This article shows why it is highly unlikely that fish feel pain:

A critique of the paper: Do fish have nociceptors: Evidence for the evolution of a vertebrate sensory system published in Proceedings of the Royal Society, 2003 by Sneddon, Braithwaite and Gentle.
James D. Rose, Ph.D.
Department of Zoology and Physiology
University of Wyoming
Laramie, WY 82071
USA

The paper by Sneddon, et al. is flawed and does not provide any legitimate evidence that trout are capable of feeling pain. There are numerous problems with methods and data interpretation in this paper but this critique will
focus only on those of greatest significance. First, an explanation of the invalid claims for evidence of pain will be presented, followed by an account of the misinterpretations of the behavioral results.

Flaws in the argument for a demonstration of pain.

1. The authors definitions of pain and nociception are invalid, consequently this paper does not actually deal with pain (a conscious experience), it deals only with nociception (unconscious responses to noxious stimuli). Pain, as defined by the International Association for the Study of Pain is purely a conscious experience, with a sensory component and a component of emotional feeling (suffering). In contrast to this conscious experience of pain, the unconscious detection, transmission and response to noxious stimulation by
lower levels of the nervous system is and defined as nociception - not pain. According to Sneddon, and associates, any behavior that is a reflex would be evidence of nociception but any behavior more complex than a
reflex would be evidence of pain. This way of distinguishing pain from nociception is invalid because there are clearly complex, non-reflexive behaviors that can be purely nociceptive and unconscious. For example, humans with extensive damage of the cerebral hemispheres can still make a complex of responses including facial grimaces, vocalizations, struggling and avoidance reactions to noxious stimuli, but they are unconscious and
unable to experience pain. From the definition of pain used by Sneddon and associates, it would be concluded that these unconscious humans are feeling pain rather than making purely unconscious, nociceptive responses,
which is clearly erroneous. There are many other examples of complex, non-reflexive, even distress-like behaviors that can be performed unconsciously. A person having a night terror, for instance, will show a compelling fear-like display, including a scream, terrified facial expression, elevated heart rate, sweating and dilated pupils, even though they are unconscious and in such deep sleep that they are difficult to awaken. The point is that complex behavioral displays that seem to reflect distress can be purely unconscious  even in humans. It should not be hard to appreciate that the behaviors of which a fish is capable could be unconscious as well.

2. In order to show that a fish experiences pain, it is necessary to show that a fish has consciousness. Without consciousness, there is no pain. None of the fish behaviors in this paper require the involvement of consciousness and the authors don't even deal with this essential issue. Furthermore, as I have shown in my 2002 Reviews in Fisheries Science paper, there is extensive scientific evidence that pain and consciousness depend on very specific brain regions, namely specialized neocortex regions of the cerebral hemispheres. These
specialized neocortical regions perform the additional levels of neural processing, beyond unconscious nociception, that make the experience of pain possible. These brain regions are absent in fishes and there are no
alternative brain systems to perform the same functions. Consequently, there is no neurological basis for assuming that a fish might have a capacity for consciousness or pain. Thus, the burden of proof that trout are conscious and potentially capable of feeling pain remains on these authors. They dealt with this issue only by citing previous studies that also used invalid criteria for pain, such avoidance learning, which actually occurs unconsciously. Only anthropomorphic speculation would lead one to conclude that the trout in this study were experiencing pain. The behavioral results allegedly showing evidence of pain were misinterpreted.

1. The behavioral studies were done by injecting large volumes of one of three solutions: bee venom, acetic acid solution or saline, into the jaw of rather small trout. For the sizes of the fish used, these injections of liquid
would have been equivalent to injecting 100 milliliters (more that 3 ounces) of solution into the lip of a human. Bee venom contains a great variety of toxins that affect the nervous system and cause a hormonal stress response in addition to stimulating receptors signaling tissue injury. In spite of the large dose of venom or acid, the activity level of these fish was not affected, they did not hide under a shelter in the tank and they resumed feeding in less than three hours. Furthermore, fish that received no injection at all or fish that
received a saline injection did not feed, on average, for an hour and 20 minutes, showing that a large saline injection produced no more effect than just handling.

