Fish fulfill several criteria proposed as indicating that non-human animals experience pain. These fulfilled criteria include a suitable nervous system and sensory receptors, opioid receptors and reduced responses to noxious stimuli when given analgesics and local anaesthetics, physiological changes to noxious stimuli, displaying protective motor reactions, exhibiting avoidance learning and making trade-offs between noxious stimulus avoidance and other motivational requirements.

Whether fish, such as this hooked salmon, can be said to feel pain is controversial.

Whether fish feel pain similar to humans or differently is a contentious issue. Pain is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in an animal, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.[1]

If fish feel pain, there are ethical and animal welfare implications including the consequences of exposure to pollutants, and practices involving commercial and recreational fishing, aquaculture, in ornamental fish and genetically modified fish and for fish used in scientific research.



The possibility that fish and other non-human animals experience pain has a long history. Initially, this was based around theoretical and philosophical argument, but more recently has turned to scientific investigation.


René Descartes (1596–1650) argued animals lack consciousness and so cannot experience pain

The idea that non-human animals might not feel pain goes back to the 17th-century French philosopher, René Descartes, who argued that animals do not experience pain and suffering because they lack consciousness.[2][3][4] In 1789, the British philosopher and social reformist, Jeremy Bentham, addressed in his book An Introduction to the Principles of Morals and Legislation the issue of our treatment of animals with the following often quoted words: "The question is not, Can they reason? nor, Can they talk? but, Can they suffer?"[5] Charles Darwin said that "The lower animals, like man, manifestly feel pleasure and pain, happiness and misery."[6]

Peter Singer, a bioethicist and author of Animal Liberation published in 1975, suggested that consciousness is not necessarily the key issue: just because animals have smaller brains, or are 'less conscious' than humans, does not mean that they are not capable of feeling pain. He goes on further to argue that we do not assume newborn infants, people suffering from neurodegenerative brain diseases or people with learning disabilities experience less pain than we would.[7]

Bernard Rollin, the principal author of two U.S. federal laws regulating pain relief for animals, writes that researchers remained unsure into the 1980s as to whether animals experience pain, and veterinarians trained in the U.S. before 1989 were taught to simply ignore animal pain.[8] In his interactions with scientists and other veterinarians, Rollin was regularly asked to "prove" that animals are conscious, and to provide "scientifically acceptable" grounds for claiming that they feel pain.[8]

Continuing into the 1990s, discussions were further developed on the roles that philosophy and science had in understanding animal cognition and mentality.[9] In subsequent years, it was argued there was strong support for the suggestion that some animals (most likely amniotes) have at least simple conscious thoughts and feelings[10] and that the view animals feel pain differently to humans is now a minority view.[2]

Scientific investigation

Cambridge Declaration on Consciousness (2012)

The absence of a neocortex does not appear to preclude an organism from experiencing affective states. Convergent evidence indicates that non-human animals have the neuroanatomical, neurochemical, and neurophysiological substrates of conscious states along with the capacity to exhibit intentional behaviors. Consequently, the weight of evidence indicates that humans are not unique in possessing the neurological substrates that generate consciousness. Non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.[11]

In the 20th and 21st centuries, there were many scientific investigations of pain in non-human animals.

Dr Lynne Sneddon, with her colleagues, Braithwaite, and Gentle, were the first to discover nociceptors (pain receptors) in fish. She stated that fish demonstrate pain-related changes in physiology and behaviour, that are reduced by painkillers, and they show higher brain activity when painfully stimulated.[12] Professor Victoria Braithwaite, in her book, Do Fish Feel Pain?, wrote that, fish, like birds and mammals, have a capacity for self-awareness, and can feel pain.[13] Donald Broom, Professor of Animal Welfare, Cambridge University, England, said that most mammalian pain systems are also found in fish, who can feel fear and have emotions which are controlled in the fish brain in areas anatomically different but functionally very similar to those in mammals.[14]

The American Veterinary Medical Association accepts that fish feel pain saying that the evidence supports the position that fish should be accorded the same considerations as terrestrial vertebrates concerning relief from pain.[15] The Royal Society for the Prevention of Cruelty to Animals, in Britain, commissioned in 1980 an independent panel of experts. They concluded that it was reasonable to believe that all vertebrates are capable of suffering to some degree or another.[16] RSPCA Australia more recently added that evidence that fish are capable of experiencing pain and suffering has been growing for some years.[17] The European Union Panel on Animal Health and Welfare European Food Safety Authority said that the balance of evidence indicates that some fish species can experience pain.[18] The British Farm Animal Welfare Committee 2014's report, Opinion on the Welfare of Farmed Fish, said that the scientific consensus is that fish can detect and respond to noxious stimuli, and experience pain.[19]



In 2001 studies were published showing that arthritic rats self-select analgesic opiates.[20] In 2014, the veterinary Journal of Small Animal Practice published an article on the recognition of pain which started – "The ability to experience pain is universally shared by all mammals..."[21] and in 2015, it was reported in the science journal Pain, that several mammalian species (rat, mouse, rabbit, cat and horse) adopt a facial expression in response to a noxious stimulus that is consistent with the expression of pain in humans.[22]



At the same time as the investigations using arthritic rats, studies were published showing that birds with gait abnormalities self-select for a diet that contains carprofen, a human analgesic.[23] In 2005, it was written "Avian pain is likely analogous to pain experienced by most mammals"[24] and in 2014, " is accepted that birds perceive and respond to noxious stimuli and that birds feel pain"[25]

Reptiles and amphibians


Veterinary articles have been published stating both reptiles[26][27][28] and amphibians[29][30][31] experience pain in a way analogous to humans, and that analgesics are effective in these two classes of vertebrates.

Argument by analogy


In 2012 the American philosopher Gary Varner reviewed the research literature on pain in animals. His findings are summarised in the following table.[32]

Argument by analogy[32]
Fish Amphibians Reptiles Birds Mammals
Has nociceptors  Y  Y  Y  Y  Y
Has brain  Y  Y  Y  Y  Y
Nociceptors and brain linked  Y ?[a] /  Y ?[b] /  Y ? /  Y  Y
Has endogenous opioids  Y  Y  Y  Y  Y
Analgesics affect responses  Y ?[c] ?[d]  Y  Y
Response to damaging stimuli similar to humans  Y  Y  Y  Y  Y


  1. ^ But see[33]
  2. ^ But see[34]
  3. ^ But see[35]
  4. ^ But see[36]

Arguing by analogy, Varner claims that any animal which exhibits the properties listed in the table could be said to experience pain. On that basis, he concludes that all vertebrates, including fish, probably experience pain, but invertebrates apart from cephalopods probably do not experience pain.[32][37]


Some studies however find crustaceans do show responses consistent with signs of pain and distress.[38]

Experiencing pain


Although there are numerous definitions of pain, almost all involve two key components.

First, nociception is required.[39] This is the ability to detect noxious stimuli which evoke a reflex response that rapidly moves the entire animal, or the affected part of its body, away from the source of the stimulus. The concept of nociception does not imply any adverse, subjective "feeling" – it is a reflex action. An example in humans would be the rapid withdrawal of a finger that has touched something hot – the withdrawal occurs before any sensation of pain is actually experienced.

The second component is the experience of "pain" itself, or suffering – the internal, emotional interpretation of the nociceptive experience. Again in humans, this is when the withdrawn finger begins to hurt, moments after the withdrawal. Pain is therefore a private, emotional experience. Pain cannot be directly measured in other animals, including other humans; responses to putatively painful stimuli can be measured, but not the experience itself. To address this problem when assessing the capacity of other species to experience pain, argument-by-analogy is used. This is based on the principle that if an animal responds to a stimulus in a similar way to ourselves, it is likely to have had an analogous experience.


Nociception: The reflex arc of a dog with a pin in her paw. Note there is no communication to the brain, but the paw is withdrawn by nervous impulses generated by the spinal cord. There is no conscious interpretation of the stimulus by the dog.

Nociception usually involves the transmission of a signal along a chain of nerve fibers from the site of a noxious stimulus at the periphery to the spinal cord and brain. This process evokes a reflex arc response generated at the spinal cord and not involving the brain, such as flinching or withdrawal of a limb. Nociception is found, in one form or another, across all major animal taxa.[39] Nociception can be observed using modern imaging techniques; and a physiological and behavioral response to nociception can often be detected. However, nociceptive responses can be so subtle in prey animals that trained (human) observers cannot perceive them, whereas natural predators can and subsequently target injured individuals.[40]

Emotional pain


Sometimes a distinction is made between "physical pain" and "emotional" or "psychological pain". Emotional pain is the pain experienced in the absence of physical trauma, for example, the pain experienced by humans after the loss of a loved one, or the break-up of a relationship. It has been argued that only primates and humans can feel "emotional pain", because they are the only animals that have a neocortex – a part of the brain's cortex considered to be the "thinking area". However, research has provided evidence that monkeys, dogs, cats and birds can show signs of emotional pain and display behaviours associated with depression during or after a painful experience, specifically, a lack of motivation, lethargy, anorexia, and unresponsiveness to other animals.[7]

Physical pain


The nerve impulses of the nociception response may be conducted to the brain thereby registering the location, intensity, quality and unpleasantness of the stimulus. This subjective component of pain involves conscious awareness of both the sensation and the unpleasantness (the aversive, negative affect). The brain processes underlying conscious awareness of the unpleasantness (suffering), are not well understood.

