A controversal topic...

[Tokis-Phoenix]

In my opinion, i think the larger, older, slower reproducing and more intelligent a fish is the more likely it is to have pain receptors- i shall give some examples of these factors;

a. YOUNG FISH=FRY; Guppy fry for example i doubt have any pain receptors in them in the early stages of their lives- when you consider the huge losses a 30 strong batch of fry experiences in the wild and the means of their deaths it seems pretty pointless to put a lot of energy into building a highly tuned pain receptor system because most things that kill them, they have no chance against for surviving anyways.
The whole point of evolving a pain receptor system is to avoid making the same mistake again, you can also only evolve it if you survive from that mistake and live on to produce offspring that may inherit the same ability that saved you, but when a fry is about to get eaten by a larger predatory fish it has little chance of ever surviving.
I believe pain receptors are somthing that grow and multiply in fish as they grow get older and this system is very undeveloped in small fry- there is little point of the fry experiencing great pain if it has no chance of survival against, say a big predatory fish eating it. When you also consider the huge amounts of fry guppys produce they have only evolved this because of the huge number of ways they can die and so need to reproduce on a fast scale to survive, but this life insurance and the insurance of instaincts like moving away from somthing that could posibly pose a threat is more than enough to ensure that some fry will always survive- animals/fish though never evolve abilitys that they don't need to survive mainly because these abilitys need energy=food to run and it is pointless wasting energy on somthing that will serve you little, like pain receptors in the early stages of life of a fry.
I think this goes for practically all types of small fry.
b. LARGE AND OLD FISH; i believe the larger the fish, the more likely it is to have pain receptors in it as size takes a while to put on and the larger you get the less ways their are for you to die in comparison to a small defenceless fry. It would make sense for a guppy for example, to start investing more and more energy into a pain receptor system as they grow simply because it becomes more useful and the chances of it working efffectivily greater and thus a much more cost effective system to invest in.
c. INTELLIGENCE; it is a known observation that the more intelligent an animal/fish, the more likely it is to have pain receptors, this partly because more intelligent animals take longer to develope and mature than less intelligent animals and also because intelligence is often found in animals that rely less on instincts and senses of the body like smell and hearing to guide them through life than animals that do.

When you are evolving you have a selection of things that can be used as life insurance but brain capacity and body size limits how many you can invest in, intelligence can be a bit overated in terms of which life insurance is the best as the majority of animals that live in the world simply do not need it to survive. Without many instincts to guide you through life at hand though it is pretty vital.
Example= what need does a fly need as intelligence when it can already produce on a rapid scale and has high tuned instincts that already succesfully ensure its survival? It would be a waste of energy to produce such a system when it is already thriving on its current ones...
A gorrila though, which does not have great or highly tuned hearing, smell, fast reproductive rate or unlimited food source, needs intelligence on a great scale to survive as its body is less invested in other forms of life insurance.
In less defined exmples though such as fish, these examples still do aply and i am sure it is the same for a fish too.
REPRODUCTIVE RATES; the final factor, i do think the speed of which a fish can reproduce and grow is also an important factor of how nesarsary a highly tuned pain receptor system is as the longer it takes for you to reach maturity and produce a small number of offspring, the more important having a pain receptor system is.
As i mentioned earlier it would be of little use for a young guppy fry to have such a system as the energy it costs to run it would rarely ever pay off and save you. Having large amounts of fry on a regular basis helps overcome the large losses of fry that are lost without this system.
But for an animal like a foal or calf, where producing and successfully raising offspring is slower and on a smaller scale and the parents have to invest more energy into the survival of the baby, any system like pain receptors becomes much more inportant in rasing offspring succesfully, im sure it is the same for fish in a sense after the other factors like size, stage of growth and intelligence have been taken into consideration.


...
I think i have missed some points but i hope you get the jist of them anyways- at this point in time i think a guppy fry or neon tetra is far less likely to feel pain at all or on a big scale as say, a full grown oscar or sailfin plec.
I think for example, using freezing as a form of euthanasia is acceptable on a tiny fry but totally unaceptable on say, a 10inch plec. This is based on my conlusions of the baove points. What do you think?

