An unemployed, self-crippled ex-greasemonkey and a reflexologist who
infect these newsgroups with their ignorance of science and the
scientific method claim on the basis of a study by Sneddon, et al, that
fish experience pain. These two misinformed charlatans have refused to
accept any other study, suggesting that the study of Sneddon, et al,
trumps every other one in the history of scientific research.

Dr James Rose, who's studied animal neurology for thirty years, has
refuted the conclusions of Sneddon, Braithwaite, and Gentle. In his
critique of their conclusions, Dr Rose pointed to specific flawed
definitions and specific flawed interpretations of the researchers in
their published findings.

Among the flaws were an *improper* distinction between pain and
nociception, as well as misinterpretations of responses of fish to
stimuli. He also noted that Sneddon, et al, misused statistical analysis
in their findings. Among Dr Rose's conclusions is that "Rather than
proving a capacity for pain, *THESE RESULTS SHOW A REMARKABLE RESISTANCE
TO ORAL TRAUMA BY THE TROUT* [my emphasis]. It comes as no surprise,
then, that many anglers have had the experience of catching the same
fish repeatedly within a span of a few minutes."

From his critique, which is available at the link below, here is Dr
Rose's case that Sneddon, et al, misinterpreted results.

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. The acid and venom-injected fish also
showed an infrequent rocking behavior that may have reflected a
difficulty by the fish in maintaining an upright posture, given
the magnitude of the toxic chemical trauma created by the
injection. But, even if the infrequent rocking was a response
to nociceptive stimulation of the mouth, there is no reason to
believe that it is any more than an unconscious nociceptive ]
response, rather than an indication of “pain”.

2. Sneddon and associates also state that the acid-injected
fish rubbed their mouths against the gravel (they don’t say how
often), but the venom-injected fish did not. They concluded
that mouth rubbing was an indication of pain because mammals,
including humans, rub injured tissues to alleviate nociceptive
input. If so, why did the venom-injected fish, that were also
supposed to be in pain, not perform this behavior? In addition,
injections of irritants into skin tissues is known to cause
hyperalgesia, where skin becomes hypersensitive, like the effect
of a sunburn. Who rubs sunburned skin against gravel to
alleviate the pain? At one point in the paper, Sneddon and
associates say that feeding was suppressed because the fish were
avoiding mouth stimulation, which would cause “pain.” But
later, they say that mouth rubbing was a way of reducing “pain.”
These are contradictory interpretations and you can’t have it
both ways. Their interpretations of the mouth-rubbing behaviors
don’t make sense nor do they show conscious experience of pain.

3. One of the few effects actually produced by the acid or
venom injections was an elevated opercular beat rate
(breathing). This response could have resulted directly from
gill irritation due to leakage or blood borne spread of the acid
or venom injections, but even if increased opercular beat rate
was due to nociceptive stimulation of the mouth, this
unconscious movement proves nothing about conscious pain.

4. One caveat regarding the behavioral data described above
is the fact that some of the statistical analyses were not done
correctly. Data for opercular beat rate and for time to resume
feeding were analyzed by one-way analysis of variance, but
conclusions were made about specific group differences in these
measures. With this type analysis, it is not legitimate to
conclude that one group (e.g. acid or venom injected differed
from any other group (e.g. handeled or saline injected), but the
authors made such conclusions, nonetheless. Given the sizes of
the standard errors of the means for these data, however, the
group differences reported by the authors would probably have
been substantiated following proper statistical analysis.

To summarize, the most impressive thing about the acid and venom
injections was the relative absence of behavioral effects, given
the magnitude of the toxic injections. How many humans would
show little change in behavior or be ready to eat less than
three hours after getting a lemon-sized bolus of bee venom or
acid solution in their lip? Rather than proving a capacity for
pain, these results show a remarkable resistance to oral trauma
by the trout. It comes as no surprise, then, that many anglers
have had the experience of catching the same fish repeatedly
within a span of a few minutes. Of course predatory fishes,
including trout, feed avidly on potentially injurious prey like
crayfish, crabs and fish that have sharp spines in their fins –
which further indicates that these fish are not highly reactive
to noxious oral stimuli.

In addition, Sneddon and associates claim to have presented the
first evidence for nociceptive sensory receptors in fish, but
their results were neither wholly original nor unexpected. In
my 2002 Reviews paper, I cited a 1971 study by Whitear that
showed the presence of C-fibers in fish. C-fibers are a
principal type of nociceptive receptor, so there was very good
reason to assume that trout would have nociceptive receptors.
Another technical issue arises in the authors’ description of
their procedure for decerebration of trout in order to make them
“insentient.” The term sentience is vague and has no standard
scientific meaning, but apparently Sneddon, et al. were
performing this decerebration in order to eliminate any
potential pain that they assumed was within the capacity of the
trout. The usual means of producing a decerebration is to
remove all brain tissue above the midbrain. According to
Sneddon, et. al, however, they removed the “…olfactory and optic
lobes and cerebellum…” This is peculiar and counterproductive
because the entire pathway for nociceptive information from the
periphery through the brainstem to the cerebral hemispheres
would have remained intact in these fish, since the “ofactory
lobes” but not entire cerebral hemispheres would have been
removed according to this description. If fish could feel pain,
as the authors contend (and I dispute), these fish probably
would have.

The bottom line of this critique is that any attempt to show
pain in fish must use valid criteria, including proof of
conscious awareness, particularly a kind of awareness that is
meaningfully like ours. This is not something that can be taken
for granted, because on neurological and behavioral grounds it
is so improbable that fish could be conscious and feel pain.
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.

I wish to emphasize that the improbability that fish can
experience pain in no way diminishes our responsibility for
concern about their welfare. Fish are capable of robust,
unconscious, behavioral, physiological and hormonal responses to
stressors, which if sufficiently intense or sustained, can be
detrimental to their health.

James D. Rose, Ph.D.
Department of Zoology and Physiology
University of Wyoming
Laramie, WY 82071
USA
http://uwadmnweb.uwyo.edu/Zoology/faculty/rose/
Full critique: http://tinyurl.com/6ucz