What Is It Like to Be a Bass? Red Herrings, Fish Pain and the Study of Animal Sentience

Abstract

Debates around fishes' ability to feel pain concern sentience: do reactions to tissue damage indicate evaluative consciousness (conscious affect), or mere nociception? Thanks to Braithwaite's discovery of trout nociceptors, and concerns that current practices could compromise welfare in countless fish, this issue's importance is beyond dispute. However, nociceptors are merely necessary, not sufficient, for true pain, and many measures held to indicate sentience have the same problem. The question of whether fish feel pain – or indeed anything at all – therefore stimulates sometimes polarized debate. Here, we try to bridge the divide. After reviewing key consciousness concepts, we identify “red herring” measures that should not be used to infer sentience because also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa (P); spines disconnected from brains (S); decerebrate mammals and birds (D); and humans in unaware states (U). These “S.P.U.D. subjects” can show approach/withdrawal; react with apparent emotion; change their reactivity with food deprivation or analgesia; discriminate between stimuli; display Pavlovian learning, including some forms of trace conditioning; and even learn simple instrumental responses. Consequently, none of these responses are good indicators of sentience. Potentially more valid are aspects of working memory, operant conditioning, the self-report of state, and forms of higher order cognition. We suggest new experiments on humans to test these hypotheses, as well as modifications to tests for “mental time travel” and self-awareness (e.g., mirror self-recognition) that could allow these to now probe sentience (since currently they reflect perceptual rather than evaluative, affective aspects of consciousness). Because “bullet-proof” neurological and behavioral indicators of sentience are thus still lacking, agnosticism about fish sentience remains widespread. To end, we address how to balance such doubts with welfare protection, discussing concerns raised by key skeptics in this debate. Overall, we celebrate the rigorous evidential standards required by those unconvinced that fish are sentient; laud the compassion and ethical rigor shown by those advocating for welfare protections; and seek to show how precautionary principles still support protecting fish from physical harm.

Environmental enrichment improves the growth rate, behavioral and physiological response of juveniles of Clarias gariepinus under laboratory conditions

“…However, Sneddon et al ( 31 ) and Brown ( 32 ) described fish as sentient beings that can experience good or bad feelings, pain or emotional states. In addition, Mason and Lavery ( 33 ) reviewed the uncertainty of the sentience nature of fish and opined that it is imperative to protect the welfare of fish and treat them as sentient animals. Consequently, the welfare of fish species must be given utmost attention to develop the aquaculture sector for sustainability.…”

Assessing tests of animal consciousness

“…However, they satisfy no other desiderata. In respect to associative learning, there is even evidence that it can occur unconsciously (Mason and Lavery 2022). This assessment suggests that the criteria for animal sentience championed by Crump et al encapsulate rather weak evidence when compared with the list of desiderata proposed here.…”

“…This further experimental confirmation makes trace conditioning a better test of animal consciousness than other non-reflexive behaviors which cannot claim the same kind of support. 4 As pioneered by Irvine (2020) and further developed by Mason and Lavery (2022), we can further evaluate putative tests of consciousness by searching for animals which pass the test but are almost certainly not conscious. 5 Irvine proposes that nematode c. elegans, whose nervous system only comprises 302 neurons, can be assumed to lack consciousness.…”

“…Of course, desideratum 1a does not entail that every behavior which is not a simple reflex is accompanied by consciousness, as (e.g.) unconscious modulation of nociception shows(Mason and Lavery 2022).…”

A Method for Improving Interspecies Welfare Comparisons

“…Using subjective, expert judgments in the Delphi method is an accepted, robust option as described in the previous section. However, in practice, such expert judgments may cause new tensions in already often politically-fraught conversations about animal welfare (e.g., the fish pain debate, Mason & Lavery [2022]; conversations about "wicked problems", Bolton & Keyserlingk, [2021]). To be clear, this is not a reason not to use this method; instead, it is a call to employ the results of the method with care for context, and with attention to how they may be received by diverse stakeholders.…”