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

[Bassun]

Hello all -- I wanted to hear thoughts and comments surrounding the article Dr. Wright posted as well as offer a counter theory which I feel is more impactuful in terms of fish relating to a floating dock. 

 

First, let me clearly define that this is NOT a troll post or anything of that nature.  I do, however, have some differing opinions on his theory.  However, I would also like to clarify that I do not completely dismiss his theory on the fishes preservation instinct completely.  It is my opinion that there are other factors beyond age old preservation which often time places bass under floating docks, and other hard surface cover.

 

To begin, I would like to expand on the temperature concept.  I absolutely agree that the water under a dock, generally, is not noticeably cooler than the surrounding water.  Given waters physical properties and what we understand of the physics of the motion of water, as well as the thermodynamics of water it makes complete sense that a small dock covering a miniscule area of water would have only the most negligible effect on water temps.  Although I agree that the water itself is not significantly warmer, we do know that sunlight heats water and the intensity of that light is rapidly diminishing as studies present that less than half of the surface intensity is present at only three feet.  These figures obviously change depending on the specific water conditions.  The more clear the sample water the deeper the penetration will be, and conversely muddy or deeply stained water will be much more capable of stopping the light.  Over 25% of surface light is incapable of penetrating even over 1 centimeter!

 

Focusing on the fact that there is a radiant intensity at three feet (and deeper), we know there is an ability for heat to be recognized.  While the water itself may not have a discernible temperature variation, any objects resting within this "radiant zone" will be capable of absorbing the heat.  So, I postulate that an object at rest is capable of absorbing heat from the sun at a greater rate than the surrounding moving and highly thermally conductive water, especially if that object is dark colored.  Given, the fact that it is surrounded by water does help negate the impact as well as the actual depth of said object noting a very quick reduction of intensity of light in water. 

 

Now having said all of that, do I believe that is the primary reason for fish under cover, no -- but to completely ignore the radiant impact of the sun is a bit dismissive. Obviously, depth change is much more effective and has other benefits and thusly I would suggest if a fish did want to cool down, it would just go to a deeper depth usually.  But, I do not think we can completely ignore the thermal impact of sunlight penetrating the surface.

 

I could be wrong, but that's how I understand it.  Now, given that, even I do not believe that is the main reason for fish in shady areas.  I do, however, believe there is more to it than just the Raptor Effect.  Let us consider vision, not of birds of prey, but of the fish.  Fish eyes are very similar, in most cases, to human eyes.  Now, let's consider a scenario of varying light intensities in which we should be familiar with, then apply those scenarios to fish.

 

If you have ever been inside your house, looking out at night you have probably noticed a couple of things.  A: It's difficult to see outside when it is bright inside, and dark outside.  B: Easy to see when it is dark inside, and a light is on outside.  Considering that bass are predatory, largely sight based feeders, it becomes evident they would naturally select a situation where they can more easily see.  We know, from our own experience, it is easier to see from a darker location looking into a well lit area. 

 

Expanding the effects of light on vision, we should also consider light blindness.  Not as in permanent or even flash blindness where the retinal pigments are bleached out; but rather the scenario where you have sunlight hitting your eye directly, and you are trying to see.  I'm doing a poor job of describing the situation - consider the following.  You are standing in the sun with no hat, and the sun is hitting you in the face.  Naturally you will squint, then probably put a hand up to block the sun from directly hitting your eyes, and eventually probably put on a hat and sunglasses.  With each of these additional shading techniques you will note that your ability to see increases.  A better example is when you are driving into the sun.  You are often "blinded" by the light, and will lower a visor to block the sun.

 

Now considering most fish can't squint, cover their eyes with a hand (Chernobyl maybe? lol) or wear hats, but have the same impacts on their vision, it stands to reason they are likely to migrate to a location where the intensity of the sun is reduced, aka shade.  One of the more significant differences in a fishes eye vs human is the way our pupils work.  Most fish have fixed pupil sizes.  Whereas a humans eye can reduce the glare of light by decreasing the amount of light passing in by reducing the pupil size a fish usually cannot.  Their eyes do adjust to different levels of light, however, it is accomplished utilizing a shift in the relative location of the rods and cones in their eyes.  This is a much slower process and depending on the fish may take up to an hour for a major shift to occur. 

