Zebrafish are used in billions of experiments annually, yet their welfare needs are less understood than those of rodents. Research into zebrafish sentience and welfare is an urgent priority.
Zebrafish welfare sits at an intersection of regulatory under-protection and scientific uncertainty. Their use at scales exceeding mice in some research areas, combined with their sentience evidence and minimal housing standards, represents a significant welfare gap. Standard zebrafish husbandry provides little environmental complexity for animals that, in the wild, inhabit structurally complex shallow streams and rice paddies. The 3Rs framework applies to zebrafish as to any regulated species, but implementation in practice lags far behind rodent welfare. As zebrafish use continues to expand, investment in welfare research — housing standards, appropriate anaesthesia, humane endpoints — is essential to prevent the repetition of the historical neglect that took decades to address in rodent models.