There have been several published lists of criteria for establishing whether non-human animals experience pain, e.g.[41][42] Some criteria that may indicate the potential of another species, including fishes, to feel pain include:[42]

  1. Has a suitable nervous system and sensory receptors
  2. Has opioid receptors and shows reduced responses to noxious stimuli when given analgesics and local anaesthetics
  3. Physiological changes to noxious stimuli
  4. Displays protective motor reactions that might include reduced use of an affected area such as limping, rubbing, holding or autotomy
  5. Shows avoidance learning
  6. Shows trade-offs between noxious stimulus avoidance and other motivational requirements
  7. High cognitive ability and sentience

Adaptive value


The adaptive value of nociception is obvious; an organism detecting a noxious stimulus immediately withdraws the limb, appendage or entire body from the noxious stimulus and thereby avoids further (potential) injury. However, a characteristic of pain (in mammals at least) is that pain can result in hyperalgesia (a heightened sensitivity to noxious stimuli) and allodynia (a heightened sensitivity to non-noxious stimuli). When this heightened sensitisation occurs, the adaptive value is less clear. First, the pain arising from the heightened sensitisation can be disproportionate to the actual tissue damage caused. Second, the heightened sensitisation may also become chronic, persisting well beyond the tissues healing. This can mean that rather than the actual tissue damage causing pain, it is the pain due to the heightened sensitisation that becomes the concern. This means the sensitisation process is sometimes termed maladaptive. It is often suggested hyperalgesia and allodynia assist organisms to protect themselves during healing, but experimental evidence to support this has been lacking.[43][44]

In 2014, the adaptive value of sensitisation due to injury was tested using the predatory interactions between longfin inshore squid (Doryteuthis pealeii) and black sea bass (Centropristis striata) which are natural predators of this squid. If injured squid are targeted by a bass, they began their defensive behaviours sooner (indicated by greater alert distances and longer flight initiation distances) than uninjured squid. If anaesthetic (1% ethanol and MgCl2) is administered prior to the injury, this prevents the sensitisation and blocks the behavioural effect. The authors claim this study is the first experimental evidence to support the argument that nociceptive sensitisation is actually an adaptive response to injuries.[40]

The question has been asked, "If fish cannot feel pain, why do stingrays have purely defensive tail spines that deliver venom? Stingrays' ancestral predators are fish. And why do many fishes possess defensive fin spines, some also with venom that produces pain in humans?"[45]

Research findings


Peripheral nervous system



Rainbow trout have nociceptors on the face, eyes, snout and other areas of the body

Primitive fish such as lampreys (Petromyzon marinus) have free nerve endings in the skin that respond to heat and mechanical pressure. However, behavioural reactions associated with nociception have not been recorded, and it is also difficult to determine whether the mechanoreceptors in lamprey are truly nociceptive-specific or simply pressure-specific.[46]

Nociceptors in fish were first identified in 2002.[47][48] The study was designed to determine whether nociceptors were present in the trigeminal nerve on the head of the trout and to observe the physiological and behavioural consequences of prolonged noxious stimulation. Rainbow trout lips were injected with acetic acid, while another group were injected with bee venom. These substances were chosen because protons of the acid stimulate nociceptive nerves in mammals and frogs,[49] while venom has an inflammatory effect in mammals[50] and both are known to be painful in humans. The fish exhibited abnormal behaviours such as side-to-side rocking and rubbing of their lips along the sides and floors of the tanks. Their respiration rate increased, and they reduced the amount of swimming. The acid group also rubbed their lips on the gravel. Rubbing an injured area to ameliorate pain has been demonstrated in humans and in other mammals.[51] Fifty-eight receptors were located on the face and head of the rainbow trout. Twenty-two of these receptors could be classified as nociceptors, as they responded to mechanical pressure and heat (more than 40 °C). Eighteen also reacted to acetic acid. The response of the receptors to mechanical, noxious thermal and chemical stimulation clearly characterised them as polymodal nociceptors. They had similar properties to those found in amphibians, birds[52][53] and mammals, including humans.[54] Trout that were injected with venom or acid took approximately 3 hours to resume eating, whereas the saline and control groups took approximately 1 hour. This may be guarding behaviour, where animals avoid using a painful limb, preventing continuing pain and harm being caused to the area.[52]

Rainbow trout (Oncorhynchus mykiss) have polymodal nociceptors on the face and snout that respond to mechanical pressure, temperatures in the noxious range (> 40 °C), and 1% acetic acid (a chemical irritant). Cutaneous receptors overall were found to be more sensitive to mechanical stimuli than those in mammals and birds, with some responding to stimuli as low 0.001g. In humans at least 0.6 g is required. This may be because fish skin is more easily damaged, necessitating nociceptors to have lower thresholds.[47][55][56][57] Further studies found nociceptors to be more widely distributed over the bodies of rainbow trout, as well as those of cod and carp. The most sensitive areas of the body are around the eyes, nostrils, fleshy parts of the tail, and pectoral and dorsal fins.[13][58]

Rainbow trout also have corneal nociceptors. Out of 27 receptors investigated in one study, seven were polymodal nociceptors and six were mechanothermal nociceptors. Mechanical and thermal thresholds were lower than those of cutaneous receptors, indicating greater sensitivity in the cornea.[59]

Bony fish possess nociceptors that are similar in function to those in mammals.[12]

Nerve fibres


There are two types of nerve fibre relevant to pain in fish. Group C nerve fibres are a type of sensory nerve fibre which lack a myelin sheath and have a small diameter, meaning they have a low nerve conduction velocity. The suffering that humans associate with burns, toothaches, or crushing injury are caused by C fibre activity. A typical human cutaneous nerve contains 83% Group C nerve fibres.[60] A-delta fibres are another type of sensory nerve fibre, however, these are myelinated and therefore transmit impulses faster than non-myelinated C fibres. A-delta fibres carry cold, pressure and some pain signals, and are associated with acute pain that results in "pulling away" from noxious stimuli.

Bony fish possess both Group C and A-delta fibres representing 38.7% (combined) of the fibres in the tail nerves of common carp and 36% of the trigeminal nerve of rainbow trout. However, only 5% and 4% of these are C fibres in the carp and rainbow trout, respectively.[60][61]

Some species of cartilagenous fish possess A-delta fibres, however, C fibres are either absent or found in very low numbers.[60][62][63] The Agnatha (hagfishes and lamprey) primarily have Group C fibres.[64]

Central nervous system

The brain regions of sharks and humans

The central nervous system (CNS) of fish contains a spinal cord, medulla oblongata, and the brain, divided into telencephalon, diencephalon, mesencephalon and cerebellum.

In fish, similar to other vertebrates, nociception travels from the peripheral nerves along the spinal nerves and is relayed through the spinal cord to the thalamus. The thalamus is connected to the telencephalon by multiple connections through the grey matter pallium, which has been demonstrated to receive nerve relays for noxious and mechanical stimuli.[64][65]

The major tracts that convey pain information from the periphery to the brain are the spinothalamic tract (body) and the trigeminal tract (head). Both have been studied in agnathans, teleost, and elasmobranch fish (trigeminal in the common carp, spinothalamic tract in the sea robin, Prionotus carolinus).[66]



If sensory responses in fish are limited to the spinal cord and hindbrain, they might be considered as simply reflexive. However, recordings from the spinal cord, cerebellum, tectum and telencephalon in both trout and goldfish (Carassius auratus) show these all respond to noxious stimuli. This indicates a nociceptive pathway from the periphery to the higher CNS of fish.[67]

Microarray analysis of gene expression shows the brain is active at the molecular level in the forebrain, midbrain and hindbrain of common carp and rainbow trout. Several genes involved in mammalian nociception, such as brain-derived neurotrophic factor (BDNF) and the cannabinoid CB1 receptor are regulated in the fish brain after a nociceptive event.[68][69]

Somatosensory evoked potentials (SEPs) are weak electric responses in the CNS following stimulation of peripheral sensory nerves. These further indicate there is a pathway from the peripheral nociceptors to higher brain regions. In goldfish, rainbow trout, Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua), it has been demonstrated that putatively non-noxious and noxious stimulation elicit SEPs in different brain regions, including the telencephalon[70] which may mediate the co-ordination of pain information.[71] Moreover, multiple functional magnetic resonance imaging (fMRI) studies with several species of fishes have shown that when suffering from putative pain, there is profound activity in the forebrain which is highly reminiscent of that observed in humans and would be taken as evidence of the experience of pain in mammals.[72][73]

Therefore, "higher" brain areas are activated at the molecular, physiological, and functional levels in fish experiencing a potentially painful event. Sneddon stated "This gives much weight to the proposal that fish experience some form of pain rather than a nociceptive event".[74]

Opioid system and effects of analgesics

Analgesics and anaesthetics are commonly used for surgery on fish

Teleost fish have a functional opioid system which includes the presence of opioid receptors similar to those of mammals.[75][76] Opioid receptors were already present at the origin of jawed vertebrates 450 million years ago.[77] All four of the main opioid receptor types (delta, kappa, mu, and NOP) are conserved in vertebrates, even in primitive jawless fishes (agnathastoma).[64]

The same analgesics and anaesthetics used in humans and other mammals, are often used for fish in veterinary medicine. These chemicals act on the nociceptive pathways, blocking signals to the brain where emotional responses to the signals are further processed by certain parts of the brain found in amniotes ("higher vertebrates").[78][79]

Effects of morphine

Five-day-old zebrafish larvae show behavioural responses indicative of pain in response to diluted acetic acid

Pre-treatment with morphine (an analgesic in humans and other mammals) has a dose-dependent anti-nociceptive effect[80] and mitigates the behavioural and ventilation rate responses of rainbow trout to noxious stimuli.

