Discussion Of "the Raptor Effect" By Dr. Howard Wright

[Paul Roberts]

A few seasons ago I was fishing an area of the lake that was a large expanse of mixed surface weeds. The water surface was flat and I was casting a frog. I made a long cast that got away from me and ended up being a very high lob cast. I was watching to see where the frog would end up landing. Much to my surprise, as the frog passed overhead along the water surface , many fish ,along the entire path of the lure ,created a disturbance in the water until the frog landed......I couldnt believe what I had just seen...Fish obviously reacting to the overhead lure, along the entire path of the bait....The whole thing was impressive.I couldnt believe how many fish were in that slice of water.

This is WAY more common than many anglers might think. A standard summer day in CO starts with brilliant sun, then giving way to overcast as thunderheads develop. Nearly every day I get to fish under brilliant blue and deep overcast. In shallow water especially, under high vis conditions, the path between us and our lure is made devoid of fish on every cast because of what you just described. Or is our difficulty catching just that the fish aren't biting under those conditions, even asleep?

 

Well, I've proved to myself that some of those fish are catchable, and I don't have to go to heavy cover to do it. Granted it's not easy to do, and hardly worth the exercise, but it's been worth it just to know. With a long rod I'd make very high casts with a white SB beyond the fish. I choose white to camouflage it against the sky. I then have to keep the line off the water as the line landing on or cutting the water surface turns the fish inside out. But, the SB bulged under the surface works! They'll hit it. Another way, if the shoreline allowed, was to cast long well off to one side and then run the shoreline until the fish were in line with my retrieve. Bang! Fish on, under "impossible" conditions.

 

Complete opposite of this is when the clouds roll in dense, and the water is dark and calm. I throw a bait and the wakes shoot toward the flying lure, rather than away, the bass often hitting at splashdown. Lighting matters -a lot.

[Paul Roberts]

...they are designed for success in and around cover vs scavaging or hunting large expanses of open water, etc.  Their bodies are designed for short powerful bursts of speed, and they will utilize structure and cover to feed from.

True, but I'd change one word; I'd change "feed from" to feed off. Bass may "ambush" from cover, but I believe this is more about opportunism than a hunting strategy bass are specifically adapted to. Their default hunting strategy is opportunistic cruising, flushing or looking for prey that is vulnerable or otherwise in a compromised position. Bass use terrain (and lots of other stuff –other bass being a particularly important one) to their advantage. This is where their true talents lie. They hunt within, amongst, and off of terrain as much as -or I would argue, more than- from terrain. Hunting in this way makes them effective not only around cover but just about anywhere they can find prey in an awkward spot. Bass even effectively hunt shad and alewives in open water, far away from "cover".

 

Sky and water conditions weigh in heavy for multiple reasons, not the least of which is that prey is more difficult to approach in high vis conditions and bass hunting success declines in accordance. More bass are apt to be resting, often under cover, during these periods.

 

But this isn’t the only reason bass head for cover under bright conditions, and bass may not be all resting either. Some are driven to cover under bright conditions because of their increased exposure to predators (raptor effect), and likely UV exposure plays some role too. It may also be that the raptor effect holds greater sway with the bass’s prey. Bluegills head to cover under bright conditions and likely the bass meet them there. Bluegills explain midsummer “frog bites” much better than “frogs” do. (And this explains why blow-ups and misses are so common with frog bites too).

 

My point is that bass aren’t likely heading to cover so they can see better so they can “ambush” prey. Bright skies don’t get into the bass’s eyes like it would for us. In fact, bright sunlight increases visibility underwater tremendously. But the whole food chain responds with a ripple effect –like a chain being shaken from one end.

[Bassun]

What's your line of work, Bassun? Just curious. Great discussion, by the way.

 

Thanks.  I think it's been a fun convo thus far, and it's forced me to think more deeply about aspects of fish and fishing than I have in a while.  As for my line of work, it's nothing even remotely related.  I am a Software Test Engineer by trade.  I dabble in too many things for fun.