 

[abstract]

well it seems that many of us have come to the conclusion that our fish have some sort of memory (another contraversial topic, i know)....why is a sunfish any different? i'm talking about catching the same sunfish a half dozen times in an hour or two span....surely the fish must "remember" being hooked...and surely, i doesn't want to do it again if it is such a painful event....that was kind of my point - that we think our tropical fish are "smart" enough to remember certain habits, so, assuming the fish felt pain from being hooked, one would assume it would not do it over and over again...a worm crawling in the muck is different than a worm dangling in the water to us, and i'm sure there is some differentiation for fish too.... if even the smallest, stupidest, whatever you want to call them tropical fish can learn from their expereiences and "remember" in essense, why is it any different for a sunfish, trout, pike, or anything else? i would consider them MORE knowledgable fish if there is such a thing lol.

and how a fish eating a worm on a hook can be compared to us eating foods with pesticides on it, i am unsure....if the pesticides physically hurt me, not long term, but right on the spot my mouth started to hurt, i am sure i would never eat it again. just as many fish "learn" that certain species of plants are dangerous/taste bad, or that eating a certain type of food can actually kill them...

and about the guppy fry...i can see that being possible. however, it seems illogical to say that based on the size of the fish it feels less...it still has the same ratio of pain receptors in its body, even if it doesnt have as many...my only question would be, do baby humans have the same numbers of pain receptors and the same ability to detect stimuli as adult humans? if so, then why not fish? if not, then i can see the reasoning behind it..

 

[gaya]

and how a fish eating a worm on a hook can be compared to us eating foods with pesticides on it, i am unsure....if the pesticides physically hurt me, not long term, but right on the spot my mouth started to hurt, i am sure i would never eat it again. just as many fish "learn" that certain species of plants are dangerous/taste bad, or that eating a certain type of food can actually kill them...

I brought it up because you mentioned that the fish just might be dumb. It made me think of people. They keep getting hooked over and over regardless of the consequence. They might still be getting the information to their brains that they are experiencing pain but they don’t plan ahead to avoid it. I think it’s comparable to our own actions. We don’t need to get a wallop in our belly to have the ability to know that some things are very harmful to us and yet we continue to consume them anyway. We actually have the intellectual ability to predict. But that still doesn’t matter. Maybe we are just dumb too on some levels.

 

[Opcn]

Sunfish are smart thought, smart enought to know that food with hook in it is better than no food at all, They may know that the hook is there but are trying to outsmar it by biting and running

 

[Tokis-Phoenix]

The reason why i believe wild fish get caught over and over again is not to do with intelligence or rememory, but to do with the fact that in the wild, food is scarce and you never know when your next meal is going to be. A fat juicy worm or similar bait may be irresistable enough for the fish to eat it over and over again despite it being a painful experience, such a meal would be a banquete for a wild fish and as far as the fish see's it, worth the pain and hassle for the meal.
The fish may have an injured mouth but for 12 worms, it is more tan enough food to heal the mouth wounds and gain extra energy for the rest of the week- the fish may actually be doing an itelligent thing in doing this because it knows that the pain and hassle pays off in the long run.

 

[Synirr]

well it seems that many of us have come to the conclusion that our fish have some sort of memory (another contraversial topic, i know)....why is a sunfish any different? i'm talking about catching the same sunfish a half dozen times in an hour or two span....surely the fish must "remember" being hooked...and surely, i doesn't want to do it again if it is such a painful event....that was kind of my point - that we think our tropical fish are "smart" enough to remember certain habits, so, assuming the fish felt pain from being hooked, one would assume it would not do it over and over again...a worm crawling in the muck is different than a worm dangling in the water to us, and i'm sure there is some differentiation for fish too....


and about the guppy fry...i can see that being possible. however, it seems illogical to say that based on the size of the fish it feels less...it still has the same ratio of pain receptors in its body, even if it doesnt have as many...my only question would be, do baby humans have the same numbers of pain receptors and the same ability to detect stimuli as adult humans? if so, then why not fish? if not, then i can see the reasoning behind it..

Memory and intelligence are not the same thing. The fish may have a good enough memory to remember being hooked, but it is probably not intelligent enough to link worms floating in water rather than crawling in muck to the pain it experienced. I know, it's hard to understand an animal not being able to differentiate between the two, but in all likelihood all the fish sees is a potential meal. Period.
I'll offer an example I read once of how animal intelligence works differently... There was a heron who learned to lurn in fish using pieces of bread because he had seen children throwing bread to ducks at a pond and noticed that it also brought in fish. However, unlike we humans, other herons are completely unable to learn the same technique by following this heron's example, so when that heron dies, his fishing technique dies with him. Get it? Many animals just aren't good at putting two and two together.