 

Certainly, beyond being able to see, we should also consider being able to be seen - but not just from above but from prey.  A fish silhouetted in bright open water is much easier to see then one hiding in the shadows both from above and below the surface.  I don't think there is any need to develop this any further as we all know bass are ambush predators and are obviously keen at utilizing structure and cover to hide themselves.  Everything about a bass is designed for ambushing from cover.

 

 

So, in conclusion, I would postulate that a bigger reason for fish staying under the surface cover of a floating dock is related to the fishes sight rather than that of being seen by raptors.  I think I have demonstrated multiple positive benefits, related to vision, and considering bass are primarily sight based predators (granted they do utilize all other senses and especially use the lateral line), those benefits would likely be high on their priority list.  I absolutly do not feel that this is the only reason a fish relates to cover, rather just one area which in this situation I felt needed to be expounded on.

 

There is much more discussion to be had surrounding light and water.  I did not delve into color spectrum which is visible at different depths or the impact of UV or polarized light.  I think all of these play a hugely important role in the life any sight oriented fish.

 

Lastly, I would like to reiterate that I am not attempting to bash Dr. Wrights article.  I found it to be quite interesting and the notion of the Raptor Effect, I think does have some merit.  The innate behavior to hide from prey is absolutely a valid and salient fact, it is the level of impact in which I am challenging.  I am not a freshwater biologist, so it is possible my theories and conclusions are completely misguided; but I felt inclined to dive a little deeper into this and to at least explore the sight related aspect to fish holding under floating cover.

[SHaugh]

Any diver will confirm that you can get sunburn underwater....   you need to be several feet underwater before you won't.

[Team9nine]

This subject has actually been studied rather extensively in fishes, both freshwater and salt water. The penchant of fishes to use shade being a pretty universal behavior. As such, the answer like most things in life, is not so cut and dried, as the research shows that it depends on whether you are the predator or the prey, solitary or in a group, or are more active during daylight or at night. All that said, the generally established conclusions are that light and shading is the most common reason fish use such objects as docks, either to hide from a (water based) predator or to use shade to your predatory advantage. I would have to believe this is the primary reason for such use by bass, especially adult bass. However, the research also suggests that for some fish (bluegills, etc., and I might assume to some degree even small bass), reared in a hatchery environment and later stocked into lakes, that the "raptor effect" is likely a very real behavioral response. 

 

-T9

[Swampstud]

Imo they like the shade or dark areas because it covers there outline/silouette. Your right about it bein difficult to see with the sunlight in your eyes. Now remember how bass utilize "edges" , that shadeline is a prime edge. The bluegill thats swimmin out around the dock right near that edge, hes got the sunlight in his eyes at some sort of angle. Shear disadvantage.

Now that bass sittin in the dark with no outline, maybe a blur of green n white is lookin out into that lit up area right infront the dock. The sun highlighting every twitch an kick of the bluegills tailfin. That bass is utilizing a prime peice of cover an a seeking that perfect feeding oppurtunity. Complete advantage for mr.bigmouth

Ive seen it a few times on hook n look.

Theyll use a clump of grass, stump, treetop in the same manner. Something to cover up that outline to keep from being spotted.

As a bowhunter we ALWAYS are searching for a tree thats got plenty of cover to prevent the deer from siloutting us.

[Paul Roberts]

... we all know bass are ambush predators and are obviously keen at utilizing structure and cover to hide themselves.  Everything about a bass is designed for ambushing from cover.

 

First of all, bass are not "ambush predators". They are not built like ambush specialists that use a very high degree of camouflage, and an entirely sedentary hunting behavior. Some even lure prey to themselves. Examples of true ambush predators are stonefishes, scorpionfishes, flatfishes, and various bathypelagic species that hunt in complete darkness.

