Do Fish Feel Pain? Implications for Management?

A Summary and Analysis of “Can fish really feel pain” by Rose et al.

2012.

By Rachel Clark, Cohen Hocking and Victoria Pollins

Contents

• Summary of Rose et al. 2012– What is pain and how is it detected?– Review and critique of fish pain literature– Are fish conscious?

• Other scientific opinions• Social side of the argument• Conclusions and discussion

“Can fish really feel pain?” Rose et al. 2012

• Critique paper on current research regarding fish pain.

• Describes how methodologies used thus far are not adequate for concluding that fish feel pain

• Most research on fish welfare driven by emotion and opinion. Lacked scientific approach

Underlying Themes

• Easy to identify pain in humans: communication!• Non-humans:– although we can use imaging to see brain activation

in response to injury infliction, we can’t conclude that this is associated with conscious feelings of pain

Defining Pain

• International Association for the Study of Pain (IASP): – pain is an unpleasant sensory and emotional

experience associated with actual or potential tissue damage. It is a subjective state.

Nociception vs. Pain

• Nociception:– “unconscious detection of injurious stimuli”– Nervous system sensing noxious stimuli

• In humans, nociception is transmitted to the cerebral cortex and is translated into pain

• Although most animals have nociception, only mammals have cerebral cortex structures necessary to create human-like pain

Nociception vs. Pain

• Back bone of Rose et al.’s (2012) paper:– Unconscious nociception ≠ conscious pain– Although, commonly grouped together

• Distinguishing between nociception and pain by analyzing behavior is very difficult– Removal of cerebral cortex in mammals results in

no behavioral changes (Berridge and Winkielman 2003)

– Avoidance learning also possible (Kotanai et al. 2003)

• Behavior can only tell you how noxious a stimulus is but not whether it’s causing pain.

Construct Validation

• Construct: an attribute or ability that happens in the brain (ex: English language proficiency)

• Construct Validation: The degree to which a test measures the construct it claims to be measuring– Is research actually testing for pain, or are they

only measuring nociception?

Construct Validation

• Le Bars et al. (2001), Blackburn-Munro (2004), Vierck (2006), Rose and Woodbury (2008), and Vierck (2006)

• “None of these tests can be legitimately viewed as tests of pain, because the target behaviors can be expressed without consciousness” (Rose et al. 2012)

• Validated model: greatest challenge to pain research

Construct Validation

• Mammals: because they have same cortical regions as humans needed for processing pain, we can infer pain by cortical activity

• However, “this approach cannot be used because the fish brain does not contain [a true cortex]… a fact that has led to the conclusion that pain experience meaningfully like humans is probably impossible for fishes” (Rose 2002, 2007, from Rose et al. 2012)

Research on Fish Pain

• Behavioral Studies• Surgery, Wounding, Electronic Tagging• Neurological Studies

Behavioral Studies

• Bateson 1992: pain detection criteria– Animals able to detect noxious stimulus, react

negatively to it, learn to avoid it, and that the behavior is not a “simple reflex”

– Rose et al. 2012: conclude that these criteria do not distinguish pain from nociception

Behavioral Studies

• Sneddon 2003a– Injections of bee venom into jaw of trout– Rocking, mouth-rubbing, increased opercular beat

rate, delayed feeding– Rose et al. 2012: not validated detectors of pain

•Sneddon 2003b- Morphine injections reduced mouth rubbing- Rose et al. 2012: morphine acts on nociception

Surgery, Wounding, Electronic Tagging

• Wagner and Stevens (2000), Newby et al. (2007), Moser et al. 2005, Connors et al. 2002, Cooke et al. (2002) – Surgical insertion of transmitters (usually into

peritoneal cavity)– No response in feeding and swimming behavior– No response to migration– No changes in social behavior, parental care

• “If these fish were experiencing pain, we would infer that they would exhibit severely altered behavior”

Neurological Studies

• A-Delta Fibers– “bright pain”: immediate, localized– Signal possible injury to trigger escape/avoidance

• C Fibers– Burning, dull pain. Long lasting, diffuse.