 

Wow a lot of thought went into all the answers.  I don't think its so much of a bird of pray thing but simply a sunglass effect. 

 

LOL, the sunglass effect.  I like it!  And I think it is surely part of the equation!

 

 

 

 

Explain to me how bass see detail color variances in the dark or very low light conditions at 45' to 60' depths.

Tom

 

Tom I’m going to take a stab at this one for fun.  Obviously there are theories out there, and I am in no position to effectively apply the scientific method to attempt to prove anything, but based on what we know I would hypothesize the following:  (again, complete conjecture and not a tested theory)

 

 

So we’re looking at how bass see detail color variances in very low light at depths of 45-60 feet.  I did remove “in the dark” as unless one is in a situation of “absolute darkness” there is some amount of light. 

 

First we would need to look at what happens to light as it filters through water.  Now, for purposes of this supposition, let’s assume no extreme factors like extreme turbidity, heavily aerated current, extreme temperatures, etc.  And that we are utilizing natural light, and only wavelengths we can see.   A “best case scenario” if you will.

 

Studies of color loss at depth give us some of the first clues.  Under our good conditions, with the sun high in the sky, we understand that red is the first colors no longer visible (meaning loss of color saturation, and effectively moved into gray scale – not “invisible”).  That occurs in around 15 feet of water.  The next to fall off is orange at around 30 feet, and we begin to lose yellow at right around 45 feet.  That leaves us with greens, purples, and blues.  There is some debate, oddly, about hues of purple.  Some suggest that much of the wavelength is lost nearly as soon as yellow, while others indicate it is somewhere between yellow and green and some follow the wavelength directly and indicate violets are the last to fade.  I think we would legitimately need to consider more factors to delve into the purples, but from what I have read I personally feel they fall off somewhere around 50 feet.

 

For the purpose of this discussion I will assume the theory that purples fall off around the same depth as yellows, leaving us with blue and green both being visible through the 45-60 foot depths.  There’s just one problem with that…we are looking at figures determined with the sun high in the sky on a bight sunny day.  The angle of inclination would be severely different, at best, which means we are no longer looking at a completely vertical penetration of light.  The wavelengths would be filtered out based on their transmission through water along a straight line, so at a low angle colors which would fade in deeper waters, would become less and less vibrant at much shallower depths since the light is effectively traveling through more water to make it to a specific depth.  

 

What this tells us, in my opinion, is that vibrant colors will be lost at a very shallow depth once the sun is on the horizon.  Reds, oranges, yellows (purples?) would all quickly lose their saturation as the water filters the wavelengths, this would obviously be compounded even further considering the low level of light to begin with.  However, studies do show that greens and blues can travel a deep distance (hundred to hundreds of feet).  So, given that I would firstly propose that blues and greens are going to be the most saturated colors at depth, with blue being the strongest.  Considering the target depth of 45-60 feet I am going to focus on only those two colors.

 

We understand that bass have rods and cones in their eyes.  Rods effectively gather light; cones effectively delineate colors.    This is a super glazed version of how they work, but this is a post on a forum, not a scientific paper lol.  An important note to consider is the work of George Wald who discovered rods are most sensitive to wavelengths around 498 nm.  Blue is about 475 nm green is about 510.  Now that is a human rod, and I cannot guarantee the exact same wavelength is most sensitive to fish, but from what I have read, it stands to reason that at least a very similar wavelength would be.  Now, as further speculation, I suspect a fishes rods are actually more tuned to a slightly lower wavelength, something in the blue spectrum.  This is anecdotal, and based purely on experience of blue/black combo colors fished at night.

 

We also understand how fish utilize rods and cones to deal with different levels of light.  During periods of bright light, the rods are shifted back into “dark pigments” to protect them from the intense light, while the cones are shifted to the surface of the retina.  This effectively puts the fish in “color mode” and they are able to see a wide range of colors with a great level of detail.  Conversely, when there is low light (some suggest less that one foot-candle for optimum rod emergence) rods fully emerge and the focus is no longer delineation of colors, rather gathering of available light.