 

Bass are not specialized pursuit hunters, stalkers, or habituaters either. They are "generalists" using all of these strategies and more. What I believe we are seeing when bass are "ambushing" (OK if used very loosely) are fish at a low activity level and resting. Bass are opportunists and will take a lure or prey that blunders too close, even when the bass are in an energy conservative state. Realize that prey doesn’t “blunder too close” all that often hence, in part, the need for both energy conservation and the more active hunting states. Energy conservation tends to be done where they are safest -under cover, and near or over deep water. What I believe Dr. Wright saw, when viewing those bass under that floating dock away from any other cover, were simply resting bass.

 

"Radiant effect" is plausible. I always wanted to test that.

We can't, and I know you didn't, preclude the raptor effect as part of the story. I fish small waters -a lot of them- and aerial threats such as kingfishers, herons, terns, osprey, and eagles are a nearly constant threat. Google any one of these birds along with "bass" and you'll see a lot of images people just happened to capture. Aerial threats create an instantaneous instinctive response from fish -especially so on sunny days. I've watched carp, bluegills, and bass bolt under passing light aircraft (500feet up!). Ever try to throw a lure over shallow fish under bright skies? Aerial threats are well understood by fish.

 

Underwater threats are real too. This could be remembered or immediate. Bass are prey for much of their (often short) lives. Everything eats bass fry. Later, larger bass, pickeral, pike, crappie, catfish, and muskie are threats. Then there are mammals. I see mink on my ponds and once saw one pop to the surface with a 10inch bass. There was a time when otters were MUCH more common than they are now.

 

No, predation is not the whole story and all your points are good ones. Thermoregulation (possibly) and energetic states are likely part of the story as well.

[Bassun]

First of all, bass are not "ambush predators". They are not built like ambush specialists that use a very high degree of camouflage, and an entirely sedentary hunting behavior. Some even lure prey to themselves. Examples of true ambush predators are stonefishes, scorpionfishes, flatfishes, and various bathypelagic species that hunt in complete darkness.

 

Bass are not specialized pursuit hunters, stalkers, or habituaters either. They are "generalists" using all of these strategies and more. What I believe we are seeing when bass are "ambushing" (OK if used very loosely) are fish at a low activity level and resting. Bass are opportunists and will take a lure or prey that blunders too close, even when the bass are in an energy conservative state. Realize that prey doesn’t “blunder too close” all that often hence, in part, the need for both energy conservation and the more active hunting states. Energy conservation tends to be done where they are safest -under cover, and near or over deep water. What I believe Dr. Wright saw, when viewing those bass under that floating dock away from any other cover, were simply resting bass.

 

Paul -- You are absolutely correct, and I was too cavalier with my declaration as ambush predators in the purest sense.  Given the discussion level, I should have thought more about that statement.  I was simply meaning to convey 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.  Your description as "generalists" and "opportunistic" is a much better description and much better conveys their feeding methods.

 

Thank you for correcting that and adding a good description of their feeding habits.

 

Imo they like the shade or dark areas because it covers there outline/silouette. Your right about it bein difficult to see with the sunlight in your eyes. Now remember how bass utilize "edges" , that shadeline is a prime edge. The bluegill thats swimmin out around the dock right near that edge, hes got the sunlight in his eyes at some sort of angle. Shear disadvantage.

Now that bass sittin in the dark with no outline, maybe a blur of green n white is lookin out into that lit up area right infront the dock. The sun highlighting every twitch an kick of the bluegills tailfin. That bass is utilizing a prime peice of cover an a seeking that perfect feeding oppurtunity. Complete advantage for mr.bigmouth

Ive seen it a few times on hook n look.

Theyll use a clump of grass, stump, treetop in the same manner. Something to cover up that outline to keep from being spotted.

As a bowhunter we ALWAYS are searching for a tree thats got plenty of cover to prevent the deer from siloutting us.

 

Swampstud -- what a great description of fish feeding from dark to light.  While not "ambush" in the sense a stonefish ambushes, this is more akin to what I was trying to convey.  You hit it spot on, and comparing it to bow hunting makes perfect sense.  You are literally trying to do the same thing, and would never find good success without good cover.  Excellent points.