When acetic acid is injected into the lips of rainbow trout, they exhibit anomalous behaviours such as side-to-side rocking and rubbing their lips along the sides and floors of the tanks, and their ventilation rate increases. Injections of morphine reduce both the anomalous, noxious-stimulus related behaviours and the increase in ventilation rate.[81] When the same noxious stimulus is applied to zebrafish (Danio rerio), they respond by decreasing their activity. As with the rainbow trout, morphine injected prior to the acid injection attenuates the decrease in activity in a dose-dependent manner.[71]

Injection of acetic acid into the lips of rainbow trout causes a reduction in their natural neophobia (fear of novelty); this is reversed by the administration of morphine.[13]

In goldfish injected with morphine or saline and then exposed to unpleasant temperatures, fish injected with saline acted with defensive behaviours indicating anxiety, wariness and fear, whereas those given morphine did not.[82]

Effects of other analgesics


The neurotransmitter, Substance P and the analgesic opioid enkephalins and β-endorphin, which act as endogenous analgesics in mammals, are present in fish.[83]

Different analgesics have different effects on fish. In a study on the efficacy of three types of analgesic, buprenorphine (an opioid), carprofen (a non-steroidal anti-inflammatory drug) and lidocaine (a local anaesthetic), ventilation rate and time to resume feeding were used as pain indicators. Buprenorphine had limited impact on the fish's response, carprofen ameliorated the effects of noxious stimulation on time to resume feeding, however, lidocaine reduced all the behavioural indicators.[84] Administration of aspirin prevents behavioural change caused by acetic acid.[85]

Tramadol also increases the nociceptive threshold in fish, providing further evidence of an anti-nociceptive opioid system in fish.[13][86]

Effects of naloxone


Naloxone is an μ-opioid receptor antagonist which, in mammals, negates the analgesic effects of opioids. Both adult and five-day-old zebrafish larvae show behavioural responses indicative of pain in response to injected or diluted acetic acid. The anti-nociceptive properties of morphine or buprenorphine are reversed if adults,[71] or larvae,[87] are co-treated with naloxone. Both naloxone and prolyl-leucyl-glycinamide (another opiate antagonist in mammals) reduced the analgesic effects of morphine to electric shocks received by goldfish, indicating they can act as an opiate antagonist in fish.[88][89]

Physiological changes


The physiological changes of fish in response to noxious stimuli include elevations of ventilation rate[68][80][81][90] and cortisol levels.[86]

Protective responses

Noxiously stimulated common carp show anomalous rocking behaviour and rub their lips against the tank walls
Noxiously stimulated zebrafish reduce their frequency of swimming and increase their ventilation rate
Noxiously stimulated Atlantic cod display increased hovering close to the bottom of the tank and reduced use of shelter
Predator fish learn to avoid sticklebacks with spines

Studies show that fish exhibit protective behavioural responses to putatively painful stimuli.

When acetic acid or bee venom is injected into the lips of rainbow trout, they exhibit an anomalous side-to-side rocking behaviour on their pectoral fins, rub their lips along the sides and floors of the tanks[91] and increase their ventilation rate.[90] When acetic acid is injected into the lips of zebrafish, they respond by decreasing their activity. The magnitude of this behavioural response depends on the concentration of the acetic acid.[71]

The behavioural responses to a noxious stimulus differ between species of fish. Noxiously stimulated common carp (Cyprinus carpio) show anomalous rocking behaviour and rub their lips against the tank walls, but do not change other behaviours or their ventilation rate. In contrast, zebrafish (Danio rerio) reduce their frequency of swimming and increase their ventilation rate but do not display anomalous behaviour. Rainbow trout, like the zebrafish, reduce their frequency of swimming and increase their ventilation rate.[92] Nile tilapia (Oreochromis niloticus), in response to a tail fin clip, increase their swimming activity and spend more time in the light area of their tank.[93]

Since this initial work, Sneddon and her co-workers have shown that rainbow trout, common carp and zebrafish experiencing a noxious stimulation exhibit rapid changes in physiology and behavior that persist for up to 6 hours and thus are not simple reflexes.[66]

Five-day-old zebrafish larvae show a concentration dependent increase in locomotor activity in response to different concentrations of diluted acetic acid. This increase in locomotor activity is accompanied by an increase in cox-2 mRNA, demonstrating that nociceptive pathways are also activated.[87]

Fish show different responses to different noxious stimuli, even when these are apparently similar. This indicates the response is flexible and not simply a nociceptive reflex. Atlantic cod injected in the lip with acetic acid, capsaicin, or piercing the lip with a commercial fishing hook, showed different responses to these three types of noxious stimulation. Those cod treated with acetic acid and capsaicin displayed increased hovering close to the bottom of the tank and reduced use of shelter. However, hooked cod only showed brief episodes of head shaking.[90]

Avoidance learning


Early experiments provided evidence that fish learn to respond to putatively noxious stimuli. For instance, toadfish (Batrachoididae) grunt when they are electrically shocked, but after repeated shocks, they grunt simply at the sight of the electrode.[94][95] More recent studies show that both goldfish and trout learn to avoid locations in which they receive electric shocks. Sticklebacks receive some protection from predator fish through their spines. Researchers found pike and perch initially snapped them up but then rejected them. After a few experiences, the pike and perch learned to avoid the sticklebacks altogether. When the stickleback spines were removed, their protection disappeared.[96] Furthermore, this avoidance learning is flexible and is related to the intensity of the stimulus.[86][97][98][99]

Trade-offs in motivation

Goldfish make trade-offs between their motivation to feed or avoid an acute noxious stimulus

A painful experience may change the motivation for normal behavioural responses.

In a 2007 study, goldfish were trained to feed at a location of the aquarium where subsequently they would receive an electric shock. The number of feeding attempts and time spent in the feeding/shock zone decreased with increased shock intensity and with increased food deprivation the number and the duration of feeding attempts increased as did escape responses as this zone was entered. The researchers suggested that goldfish make a trade-off in their motivation to feed with their motivation to avoid an acute noxious stimulus.[98]

Rainbow trout naturally avoid novelty (i.e. they are neophobic). Victoria Braithwaite describes a study in which a brightly coloured Lego brick is placed in the tank of rainbow trout. Trout injected in the lip with a small amount of saline strongly avoided the Lego brick, however, trout injected with acetic acid spent considerably more time near the Lego block. When the study was repeated but with the fish also being given morphine, the avoidance response returned in those fish injected with acetic acid and could not be distinguished from the responses of saline injected fish.[13][100]

To explore the possibility of a trade-off between responding to a noxious stimulus and predation, researchers presented rainbow trout with a competing stimulus, a predator cue. Noxiously stimulated fish cease showing anti-predator responses, indicating that pain becomes their primary motivation. The same study investigated the potential trade-off between responding to a noxious stimulus and social status. The responses of the noxiously treated trout varied depending on the familiarity of the fish they were placed with. The researchers suggested the findings of the motivational changes and trade-offs provide evidence for central processing of pain rather than merely showing a nociceptive reflex.[100][101]

Paying a cost for analgesia


Zebrafish given access to a barren, brightly lit chamber or an enriched chamber prefer the enriched area. When these fish are injected with acetic acid or saline as a control they still choose the same enriched chamber. However, if an analgesic is dissolved in the barren, less-preferred chamber, zebrafish injected with noxious acid lose their preference and spend over half their time in the previously less-favourable, barren chamber. This suggests a trade-off in motivation and furthermore, they are willing to pay a cost to enter a less preferred environment to access pain relief.[41]

Cognitive ability and sentience


The learning abilities of fish demonstrated in a range of studies indicate sophisticated cognitive processes that are more complex than simple associative learning. Examples include the ability to recognise social companions, avoidance (for some months or years) of places where they encountered a predator or were caught on a hook and forming mental maps.[83]

It has been argued that although a high cognitive capacity may indicate a greater likelihood of experiencing pain, it also gives these animals a greater ability to deal with this, leaving animals with a lower cognitive ability a greater problem in coping with pain.[102]

Criteria for pain perception


Scientists have also proposed that in conjunction with argument-by-analogy, criteria of physiology or behavioural responses can be used to assess the possibility of non-human animals perceiving pain. The following is a table of criteria suggested by Sneddon et al.[41]

Criteria for pain reception in fish
Jawless fish


Cartilaginous fish


Bony fish


Lobe-finned fish


Has nociceptors ? ?  Y ?
Pathways to central nervous system ? ?  Y ?
Central processing in brain ? ?  Y ?
Receptors for analgesic drugs ? ?  Y ?
Physiological responses ? ?  Y ?
Movement away from noxious stimuli ? ?  Y ?
Behavioural changes from norm ? ?  Y ?
Protective behaviour ? ?  Y ?
Responses reduced by analgesic drugs ? ?  Y ?
Self-administration of analgesia ? ?  Y ?
Responses with high priority over other stimuli ? ?  Y ?
Pay cost to access analgesia ? ?  Y ?
Altered behavioural choices/preferences ? ?  Y ?
Relief learning ? ?  Y ?
Rubbing, limping or guarding ? ?  Y ?
Paying a cost to avoid stimulus ? ?  Y ?
Tradeoffs with other requirements ? ?  Y ?

