Review of some scientific issues related to crustacean welfare

The scientific literature on the subject of welfare and pain in crustaceans is immature. It is based largely on a few dubious and disputed studies done on a small number of decapod species in instances where nociception was not confirmed, laboratory artefacts occurred, all variables that potentially influence the results were not fully controlled, and interpretations of results were questionable or contradictory. The proposed criteria for pain being applied to crustaceans since 2014 has set the evidential bar for pain so low it is impossible to have confidence that the behaviours observed in many experiments are even due to nociception, extinguishing scientific confidence that these behaviours are in any way analogous to how the word pain is defined, used, and understood by humans. Given the critical flaws in design and interpretation of several crustacean pain studies, acceptance of claims of pain for these animals, even as a precautionary measure, represents acceptance of a much lower evidential bar than is usually dictated by normal scientific standards. This may lead to circumstances whereby the precautionary principle, underpinned by weak science, is used by decision makers to justify unnecessary constraints on scientific research or other uses of crustaceans, imparting significant costs to scientific programs (and potentially food production industries), which are likely to exceed any benefits from changes in welfare status that may (or may not) accrue to these animals.