 

Given we know that rods are most effective at seeing the 498 nm wavelength (blue-green), anything around that color will become the most visible.  Reflective materials would also, obviously, provide higher levels of light as they are reflecting the full spectrum of light available, not just a specific wavelength.  It should be noted, however, the color of the water which “clear” has a blue hue, would effectively influence the perceived reflected color.  Given this, I would also surmise that reflective materials would be most effective in clear (technically lightly blue) or slightly green waters as there would not only be a total reflection of all available light, but that light would also be “tinted” the color of the water.  If that puts it closer to the 498 nm wavelength (or whatever bass technically receive the best) then the rods would be most capable of photoreception effectively allowing the fish to see the reflected light even better.

 

So, to answer the original question, “Explain to me how bass see detail color variances in the dark or very low light conditions at 45' to 60' depths.”  I pose that they largely do not see “color” variances in that scenario.  My supposition, given the above info, is that they see most colors in gray-scale during this situation as the wavelengths of most colors would be too muted to see.  However, given their rod sensitivity to a specific wavelength, it is most effective to use a mix of blue/green (again whatever wavelength determined) for their eyes to be most receptive of light.  Now, in terms of fishing, given all of the above – I would suggest using a blue/green and black color bait for the best visibility to the fish.  If conditions are appropriate, adding flash would certainly be a potential advantage.

 

Why blue and black vs blue and white?  Black is the color recognized when all effective light is absorbed, white is when the entire spectrum is reflected.  Given the rods are tuned to a specific color, (assuming blue or blue/green) and often water also has a hue of blue (naturally) or a mix of blue/green during many conditions, any white light reflected would naturally be perceived with a blue / green hue.  Conversely, black will always be black.  The highest contrast would be a mix of the most photoreceptive wavelength and black.  I think this is why we often see the best success in low light with a mix of blue and black lures – this is NOT accounting for lures fished above the fish where black becomes an extremely strong solution as it is actually being silhouetted against a slightly lighter sky.  I would also add, that any color in the spectrum, although effectively received as a scale of grays, could be a target color.  While it may not be the most contrasting, it is plausible that a shade of gray could be a trigger color vs a blue.  Obviously, it depends on forage and what the bass are “looking” for.

 

Now again, this is PURELY SPECULATION, and would need considerable testing to validate my claims.  But, I thought it would be a fun exercise to expound upon.   I could be completely off…

[Bassun]

True, but I'd change one word; I'd change "feed from" to feed off. Bass may "ambush" from cover, but I believe this is more about opportunism than a hunting strategy bass are specifically adapted to. Their default hunting strategy is opportunistic cruising, flushing or looking for prey that is vulnerable or otherwise in a compromised position. Bass use terrain (and lots of other stuff –other bass being a particularly important one) to their advantage. This is where their true talents lie. They hunt within, amongst, and off of terrain as much as -or I would argue, more than- from terrain. Hunting in this way makes them effective not only from cover but just about anywhere they can find prey in an awkward spot. Bass even effectively hunt shad and alewives in open water, far away from "cover".

 

Sky and water conditions weigh in heavy for multiple reasons, not the least of which is that prey is more difficult to approach in high vis conditions and bass hunting success declines in accordance. More bass are apt to be resting, often under cover, during these periods.

 

But this isn’t the only reason bass head for cover under bright conditions, and bass may not be all resting either. Some are driven to cover under bright conditions because of their increased exposure to predators (raptor effect), and likely UV exposure plays some role too. It may also be that the raptor effect holds greater sway with the bass’s prey. Bluegills head to cover under bright conditions and likely the bass meet them there. Bluegills explain midsummer “frog bites” much better than “frogs” do. (And this explains why blow-ups and misses are so common with frog bites too).

 

My point is that bass aren’t likely heading to cover so they can see better so they can “ambush” prey. Bright skies don’t get into the bass’s eyes like it would for us. In fact, bright sunlight increases visibility underwater tremendously. But the whole food chain responds with a ripple effect –like a chain being shaken from one end.