 

This subject has actually been studied rather extensively in fishes, both freshwater and salt water. The penchant of fishes to use shade being a pretty universal behavior. As such, the answer like most things in life, is not so cut and dried, as the research shows that it depends on whether you are the predator or the prey, solitary or in a group, or are more active during daylight or at night. All that said, the generally established conclusions are that light and shading is the most common reason fish use such objects as docks, either to hide from a (water based) predator or to use shade to your predatory advantage. I would have to believe this is the primary reason for such use by bass, especially adult bass. However, the research also suggests that for some fish (bluegills, etc., and I might assume to some degree even small bass), reared in a hatchery environment and later stocked into lakes, that the "raptor effect" is likely a very real behavioral response. 

 

-T9

Team9nine - Perhaps I should have researched and referenced that information vs posing my own suppositions, but it's good to hear my thought process and understanding isn't devoid of proven fact.  And I absolutely agree that there are TONS of other factors which should be considered.  And surely there is merit to the raptor effect.

 

 

 

All said, perhaps I am being too dismissive and potentially being too locked into the singular reasoning given in the article.  I'm sure Dr. Wright had not intended to pose that the "only" reason is the raptor effect. 

 

I should also consider the locale and types of raptors in the population.  I think truely one would need to consider a least a few factors to effectively suggest the raptor effect as a primary reason for use of open cover.  The number of birds of prey vs the amount of available prey outside of water would certianly be a contributing factor.  If you are in an area with a high density of predators, and a low level of mammalian prey then it would seem likely fish would be a higher staple regardless of the raptor.  In the same sense, water predators like eagles and osprey are absolutely going to target fish more often then say a Broad-winged or Red-tailed Hawks. 

 

Locally, we have a higher density of non-fishing raptors - I think that has somewhat jaded my notion of the raptor effect.  (South-Western VA)  I suspect, someone in an area with a greater density of fishing birds would be more likely to be impacted by the raptor effect.  My suspicion is that Dr Wright is in an area such as that, and given those factors his conclusion certainly holds a greater merit.  Locally, I've only seen the smallest fish taken by any birds.  But, our density of Osprey and Eagle is fairly low where as our Hawk density is much higher.  The fish I personally have seen taken mostly come from Great Blue Herons and I have never personally seen an Eagle take any fish from the local waters.  That's not to say they don't, only that it is something I have not personally witnessed.

 

Thanks for the conversation y'all.  This article has certainly opened up an interesting conversation, and I think legitimatly offers another reason for the positioning of bass.

[bighed]

Wow dude, that would have taken me three days to formulate and write!  As far as birds of prey, bass in this area will rarely encounter an eagle or osprey.  They do however encounter comorants constantly and overhead cover does little to protect them from these birds.  The tell tail V mark on the backs of bass have become so prevalant it's very rare that a trip to the lake doesn't produce a fish with that scare.  However, the bass still do relate to docks I believe for the reasons you explained. 

[Bassun]

lol sometimes I get to rambling...

 

We don't have any perminate populate of cormorant's here, at least as far as I know.  Have you noticed any difference in how the bass react when there is a cormorant on the water?  I'm curious if they tend to get defensive and hole up or if they continue to hit and feed as normal?

[bighed]

The comorants are pretty easily spooked where I fish.  They do not hang around when a boat approaches so it's a little hard to say if their presence affects the bite.  It does seem that a bass will bite as soon as the bird is run off by an approaching angler so I would say the fish are not leaving the area.

[roadwarrior]

WOW!

 

Very interesting discussion.

 

 

 

[Dwight Hottle]

The comorants are pretty easily spooked where I fish.  They do not hang around when a boat approaches so it's a little hard to say if their presence affects the bite.  It does seem that a bass will bite as soon as the bird is run off by an approaching angler so I would say the fish are not leaving the area.

 

I agree with that observation completely. Here on lake erie the cormorants are boat wary & leave the area.

 

I have observed the exact opposite down off SW Florida in the gulf. Down there I have seen cormorants hanging around boats like pelicans waiting for undersized or catch & release  fish like sea trout. You could release a small trout on the port side of the boat & see the cormorants swim up on the starboard side surface & swallow the fish you just released. It must be a learned behaviour.

[SHaugh]

If fish are overly concerned with remaining hidden from overhead predators why do they approach lighted areas at night ?

