Ethics & Suffering - Pain & Suffering
Can fish feel pain and can they suffer? These are central issues when considering fish welfare. Suffering can be described as a conscious experience of events or circumstances as unpleasant. If fish cannot suffer then does it really matter if they are exposed to such events or circumstances? Suffering is central to many concepts of welfare and the necessity to safeguard fish welfare may be questioned without evidence that fish are capable of perceiving pain and experiencing some form of suffering as a result. This continues to be a subject of hot scientific debate.
One way of approaching this problem of suffering in fish is to consider whether fish experience physical damage as pain. Some researchers put forward the view that fish do have the capacity to experience pain and emotional distress even though it may not be the same as that experienced by humans. Regardless of personal opinion there is growing consensus that even if fish cannot suffer we have a duty of responsible stewardship for them.
Some researchers are adamantly opposed to the idea that fish are capable of experiencing pain and suffering. Rose (2002) argued that the experience of pain and emotion in fish is untenable as fish lack any functional equivalent to the mammalian neocortex. Although Rose acknowledges the ability of fish to display a wide array of non-conscious, neuroendocrine and stress responses, he was largely dismissive of evidence of learning behaviour and suggested any such evidence was merely associated or implicit learning i.e. learning relationships between a stimulus or stimuli and a behavioural response. Rose suggests that awareness of pain in humans is dependent on functions of specific regions of the cerebral cortex and that the absence of such a region or functional equivalent in fish means that they are incapable of awareness of fear, or experiencing pain. In fact, following this line of thinking would mean humans and higher primates are exclusive in their capacity to suffer.
Recent work that has generated much media interest has focused on nociceptive capacities in the rainbow trout (Sneddon 2002; 2003b; Sneddon et al., 2003). Physiological (electrophysiology) and anatomical findings showed that rainbow trout possess A-delta and C fibres in the trigeminal nerve ganglion akin to those responsible for nociception in higher vertebrates (Sneddon, 2002). Other work has shown that a fish’s natural tendency to avoid a novel object was reduced in groups of fish that were exposed to noxious stimuli (Sneddon et al. 2003). This work also showed that morphine acted as an analgesic: avoidance of the novel object by fish exposed to a noxious stimuli (acetic acid) was similar to control fish when they were also given morphine, suggesting that fish treated with the acid alone may have been distracted by the pain. Another experiment that used the same noxious stimuli demonstrated that following exposure to the acid, rainbow trout displayed anomalous behaviour (rocking from side to side on pectoral fins and rubbing snouts in the gravel), increased opercular beat rate and took a longer to resume feeding (Sneddon, 2003). The anomalous behaviours and the time taken to resume feeding were reduced in groups treated with acid and morphine compared with acid alone. Sneddon (2003) concluded that they had fulfilled all of the criteria for animal pain as proposed by Zimmerman (1986), where pain in animals is defined as an adverse sensory experience that is caused by a stimulus that can or potentially could cause tissue damage; this experience should elicit protective motor (move away from) and vegetative reactions (e.g. inflammation and cardiovascular responses) and should also have an adverse effect on the animal’s general behaviour (e.g. cessation of normal behaviours).
There are strong arguments both for and against the ability of fish to experience pain, although scientists representing both sides of the argument agree that fish should be treated humanely and that stressful procedures should be avoided. If you accept that there is a possibility that fish can experience pain and suffer, then exposing them to adverse conditions or damage is a welfare issue. The discussion in this area has included debate on the nature and function of the central and peripheral nervous systems and evidence from cognitive studies. These arguments are reviewed in the following papers:
Huntingford, F.A., Adams, C., Braithwaite, V.A., Kadri, S., Pottinger, T.G., Sandøe, P. and Turnbull, J.F. (2006). Current understanding on fish welfare: a broad overview. Journal of Fish Biology. 68, 332-372.
Braithwaite, V. A. & Huntingford, F. A. (2004). Fish and welfare: do fish have the capacity for pain perception and suffering? Animal Welfare S87-92.