 

I think you may have just swayed me somewhat, again “opportunistic” being the key. 

 

I agree bright light does increase underwater visibility, obviously; but the position of the sun plays a key role as well.  Now considering the extreme range of view bass have, I think positioning would be important in such that the bass would ideally position itself to have the best “lighting” available, while not being “blinded” by the same light.  Perhaps my perception is wrong, and they have no problems staring into the sun, but given the UVA, UVB, etc associated with that, as well as the flooding of photonic receptors I cannot imagine it has no impact.  But, I could just as easily be wrong.

 

Great thoughts Paul, thanks for sharing!

[Paul Roberts]

...

I agree bright light does increase underwater visibility, obviously; but the position of the sun plays a key role as well.  Now considering the extreme range of view bass have, I think positioning would be important in such that the bass would ideally position itself to have the best “lighting” available, while not being “blinded” by the same light.  Perhaps my perception is wrong, and they have no problems staring into the sun, but given the UVA, UVB, etc associated with that, as well as the flooding of photonic receptors I cannot imagine it has no impact.  But, I could just as easily be wrong.

 

Not all that sure they'd need to be "staring into the sun". They can look all around into a well lit landscape around them. Don't picture them staring up at the sky exactly. But I dunno, I've scuba and free-dived, but I'm not built like a bass. If I roll over on my back in a flat calm swimming pool, and lay on the bottom, the sun can be bright. But I literally have to roll over onto my back to see this. Any other orientation and I'm simply looking at the well-lit background -the pool walls and floor. And they are painted white. Even the underside of the water is not difficult to look at. Remember, sunlight attenuates as it passes through water, not just vertically but horizontally too. It's pretty easy to avoid looking directly into the sun's shortest path. Further, any surface ripples greatly increases scatter.

 

UV light is an issue that affects more than eyes, so it may play a role. There was some interesting research that suggested that UV light affected nest depth and nest success for bluegills. Apparently at least they are aware of UV.

 

Good topic and good discussion. Thanks for tackling it.

[SHaugh]

I think it's pretty hard to even imagine what the world looks like through another creatures eyes... I was reading something the other day that a donkey can see all 4 of his feet at the same time... while looking forward.....

I imagine a fishes view of the world has similar scope and that they are unable to avoid having the sun directly in their field of view at some times during the day...

here's an interesting diagram:

 

http://astarmathsandphysics.com/o-level-physics-notes/o-level-physics-notes-a-fishs-view-of-the-world.html

 

What this translates into is something like this:

 

 

A bright sun in that patch of blue sky would be very uncomfortable I think.

 

Certainly just like you or I we can function in bright sunlight... oppressive heat or whatever else we need to do to survive, but all creatures desire rest and comfort at certain times and will seek it out when possible...

[Bassun]

I agree, SHaugh, with the extended FOV a bass has, positioning would be key if they wanted to avoid light.  If I remember correctly, the only real blind spots bass have when combining the monocular and binocular fields of view is basically directly below them and a trailing angle directly behind them.  It's kind of crazy to imagine how much more they can see just by moving an eye then we can.  I guess its a good think I only have to look at my plate to find my food, lol.

[Choporoz]

  As for my line of work, it's nothing even remotely related.  I am a Software Test Engineer by trade. 

 

No offense intended, Bassun, but I doubt that I'm not the only one who is NOT surprised that you're an engineer.   LOL 

Thanks for the discussion!

[Bassun]

LOL --- You know I was actually thinking about the same thing when I replied.  ..... now "I'm" that guy....   It's all good though, and absolutly no offense taken. 

[SHaugh]

I guess our engineer genes are showing...

 

From a fishing aspect I think the fish eye view photo and the diagram can tell us something.

 

What it tells me is that when the sun is bright overhead I'm going to try to make my presentations below and to the side of the fish.. never directly above.