While I'm sure there is an instinctive avoidance mechanism toward this type of predation, I don't think it explains the behavior very well. Does a fish need to worry about a crane or heron in 6 feet of water ? Yet we all know that they will still migrate toward the deep shade even on a floating dock out in 20 feet of water.

I think you are much more on the right track when you talk about UV radiation and how fishes eyes work. They are very sensitive but slow to adapt to changing light levels. the kind of sharp contrasts that occur in a sunny shallow environment are exactly what they would want to avoid. If their eyes are adjusted to some level of very bright sunlight, then shaded areas must appear very black and unknown to them. For this reason they would seek out the middle ground because that is simply where their eyes function best and have the greatest range of visual adjustment.

Their sensitive eyes are undoubtedly affected by UV exposure as well... they probably get "sore" when they spend too much time in direct sun.... As I said about sunburn above, most organisms are not 100% adapted to full sun exposure, and will avoid it when possible.

If you observe natural design and evolution you will quickly notice that nature abhors excess capacity. Organs like eyes are simply not designed to be very robust at the extremes of their requirements. This is what allows the organ to function well through a broader range of conditions. If I want to design an eye to see well in the dark, it is a given that it will not work so well in bright sunlight. I think this train of thought goes a lot further in explaining why fish prefer the "middle ground" of their environment.

Another analogy would be how humans design a building that they will inhabit. What temperature do they select ? What light level ? Etc. We choose to occupy areas that are most "comfortable" to us.

[Choporoz]

Fascinating discussion!!  Everything you've  written Bassun makes sense to me.   Unfortunately, every time I read more about bass instincts and tendencies, I manage to amuse myself to the point of distraction.....I want to know what the bass was thinking!....but, really....who the heck is ever going to know what a fish was thinking....what was I thinking....lol

 

I'd like to coax the discussion towards a little more empirical aspects.  

 

Are bass as likely to gravitate towards the underside of dock if it is cloudy?  What about at night?

[Team9nine]

I'd like to coax the discussion towards a little more empirical aspects.  

 

Are bass as likely to gravitate towards the underside of dock if it is cloudy?  What about at night?

 

 

While those conditions don't preclude bass from using such structures for a variety of reasons, on cloudy days and at night, the relative visual advantages offered by them (docks) on brighter days are decreased considerably, and hence studies have shown a corresponding decrease in the attractiveness of such overhead objects. It's been suggested that bass and similar predators are actually more likely to move down and away in the water column to be better able to silhouette prey against a potentially lighter background (sky) at night, as well as to use a "flushing" behavior (Doug Hannon, John Hope) during active low light feeding periods (see: http://www.bassresource.com/fish_biology/ambush_bass.html). 

 

-T9

[bighed]

No doubt in my mind that the bass do not hug as tightly to a dock on a cloudy day as a sunny one.  Also, for me, dock fishing is something that I don't start doing until the sun is high.  The later in the day the more bass will load up in the shade of a dock

[WRB]

I haven't read the referenced article "the raptor effect" and will commit later.

What sentence the caught my eye was bass eyes are like humans, not true. The fact is we don't know how bass see. There are lots of assumptions based on eye constructions for example Dr Keith Jones.

Keep in mind a simple fact; bass have evolved as a sight feeding predator living underwater and have developed keen senses to work as a system to located prey like lateral line nerves, hearing, odors, etc.

What has been written to date doesn't explain how bass see in the dark, low light or very bright light in clear water. Having caught bass in all those conditions over a 60 year period, my experiences are not answered by current science. I believe bass have far better color vision and low light vision than a human. Slight changes in color can make a big difference in total darkness or very bright clear water.

Water wave action defuses light and creates light movement that acts to camouflage bass to their prey.

In regards to water temperature variations within the water column consider water density layers and current.

It would be nice if folks simply swam in the lake they fish, water temperature isn't homogenous, it's both warmer and cooler same areas within an area is common.

All cover isn't equal, aquatic green vegetation produces dissolved oxygen a key factor for bass. The cover aids prey seeking sanctuary from predators like bass and food, both reasons bass use cover areas.

Tom

[tatertester]

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.

[SHaugh]

I agree that we should not imagine how a fish sees by imagining a human underwater with a mask on.  One of the key differences between men and fish is that a fish has an extremely large and upward facing field of view.  They also don't have necks which allow humans to angle their eyes away from strong light sources.

