/riffles. In addition to light bouncing everywhere under water, and above water images being broken up (from the viewpoint of a fish), there are a TON of vibrations in the water. This makes footsteps less noticeable to the fish. PS GONZO--maybe something even more anonymous, like "that guy." | |
| David | ||
| Troutnut | December 7th, 2006, 12:13 am | |
| Fairbanks, AK Posts: 1213 | Hope the walleye reference doesn't offend any of you salmonophiles, but get used to it because there are more non-salmon examples to come. It's okay. There are plenty of things we can learn about salmonids by studying lesser fishes. ;) Great explanation of the lateral line sense! | |
| Jason Neuswanger The Troutnut | ||
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