Lynne U . Sneddon Pain Perception in Fish Evidence and Implications for the Use of Fish

Pain assessment in fish is particularly challenging due to their evolutionary distance from humans, their lack of audible vocalization, and apparently expressionless demeanour. However, there are criteria that can be used to gauge whether pain perception occurs using carefully executed scientific approaches. Here, the standards for pain in fish are discussed and can be considered in three ways: neural detection and processing of pain; adverse responses to pain; and consciously experiencing pain. Many procedures that we subject fish to cause tissue damage and may give rise to the sensation of pain. Fish are popular as pets, in animal exhibits, and as experimental models, but are also cultured or caught for food. There is little legislation for the protection of fish welfare. Many countries are now exploring the welfare cost to fish, and current practices may need to be reviewed with respect to the current evidence for fish perceiving pain. Proving the existence of pain perception in an animal is inherently difficult. Humans can relate their internal experiences to one another through language, but without this, pain assessment is problematic as it requires knowledge of how someone else ‘feels’. Therefore, understanding what an animal experiences is particularly challenging. However, by drawing up a number of standards, and with insightful experimentation, it is possible to obtain meaningful conclusions upon the capacity for pain perception and indeed how important the experience is to the animal. Amongst vertebrates, fish evoke the most Journal of Consciousness Studies, 18, No. 9–10, 2011, pp. 209–29 Correspondence: Lynne U. Sneddon, University of Liverpool, School of Biological Sciences, The Bioscience Building, Liverpool, L69 7ZB Email: [email protected] Copyright (c) Imprint Academic 2011 For personal use only -not for reproduction opposition when discussing the capacity for pain due to their evolutionary distance from humans and the composition of their central nervous system. However, the opinions against condense into a semantic argument that if the pain is not identical to that experienced by humans then it is not pain per se and just a reflex response. This suggests that any pain or damage endured by an animal is unimportant as there is no suffering or discomfort involved. The majority of animal scientists disagree with this notion since pain must have evolved throughout the vertebrate groups in a similar way to all other sensory systems. Therefore, it is likely that animals do experience pain when injured and that this event will have a negative impact on their internal state. Here, the standards for fish perceiving pain are discussed and can be summarized in three parts: the possession of the neural apparatus to detect and process pain; adverse behavioural and physiological responses in vivo to a painful stimulus; and whether the individual has a conscious experience of pain. If fish do indeed suffer or experience discomfort as a result of tissue damage, then the way in which we use fish may need to be reviewed. Fish are popular as pets, used in animal exhibits, and as experimental models, but are also cultured or caught for food. Many practices during these procedures result in injury to the fish yet there is little legislation for the protection of fish from harm. Although many countries are now examining the welfare cost to fish in various scenarios, current practices may need to be revised in light of current evidence for fish perceiving pain.