In the table,  Y indicates positive evidence and ? denotes it has not been tested or there is insufficient evidence.

Societal implications

There are concerns that angling causes pain in fish.

Given that some have interpreted the existing scientific information to suggest that fish may feel pain,[103] it has been suggested that precautionary principles should be applied to commercial fishing, which would likely have multiple consequences.[103]

Both scientists and animal protection advocates have raised concerns about the possible suffering (pain and fear) of fish caused by angling.[104][105][106]

Other societal implications of fish experiencing pain include acute and chronic exposure to pollutants, commercial and sporting fisheries (e.g. injury during trawling, tagging/fin clipping during stock assessment, tissue damage, physical exhaustion and severe oxygen deficit during capture, pain and stress during slaughter, use of live bait), aquaculture (e.g. tagging/fin clipping, high stocking densities resulting in increased aggression, food deprivation for disease treatment or before harvest, removal from water for routine husbandry, pain during slaughter), ornamental fish (e.g. capture by sub-lethal poisoning, permanent adverse physical states due to selective breeding), scientific research (e.g. genetic-modification) may have detrimental effects on welfare, deliberately-imposed adverse physical, physiological and behavioural states, electrofishing, tagging, fin clipping or otherwise marking fish, handling procedures which may cause injury.[46][107]

Browman et al.[108] suggest that if the regulatory environment continues on its current trajectory (adding more aquatic animal taxa to those already regulated), activity in some sectors could be severely restricted, even banned. They further argue that extending legal protection to aquatic animals is a societal choice, but they emphasize that choice should not be ascribed to strong support from a body of research that does not yet exist, and may never exist, and the consequences of making that decision must be carefully weighed.



In the UK, the legislation protecting animals during scientific research, the "Animals (Scientific Procedures) Act 1986", protects fish from the moment they become capable of independent feeding.[109] The legislation protecting animals in most other circumstances in the UK is "The Animal Welfare Act, 2006" which states that in the Act, " "animal" means a vertebrate other than man",[110] clearly including fish.

In the US, the legislation protecting animals during scientific research is "The Animal Welfare Act".[111] This excludes protection of "cold-blooded" animals, including fish.[112]

The 1974 Norwegian Animal Rights Law states it relates to mammals, birds, frogs, salamander, reptiles, fish, and crustaceans.[113]

A 2018 article by Howard Browman and colleagues provides an overview of what different perspectives regarding fish pain and welfare mean to in the context of aquaculture, commercial fisheries, recreational fisheries, and research.[108]



Nervous system


Receptors and nerve fibres


It has been argued that fish cannot feel pain because they do not have a sufficient density of appropriate nerve fibres. A typical human cutaneous nerve contains 83% Group C nerve fibres,[114] however, the same nerves in humans with congenital insensitivity to pain have only 24–28% C-type fibres.[114] Based on this, James Rose, from the University of Wyoming, has argued that the absence of C-type fibres in cartilagenous sharks and rays indicates that signalling leading to pain perception is likely to be impossible, and the low numbers for bony fish (e.g. 5% for carp and trout) indicate this is also highly unlikely for these fish.[114] A-delta-type fibres, believed to trigger avoidance reactions, are common in bony fish, although they have not been found in sharks or rays.[114] Rose concludes that fish have survived well in an evolutionary sense without the full range of nociception typical of humans or other mammals.[114] Professor Culum Brown of Macquarie University, Sydney, states that lack of evidence has been used as evidence of lack; a fundamental misinterpretation of the scientific method, and has been taken to suggest that sharks and rays cannot feel pain. He asserts that the fact that nociception occurs in jawless fish,[115] as well as in bony fish,[116] suggests the most parsimonious explanation is that sharks do have these capacities but that we have yet to understand that the receptors or the fibres we have identified operate in a novel manner. He points out that the alternative explanation is that elasmobranchs have lost the ability of nociception, and one would have to come up with a very convincing argument for the adaptive value of such a loss in a single taxon in the entire animal kingdom.[117] Professor Broom of Cambridge University, submits that feeling pain gives active complex vertebrates a selective advantage through learning and responding, allowing them to survive in their environment. Pain and fear systems are phylogenetically extremely ancient and so are unlikely to have suddenly appeared in mammals or humans.[118]



In 2002, Rose published reviews arguing that fish cannot feel pain because they lack a neocortex in the brain.[119][120] This argument would also rule out pain perception in most mammals, and all birds and reptiles.[52][72] However, in 2003, a research team led by Lynne Sneddon concluded that the brains of rainbow trout fire neurons in the same way human brains do when experiencing pain.[121][122] Rose criticized the study, claiming it was flawed, mainly because it did not provide proof that fish possess "conscious awareness, particularly a kind of awareness that is meaningfully like ours".[123]

Rose, and more recently Brian Key[124][125] from The University of Queensland, argue that because the fish brain is very different from the human brain, fish are probably not conscious in the manner humans are, and while fish may react in a way similar to the way humans react to pain, the reactions in the case of fish have other causes. Studies indicating that fish can feel pain were confusing nociception with feeling pain, says Rose. "Pain is predicated on awareness. The key issue is the distinction between nociception and pain. A person who is anaesthetised in an operating theatre will still respond physically to an external stimulus, but he or she will not feel pain."[126] According to Rose and Key, the literature relating to the question of consciousness in fish is prone to anthropomorphisms and care is needed to avoid erroneously attributing human-like capabilities to fish.[127] However, no other animal can directly communicate how it feels and thinks, and Rose and Key have not published experimental studies to show that fish do not feel pain.[128] Sneddon suggests it is entirely possible that a species with a different evolutionary path could evolve different neural systems to perform the same functions (i.e. convergent evolution), as studies on the brains of birds have shown.[129] Key agrees that phenomenal consciousness is likely to occur in mammals and birds, but not in fish.[124] Animal behaviouralist Temple Grandin argues that fish could still have consciousness without a neocortex because "different species can use different brain structures and systems to handle the same functions."[122] Sneddon proposes that to suggest a function suddenly arises without a primitive form defies the laws of evolution.[130]

Other researchers also believe that animal consciousness does not require a neocortex, but can arise from homologous subcortical brain networks.[11] It has been suggested that brainstem circuits can generate pain. This includes research with anencephalic children who, despite missing large portions of their cortex, express emotions. There is also evidence from activation studies showing brainstem mediated feelings in normal humans and foetal withdrawal responses to noxious stimulation but prior to development of the cortex.[131]

In papers published in 2017 and 2018, Michael Woodruff[132][133] summarized a significant number of research articles that, in contradiction to the conclusions of Rose and Key, strongly support the hypothesis that the neuroanatomical organization of the fish pallium and its connections with subpallial structures, especially those with the preglomerular nucleus and the tectum, are complex enough to be analogous to the circuitry of the cortex and thalamus assumed to underlie sentience in mammals. He added neurophysiological and behavioral data to these anatomical observations that also support the hypothesis that the pallium is an important part of the hierarchical network proposed by Feinberg and Mallatt to underlie consciousness in fishes.[134]

Protective responses


Work by Sneddon characterised behavioural responses in rainbow trout, common carp and zebrafish.[66] However, when these experiments were repeated by Newby and Stevens without anaesthetic, rocking and rubbing behaviour was not observed, suggesting that some of the alleged pain responses observed by Sneddon and co-workers were likely to be due to recovery of the fish from anaesthesia. But, Newby and Stevens, in an attempt to replicate research conducted by Sneddon's laboratory, used a different protocol to the one already published. The lack of abnormal rubbing behaviours and resumption of feeding in the Newby and Stevens experiment can be attributed to them injecting such a high concentration of acid. If no nociceptive information is being conducted to the central nervous system then no behavioural changes will be elicited. Sneddon states that this demonstrates the importance of following experimental design of published studies to get comparable results.[135][136][137]

Several researchers argue about the definition of pain used in behavioural studies, as the observations recorded were contradictory, non-validated and non-repeatable by other researchers.[60] In 2012, Rose argued that fishes resume "normal feeding and activity immediately or soon after surgery".[60] But Stoskopf suggested that fish may respond to chronic stimuli in subtle ways. These include colour changes, alterations in posture and different utilization of the water column, and that these more nuanced behaviours, may be missed, while Wagner and Stevens said that further testing examining more behaviours is needed.[138][139]

Nordgreen said that the behavioural differences they found in response to uncomfortable temperatures showed that fish feel both reflexive and cognitive pain.[140] "The experiment shows that fish do not only respond to painful stimuli with reflexes, but change their behavior also after the event," Nordgreen said. "Together with what we know from experiments carried out by other groups, this indicates that the fish consciously perceive the test situation as painful and switch to behaviors indicative of having been through an aversive experience."[140] In 2012, Rose and others reviewed this and further studies which concluded that pain had been found in fish. They concluded that the results from such research are due to poor design and misinterpretation, and that the researchers were unable to distinguish unconscious detection of injurious stimuli (nociception) from conscious pain.[60]