 

If you've ever looked upward at the sun from underwater you will notice that the bright halo of light that is created is very large... I'm thinking if my lure goes through that bright halo my chances are slim.

[Bassun]

I think you're right, as tatertester and Paul both conveyed the same in that casting directly over the fish has a negative impact in which they have personally noticed.  I'm not sure that I would focus on being "below" the fish (if I understand what you meant correctly), but certainly coming alongside vs directly from behind would probably yield better results. 

 

I read somewhere that a fishes visual acuity is greatest at roughly 90 degrees.  I took that to mean in the lateral monocular vision, so it would stand to reason that a lure presented beside or to the side of the fish would certainly be noticed.  They would then utilize their binocular vision upon approach where their depth perception is best to hopefully target and attack your lure.  If only it were really that easy to get these critters to hit lol.

[Team9nine]

The problem, of course, is that most of this color discussion (as has been already stated) is merely speculation. So while fun to discuss, it likely has little relevance to whether or not we each experience successful fishing, witness the differences in personal experiences shared on this forum topic. There is some stuff we do know, provided by detailed examination of the largemouth bass' eye from studies such as the 2002 Kawamura & Kishimoto paper which appears to be the most recent and heavily cited example in literature. From that study we know the following:

 

• The occurrence of C-response provides direct evidence for the possession of color vision. In this study, therefore, it is concluded that the largemouth bass can discriminate colors.
• The dominant L-response with a maximum at 673nm and three variations in C-responses might indicate a better color analysis at longer wavelengths, implying that the largemouth bass is able to discriminate red better than blue.
• In the largemouth bass, the visual axis is found in the nasal-temporal direction and the near point is 13.5 cm, indicating that sharp image formation is not performed when an object comes closer than 13.5cm from the eyes. This near point is slightly shorter than those of other teleosts.
• The retina of the largemouth bass is specialized to both movement and form perceptions.

Part of the problem is that while science can determine things like optimal color sensitivity (red) of a bass' eye, that doesn't necessarily indicate that the color red is therefore more attractive to bass, since attractiveness is determined only behaviorally, and behavior is largely an adaptation to (specific) environment. As such, it wouldn't be unexpected to see angler color experiences that seem to contradict each other (or the research), and it therefore shouldn't suggest that one example/person is right and so the other must be wrong. Then there are the areas of inconsistent opinion or (dis)agreement amongst even the researchers themselves on subjects like UV perception by bass.

 

Of course, this is all part of what makes bass fishing so interesting.   Ultimately, each angler has to determine for himself how important (or not) any of this "color stuff" is to his own fishing.

 

-T9

[J Francho]

I seem to recall that bass' eyes adjust quicker to lighting changes, faster than many prey items, hence their heightened activity during crepuscular periods (dawn and dusk).

[SHaugh]

Another interesting idea is the refractive index as shown in the diagram:

http://astarmathsandphysics.com/o-level-physics-notes/o-level-physics-notes-a-fishs-view-of-the-world.html

 

 

 

 

 

 

In the fish eye view photo this is represented by the point where the blue sky ends and the band of bright green is present.  This is the point where light reflects off the surface rather than traveling straight into the water.

 

This appears to be dependent on how deep the fish is as well.  So the deeper the fish is the less direct sun spotlight area (blue sky) will be seen.

 

This could explain why it appears that fish are most affected by bright sun at the very narrow band of time when the sun is in that center blue area.

[Bassun]

The problem, of course, is that most of this color discussion (as has been already stated) is merely speculation. So while fun to discuss, it likely has little relevance to whether or not we each experience successful fishing, witness the differences in personal experiences shared on this forum topic.

 

-T9

 

I absolutely agree 100% with this.  Mostly conjecture and supposition - but lots of fun discussion.  And I hope my views are not taken as insulting to any opposing views, that certainly is not my intent.  Just fun debate and discussion.

 

And wow, yeah there is a ton of debate in the field especially about UV sensitivity.  In regards to that, I think the science is behind the tech and we are seeing lure manufacturers prove more in the UV arena than anyone! 

