What evidence do we have to support the hypothesis

Based on the previous thread in relation to fish being able to see and recognise colours in the same way in which we do. I was discussion this with a PhD in Evolutionary Anthropology only last night and he claimed science suggested that fish don`t see colors in the way humans do, but because of light reflection below water, depth and angles they actually see patterns, ie yellows reds and blacks in striped patterns may have better attraction triggers than plain red or yellow patterns. The way fish sense and smell bait under water is of course different than how odours travel in the air, underwater senses are based on larger particle dissemination dispersal throw the medium with the causal effect being movement/ currents if you like. Basically smell travels slower under water. Which brings up the question of oils and bait flavours and how fast they disperse, an heavier attractants will dispease slower than a bouyant one and a surface floating attractant will be sujected to air and environmental conditions and disperse much fasters. An heavier oil will always try to disperse down wards because of the gravitational effect.

appologies for the bad grammar and spelling, I`m having a blonde moment

I don't really think any of us can even begin to understand how a fish sees, senses or whatever......all we can do is base our thoughts on our own experiences.

I would never by anything on the principle that fish can't see it..eg red line.....because i believe they know it's there and see it.

If i had to choose a line that i thought gave me best chance of the fish sensing it less it would be one were the colouring is broken up into different colours/shades thus possibly and i emphasise "possibly" it may "confuse" the fishes awareness?

I'm not so sure about smells etc and how they travel in water..... but again i'm aware of just how a fish can home in on a food item from a distance, i have seen chub react veryfast to a black slug?

don't really think any of us can even begin to understand how a fish sees, senses or whatever......all we can do is base our thoughts on our own experiences.


We know how fish vision works, fish eyes can be identified and modelled bases on the natural cone design, so we know how the eye works and what it will see, i think the problem is how the fish tranfers that information to the brain, we can only suggest this based on how humans transfer this information to the brain based on the logic and mechanics of the design. mechanics have common factors of course and this is usually constant, the variable could be the transfer of information, which we can assume from known knowledge and analytical research. I can remember reading about the fish tank experiments with tubes hidden in the gravel and flavours being dispearsed through the tubes and the time reaction factor of the fish. I`ve done this myself and the results are quite interesting. Even if the flavore is not attractive to the fish, the fish indicates some type of reaction as the flavour is released from the tube.

Thats exactly what i mean mate......we (or our scientists) can work out the mechanics as far as is possible....but not give us the real "act" in practice.

Is it really true that our scientists cannot work out how a bumble bee can fly?....my point is that even the best brains cannot get it all?

In mammalia we have cone cells and rod cells in the eye mechanics, the cone cell is designed to pick out greater definition than the rod cell, the latter design is to pick up moment.

My understanding is that fish generally have rod cells, which suggests they are designed to identify movement, an intersting paper on this is the Proliferation of rod cells in the mature retina of the Japanese flounder Paralichthys olivaceus

Striped patterns eh! Mr Monk, You realise you have now started a trend towards boilies coloured like barber shop poles and multi coloured boiles like our favourite marbles when we kids.


Seriously though, I remember times when a red and white together was supposed to outfish a single colour maggot on certain venues, if I were truthful I would also say that I have never had much success fishing a bait like that. I also believe that we falsely give fish credit for having the sense to choose a particular colour bait in preference to another, to me its in the same box as my wife who thinks our dog understands the English language.

As far as taste/flavour goes....Cakey made what i thought a good case for why some baits seem to be long term.....eg tutti, it could be a good "label" "flavour" whatever you want to call it because it is a mix and gives off different "labels" in different conditions and therefore may seem different to the fish on each occasion?

I found that thought provoking.

Heres an interesting peice by By Mark Evans Paul, it certainly gives food for though

One, two, three... Uhhhh? Where is the fourth fish I just bought? Ohhhh! Perhaps if I look in from the sides of the tank or peer down from the top or contort my head at just the right angle, I?ll be able see it hiding within the rocks or corals or algae. Or maybe not. Or perhaps if I wait until lights-out and stare into the tank with a flashlight I?ll see it. Or perhaps if I stop sticking my face against the glass, the fish will stop being frightened and come out on its own.

After all, we do watch fish for pleasure. And in order to maintain our fishes? health, we scrutinize their appearance and behavior.

