Kayak Color and sharks...

[dos ballenas]

And then food for thought... Are Sharks Color Blind? ScienceDaily (Jan. 19, 2011) — Sharks are unable to distinguish colors, even though their close relatives rays and chimaeras have some color vision, according to new research by Dr. Nathan Scott Hart and colleagues from the University of Western Australia and the University of Queensland in Australia. Their study shows that although the eyes of sharks function over a wide range of light levels, they only have a single long-wavelength-sensitive cone* type in the retina and therefore are potentially totally color blind. Hart and team's findings are published online in Springer's journal Naturwissenschaften. "This new research on how sharks see may help to prevent attacks on humans and assist in the development of fishing gear that may reduce shark bycatch in long-line fisheries. Our study shows that contrast against the background, rather than colour per se, may be more important for object detection by sharks. This may help us to design long-line fishing lures that are less attractive to sharks as well as to design swimming attire and surf craft that have a lower visual contrast to sharks and, therefore, are less 'attractive' to them," said Prof. Hart. Sharks are efficient predators and their evolutionary success is thought to be due in part to an impressive range of sensory systems, including vision. To date, it is unclear whether sharks have color vision, despite well-developed eyes and a large sensory brain area dedicated to the processing of visual information. In an attempt to demonstrate whether or not sharks have color vision, Hart and colleagues used a different technique -- microspectrophotometry -- to identify cone visual pigments in shark retinas and measure their spectral absorbance. They looked at the retinas of 17 shark species caught in a variety of waters in both Queensland and Western Australia. Rod cells were the most common type of photoreceptor in all species. In ten of the 17 species, no cone cells were observed. However, cones were found in the retinae of 7 species of shark from three different families and in each case only a single type of long-wavelength-sensitive cone photoreceptor was present. Hart and team's results provide strong evidence that sharks possess only a single cone type, suggesting that sharks may be cone monochromats, and therefore potentially totally color blind. The authors conclude: "While cone monochromacy on land is rare, it may be a common strategy in the marine environment. Many aquatic mammals ? whales, dolphins and seals ? also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution, in other words, they acquired the same biological trait in unrelated lineages." *Note: There are two main types of photoreceptor cells in the retina of the eye. Rod cells are very sensitive to light and allow night vision. Cone cells also react to light but are less sensitive to it. Eyes with different spectral types of cone cells can distinguish different colors. Rod cells cannot tell colors apart. Journal Reference: Nathan Scott Hart, Susan Michelle Theiss, Blake Kristin Harahush, Shaun Patrick Collin. Microspectrophotometric evidence for cone monochromacy in sharks. Naturwissenschaften, 2011; link to paper abstract provided below...... DOI: 10.1007/s00114-010-0758-8

[Fiskadoro]

Originally Posted by dos ballenas

.....

Originally Posted by Original post

.....the best colors for surface jigs not diving jigs are not bright colors but dark colors purple, black and dark green.... these colors make the sharpest silhouette or cast a better shadow (high contrast) and they are the easiest for makos that are hanging deep looking up for prey on the surface to see....a shark looking up sees your yak against a whiteish light blue back ground of water and sky, but a shark that sees you from the side sees your yak against a green or dark blue background.... the lures that dived deep got bit best if they were bright colors because the sharks were seeing them from the side not from underneath them.(high contrast)...Ultimately this is all about visibility, what get's seen due to high contrast is the most likely thing to get attacked or probed for scavenge....

Good stuff!!! That pretty much goes along with what I said in the beginning.

There is no doubt that sharks do not perceive color the way we do, the truth is few animals do. What they do definitely see is the amount of light reflected off the object, how it contrasts to the background light, and different colors reflect different spectrum of light or essentially different amounts of light in relation to various backgrounds.

Jim

[dos ballenas]

nice... it only took 11 minutes for your response... I was expecting less I can tell you have thought about this a lot...

A wise man once said "always cast your surface iron into the sun and then fan out from there until you see which angle is getting bit best"

I think the important thing is to learn as much as we can from shark attacks that occured in the past. Most occured in low visibility conditions.

[Fiskadoro]

Originally Posted by dos ballenas

nice... it only took 11 minutes for your response... I can tell you have thought about this a lot.......

Yeah well... Though that was from a recent article it was hardly a new concept.

Actually when I get some time though I will read up on their research.

Past studies have shown that sharks have both rod and cone photoreceptors in their eyes, which would suggest they could see color in some manner, but studies have shown that their vision seems to be set up to enhance the contrast of targets silhouetted against a background, or more technically that the cones are specialized for contrast over wide range color perception.

This specialization though is not anything new as I could find you papers about it that are more then fifty years old. That is why I kept talking about color in relation to how it contrasts to it's background. Sharks eyes key on contrast.

That said: I did find your post interesting. especially this part which is about roughly half of the sharks they studied.

Originally Posted by dos ballenas

"However, cones were found in the retinae of 7 species of shark from three different families and in each case only a single type of long-wavelength-sensitive cone photoreceptor was present. "

You may not know this but the long-wavelength colors that those specialized cone photoreceptors are keyed for are yellow orange and red.