[Bassun]

This could explain why it appears that fish are most affected by bright sun at the very narrow band of time when the sun is in that center blue area.

 

I think that's quite plausable.  Considering that and how the lower angle of inclination of the sun would increase the traveled distance of light in water, thereby reducing its intensity - combined with the vertical field of view, it does make sense that they would be most impacted when the sun is high.  Seems reasonable to me.

[einscodek]

Like most hypothesis, there are experiences which dont quite fit as an all-pervasive explanation

such as seeing bass schools roaming only a few feet from shore in crystal clear water in less than a foot of depth in mid-afternoons and bright daylight

I too believe in the raptor effect.. but I wouldnt say that bass are always on the watchout for raptors under all conditions

[WRB]

The hypothesis that raptors flying overhead affect bass location is BS!

The conversation regarding bright blue sky affecting bass location is also ordering on speculation, not fact.

Bass don't have the brain capacity to have fear, moving objects above the water can alarm bass as an instinctive warning and they react to warning.

The 1st Bassmaster Classic held on lake Mead, a extremely clear water lake at that time, was won by Murray using white spinner baits in shallow water with the sun overhead. Everyone else target cliff shaded areas believing the bass couldn't be in bright sun lite shallow water with no shad. When asked why he fished in clear shallow water with a spinnerbait he stated that is where I also fish! The wasn't any wind, maybe a slight breeze with temperatures over 110 degrees.

One of my best big bass spots is very close to a osprey nesting tree. I have to watch closely when casting trout swimbaits for those osprey, so they catch the lure in mid cast.

We have no idea how a bass brain processes the images their eyes captures and bass have big eyes for a good reason, to find prey.

Tom

[SHaugh]

I have no doubt that at times there are overriding concerns for fish.. they simply follow whatever driving force compels them most at that moment.

 

I also have no doubt that most small creatures have a raptor effect to some degree.   I have chickens in my yard.   When I play with the dog sometimes I will throw the toy directly over the top of them.  They invariably panic.  Even when I do it repeatedly they will continue to react almost every time.  I think this is what Tatertester experienced throwing a frog over resting fish.  

 

I'm not sure a chicken is much smarter than a bass, but it would seem that the reaction is pretty much involuntary and not easily unlearned.

 

There is no doubt that fish are very aware and attuned to what is going on inside that small blue window directly over their heads.

 

Perhaps the occasional appearance of a blazing sun "god" within that little window might be all it takes for them to seek a place where he is no longer there ?

[geo g]

The hypothesis that raptors flying overhead affect bass location is BS!

The conversation regarding bright blue sky affecting bass location is also ordering on speculation, not fact.

Bass don't have the brain capacity to have fear, moving objects above the water can alarm bass as an instinctive warning and they react to warning.

The 1st Bassmaster Classic held on lake Mead, a extremely clear water lake at that time, was won by Murray using white spinner baits in shallow water with the sun overhead. Everyone else target cliff shaded areas believing the bass couldn't be in bright sun lite shallow water with no shad. When asked why he fished in clear shallow water with a spinnerbait he stated that is where I also fish! The wasn't any wind, maybe a slight breeze with temperatures over 110 degrees.

One of my best big bass spots is very close to a osprey nesting tree. I have to watch closely when casting trout swimbaits for those osprey, so they catch the lure in mid cast.

We have no idea how a bass brain processes the images their eyes captures and bass have big eyes for a good reason, to find prey.

Tom

 

 

 

One thing we have a lot of in Florida is Cypress trees in lakes, and lots of Osprey nests.  I agree with your statement one of the best spots for big bass is very close to osprey nesting sites.  The reason for this is, Ospreys and their chicks are messy eaters with lots of fish parts and dung in the water.  Small fish flock to these areas for an easy meal.  Big bass flock to the same area to feed on the bait fish and small bass.  Where there is bait,  big bass will follow.

 

We also have lots of pad fields, and thick weed growth in our lakes.  If the shade is there, under bright conditions, bass will take advantage of the shade.  If your fishing clear rocky lakes without pads and weeds they will not seek out what is not there!