• Roques et al. (2010) – 5% of sensory fibers in common carp are C fibers– However, it wasn’t determined if these C fibers

were nociceptors or non-nociceptors

Are Fish Conscious?

Consciousness

• “… [meaningful] pain experiences like in humans is probably impossible for fish” (Rose 2007)

• Pain is a process dependent on consciousness– Need to prove fish are conscious to prove they feel

pain

Are fish conscious?

• What is consciousness and how is it identified?• How plausible is it the fish could be conscious• What evidence is there for consciousness in

fishes• What value would consciousness be to fishes

and at what cost• If fishes were conscious could we comprehend

what that consciousness is like (Ross et al. 2012)• Effects on scientifically-based fisheries policy

Are fish conscious

“Wakefulness is not evidence of consciousness because it can exist in situations where

consciousness is absent” (Laureys 2005).

“Assessment of pain depends on verbal interaction, thus an animal under anesthesia

that awakens, is mistermed when you say it has regained consciousness” (Rose et al. 2012)

What is consciousness and how is it identified?

• No agreed definition of consciousness in animals (Rose et al. 2012)

• Can only agree on consciousness based on verbal communication (Bruno et al. 2011)– Exception: locked-in syndrom– Science cannot elaborate on behaviour

How plausible is it the fish could be conscious?

• Consciousness depends on specific identified neural structures (Rose 2002).

• In mammals the cingulate gyrus is a layer of the mesocortex which is critical for conscious awareness of pain, emotional feelings, and self awareness

Why can’t we say fish feel pain?

• Fish pallium cannot function like the cortex for the purpose of pain and consciousness (Rose 2002)

• Inadequate techniques used to identify nociceptic activity reaching the pallium

“Anyone proposing that a fish pallium could function like a human or mammalian

neocortex or that there might be a substitute system in fish brains for generating

consciousness, must provide convincing, empirical evidence that such a proposal is

worth consideration. This has not been done.” (Rose et al. 2012)

So if you’re confused, it’s okay

So are fish unconscious?

So fish are unconscious?

• Behavioural complexity is not evidence for consciousness– Eg. Individual recognition; avoidance learning

(Rose et al. 2012)

• Much of human survival behaviour is actually conducted by the unconscious (Wilson 2004)– Sizing up the world– Warning of danger– Setting goals and sophisticated action

But really, are they conscious??

• Basic patterns of fish behavior controlled by lower brain structures (diencephalon, brainstem, and spinal cord)

• Removal of the cerebral hemisphere results in minimal changes to neurological behavior (Overmier and Hollis 1983)– Food (yes)– Spawning (yes)– Intraspecies aggression (yes)– Smell (no)– Avoidance conditioning (yes, but difficult)

If fishes were conscious, what would it be like?

• Rose argues that if fish were conscious, it would be so different from human consciousness, no one can speculate on what that would infer

• No one knows!– Those who argue consciousness, assume they

would experience human-like pain and suffering (Rose et al. 2012)

Value of consciousness

• Most behavior in fish is reactive– Not much value in conscious behavior (ie,

natural selection)– Conscious suffering would likely be selected

against since it is unlikely to benefit fishes (ie, little can be done to treat wounds) (Rose et al. 2012)

Primary consciousness and self-awareness

• Even scientists who believe in primary consciousness, do not believe fish are self-aware (Donald 2001, Tulving 2005)– Self awareness facilitate dissociation techniques

for reducing pain (Price 1999)– Yet, others believe a lack of self-awareness would

make pain and suffering more intolerable (Sneddon 2011)

Cost of misrepresenting fish suffering

• Misinformation on policy making (Rose et al. 2012)

– Describes EU fish policies as scientifically unsound– Benefit of the doubt ideology is not scientific

justification (Dawkins 2012)– Too much focus on feelings, not enough on

function

“We believe that in fostering fish welfare, implementation of

legislation must be intelligently considered to ensure that it would

not adversely impact humans socially and economically without

necessarily benefiting fishes” (Rose et al. 2012)

Contradictory Arguments

• Though teleost fish are different in brain structure than tetrapods, brain function is similar (Chandroo, Duncan, and Moccia 2004)