This scenario probably sounds familiar to many aquarists. After all, we do watch fish for pleasure. And in order to maintain our fishes? health, we scrutinize their appearance and behavior. But we are apt to gloss over the fact that the fish are capable of staring back. Not that they would since they don?t ponder the world in quite the same manner as we humans do. Our relationship with our fish then is mostly one sided. The fishes don?t care about our health one iota. They are incapable and are too busy dealing with the their own immediate needs in their own environment, within the confines of a tank?s walls. Their problems are all survival related, from competition for food or territory to hierarchical aggression from conspecifics to presentations of possible reproductive opportunities. But most of the cues that set off the behavioral responses from individual fishes are, in fact, visual in nature. The fishes of our aquariums apprehend a wide range of colors and shapes. They perceive allies and rivals thru color. And a pair of gawking eyes is an easily recognizable threat as is the shape of a gaping mouth. This is why we, as aquarists, should take a moment to appreciate life from the perspective of a fish by delving into some of the aspects of the fish eye.

We begin with a generalized discussion of fish eye anatomy. ?Generalized? because the term ?fish? is not scientifically descriptive of the wide ranging and often distantly related species we think of as fish. Basically, there are too many idiosyncracies in eye structure among the various fish groups to be covered here. But we can start by stating that the structure of the generalized fish eye is not far removed from other vertebrate eyes like our own human eyes. Like the eyes of terrestrial vertebrates, fish eyes have a cornea, an iris and a pupil, a lens, and a retina. The process of actually turning light into images begins at the retina, the parabolic shaped surface at the back of the eye, where photons of light are received and transformed into electrical impulses for interpretation by the brain. The retina contains the photosensitive receptors, cells called rods and cones, which accomplish the task of receiving light, transforming it into impulses, and directing it through nerve fibers leading to the brain. We can appreciate the amount of information transmitted thru the nerve fibers when we realize that the vertebrate eye houses millions of nerve fibers relaying information from millions of photosensitive cells.

Generalized fish eye in cross section. Spherical lens (center) with muscle and ligament attached, protruding through pupil ofyellow iris. Cornea (right) covering iris and lens.Retina (dark area) containing the millions of lightsensitive cells.Optic nerve (lower left) extending from eye.

A prominent characteristic of the fish eye, from the outside at least, is its bulbous nature. Some of the reasons for this will become apparent. The outer layer of the eye, the cornea, is dome-shaped and transparent. It is the first to receive light. With the terrestrial vertebrate eye, light travels through the air and hits the cornea. Because the air and cornea are of differing densities, the light is refracted (bent and directed) into the opening called the pupil. Water and cornea are of about equal densities so there is little refraction with the cornea of a fish eye. Again, with terrestrial vertebrates, the iris is the colored aperture that opens and closes, adjusting the size of the pupil and the amount of light entering the eye.

But in most teleost fishes, because of the protruding lens, the iris is rigid, making the pupil a fixed size. Therefore, to compensate for the amount of light entering the eye, an amount which could be too intense or not intense enough to measure, the retina adjusts the position of the photo receptors. And whereas our terrestrial eyes adjust to light levels within a few moments, fish eyes take much longer. We can observe this in aquarium fish that have been subjected to suddenly having their tank light turned on. Such fish typically hide until their eyes have adjusted to the light, which can take fifteen or twenty minutes. Certain lucky shark species have eyes equipped with an adjustable iris. The silky shark, for example, has an iris that is a vertical slit similar in appearance to a cat?s eye. (It is interesting to note that in vertebrates, eye color and skin color are often genetically linked. Like in house cats, for example, where coat color and eye color change according to breed. Fish eyes are no different.) Behind the iris is the most noteworthy feature of the fish eye, the lens. In fish the lens is usually sphere shaped and rigid and protrudes into the pupil opening, a very different arrangement than the lens of the human eye, which is almost flattened and positioned behind the pupil. In both the fish and the human eye, it is muscles acting on the lens that determine whether an image is properly focused on the retina. The difference is that in the human eye the shape of the lens is altered, whereas in the fish eye focusing is accomplished by changing the position of the lens.