[WRB]

The osprey tree I am referring to is at least 100' away from water. It's the raptors shadow that a bass or other fish see. The problem with that theory is lots of non raptor birds fly over the water creating shadows all day long, the bass and other fish would be in a constant state panic.

Yes, when bass are young of the year living in cover they are prone to being a food source to birds, birds on the water like cormorants, grebes, herons. Gulls are the common airborne fish eating bird and bass often push smaller baitfish up to the surface where gulls take advantage of the baitfish along with the bass.

Dozens of gull shadows on the water doesn't panic the bass, they are conditioned to feed, not panic.

I present jigs to bass by making very long cast over 100', because the big bass are conditioned to be wary of boats. Deer or cattle walking along the shoreline or in the water doesn't seem to spook the bass, they have become conditioned to these events as not being a threat. If a 30' cast would produce strikes it would be a lot easier, that only works at night where I fish.

Tom

[WRB]

Another interesting idea is the refractive index as shown in the diagram:

http://astarmathsandphysics.com/o-level-physics-notes/o-level-physics-notes-a-fishs-view-of-the-world.html

 

 

 

 

 

 

In the fish eye view photo this is represented by the point where the blue sky ends and the band of bright green is present.  This is the point where light reflects off the surface rather than traveling straight into the water.

 

This appears to be dependent on how deep the fish is as well.  So the deeper the fish is the less direct sun spotlight area (blue sky) will be seen.

 

This could explain why it appears that fish are most affected by bright sun at the very narrow band of time when the sun is in that center blue area.

Interesting sketch of a 2 dimensional world. How does this look from facing the bass with the eyes on the upper sides of it's head? Bass eyes don't rotate, the are fixed position and see very well except directly overhead or under head or from behind, those are considered blind spots.

Tom

[Paul Roberts]

... as tatertester and Paul both conveyed the same in that casting directly over the fish has a negative impact in which they have personally noticed. ...

Think about why would fish respond so violently to something zipping overhead!

 

The problem, of course, is that most of this color discussion (as has been already stated) is merely speculation. So while fun to discuss, it likely has little relevance to whether or not we each experience successful fishing, witness the differences in personal experiences shared on this forum topic. There is some stuff we do know, provided by detailed examination of the largemouth bass' eye from studies such as the 2002 Kawamura & Kishimoto paper which appears to be the most recent and heavily cited example in literature. From that study we know the following:

 

• The occurrence of C-response provides direct evidence for the possession of color vision. In this study, therefore, it is concluded that the largemouth bass can discriminate colors.
• The dominant L-response with a maximum at 673nm and three variations in C-responses might indicate a better color analysis at longer wavelengths, implying that the largemouth bass is able to discriminate red better than blue.
• In the largemouth bass, the visual axis is found in the nasal-temporal direction and the near point is 13.5 cm, indicating that sharp image formation is not performed when an object comes closer than 13.5cm from the eyes. This near point is slightly shorter than those of other teleosts.
• The retina of the largemouth bass is specialized to both movement and form perceptions.

Part of the problem is that while science can determine things like optimal color sensitivity (red) of a bass' eye, that doesn't necessarily indicate that the color red is therefore more attractive to bass, since attractiveness is determined only behaviorally, and behavior is largely an adaptation to (specific) environment. As such, it wouldn't be unexpected to see angler color experiences that seem to contradict each other (or the research), and it therefore shouldn't suggest that one example/person is right and so the other must be wrong. Then there are the areas of inconsistent opinion or (dis)agreement amongst even the researchers themselves on subjects like UV perception by bass.

 

Of course, this is all part of what makes bass fishing so interesting.   Ultimately, each angler has to determine for himself how important (or not) any of this "color stuff" is to his own fishing.