 

So imagining a fishes world I believe that when the sun is high in the sky their eyes are literally being overloaded with direct sunlight.. and there is no way for them to squint or avoid it... similar to if you were forced to turn your face upward directly toward the sun and then attempt to open your eyes and see what is in front of you.  Naturally your vision would be seriously compromised by all that direct sunlight flowing into your eye.

 

This would compel you to find places where that bright overhead sun was not directly shining in your eyes.

[Bassun]

I agree that we should not imagine how a fish sees by imagining a human underwater with a mask on.  One of the key differences between men and fish is that a fish has an extremely large and upward facing field of view.  They also don't have necks which allow humans to angle their eyes away from strong light sources.

 

So imagining a fishes world I believe that when the sun is high in the sky their eyes are literally being overloaded with direct sunlight.. and there is no way for them to squint or avoid it... similar to if you were forced to turn your face upward directly toward the sun and then attempt to open your eyes and see what is in front of you.  Naturally your vision would be seriously compromised by all that direct sunlight flowing into your eye.

 

This would compel you to find places where that bright overhead sun was not directly shining in your eyes.

 

I think your assertion that this would compel fish to "shade" their eyes is spot on. 

 

I haven't read the referenced article "the raptor effect" and will commit later.

What sentence the caught my eye was bass eyes are like humans, not true. The fact is we don't know how bass see. There are lots of assumptions based on eye constructions for example Dr Keith Jones.

Keep in mind a simple fact; bass have evolved as a sight feeding predator living underwater and have developed keen senses to work as a system to located prey like lateral line nerves, hearing, odors, etc.

What has been written to date doesn't explain how bass see in the dark, low light or very bright light in clear water. Having caught bass in all those conditions over a 60 year period, my experiences are not answered by current science. I believe bass have far better color vision and low light vision than a human. Slight changes in color can make a big difference in total darkness or very bright clear water.

 

 

I agree with some of your points, but have to completely disagree in regards to the similarities of the eye.  I also agree there is not tons of research about the eyesight of bass specifically, but I believe we can actually say that functionally the eyes are quite similar. 

 

Comparing the two you have the same basic structure:  lens, cornea, iris, pupil, retina and so forth.  Fish eyes also have rods and cones just as human eyes do.  The eyes work, generally, to the same end.  Some of the specific methods are different, but the overall design and function is quite similar.

 

Some of the more notable differences would be:  a much-expanded monocular vision, how the lenses adjust, and how they regulate photic conditions.  Expanding on a few of the notable differences, but certainly not to be considered all inclusive, I think we can explore some of the structural differences. 

 

Let’s start with the lens.  In a human eye our lens is flexed and relaxed in order to adjust focus.  A bass lens is comparatively larger and shaped more round versus the convex shape of a human lens.  Given the shape, it stands to reason that flexing would not be the method used to change focus – rather a retractor muscle adjusts the positioning to create focus.

 

An added benefit of the round lens is that it allows for correction of spherical aberration, which ultimately leads to fish being able to focus any available light very sharply. 

 

Now the Iris and Pupil work differently as well.  And while there are a variety of pupil types in fish, some such as shark are even capable contraction and dilation to control the amount of light entering the eye, bass do not have quickly changing pupil sizes.  It was mentioned earlier that bass are quite slow to adjust from light to dark vision.  The reason for this is that they simply do not dilate their pupils and allow more light in or contract them to restrict light; rather they use retinomotor activity, a change in the positioning and ratio of rods and cones effectively active, as well as their pigment proportions, in the eye to control the sensitivity to light.

 

Obviously I am just glazing the surface on some of the more complicated differences in our eyes, but as a whole they are quite similar.  They have a pupil to let light in, focus that light with a lens on the retina, and the optic never carries the signals to the optic lobe in their brain.  There has been a lot of research on fish vision, although not as much specific to bass only.  Admittedly, I have not done the research myself, and am just referencing others work.

 

Now I would have to agree things are based on assumptions, but realistically how can we have any empirical data on exactly how a fishes brain decodes the nerve signals.