Angelfish eye with tear-dropped shaped pupil. Grouper eye with an almost rectangularshaped pupil. Grouper face (right) showing the advantage of having a non-circular pupil, the ability to see more clearly forward.

Now that we know by what morphological mechanisms fish see, the question arises, what do they actually see through their fishy eyes. Anyone who has been involved with photography has probably heard of a fish eye lens. The image through such a lens is so wide that it is distorted. Moving from the center out, objects appear curved, the light bent inward. Originally, fish eyes lenses were used to photograph the night sky, because of their capacity to capture a lot of information. But for the purposes of our biological discussion, they probably do not provide a completely accurate representation of what fish actually see through their eyes. One reason is that the lens of a teleost fish eye is eccentrically positioned, which alters the lens-to-retina distance in certain parts of the image. This provides fish with close up vision forward and far vision to the side. Essentially, the fish is nearsighted when looking forward at a food item near its mouth, but is farsighted to the side and is able to locate possible predators lurking in the distance. But because most fish have eyes situated on the sides of the heads, their ability to judge distance is not as acute as it is with terrestrial vertebrates. (As humans our eyes look forward so we have binocular vision and are able to judge distances fairly accurately). And because their eyes are situated on the sides of their heads, fish almost have a three hundred and sixty degree view of their world. Of course, fish with broad heads or large tails have blind spots they must compensate for by sweeping their heads from side to side.

Spherical lens of fish eye protruding through pupil opening of iris. Flattened camera-like lens of human eye sitting below iris and pupil.The human iris is therefore adjustable according to light intensity,while the fish eye iris is not.

Because fish inhabit water, a dense medium that absorbs, scatters, and bends light to a degree that makes seeing under water different and more complex than seeing in air, they have evolved, our of necessity, specific anatomical characteristics of the eye. In water colors ?behave? differently, and are not so easily differentiated. Therefore, fish eyes, to varying degrees, are equipped with retinal cones, which detect color ranges of color. Remember that there are two types of photo-receptors on the retina of the eye, rods which are sensitive to light in general, and cones which are sensitive to colored light. The ratio of rods to cones varies according to fish habitat. A deep sea fish, for example, which lives in dim light where rods are more useful than cones, may have a rod to cone ratio of several hundred to one. Conversely, a coral reef fish, which inhabits relatively shallow water where color abounds, may have a rod to cone ratio of ten to one. In both cases rods outnumber cones, but cones are clearly more useful on the coral reef. However, there is still much research going on into why coral reef fish are themselves so colorful. One theory involves the flaunting of bright colors as a warning to predators and another involves colors as camouflage. But the salient point here is that most aquarium fish do indeed perceive a complex range of colors, although their perception of color is slightly different than ours. There are different types of cones in a fish retina, and each one is sensitive to a different range of color. Most fish, like humans, have red, green, and blue sensing cones, but the range of each color sensed varies. Additionally, some reef fishes, like damselfish, have been found to perceive UV (ultra violet) light, and to have patterns on their bodies that can only be seen under UV light, presumably for attracting the attention of conspecifics. This is similar to markings that are found on some flowers, and that are only visible to UV sensing insects like bees. There is much going on in the natural world that is undetectable by our human eyes.

References and Further Reading
Castro, Peter and Huber, Michael E. ; Marine Biology; McGraw-Hill College, 3rd Edition, 1999
Gratzek, John B. (Editor); Aquariology: The Science of Fish Health Management; Tetra Press Publication, 1992
Moyle, Peter B. and Cech Jr., Joseph J.; Fishes: An Introduction to Ichthyology; Prentice-Hall Inc., 2000
Stoskopf, Michael K.; Fish Medicine; W. B. Saunders Company, 1993

stitch that!

)))))

The last sentence sums it all up for me mate....

"There is so much going on in the natural world that is undetectable by our human eyes"

But being out there trying to look in is part and parcel of fishing...surely?

Yes I agree to an extent Paul, but its nice to try and understand these things, least for me, heres another interesting one mate

Can fish fish smell?
Fish have little holes that look like nostrils. Does that mean they can smell, yes I know old ones smell bludi awful?