In 2018, Sneddon, Donald Broom, Culum Brown and others, published a paper that found that despite the empirical proof, sceptics still deny anything beyond reflex responses in fishes and state that they are incapable of complex cognitive abilities. Recent studies[141][142] on learning have shown that cleaner wrasse fish, as well as parrots, perform better than chimpanzees, orangutans or capuchin monkeys in a complex learning task in which they have to learn to discriminate reliable food sources from unreliable ones. Goldfish learn to avoid an area where they have received an electric shock. Even when food has been previously provided in this area and the fish are strongly motivated to spend time there, they avoid it for three days, at which time they trade off their hunger with the risk of receiving another shock. This shows complex decision-making beyond simple reflexes.[128]

See also



  1. ^ Abbott FV, Franklin KB, Westbrook FR (January 1995). "The formalin test: scoring properties of the first and second phases of the pain response in rats". Pain. 60 (1): 91–102. doi:10.1016/0304-3959(94)00095-V. PMID 7715946. S2CID 35448280.
  2. ^ a b Carbone L (2004). What Animals Want: Expertise and Advocacy in Laboratory Animal Welfare Policy. Oxford University Press. p. 149. ISBN 978-0-19-516196-0.
  3. ^ Radner D, Radner M (1989). Animal Consciousness. Buffalo: Prometheus Books. ISBN 978-0-87975-459-4.
  4. ^ Harrison P (1992). "Descartes on animals". The Philosophical Quarterly. 42 (167): 219–227. doi:10.2307/2220217. JSTOR 2220217.
  5. ^ Bentham J (1879). An Introduction to the Principles of Morals and Legislation. Clarendon Press.
  6. ^ Darwin, Charles (1871). The Descent of Man in Relation to Sex.
  7. ^ a b Sneddon LU. "Can animals feel pain?". The Welcome Trust. Archived from the original on 13 April 2012. Retrieved 24 September 2015.
  8. ^ a b Rollin B (1989). The Unheeded Cry: Animal Consciousness, Animal Pain, and Science. Oxford University Press. pp. 117–118. ISBN 978-0-19-286104-7. cited in Carbone 2004, p. 150
  9. ^ Allen C (January 1998). "Assessing animal cognition: ethological and philosophical perspectives". Journal of Animal Science. 76 (1): 42–7. doi:10.2527/1998.76142x. PMID 9464883.
  10. ^ Griffin DR, Speck GB (January 2004). "New evidence of animal consciousness". Animal Cognition. 7 (1): 5–18. doi:10.1007/s10071-003-0203-x. PMID 14658059. S2CID 8650837.
  11. ^ a b Low P (7 July 2012). Panksepp J, Reiss D, Edelman D, Van Swinderen B, Low P, Koch C (eds.). "The Cambridge declaration on consciousness" (PDF). University of Cambridge.
  12. ^ a b Sneddon, Lynne U. (1 April 2015). "Pain in aquatic animals". Journal of Experimental Biology. 218 (7): 967–976. doi:10.1242/jeb.088823. ISSN 0022-0949. PMID 25833131. S2CID 130495.
  13. ^ a b c d e Braithwaite V (2010). Do Fish Feel Pain?. Oxford University Press. ISBN 978-0-19-161396-8.
  14. ^ Broom, Donald (1 January 2016). "Fish brains and behaviour indicate capacity for feeling pain". Animal Sentience. 1 (3). doi:10.51291/2377-7478.1031. ISSN 2377-7478.
  15. ^ "AVMA Guidelines for the Euthanasia of Animals: 2013 Edition" (PDF). The American Veterinary Medical Association. 2013. p. 12. Retrieved 4 October 2021.
  16. ^ Chairman, Lord Medway (1980). RSPCA's Report of the Panel of Enquiry into Shooting & Angling (1976–1979). Published by the Panel of Enquiry into Shooting and Angling. Archived from the original on 3 March 2021.
  17. ^ "Do fish feel pain? – RSPCA Knowledgebase". Retrieved 16 October 2021.
  18. ^ "General approach to fish welfare and to the concept of sentience in fish". EFSA Journal. 7 (2): 954. 2009. doi:10.2903/j.efsa.2009.954. ISSN 1831-4732.
  19. ^ The Farm Animal Welfare Committee (2014). "The Farm Animal Welfare Committee 2014's report, Opinion on the Welfare of Farmed Fish" (PDF): 30. Retrieved 19 October 2021. {{cite journal}}: Cite journal requires |journal= (help)
  20. ^ Colpaert FC, Tarayre JP, Alliaga M, Bruins Slot LA, Attal N, Koek W (March 2001). "Opiate self-administration as a measure of chronic nociceptive pain in arthritic rats". Pain. 91 (1–2): 33–45. doi:10.1016/s0304-3959(00)00413-9. PMID 11240076. S2CID 24858615.
  21. ^ Mathews K, Kronen PW, Lascelles D, Nolan A, Robertson S, Steagall PV, et al. (June 2014). "Guidelines for recognition, assessment and treatment of pain: WSAVA Global Pain Council members and co-authors of this document". The Journal of Small Animal Practice. 55 (6): E10-68. doi:10.1111/jsap.12200. PMID 24841489.
  22. ^ Chambers CT, Mogil JS (May 2015). "Ontogeny and phylogeny of facial expression of pain". Pain. 156 (5): 798–799. doi:10.1097/j.pain.0000000000000133. PMID 25887392. S2CID 2060896.
  23. ^ Danbury TC, Weeks CA, Chambers JP, Waterman-Pearson AE, Kestin SC (March 2000). "Self-selection of the analgesic drug carprofen by lame broiler chickens". The Veterinary Record. 146 (11): 307–11. doi:10.1136/vr.146.11.307. PMID 10766114. S2CID 35062797.
  24. ^ Machin KL (2005). "Avian analgesia". Seminars in Avian and Exotic Pet Medicine. 14 (4): 236–242. doi:10.1053/j.saep.2005.09.004.
  25. ^ Paul-Murphy J, Hawkins MG (2014). "Chapter 26 – Bird-specific considerations: recognizing pain in pet birds.". In Gaynor JS, Muir III WW (eds.). Handbook of Veterinary Pain Management. Elsevier Health Sciences. ISBN 978-0-323-08935-7.
  26. ^ Mosley CA (2005). "Anesthesia & Analgesia in reptiles". Seminars in Avian and Exotic Pet Medicine. 14 (4): 243–262. doi:10.1053/j.saep.2005.09.005.
  27. ^ Mosley C (January 2011). "Pain and nociception in reptiles". The Veterinary Clinics of North America. Exotic Animal Practice. 14 (1): 45–60. doi:10.1016/j.cvex.2010.09.009. PMID 21074702.
  28. ^ Sladky KK, Mans C (2012). "Clinical analgesia in reptiles". Journal of Exotic Pet Medicine. 21 (2): 158–167. doi:10.1053/j.jepm.2012.02.012.
  29. ^ Machin KL (March 1999). "Amphibian pain and analgesia". Journal of Zoo and Wildlife Medicine. 30 (1): 2–10. JSTOR 20095815. PMID 10367638.
  30. ^ Machin KL (January 2001). "Fish, amphibian, and reptile analgesia". The Veterinary Clinics of North America. Exotic Animal Practice. 4 (1): 19–33. doi:10.1016/S1094-9194(17)30048-8. PMID 11217460.
  31. ^ Stevens CW (January 2011). "Analgesia in amphibians: preclinical studies and clinical applications". The Veterinary Clinics of North America. Exotic Animal Practice. 14 (1): 33–44. doi:10.1016/j.cvex.2010.09.007. PMC 3056481. PMID 21074701.
  32. ^ a b c Varner GE (2012). "Chapter 5: Which Animals Are Sentient?". Personhood, Ethics, and Animal Cognition: Situating Animals in Hare's Two Level Utilitarianism. Oxford University Press. doi:10.1093/acprof:oso/9780199758784.001.0001. ISBN 978-0-19-975878-4. The table in the article is based on table 5.2, page 113.
  33. ^ Guénette SA, Giroux MC, Vachon P (2013). "Pain perception and anaesthesia in research frogs". Experimental Animals. 62 (2): 87–92. doi:10.1538/expanim.62.87. PMID 23615302.
  34. ^ Mosley C (2006). "Pain, nociception and analgesia in reptiles: when your snake goes 'ouch!'" (PDF). The North American Veterinary Conference. 20: 1652–1653.
  35. ^ Coble DJ, Taylor DK, Mook DM (May 2011). "Analgesic effects of meloxicam, morphine sulfate, flunixin meglumine, and xylazine hydrochloride in African-clawed frogs (Xenopus laevis)". Journal of the American Association for Laboratory Animal Science. 50 (3): 355–60. PMC 3103286. PMID 21640031.
  36. ^ Baker BB, Sladky KK, Johnson SM (January 2011). "Evaluation of the analgesic effects of oral and subcutaneous tramadol administration in red-eared slider turtles". Journal of the American Veterinary Medical Association. 238 (2): 220–7. doi:10.2460/javma.238.2.220. PMC 3158493. PMID 21235376.