• (Response to Rose et al. 2002) says nociceptors are actually similar to high animals like humans (Braithwaite and Huntingford 2004)

• Studies in zebrafish opioid receptors and peptides have been shown to function in a similar way to tetrapods (Gonzales-Nunez and Rodriguez 2009)

Sneddon 2009

• Can’t communicate a subjective account of pain (human standard), so observing behavior must be our only criteria for animal pain (Sneddon 2009)

• Behavior is altered by noxious stimuli showing they’re making decisions, not simply reacting impulsively (Sneddon 2009)

Fish Studies

• Studies have shown fish display adverse behavior to physical injury to tissue as well as suspend normal behavior (Sneddon 2009, Sneddon 2003, Ehrensing 1982)

Animal Brains

• In recent years, animal brain function has been shown to be higher than ever thought for non-higher order primates

1) Corvids capacity to learn to anticipate the intensions of others (Emery and Clayton 2001)

2) Rats show pessimism and optimism (Harding and Mendl 2001)

3) Rhesus macaques can give perception of their memory for a specific event (Hampton 2001)

4)Fish have shown to create mental maps (Braithwaite and Huntingford 2004)

From Science to Philosophy

From Science to Philosophy

• Solipsism: “idea that only one’s own mind is sure to exist… outside of one’s own mind is unsure” (online etymology dictionary)

From Science to Philosophy

• Until 1989 Vets were taught that animals didn’t feel pain (Rollin and Bernard, 1989)

• Animal intelligence research

From Science to Philosophy

“Less sensitive are their bodies, the more can they tolerate extreme pain or the rapid alteration of heat and cold; when they are exposed to illness, the more rapid their recovery from wounds that would be fatal for more sensitive peoples”

Christopher Meiners (1747 – 1810)

From Science to Philosophy

“All the arguments to prove man's superiority cannot shatter this hard fact: in suffering the animals are our equals.” Peter Singer (1946 - present)

Conservation And Management

Conservation And Management

“the results of many studies lead to believe that fish have the structures necessary and the capacity to experience fear and pain and can thus suffer and therefore, welfare considerations for farmed fish should take these into accounts” –EFSA (European Food Safety Authority)

Conservation And Management

• Sneddon believes that research is needed for “species specific response to pain, analgesics and doses” (p.341 Sneddon 2009)

Conservation And Management

• Sneddon believes that research is needed for “species specific response to pain, analgesics and doses” (p.341 Sneddon 2009)

• But what about the wild fish?

Citation: Hinch 2015

Conservation And Management

• Estimates of global fish catch are as high as almost 3 trillion individual fish per year (Mood and Brooke 2010)

• If sentient, should we regulate how we handle fish?

• How will this effect the fishing industry?

Conservation And Management

• “many existing commercial killing methods expose fish to substantial suffering over a prolonged period of time” (EFSA 2004)

Conservation And Management

• Currently no fish welfare regulations are in place anywhere in the world (Singer 2010)

Except for fish farms• Norway has banned C02 stunning and• Germany has banned ammonia baths

Legislation for BC livestock:

• Prevention of Cruelty to Animals Act • Milk Industry Act/Milk Industry Standards

Regulation (for cattle)• Meat Inspection Regulation (for animals

during slaughter)• Food Safety Act Agricultural Produce Grading

Act (i.e. for poultry)

Fishing methods

Recreational• Hook and line, throw nets, spear fishing, noodlingCommercial• Long line• Trawls and dredges• Seine• Traps and pots• Gill nets

Bycatch?(Hinch 2015)

Conclusion

Currently the scientific community remains divided on whether fish feel pain

An “ethical” transformation of the global fishing industry may be unrealistic

Discussion

• So do you think fish feel pain?

Discussion

• If they do feel pain, should this affect our fishing practices?

• Is scientific uncertainty enough to justify a change in fishing practices?

Discussion

• Given the array of studies on fishes (and other animals) to feel pain, do you think this poses issues of animal cruelty (eg. Injecting acid into the mouths of animals to test pain response)? Or is the research justified in the name of science and policy making decisions?

• Do you think it is to the advantage of marine fisheries for a paper like this to be published?

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