I agree that the size of the fish shouldn't really have much of a direct correlation as to how capable they are of feeling pain, though. However, very young baby humans actually AREN'T as capable of feeling pain as adults. Babies only a few months old are still developing many of their senses and can't see clearly or hear as well as adults can. When a baby is only a couple of weeks old it can feel pain, but probably not as intensely as we do and it can't determine exactly where that pain is coming from (in other words, and injury to the foot might as well be and injury to the hand... they can't tell the difference.) Interesting, neh?
In the same way, young fry are not yet fully developed, but by the time they resemble miniatures of adults, I'm sure their senses are fully developed. I think that fish which have a long lifespan and/or reproduce slowly are some of the most likely candidates to feel pain. The longer it takes a fish to reach sexual maturity, the more important it is for them to live longer and the more important survival mechanisms like pain become.

 

[hellohefalump]

interesting topic!
I think bigger fish are more 'aware' of what's going on around them than a tiny fry... Personally I would find it extremely hard to euthanise a bigger/older fish just because I get too attached to them and even though I know it's wrong, I can't bring myself to end their lives. I have euthanised a couple of smaller fish (danio and small tetras) who looked beyond the point of no return. I used clove oil, they became unconcious very quickly (seconds) but took a while longer to actually die (gills stop moving). On the subject of clove oil... I use it to aneasthetise my collomessus puffer when he needs his teeth trimming, and I've done it about five times now and he's fine. I use the smallest amount possible, just to knock him out so he won't struggle or puff up. I use about 1 drop per pint of water.

 

[Tokis-Phoenix]

With the subject of fry and pain, does everyone pretty much agree that it is unlikely that fry feel pain at all in some respects and that a form of euthanasia like freezing is much more humane on a tiny fry than it is on a large adult fish?
I just want to clear this part of the debate up in particular as in the last couple of months some of the guppys i have bought recently to introduce new blood into my guppy group gene lines, but were already in the early stages of pregnancy and they have produced some very inbred fry(my lfs gets alot of badly inbred guppys), like deformed tails in particular. I've tried raising these fry but they always die of swimbladder disorders in the first month which i believe is genetic and due to the inbreeding, im tired of raising these types of fry as they are never going to have much of a life.
As to euthanasia, its quite difficult to squish such little fry and i would much prefer freezing them as i have done in the past as it literally takes under 4seconds and is a much cleaner method of euthanasia and i would return back to using it if it were an acceptable method of euthanasia on fry...
What do you think?

 

[abstract]

i do not believe that you should euthanise them any differently just because they are a smaller fish....theoretically we do not know for SURE that the fry would suffer less than a larger fish, so should have the same treatment..


as for the heron example, Synirr, that is absolutely amazing...i recently read an article on CNN that dolphins have learned to carry around natual sponges on their noses while they are hunting for food to protect them from getting stung or damaged searching in the corals (or wherever they hunt)....the more amazing thing about it was that certain families of directly related dolphins are the only ones to do this...meaning that they learn it from their parents and siblings - off topic, i know, but equally as amazing as the heron example!

and i do agree with you all that the tasty worm on the hook is worth biting every time because you never know when your next meal is...but then again, that kind of reinforces that it must not be THAT painful of an event if they are willing to accept the tradeoff to get some food....that being said, i am pretty pulled by either direction of the debate...it is more of a philisophical debate in my mind more than a biological one....what exactly do fish "think"?

 

[OohFeeshy]

Well, I don't nkow for sure, but I think they do. Pain is a nessecary thing- If you didn't feel pain, you'd be dead. Taking a situation that could happen in the wild.. Say a fish gets its tail caught under a rock. If it feels pain, it wil try to stop the pain by swimming away. If it doesn't, it is entirely possible it will not move, and die. Or something like that. Going back to the hook thing- it is an awful lot easier to take a worm from a hook than it is to hunt down something that is potentially less nutritious. I doubt it hurts that much, it probably only hurts when the fish struggles. The mouth is an area that doesn't feel much pain- you can bite the inside of your lip and it doesn't hurt much.