Smell, or olfaction, as scientists call it, is an important sense for many fish. Those little holes that look like nostrils are called nares. Nares don't lead to the throat the way nostrils do in mammals, but open up into a chamber lined with sensory pads. Not all fish move water in and out through these nares in quite the same ways, but the key to a strong sense of smell for fish is the ability to move water rapidly over these sensory pads. Some fish can pick up chemical signals when immobile by pumping water through their olfactory system via tiny hairs called cilia. Other fish can pump water by a muscular movement. Some fish, such as smaller species of mackerel, have an olfactory system that requires them to swim in order to get water moving through their nares. When the sensory pads pick up chemical signals, they transmit them to the fish's forebrain, which interprets the signal and incites the fish to respond appropriately.

if the chemicals signal food, the fish will pursue the food. Or if the chemicals signal danger, it'll flee.

But fish use chemical cues in all sorts of ways. For instance, a large group of fishes, including minnows, release a chemical when they're wounded that incites other fish to flee. And then there are salmon, which are known for a superb sense of smell that enables them to sense the stream where they were born, so that they may return to it to spawn.

Perhaps it is better that we never know what fish see or what attracts them, angling would be a very dull pastime if we knew exactly what we were going to catch and be able to use a bait that would definitely catch a particular species. The unpredictability is the very reason why we are attracted to the sport and its the very reason that we continue to fish.

Another similar case, and i'm sure a lot of us have seen it is the shoal of roach happily passing or swimming with a pike.

There must be something that tells them it is not in eating mode?

Yes you are possibly right Graham, but angling is forever evolving towards the identification of what fish like and methods in which to be more successful in catching them, basically we get better at how we fish, otherwise we would still all be using cane rods and wooden reels with catgut, we increase the odds against blanking, so why not learn more about the fishes perceptions of what they see and smell and what are the best colours and baits to use under given conditions, surely this is what we work towards anyway?

Yes an interesting one that Paul and one which has also interested me, I really don`t have a clue, but you would presume the predatry gives out some kind of signal, we see it on the African plains with Lions (well Ron has)? Have you ever been on one of your walks and crossed a field with a bull in it, when do you consider it safe to do so? I was out on the PW a few years ago with Steve King and we came across a field with a large evil looking bull in it, we felt apprehensive but did eventually cross the field and fortunately the bull ignored us, we were nervous though, I wonder if the roach feel the same as they pass the pike?

How does the Mexican Blind Cave Fish find its food???It doesn't have any eyes !!

The answer is in this article -- maybe it's how other fish can sense fishing lines no matter what colour ...

New research on Blind cave fish has found that they can put even dogs to shame in the intelligence stakes.

Dr Theresa Burt de Perera, an ethologist at Keble College Oxford, studied the behaviour of the Mexican Blind cave fish, Astyanax fasciatus, which in the absence of working eyes, relies on minute changes in pressure to detect the presence of objects in the water.

By using the sensitive lateral line system to detect changes in pressure, they're able to swim around without banging their heads against the glass, rocks or other fish. Blind cave fish swim much more quickly when they are faced with landmarks, like rocks, which they haven't encountered before, presumably to enhance lateral line stimulation.

However, besides the well-known ability for the cave fish to swim around obstacles in its path without bumping in to them, Burt de Perera also found that the fish built a complex spatial map of their surroundings only a few hours after being added to the tank.

Burt de Perera added four obstacles to the tank and found that the fish learnt the square configuration of it. However, when the landmarks were removed and replaced with another one, the fish showed a change in their behaviour. Burt de Perera says that the change in behaviour shows that the fish had produced a mental map of the obstacles and were comparing it to what they were sensing with their lateral lines.

She told The Telegraph: "The public perception of them is that they are pea-brained numbskulls that can't remember things for more than a few seconds. We're now finding that they are very capable of learning and remembering, and possess a range of cognitive skills that would surprise many people."

PFK's Editor, Karen Youngs, was also quoted by The Telegraph. Karen told the paper: "They are totally misunderstood. We know from our readers that fish can recognise their owners, and some will go into a sulk if someone else tries to feed them. We also know that fish such as oscars do enjoy having a table-tennis ball to bash about."

For more information see: Burt de Perera, T. (2004) A study of spatial parameters encoded in the spatial map of the blind Mexican cave fish (Astyanax fasciatus). Animal Behaviour. In Press.