  37. ^ Andrews K (2014). "Section 3.6.2: Fish Pain". The Animal Mind: An Introduction to the Philosophy of Animal Cognition. Routledge. ISBN 978-1-317-67675-1.
  38. ^ "What is the most humane way to kill crustaceans for human consumption?". RSPCA Knowledgebase. Royal Society for the Prevention of Cruelty to Animals (RSPCA) Australia. Retrieved 20 September 2020.
  39. ^ a b Sneddon LU (October 2004). "Evolution of nociception in vertebrates: comparative analysis of lower vertebrates". Brain Research. Brain Research Reviews. 46 (2): 123–30. doi:10.1016/j.brainresrev.2004.07.007. PMID 15464201. S2CID 16056461.
  40. ^ a b Crook RJ, Dickson K, Hanlon RT, Walters ET (May 2014). "Nociceptive sensitization reduces predation risk". Current Biology. 24 (10): 1121–5. Bibcode:2014CBio...24.1121C. doi:10.1016/j.cub.2014.03.043. PMID 24814149.
  41. ^ a b c Sneddon LU, Elwood RW, Adamo SA, Leach MC (2014). "Defining and assessing animal pain". Animal Behaviour. 97: 201–212. doi:10.1016/j.anbehav.2014.09.007. S2CID 53194458.
  42. ^ a b Elwood RW, Barr S, Patterson L (2009). "Pain and stress in crustaceans?". Applied Animal Behaviour Science. 118 (3): 128–136. doi:10.1016/j.applanim.2009.02.018.
  43. ^ Price TJ, Dussor G (May 2014). "Evolution: the advantage of 'maladaptive' pain plasticity". Current Biology. 24 (10): R384-6. Bibcode:2014CBio...24.R384P. doi:10.1016/j.cub.2014.04.011. PMC 4295114. PMID 24845663.
  44. ^ "Maladaptive pain". Oxford Reference. Retrieved 16 May 2016.
  45. ^ Safina C (2016). "Fish pain: A painful topic". Animal Sentience. 1 (3): 41. doi:10.51291/2377-7478.1076.
  46. ^ a b Huntingford FA, Adams C, Braithwaite VA, Kadri S, Pottinger TG, Sandøe P, Turnbull JF (2006). "Review paper: Current issues in fish welfare" (PDF). Journal of Fish Biology. 68 (2): 332–372. doi:10.1111/j.0022-1112.2006.001046.x.
  47. ^ a b Sneddon LU, Braithwaite VA, Gentle MJ (June 2003). "Do fishes have nociceptors? Evidence for the evolution of a vertebrate sensory system". Proceedings. Biological Sciences. 270 (1520): 1115–21. doi:10.1098/rspb.2003.2349. PMC 1691351. PMID 12816648.
  48. ^ Sneddon L (12 April 2021). "There is ample evidence that fish feel pain | Letter". The Guardian. Retrieved 28 August 2021.
  49. ^ Hamamoto DT, Forkey MW, Davis WL, Kajander KC, Simone DA (April 2000). "The role of pH and osmolarity in evoking the acetic acid-induced wiping response in a model of nociception in frogs". Brain Research. 862 (1–2): 217–29. doi:10.1016/S0006-8993(00)02138-7. PMID 10799688. S2CID 7290178.
  50. ^ Lariviere WR, Melzack R (August 1996). "The bee venom test: a new tonic-pain test". Pain. 66 (2–3): 271–7. doi:10.1016/0304-3959(96)03075-8. PMID 8880850. S2CID 34628083.
  51. ^ Roveroni RC, Parada CA, Cecília M, Veiga FA, Tambeli CH (November 2001). "Development of a behavioral model of TMJ pain in rats: the TMJ formalin test". Pain. 94 (2): 185–191. doi:10.1016/S0304-3959(01)00357-8. PMID 11690732. S2CID 15199427.
  52. ^ a b c Gentle MJ (November 1992). "Pain in birds". Animal Welfare. 1 (4): 235–47. doi:10.1017/S0962728600015189. S2CID 255884717.
  53. ^ Stevens CW (1992). "Alternatives to the use of mammals for pain research". Life Sciences. 50 (13): 901–12. doi:10.1016/0024-3205(92)90167-N. PMID 1548975.
  54. ^ Handwerker HO, Anton F, Reeh PW (1 February 1987). "Discharge patterns of afferent cutaneous nerve fibers from the rat's tail during prolonged noxious mechanical stimulation". Experimental Brain Research. 65 (3): 493–504. doi:10.1007/BF00235972. PMID 3556477. S2CID 22840458.
  55. ^ Sneddon LU (May 2003). "Trigeminal somatosensory innervation of the head of a teleost fish with particular reference to nociception". Brain Research. 972 (1–2): 44–52. doi:10.1016/s0006-8993(03)02483-1. PMID 12711077. S2CID 14616224.
  56. ^ Ashley PJ, Sneddon LU, McCrohan CR (August 2007). "Nociception in fish: stimulus-response properties of receptors on the head of trout Oncorhynchus mykiss". Brain Research. 1166: 47–54. doi:10.1016/j.brainres.2007.07.011. PMID 17673186. S2CID 15837167.
  57. ^ Mettam JJ, McCrohan CR, Sneddon LU (February 2012). "Characterisation of chemosensory trigeminal receptors in the rainbow trout, Oncorhynchus mykiss: responses to chemical irritants and carbon dioxide". The Journal of Experimental Biology. 215 (Pt 4): 685–93. doi:10.1242/jeb.060350. PMID 22279076.
  58. ^ Chervova LS, Lapshin DN (2004). "Pain sensitivity of fishes and analgesia induced by opioid and nonopioid agents" (PDF). In Proceedings of the Fourth International Iran & Russia Conference.
  59. ^ Ashley PJ, Sneddon LU, McCrohan CR (December 2006). "Properties of corneal receptors in a teleost fish". Neuroscience Letters. 410 (3): 165–8. doi:10.1016/j.neulet.2006.08.047. PMID 17101221. S2CID 14375428.
  60. ^ a b c d e f Rose JD, Arlinghaus R, Cooke SJ, Diggles BK, Sawynok W, Stevens ED, Wynne CD (2012). "Can fish really feel pain?" (PDF). Fish and Fisheries. 15 (1): 97–133. doi:10.1111/faf.12010.
  61. ^ Sneddon LU (February 2002). "Anatomical and electrophysiological analysis of the trigeminal nerve in a teleost fish, Oncorhynchus mykiss". Neuroscience Letters. 319 (3): 167–71. doi:10.1016/S0304-3940(01)02584-8. PMID 11834319. S2CID 14807046.
  62. ^ Snow PJ, Plenderleith MB, Wright LL (August 1993). "Quantitative study of primary sensory neurone populations of three species of elasmobranch fish". The Journal of Comparative Neurology. 334 (1): 97–103. doi:10.1002/cne.903340108. PMID 8408762. S2CID 32762031.
  63. ^ Braithwaite VA, Boulcott P (May 2007). "Pain perception, aversion and fear in fish". Diseases of Aquatic Organisms. 75 (2): 131–8. doi:10.3354/dao075131. PMID 17578252.
  64. ^ a b c Weber ES (January 2011). "Fish analgesia: pain, stress, fear aversion, or nociception?". The Veterinary Clinics of North America. Exotic Animal Practice. 14 (1): 21–32. doi:10.1016/j.cvex.2010.09.002. PMID 21074700.
  65. ^ Nordgreen J, Horsberg TE, Ranheim B, Chen AC (December 2007). "Somatosensory evoked potentials in the telencephalon of Atlantic salmon (Salmo salar) following galvanic stimulation of the tail". Journal of Comparative Physiology A. 193 (12): 1235–42. doi:10.1007/s00359-007-0283-1. PMID 17987296. S2CID 19654379.
  66. ^ a b c Sneddon LU (2009). "Pain perception in fish: indicators and endpoints". ILAR Journal. 50 (4): 338–42. doi:10.1093/ilar.50.4.338. PMID 19949250.
  67. ^ Dunlop R, Laming P (September 2005). "Mechanoreceptive and nociceptive responses in the central nervous system of goldfish (Carassius auratus) and trout (Oncorhynchus mykiss)". The Journal of Pain. 6 (9): 561–8. doi:10.1016/j.jpain.2005.02.010. PMID 16139775.
  68. ^ a b Reilly SC, Quinn JP, Cossins AR, Sneddon LU (May 2008). "Novel candidate genes identified in the brain during nociception in common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss)". Neuroscience Letters. 437 (2): 135–8. doi:10.1016/j.neulet.2008.03.075. PMID 18440145. S2CID 18763423.
  69. ^ Posner LP (2009). "Introduction: pain and distress in fish: a review of the evidence". ILAR Journal. 50 (4): 327–8. doi:10.1093/ilar.50.4.327. PMID 19949248.
  70. ^ Ludvigsen S, Stenklev NC, Johnsen HK, Laukli E, Matre D, Aas-Hansen Ø (February 2014). "Evoked potentials in the Atlantic cod following putatively innocuous and putatively noxious electrical stimulation: a minimally invasive approach". Fish Physiology and Biochemistry. 40 (1): 173–81. Bibcode:2014FPBio..40..173L. doi:10.1007/s10695-013-9834-2. PMC 3901938. PMID 23896862.