 

-T9

Well.. we know a bit more than that. We also know that cones are much less light sensitive than rods and are not even employed at very low light. Night adapted (scotopic) vision is entirely rod vision. Photopic and scotopic vision are entirely different. Rod vision is not color vision. Bass, like us, don’t see color at night, and probably little of it in low light. Although the bass' pupil cannot regulate light coming in, pigments do, their chief job being to protect those sensitive rods. Although bass haven’t been looked at specifically, in other fishes adaption to photopic vision occurs in less than half the time it takes for scotopic adaption -something like 20 minutes for fish studied. If you consider how long it takes for lighting to build starting at dawn, such a time period appears aptly quick.

 

As John mentions, bass appear to be adapted to crepuscular activity, and various studies have shown they have advantages over prey under reduced light.

Bottom line, pertaining to this thread is that bass appreciate reduced light levels. There is not one reason, or “cause”, for this. Like many things when dealing with evolutionary adaptations within complex environments, it’s a matter of multiple selective forces over a long period of time. There’s “wisdom” in there that is darn difficult to deconstruct.

Major selective forces for bass use of shade likely include:

• Lighting in the aquatic environment and all that affects it: Atmosphere, depth, surface conditions, water clarity.
• Visual capabilites of prey
• Visual signatures produced by prey
• The need for security from predators (including “raptor effect”) –real (immediate) or remembered (instinctual).
• Limitations such as competing needs (reproduction) and historical constraints (evol changes occur in steps, modifications rather than complete instantaneous overhauls), i.e. bass anatomy (including eye placement and functions) serve multiple roles from competing requirements. If bass had hooves, yes, they could see them all at once. Bass are doing the best they can in an immensely complex world. They certainly keep us predators on our toes.

[Team9nine]

 

Well.. we know a bit more than that. We also know that cones are much less light sensitive than rods and are not even employed at very low light. Night adapted (scotopic) vision is entirely rod vision. Photopic and scotopic vision are entirely different. Rod vision is not color vision. Bass, like us, don’t see color at night, and probably little of it in low light. Although the bass' pupil cannot regulate light coming in, pigments do, their chief job being to protect those sensitive rods. Although bass haven’t been looked at specifically, in other fishes adaption to photopic vision occurs in less than half the time it takes for scotopic adaption -something like 20 minutes for fish studied. If you consider how long it takes for lighting to build starting at dawn, such a time period appear aptly quick.

 

 

 

LOL - that wasn't meant as an absolute statement/post of the only things we know about bass vision, Paul   but it is one of the few published studies carried out directly on largemouth bass eyes and not inferred from the eyes/research of other similar fish. As such, it gets heavily cited. So while generalities certainly apply such as the rods and cones function you mention, one still needs to be careful about stating anything specific to a bass that hasn't been proven otherwise. A good example of this overgeneralization would be UV vision in juvenile sunfish members, where one published study found that juvenile pumpkinseed do use UV vision for some degree of feeding advantage, while another (different) study demonstrated that juvenile bluegill do not. So where would a juvenile bass fall, being in the same family? Schrodinger's Cat?

 

-T9

[Paul Roberts]

LOL - that wasn't meant as an absolute statement/post of the only things we know about bass vision, Paul   but it is one of the few published studies carried out directly on largemouth bass eyes and not inferred from the eyes/research of other similar fish. As such, it gets heavily cited. So while generalities certainly apply such as the rods and cones function you mention, one still needs to be careful about stating anything specific to a bass that hasn't been proven otherwise. A good example of this overgeneralization would be UV vision in juvenile sunfish members, where one published study found that juvenile pumpkinseed do use UV vision for some degree of feeding advantage, while another (different) study demonstrated that juvenile bluegill do not. So where would a juvenile bass fall, being in the same family? Schrodinger's Cat?

 

-T9

Very true, Brian. We should be careful assuming too much across taxa. But, I don't think it should be ignored -some things are older and shared across taxa. As an example, the red and green peak sensitivities measured in bass are similar (but not the same) to those measured in bluegill. Bass behavior (crepuscular activity, use of shade, prey capture rates) tends to conform pretty well to what's known about light regulation in fish eyes.