Zebrafish are the most widely used vertebrate in developmental biology and genetic research, and their welfare status and appropriate 3Rs application is increasingly important given their regulatory and scientific prominence.
Zebrafish welfare science has advanced substantially alongside their rise as a premier model organism. The recognition that zebrafish can experience pain and stress — supported by behavioural evidence of nociception and stress responses — has driven improvements in housing, handling, and experimental design. Key refinements include social group housing rather than isolation, enriched tanks with shelter objects, reduced handling stress through acclimation protocols, and improved anaesthesia and euthanasia methods. The regulatory status of zebrafish larvae is inconsistent — most welfare protections do not apply until later developmental stages — creating welfare gaps that good practice fills voluntarily. The very high numbers of zebrafish used in research mean that even modest refinements in individual welfare standards have large aggregate effects. The 3Rs applied to zebrafish research represents a genuine opportunity for high-impact welfare improvement in a high-volume research model.