[geo g]

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.  With bright skies, we put on a hat and sunglasses seeking shade and eye relief.  Fish seek shade in thick cover, and structure like docks.  In early morning the fish are often scattered and away from the tight cover.  As the sun gets high in the sky, bass will often seek out shade and relief from the intense sun.  In Florida we have many birds of pray that seek out fish.  To me I don't see that as a  big factor.  Just like us, bass seek eye relief from the intense rays of the tropical sun, and sunglasses are just too dam expensive!

[Paul Roberts]

...

What has been written to date doesn't explain how bass see in the dark, low light or very bright light in clear water. Having caught bass in all those conditions over a 60 year period, my experiences are not answered by current science. I believe bass have far better color vision and low light vision than a human. ...

There is a fair amount of research on night activity and hunting success at various light intensities, as well as turbidity. My take-home is that mature bass see quite well in dim light -are even adapted to it. It takes some time to adapt after nightfall (as it does for humans). That hunting success rates fall as lighting approaches complete darkness. And that the lateral line system becomes more important in very low light and as turbidity increases.

 

...So imagining a fishes world I believe that when the sun is high in the sky their eyes are literally being overloaded with direct sunlight. ...

I've often fished to bass under brilliant skies and clear water. They don't seem to mind being exposed at times, and the light certainly doesn't appear to bother their eyes. But, they can be darn tough to catch, able to scrutinize every stupid move my baits make!

 

That said, there is plenty of research documenting deleterious effects of UV to fish and fish eggs and larvae. UV is a plausible part of the story too.

[Brian6428]

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

[WRB]

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

Anyone who has tournament fished our SoCal lakes year around will understand how very important color on soft plastics can be.

You can be fishing a 4 1/2" straight tail worm at 40' to 60' and only 1 specific color combination will catch bass, this happens year after year, tournament after tournament....you don't have the hot color you are donating your money. I have given my partner a hot worm and they instantly start catching bass and have been on the receiving end of this exchange. Same everything, location, depth, line, hooks, speed and presentation.

I also tie some very special hair jigs with multiple colors of dyed deer hair combined with custom dyed pork trailers. Some of these jigs have a few strands of flash to add reflective color. Fishing night tournaments in darkness bass will prefer a jig with or without the flash strands and it can make the difference between a good limit and being blanked. The human eye can't see color without the aid of good light, we see shades of gray without light.

Our deep structured lakes have clear water with very good depth of light that averages about 10' and up to 25'. The bass in these lakes have keen eye sight.

The SoCal lakes have very little surface vegetation or weed mats and very little aquatic vegetation for about 10 months of the year. The lakes do not have any boat docks except at the marina, therefor the bass are exposed to predator birds the majority of the lives. We have osprey, eagle, gulls, herons, cormorants, grebes, etc that prey on baby bass to adult bass. No cover, no problem the learn to survive or they don't.

Tom

[Paul Roberts]

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

...

They don't.

 

I guess I've seen too many color theories just not hold up. Here's a fun one:

 

Kevin Van Dam relates a story in one of his books" (paraphrased):

Four top pros were sharing a large main lake point, and catching bass on worms. Each found a particular color that drew the most strikes. "The only one that worked", they each said when it was over. Interesting thing was, all four ended up "divining" 4 entirely different colors.

[WRB]

Bill Murphy wrote in his book about a night fishing experience he had regarding a night tournament.

The bite was very slow, he reached in a bag of his worms thinking it was the Otay Special chocolate brown with black blood vain that he was using. Bill instantly started to catch good size bass, handed his partner a worm and he caught another good bass. The worm bag only had a few worms in it and when they were gone he got out another bad of Otay Specials and the bite stooped. Bill picked up one of the torn up worms and looked at it with a flash light, it wasn't the Otay Special that caught the bass, it was a chocolate brown with neon blue vain worm, same size, same make, slightly different color. Found another bag of the neon blue blood vain and the bite returned.

I can't tell you how many times that has happened to me over the years where worm color was critical.

I have also experienced were size was important, color secondary.

Our eyes can only determine color spectrum our brain can interpret, same with fish.

Keep an open mind when it comes to what bass see, it's far different then a human.

Tom