 

[Synirr]

as for the heron example, Synirr, that is absolutely amazing...i recently read an article on CNN that dolphins have learned to carry around natual sponges on their noses while they are hunting for food to protect them from getting stung or damaged searching in the corals (or wherever they hunt)....the more amazing thing about it was that certain families of directly related dolphins are the only ones to do this...meaning that they learn it from their parents and siblings - off topic, i know, but equally as amazing as the heron example!

I hadn't heard that one, how interesting!! Dolphins are indeed capable of learning from one-another... I've heard that killer whales teach their young how to beach and unbeach themselves as a hunting technique
The mothers actually help push their young up the beach and then block them from swimming back into deeper water to help them get used to being in the shallows.

OohFeeshy -- Pain isn't actually necessary for all living things... think of insects. Most of them aren't capable of "feeling" pain but survive well enough on reflex reaction and instinct
A fish with its tail caught under a rock will move because... well... who the heck wants to be stuck immobile under a rock?? I mean, if you had your leg caught under something, you'd eventually want to move whether or not it hurt, wouldn't you?

 

[sylvia]

Isn't 'itching' the same as pain but in a milder form? Fish that have ich or parasites or are being irritated by a chemial in the water will flash against things to scratch themselves. And no one can argue that they can't feel it when they rub against something. It is logical to think that fish feel pain. I can't think of a vertabrate animal that cannot.

Anyway, about euthanising the fry to however asked about that - freezing isn't a nice thing to do but you CAN try 'shocking' them instead and, when a fish is so young, it is also very fragile and they usualy die immediately as a result. Basicaly, put a cup of water in the freezer until the top has freezed over and there's a thin layer of ice. Then break that and catch the fry and dump it/them into the ice water. Provided this realy is just a very young fry, it should die instantly. If it is even slightly developed, however, I wouldn't consider this humane enough and would use clove oil. You wouldn't need much at all. If you see the fry in the ice water aren't dying immediately, you're going to have to switch back to 'crushing them'.

 

[Tokis-Phoenix]

Yeah i would never euthanise a fry in such a way if it was more than a couple of weeks old, most mutations are obvious as soon as the fry are born so i usually make the decision to euthanise them in the first week or so...The way i euthanised them before was i took them out in a net from a bowl next to the freezer and automatically put the net they were in on the bare ice in the freezer, they were dead within seconds of this and then i simply took them out and put them in the bin...
If i could, i would set up 2 separate gender large tanks where i could but inbred fish in so they couldn't mate with each other and pass on the bad genes but in my current apartment i simply don't have the space for anymore tanks...
Im actually thinking about buying a predatory fish or invertebrate like blue lobster in the future when i get a bigger place to live in where i could feed it inbred livebearers as feeder fish to it, its what would naturally happen to inbred fish in the wild anyways and would mean having to "waste" these fish...i do feel so sorry for them though...I tend to end up with alot of inbred livebearers from my lfs as my lfs gets the type of fish that the breeders couldn't sell because of their bad quality, i've tried persuading the guy who runs the place to get better quality livebearers but he doesn't seem to have much money and he has only been running the store for about 6months... .
Im trying to run a guppy project into breeding guppys with better genes and imune systems and hopefully suply him with livebearers in the future so he doesn't have to buy bog standard ones all the time, the guppys and people who buy them would also benefet from the project alot if it goes successfully .

 

[Synirr]

Isn't 'itching' the same as pain but in a milder form? Fish that have ich or parasites or are being irritated by a chemial in the water will flash against things to scratch themselves. And no one can argue that they can't feel it when they rub against something. It is logical to think that fish feel pain. I can't think of a vertabrate animal that cannot.

The simple answer to your original question is no
Only certain types of nerve ending are capable of sending the "pain" signal to the brain. Just because an animal has a sense of touch doesn't mean it's capable of feeling pain. The real controvercy over whether or not fish feel pain is whether they have an area in their brains in which the signals their nerves send them are interpreted as the "feeling" of pain. The general belief has been that those signals only result in reflex reaction (like drawing your hand away from a hot stove before you even think about it) and no actual "feeling," but considering how little we actually know about the entire process, we may learn otherwise in the future (and indeed, I'd be surprised if we didn't)

 

[Tokis-Phoenix]

I do think what type of fish you have depends on its ability to feel pain, but if size isn't an issue to wether a fish feels pain or not thats like saying a neon tetra can feel pain as much as a large pike or salmon- i personally think the size and type of fish has alot to do with wether it feels pain or not.