So though ten out of seventeen sharks species they studied did not perceive color so much as contrast those that did had eyes set up for enhanced yellow orange an red perception, at least that is what I got on a quick glance over.

Jim

[surfnutnj]

Originally Posted by Jim Day

Yeah well... Though that was from a recent article it was hardly a new concept.

Actually when I get some time though I will read up on their research.

Past studies have shown that sharks have both rod and cone photoreceptors in their eyes, which would suggest they could see color in some manner, but studies have shown that their vision seems to be set up to enhance the contrast of targets silhouetted against a background, or more technically that the cones are specialized for contrast over wide range color perception.

This specialization though is not anything new as I could find you papers about it that are more then fifty years old. That is why I kept talking about color in relation to how it contrasts to it's background. Sharks eyes key on contrast.

That said: I did find your post interesting. especially this part which is about roughly half of the sharks they studied.

[/FONT][/I]

You may not know this but the long-wavelength colors that those specialized cone photoreceptors are keyed for are yellow orange and red.

So though ten out of seventeen sharks species they studied did not perceive color so much as contrast those that did had eyes set up for enhanced yellow orange an red perception, at least that is what I got on a quick glance over.

Jim

sooooo.....anyone want to buy a RED Tarpon 120?

J/K...hopefully the tax man does not try to eat me while I am fishing. If he does at least I died doing what I love to do. (not driving to work) I always say that.

[Hobie-Pedaller]

very interesting & thought provoking points & topics in this thread.

yum, yum, yellow..... i resemble that.

[dos ballenas]

very interesting indeed...

even more interesting in the resurfacing of the infamous Hobie-pedaler! that sure was a long breath hold

[dos ballenas]

Originally Posted by Jim Day

This specialization though is not anything new as I could find you papers about it that are more then fifty years old.

Jim

fifty years ago? lets see it.... I love papers from the good old days...

so have you learned anything you didnt already know from the replies to this post?

You should talk to Keith Poe...

[bubblehide]

Originally Posted by dos ballenas

fifty years ago? lets see it.... I love papers from the good old days...

so have you learned anything you didnt already know from the replies to this post?

You should talk to Keith Poe...

I think Keith and Jim are pretty good friends, but i could be mistaken.

[Fiskadoro]

Originally Posted by dos ballenas

fifty years ago? lets see it.... I love papers from the good old days...

I don't have time to look it up but Sam Gruber was I think the guy who was writing about this back in the sixties. Before him they thought that sharks mainly just fed by their sense of smell. If I remember correctly his definitive paper sharks and their vision was published in 1965, but he was pushing his theories back before that in something like 1961. There is probably some shit about him online somewhere. I first read about him in Scientific America or some other Science mag back when I was fishing Tigers, Hammers, and Bullsharks in the surf in Texas as a kid.

Originally Posted by dos ballenas

...so have you learned anything you didnt already know from the replies to this post?

Nope. Not really, I wish. The article you talked about just kinda backs up what I already knew, though I'm not sure you get that. On the bright side, I could say this thread has given me some insight in regards to you.

How about you... Have you learned anything?

Originally Posted by dos ballenas

You should talk to Keith Poe...

I've known Kieth for almost a couple decades now. I fished with him mainly back in the 90s. I designed and built his bait tank for his current boat, and some other gear, and even painted it for him. I know him pretty well, better then most as I've spent many hours on the water with him. Kieth and I have talked endless hours about every aspect of shark behavior that we could think of. I was already building shark jigs when I first met Kieth, so I'm sure the topic jig color and sharks came up more then once.

Kieth is Kieth: people either love him or sometimes hate him, but deep down he's got a good soul and he just loves to fish sharks. Ultimately when shark fishing really started taking off back in early 2000s Kieth and I took different paths. I used to post all kinds of info about them and just quit. If I'd been smart I would of written a book like Archer and made some money off it, but I basically just quit posting about them online, and giving out info about fishing them, because I was concerned that they were going to get over fished. Kieth felt that by posting he could direct peoples attitudes, and influence them into preserving the resource, I'm far more cynical when it comes to people then he is.

Jim

[Gigafish]

Great read.

[bus kid]

Originally Posted by Fiskadoro

I've known Kieth for almost a couple decades now. I fished with him mainly back in the 90s. I designed and built his bait tank for his current boat, and some other gear, and even painted it for him. I know him pretty well, better then most as I've spent many hours on the water with him. Kieth and I have talked endless hours about every aspect of shark behavior that we could think of. I was already building shark jigs when I first met Kieth, so I'm sure the topic jig color and sharks came up more then once.

Kieth is Kieth: people either love him or sometimes hate him, but deep down he's got a good soul and he just loves to fish sharks. Ultimately when shark fishing really started taking off back in early 2000s Kieth and I took different paths. I used to post all kinds of info about them and just quit. If I'd been smart I would of written a book like Archer and made some money off it, but I basically just quit posting about them online, and giving out info about fishing them, because I was concerned that they were going to get over fished. Kieth felt that by posting he could direct peoples attitudes, and influence them into preserving the resource, I'm far more cynical when it comes to people then he is.

Jim

so Jim how is Keith, last I heard he was chasing swords off cat.

and yes I see that the post is waaayyy old.