Furthermore, the behavioral results of this study show that in spite of very large injections of acid solution or venom, the fish showed little adverse effect, hardly supporting the claim that they were in pain.

Cited reference: Rose, J. D. 2002. The neurobehavioral nature of fishes and the question of awareness and pain.
Reviews in Fisheries Science, 10: 1-38. This paper can be obtained in electronic form from the author.

Whales and dolphins are far more akin to humans than to fish.

So what? Is similarity to humans now a valid criteria for deciding which animals we can eat? Can you provide an objective basis for judging whether an animal is too close? Same order, same family???


Well as Walter pointed out. Their brain size and structure, their social structures and behaviours which indicate a level of intelligence and self awareness.

This article shows why it is highly unlikely that fish feel pain

No it doesn't. Saying that fish cannot feel pain because they appear different to humans is like saying they cannot move because they have no arms or legs. It is based on assumptions about what pain is that are philosophically baseless. Bottom line is, we have no clue at all what fish are experiencing in psychological terms.

Of course it does. Fish lack the neural regions and structures in their brains which are associated with self awareness and pain perception. Their responses to injury do not match the hypothesis that they feel pain.

Their brain size and structure, their social structures and behaviours which indicate a level of intelligence and self awareness.

You could end up with a very long list of candidates for non-consumption based on that criteria. Pigs being one.

The facts are there are no conclusive tests to determine sentience- your argument is based solely on an emotional attachment

No the're based on a considerable amount of evidence.

Where?

you have to look at the balance of evidence and make a moral judgement.

Based on who's morals?

Obviously you have to draw a line somewhere.

You also need to have defined prerequisites before you draw that line

I could make up similar arguments for the other side, eg if killings whales and dolphins is deemed OK then our animal cruelty laws will go out the window.

So far, this is the only basis for banning whaling..period.

Sounds more like a debating trick than a reasonable propostion.

Just because you are unable to debate it does not make it an unreasonable proposition

No the're based on a considerable amount of evidence.

Where?

I have put some up. Then I reiterated for freediver. I am not going to turn it into a thesis. If you want to learn more about the behaviour and intelligence of whales and dolphins then why don't you do your own research/ reading?

you have to look at the balance of evidence and make a moral judgement.

Based on who's morals?

Societies of course. 'Do unto others as you would do unto them' is a good starting point. The 'others' in this case are species that are close to us in terms of awareness and intelligence.  

Obviously you have to draw a line somewhere.

You also need to have defined prerequisites before you draw that line

We are drawing a line already and our world hasn't fallen apart has it? Whaling has been banned in Australia and most other countries for decades. Our livestock industries are still intact are they not? Surely thats good evidence you propostion is not a plausible one! Only a couple of countries still practice whaling and it has not done much for their international reputations.

I could make up similar arguments for the other side, eg if killings whales and dolphins is deemed OK then our animal cruelty laws will go out the window.

So far, this is the only basis for banning whaling..period.

Sounds more like a debating trick than a reasonable propostion.

Just because you are unable to debate it does not make it an unreasonable proposition.

Well lets see what you make of these comments and I'll let others decide who is able to debate.

The orginal ban was based on sustainability. It was a stock management tool, not a tool of cultural imperialism.

Whatever the reason it puts a huge hole in your argument that a ban on whaling will lead to ban on other harvesting, even that of fish. Certainly sustainability is only part of the issue. The IWC is a whaling body afer all and the issue is much wider than what they decide. Eg in the world of public opinion and politics the moral dimension is a big part of the whaling issue.

As to 'cultutal imperialism', isn't it true that whaling was never a big part of Japanese culture and it only took off after WW2? For indigneous hunter gatherers then this is different case. Are ther not exemptions in place for them to take protected species?