Jeremy
24-03-2006, 08:18 AM
There is another thread on here "PETA attacks fishing". In response to this, I have done some research to find out the facts regarding whether fish can/do indeed feel pain. The answer is that they do not have the anatomical structures to be able to process and experience pain.
For those interested, I have posted what I put together as a result of my research below.
DO FISH FEEL PAIN: FACT VS. FICTION
Pain is defined as having two components (Cambridge dictionary online). The first is sensory, the feeling of physical suffering caused by injury or illness, and is also known as nociception. The second is affective, which is the emotional or mental suffering.
One of the functions of sensory component of pain is to sense damage so action can be taken to avoid further damage. Pain receptors are free nerve endings connected to the central nervous system by both AƒÔ-fibers and C-fibres. There are mechanical, thermal and chemical pain receptors. From here the pain can be relayed to the thalmus, in which pain perception occurs, and then the signal travels to the somatosensory cortex in the cerebrum, at which point the individual becomes fully aware of the pain.
All vertebrates possess the primitive areas of the brain to process nociceptive information (thalmus), but the size of the cortex decreases down the evolutionary tree, with fish having only a rudimentary cortex, and only only mammals have the neocortex ¡V the thinking area of the cortex. The fishes brain is dominated by brainstem components and features very primitive cerebral hemispheres. Indeed, in fish a higher level of cortical sensory interpretation appears non-existent, since fish behaviour is unaffected by cortical damage. Pain and consciousness depend on very specific brain regions, namely specialized neocortical region of the cerebral hemispheres. The neocortex is absent in fish and there are no likely alternative systems to perform the same tasks. Consequently, there is no basis for assuming that a fish might have a capacity for consciousness or pain.
Reactions to noxious stimuli are present in all forms of animal life, but these responses do not mean that pain is experienced. For example, the single celled ameba will move away from irritating chemical or mechanical stimuli. These reactions are automatic because the ameba does not have a nervous system. Similarly, the starfish moves away from noxious stimuli but has only a few nerve cells and no brain. These animals can percieve noxious stimuli, but cannot feel pain.
There is no doubt then that fish can percieve and react to noxious stimuli Experiments have shown that trout possess receptors on the head and neck able to detect noxious stimuli such as mechanical pressure, temperature and chemical stimuli. Behavioural chhanges have also been observed to occur after noxious stimuli (Sneddon et al., 2003 Proceedings of the Royal Society London, Series B 270: 1115-1121). This study proves only that fish can react to noxious stimuli. It does not prove that fish experience pain.
It is the brain where the pain signals are processed and experienced, not the peripheral nervous system. The reaction to noxious stimuli is not the same as the psychological experience of pain, and the former does not prove the latter. Indeed, human experiments have proven that pain is experienced in the brain (eg coma, anaesthesia) and the sensation of and reaction to noxious stimuli can occur without the experience of pain.
In conclusion, fish can percieve and react to noxious stimuli such as a fish hook by trying to get away. This is a flight response (protective reaction) which is the result of brainstem and spinal patterns of activity that are automatically elicited by the stimulation of being hooked. There is no evidence however that they can process these signals as pain and experience the physical and physhological feelings of pain as we know it. In fact, the anatomy of the fishes brain suggests that they cannot.
Acknowledgements:
The information contained in the report above was taken from a number of sources publically available on the internet including:
www.cotrout.org/do_fish_feel_pain.htm
www.wellcome.ac.uk/en/pain/microsite/culture2.html
www.vet.ed.ac.uk/animalwelface/Fish%20pain/pain.htm
www.nature.com/news/2003/030428/full/030428-0.html
Further reading:
Rose, J.D. 2002. The Neurobehavioral Nature of Fishes and the Question of Awareness and Pain. Reviews in Fisheries Science. 10(1): 1-38.
For those interested, I have posted what I put together as a result of my research below.
DO FISH FEEL PAIN: FACT VS. FICTION
Pain is defined as having two components (Cambridge dictionary online). The first is sensory, the feeling of physical suffering caused by injury or illness, and is also known as nociception. The second is affective, which is the emotional or mental suffering.
One of the functions of sensory component of pain is to sense damage so action can be taken to avoid further damage. Pain receptors are free nerve endings connected to the central nervous system by both AƒÔ-fibers and C-fibres. There are mechanical, thermal and chemical pain receptors. From here the pain can be relayed to the thalmus, in which pain perception occurs, and then the signal travels to the somatosensory cortex in the cerebrum, at which point the individual becomes fully aware of the pain.
All vertebrates possess the primitive areas of the brain to process nociceptive information (thalmus), but the size of the cortex decreases down the evolutionary tree, with fish having only a rudimentary cortex, and only only mammals have the neocortex ¡V the thinking area of the cortex. The fishes brain is dominated by brainstem components and features very primitive cerebral hemispheres. Indeed, in fish a higher level of cortical sensory interpretation appears non-existent, since fish behaviour is unaffected by cortical damage. Pain and consciousness depend on very specific brain regions, namely specialized neocortical region of the cerebral hemispheres. The neocortex is absent in fish and there are no likely alternative systems to perform the same tasks. Consequently, there is no basis for assuming that a fish might have a capacity for consciousness or pain.
Reactions to noxious stimuli are present in all forms of animal life, but these responses do not mean that pain is experienced. For example, the single celled ameba will move away from irritating chemical or mechanical stimuli. These reactions are automatic because the ameba does not have a nervous system. Similarly, the starfish moves away from noxious stimuli but has only a few nerve cells and no brain. These animals can percieve noxious stimuli, but cannot feel pain.
There is no doubt then that fish can percieve and react to noxious stimuli Experiments have shown that trout possess receptors on the head and neck able to detect noxious stimuli such as mechanical pressure, temperature and chemical stimuli. Behavioural chhanges have also been observed to occur after noxious stimuli (Sneddon et al., 2003 Proceedings of the Royal Society London, Series B 270: 1115-1121). This study proves only that fish can react to noxious stimuli. It does not prove that fish experience pain.
It is the brain where the pain signals are processed and experienced, not the peripheral nervous system. The reaction to noxious stimuli is not the same as the psychological experience of pain, and the former does not prove the latter. Indeed, human experiments have proven that pain is experienced in the brain (eg coma, anaesthesia) and the sensation of and reaction to noxious stimuli can occur without the experience of pain.
In conclusion, fish can percieve and react to noxious stimuli such as a fish hook by trying to get away. This is a flight response (protective reaction) which is the result of brainstem and spinal patterns of activity that are automatically elicited by the stimulation of being hooked. There is no evidence however that they can process these signals as pain and experience the physical and physhological feelings of pain as we know it. In fact, the anatomy of the fishes brain suggests that they cannot.
Acknowledgements:
The information contained in the report above was taken from a number of sources publically available on the internet including:
www.cotrout.org/do_fish_feel_pain.htm
www.wellcome.ac.uk/en/pain/microsite/culture2.html
www.vet.ed.ac.uk/animalwelface/Fish%20pain/pain.htm
www.nature.com/news/2003/030428/full/030428-0.html
Further reading:
Rose, J.D. 2002. The Neurobehavioral Nature of Fishes and the Question of Awareness and Pain. Reviews in Fisheries Science. 10(1): 1-38.