  71. ^ a b c d Ribeiro MM, Pinto A, Pinto M, Heras M, Martins I, Correia A, et al. (July 2011). "Inhibition of nociceptive responses after systemic administration of amidated kyotorphin". British Journal of Pharmacology. 163 (5): 964–73. doi:10.1111/j.1476-5381.2011.01290.x. PMC 3130928. PMID 21366550.
  72. ^ a b Brown C (January 2015). "Fish intelligence, sentience and ethics". Animal Cognition. 18 (1): 1–17. doi:10.1007/s10071-014-0761-0. PMID 24942105. S2CID 207050888.
  73. ^ Sneddon LU, Leach MC (2016). "Anthropomorphic denial of fish pain". Animal Sentience. 1 (3): 28. doi:10.51291/2377-7478.1048.
  74. ^ Sneddon LU (2011). "Pain perception in fish evidence and implications for the use of fish". Journal of Consciousness Studies. 18 (9): 209–229.
  75. ^ Buatti MC, Pasternak GW (August 1981). "Multiple opiate receptors: phylogenetic differences". Brain Research. 218 (1–2): 400–5. doi:10.1016/0006-8993(81)91319-6. PMID 6268247. S2CID 6870252.
  76. ^ Marron Fdez de Velasco E, Law PY, Rodríguez RE (September 2009). "Mu opioid receptor from the zebrafish exhibits functional characteristics as those of mammalian mu opioid receptor". Zebrafish. 6 (3): 259–68. doi:10.1089/zeb.2009.0594. PMID 19761379.
  77. ^ Dreborg S, Sundström G, Larsson TA, Larhammar D (October 2008). "Evolution of vertebrate opioid receptors". Proceedings of the National Academy of Sciences of the United States of America. 105 (40): 15487–92. Bibcode:2008PNAS..10515487D. doi:10.1073/pnas.0805590105. PMC 2563095. PMID 18832151.
  78. ^ Viñuela-Fernández I, Jones E, Welsh EM, Fleetwood-Walker SM (September 2007). "Pain mechanisms and their implication for the management of pain in farm and companion animals". Veterinary Journal. 174 (2): 227–39. doi:10.1016/j.tvjl.2007.02.002. PMID 17553712.
  79. ^ Sneddon LU (2012). "Clinical Anesthesia & Analgesia in fish". Journal of Exotic Pet Medicine. 21: 32–43. doi:10.1053/j.jepm.2011.11.009. S2CID 78473.
  80. ^ a b Jones SG, Kamunde C, Lemke K, Stevens ED (December 2012). "The dose-response relation for the antinociceptive effect of morphine in a fish, rainbow trout". Journal of Veterinary Pharmacology and Therapeutics. 35 (6): 563–70. doi:10.1111/j.1365-2885.2011.01363.x. PMID 22229842.
  81. ^ a b Sneddon LU (2003). "The evidence for pain in fish: The use of morphine as an analgesic". Applied Animal Behaviour Science. 83 (2): 153–162. doi:10.1016/s0168-1591(03)00113-8.
  82. ^ Nordgreen J, Joseph P, Garner JP, Janczak AM, Ranheim B, Muir WM, Horsberg TE (2009). "Thermonociception in fish: Effects of two different doses of morphine on thermal threshold and post-test behaviour in goldfish (Carassius auratus)". Applied Animal Behaviour Science. 119 (1–2): 101–107. doi:10.1016/j.applanim.2009.03.015.
  83. ^ a b Broom DM (May 2007). "Cognitive ability and sentience: which aquatic animals should be protected?". Diseases of Aquatic Organisms. 75 (2): 99–108. doi:10.3354/dao075099. PMID 17578249.
  84. ^ Mettam JJ, Oulton LJ, McCrohan CR, Sneddon LU (2011). "The efficacy of three types of analgesic drugs in reducing pain in the rainbow trout, Oncorhynchus mykiss". Applied Animal Behaviour Science. 133 (3): 265–274. doi:10.1016/j.applanim.2011.06.009.
  85. ^ Lopez-Luna J, Al-Jubouri Q, Al-Nuaimy W, Sneddon LU (April 2017). "Reduction in activity by noxious chemical stimulation is ameliorated by immersion in analgesic drugs in zebrafish". The Journal of Experimental Biology. 220 (Pt 8): 1451–1458. doi:10.1242/jeb.146969. PMID 28424313. S2CID 24635067.
  86. ^ a b c Wolkers CP, Barbosa Junior A, Menescal-de-Oliveira L, Hoffmann A (2013). "Stress-induced antinociception in fish reversed by naloxone". PLOS ONE. 8 (7): e71175. Bibcode:2013PLoSO...871175W. doi:10.1371/journal.pone.0071175. PMC 3728202. PMID 23936261.
  87. ^ a b Steenbergen PJ, Bardine N (2014). "Antinociceptive effects of buprenorphine in zebrafish larvae: An alternative for rodent models to study pain and nociception?". Applied Animal Behaviour Science. 152: 92–99. doi:10.1016/j.applanim.2013.12.001.
  88. ^ Ehrensing RH, Michell GF, Kastin AJ (October 1982). "Similar antagonism of morphine analgesia by MIF-1 and naloxone in Carassius auratus". Pharmacology, Biochemistry, and Behavior. 17 (4): 757–61. doi:10.1016/0091-3057(82)90358-6. PMID 6129644. S2CID 31113845.
  89. ^ Chervova LS, Lapshin DN (2000). "Opioid modulation of pain threshold in fish". Doklady Biological Sciences. 375 (1): 590–1. doi:10.1023/a:1026681519613. PMID 11211504. S2CID 1180288.
  90. ^ a b c Eckroth JR, Aas-Hansen Ø, Sneddon LU, Bichão H, Døving KB (2014). "Physiological and behavioural responses to noxious stimuli in the Atlantic cod (Gadus morhua)". PLOS ONE. 9 (6): e100150. Bibcode:2014PLoSO...9j0150E. doi:10.1371/journal.pone.0100150. PMC 4061104. PMID 24936652.
  91. ^ Grandin T (2015). "Chapter 2 – The importance of measurement to improve the welfare of livestock, poultry, and fish.". In Grandin T (ed.). Improving Animal Welfare: A Practical Approach. ISBN 978-1-78064-468-4.
  92. ^ Reilly SC, Quinn JP, Cossins AR, Sneddon LU (2008). "Behavioural analysis of a nociceptive event in fish: Comparisons between three species demonstrate specific responses". Applied Animal Behaviour Science. 114 (1): 248–259. doi:10.1016/j.applanim.2008.01.016.
  93. ^ Roques JA, Abbink W, Geurds F, van de Vis H, Flik G (November 2010). "Tailfin clipping, a painful procedure: Studies on Nile tilapia and common carp". Physiology & Behavior. 101 (4): 533–40. doi:10.1016/j.physbeh.2010.08.001. PMID 20705079. S2CID 25859917.
  94. ^ Dunayer J (July–August 1991). "Fish: Sensitivity Beyond the Captor's Grasp". The Animals' Agenda: 12–18 – via
  95. ^ "Animal Cognition". 22 April 2015. Retrieved 15 September 2015.
  96. ^ Hoogland R, Morris D, Tinbergen N (1956). "The Spines of Sticklebacks (Gasterosteus and Pygosteus) as Means of Defence against Predators (Perca and Esox)". Behaviour. 10 (3/4): 205–236. doi:10.1163/156853956X00156. ISSN 0005-7959. JSTOR 4532857.
  97. ^ Dunlop R, Millsopp S, Laming P (2006). "Avoidance learning in goldfish (Carassius auratus) and trout (Oncorhynchus mykiss) and implications for pain perception". Applied Animal Behaviour Science. 97 (2): 255–271. doi:10.1016/j.applanim.2005.06.018.
  98. ^ a b Millsopp S, Laming P (2007). "Trade-offs between feeding and shock avoidance in goldfish (Carassius auratus)". Applied Animal Behaviour Science. 113 (1–3): 247–254. doi:10.1016/j.applanim.2007.11.004.
  99. ^ Zerbolio DJ, Royalty JL (1 September 1983). "Matching and oddity conditional discrimination in the goldfish as avoidance responses: Evidence for conceptual avoidance learning". Animal Learning & Behavior. 11 (3): 341–348. doi:10.3758/BF03199786. ISSN 1532-5830.
  100. ^ a b Sneddon LU, Braithwaite VA, Gentle MJ (October 2003). "Novel object test: examining nociception and fear in the rainbow trout". The Journal of Pain. 4 (8): 431–40. doi:10.1067/S1526-5900(03)00717-X. PMID 14622663.
  101. ^ Ashley PJ, Ringrose S, Edwards KL, Wallington E, E, McCrohan CR, Sneddon LU (2009). "Effect of noxious stimulation upon antipredator responses and dominance status in rainbow trout". Animal Behaviour. 77 (2): 403–410. doi:10.1016/j.anbehav.2008.10.015. S2CID 19225428.
  102. ^ Broom DM (2001). "Evolution of pain" (PDF). Vlaams Diergeneeskundig Tijdschrift. 70 (1): 17–21. doi:10.21825/vdt.89895. S2CID 38767856. Archived from the original (PDF) on 30 December 2022. Retrieved 25 September 2015.
  103. ^ a b Brown C (2016). "Fish pain: an inconvenient truth". Animal Sentience. 1 (3): 32. doi:10.51291/2377-7478.1069.
  104. ^ Cooke SJ, Sneddon LU (2007). "Animal welfare perspectives on recreational angling". Applied Animal Behaviour Science. 104 (3–4): 176–198. CiteSeerX doi:10.1016/j.applanim.2006.09.002. S2CID 49233569.
  105. ^ Leake J (14 March 2004). "Anglers to Face RSPCA Check". The Sunday Times. Archived from the original on 23 September 2015. Retrieved 15 September 2015.
  106. ^ Diggles BK (2016). "Fish pain: Would it change current best practice in the real world?". Animal Sentience. 1 (3): 35. doi:10.51291/2377-7478.1068.
  107. ^ Sneddon LU (2006). "Ethics and welfare: Pain perception in fish". Bull. Eur. Assoc. Fish. Pathol. 26 (1): 6–10.
  108. ^ a b Browman HI, Cooke SJ, Cowx IG, Derbyshire SW, Kasumyan A, Key B, et al. (2018). "Welfare of aquatic animals: where things are, where they are going, and what it means for research, aquaculture, recreational angling, and commercial fishing". ICES Journal of Marine Science. 76 (1): 82–92. doi:10.1093/icesjms/fsy067. ISSN 1054-3139.
  109. ^ "Animals (Scientific Procedures) Act 1986" (PDF). Home Office (UK). Retrieved 23 September 2015.
  110. ^ "Animal Welfare Act 2006". UK Government. 2006. Retrieved 25 September 2015.
  111. ^ "U.S.C. Title 7 – Agriculture".
  112. ^ "Animals in research". neavs. Archived from the original on 18 September 2015. Retrieved 25 September 2015.
  113. ^ Henriksen S, Vaagland H, Sundt-Hansen L, May R, Fjellheim, A (2003). "Consequences of pain perception in fish for catch and release, aquaculture and commercial fisheries" (PDF).
  114. ^ a b c d e Rose JD, Arlinghaus R, Cooke SJ, Diggles BK, Sawynok W, Stevens ED, Wynne CD (2012). "Can fish really feel pain?" (PDF). Fish and Fisheries. 15 (1): 97–133. doi:10.1111/faf.12010.
  115. ^ Matthews, Gary; Wickelgren, Warren O. (1978). "Trigeminal sensory neurons of the sea lamprey". Journal of Comparative Physiology A. 123 (4): 329–333. doi:10.1007/bf00656966. ISSN 0340-7594. S2CID 1631932.
  116. ^ Sneddon LU (April 2015). "Pain in aquatic animals". The Journal of Experimental Biology. 218 (Pt 7): 967–76. doi:10.1242/jeb.088823. PMID 25833131.
  117. ^ Brown, Culum (1 January 2017). "A risk assessment and phylogenetic approach". Animal Sentience. 2 (16). doi:10.51291/2377-7478.1219. ISSN 2377-7478.
  118. ^ Broom, Donald (1 January 2016). "Fish brains and behaviour indicate capacity for feeling pain". Animal Sentience. 1 (3). doi:10.51291/2377-7478.1031. ISSN 2377-7478.
  119. ^ Rose JD (2002). "The neurobehavioral nature of fishes and the question of awareness and pain" (PDF). Reviews in Fisheries Science. 10 (1): 1–38. Bibcode:2002RvFS...10....1R. CiteSeerX doi:10.1080/20026491051668. S2CID 16220451. Archived from the original (PDF) on 10 October 2012.
  120. ^ Rose JD (2002). "Do fish feel pain?". Archived from the original on 20 January 2013. Retrieved 27 September 2007.
  121. ^ "Fish do feel pain, scientists say". BBC News. 30 April 2003. Retrieved 20 May 2010.
  122. ^ a b Grandin T, Johnson C (2005). Animals in Translation. New York: Scribner. pp. 183–184. ISBN 978-0-7432-4769-6.
  123. ^ Rose JD (2003). Erickson HE (ed.). "A Critique of the paper: "Do fish have nociceptors: Evidence for the evolution of a vertebrate sensory system"" (PDF). Information Resources on Fish Welfare 1970–2003, Animal Welfare Information Resources. Beltsville, MD: U. S. Department of Agriculture. pp. 49–51. Archived from the original (PDF) on 19 November 2008.
  124. ^ a b Key B (2015). "Fish do not feel pain and its implications for understanding phenomenal consciousness". Biology & Philosophy. 30 (2): 149–165. doi:10.1007/s10539-014-9469-4. PMC 4356734. PMID 25798021.
  125. ^ Key B (2016). "Why fish do not feel pain". Animal Sentience. 1 (3): 1. doi:10.51291/2377-7478.1011.
  126. ^ "Fish lack the brains to feel pain, says the latest school of thought". The Telegraph. 10 February 2003.
  127. ^ Rose JD (May 2007). "Anthropomorphism and 'mental welfare' of fishes". Diseases of Aquatic Organisms. 75 (2): 139–54. doi:10.3354/dao075139. PMID 17578253.
  128. ^ a b Sneddon, Lynne; Lopez-Luna, Javier; Wolfenden, David; Leach, Matthew; Valentim, Ana; Steenbergen, Peter; Bardine, Nabila; Currie, Amanda; Broom, Donald; Brown, Culum (1 January 2018). "Fish sentience denial: Muddying the waters". Animal Sentience. 3 (21). doi:10.51291/2377-7478.1317. ISSN 2377-7478. S2CID 55070090.   Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
  129. ^ Sneddon LU (28 August 2012). "Pain perception in fish: Why critics cannot accept the scientific evidence for fish pain" (PDF). Archived from the original (PDF) on 23 September 2015.
  130. ^ Bekoff M, Sherman PW (April 2004). "Reflections on animal selves". Trends in Ecology & Evolution. 19 (4): 176–80. doi:10.1016/j.tree.2003.12.010. PMID 16701251. S2CID 17877550.
  131. ^ Derbyshire SW (2016). "Fish lack the brains and the psychology for pain". Animal Sentience. 1 (3): 18. doi:10.51291/2377-7478.1047.
  132. ^ Woodruff M (2017). "Consciousness in teleosts: There is something it feels like to be a fish". Animal Sentience. 2 (13): 1. doi:10.51291/2377-7478.1198. S2CID 56306955.
  133. ^ Woodruff M (2018). "Sentience in fishes: More on the evidence". Animal Sentience. 3 (13): 16.
  134. ^ Feinberg TE, Mallatt JM (2016). The ancient origins of consciousness: how the brain created experience. Cambridge, MA: MIT Press. ISBN 978-0-262-03433-3.
  135. ^ Newby NC, Stevens ED (2008). "The effects of the acetic acid "pain" test on feeding, swimming and respiratory responses of rainbow trout (Oncorhynchus mykiss)". Applied Animal Behaviour Science. 114 (1): 260–269. doi:10.1016/j.applanim.2007.12.006.
  136. ^ Sneddon LU (2009). "The effects of the acetic acid "pain" test on feeding, swimming, and respiratory responses of rainbow trout (Oncorhynchus mykiss): A critique on Newby and Stevens (2008)". Applied Animal Behaviour Science. 116 (1): 96–97. doi:10.1016/j.applanim.2008.07.006.
  137. ^ Newby NC, Stevens ED (2009). "The effects of the acetic acid "pain" test on feeding, swimming, and respiratory responses of rainbow trout (Oncorhynchus mykiss): A critique on Newby and Stevens (2008) — response". Applied Animal Behaviour Science. 116 (1): 97–99. doi:10.1016/j.applanim.2008.07.009.
  138. ^ Stoskopf, M. K. (1 February 1994). "Pain and analgesia in birds, reptiles, amphibians, and fish". Investigative Ophthalmology & Visual Science. 35 (2): 775–780. ISSN 1552-5783. PMID 8113029.
  139. ^ Wagner, Glenn N.; Stevens, E. Don (1 May 2000). "Effects of different surgical techniques: Suture material and location of incision site on the behaviour of rainbow trout (Oncorhynchus mykiss)". Marine and Freshwater Behaviour and Physiology. 33 (2): 103–114. Bibcode:2000MFBP...33..103W. doi:10.1080/10236240009387084. ISSN 1023-6244. S2CID 83911821.
  140. ^ a b "Fish may actually feel pain and react to it much like humans". Purdue University. 29 April 2009. Archived from the original on 5 December 2022. Retrieved 13 September 2009.
  141. ^ Salwiczek, Lucie H.; Prétôt, Laurent; Demarta, Lanila; Proctor, Darby; Essler, Jennifer; Pinto, Ana I.; Wismer, Sharon; Stoinski, Tara; Brosnan, Sarah F.; Bshary, Redouan (21 November 2012). "Adult Cleaner Wrasse Outperform Capuchin Monkeys, Chimpanzees and Orang-utans in a Complex Foraging Task Derived from Cleaner – Client Reef Fish Cooperation". PLOS ONE. 7 (11): e49068. Bibcode:2012PLoSO...749068S. doi:10.1371/journal.pone.0049068. ISSN 1932-6203. PMC 3504063. PMID 23185293.
  142. ^ Pepperberg, Irene M.; Hartsfield, Leigh Ann (2014). "Can Grey parrots (Psittacus erithacus) succeed on a "complex" foraging task failed by nonhuman primates (Pan troglodytes, Pongo abelii, Sapajus apella) but solved by wrasse fish (Labroides dimidiatus)?". Journal of Comparative Psychology. 128 (3): 298–306. doi:10.1037/a0036205. ISSN 1939-2087. PMID 24798239.