Zebrafish have become one of the most widely used vertebrate research models, and their status as sentient animals with genuine welfare needs is increasingly recognised in research ethics.
Zebrafish welfare has historically received less attention than mammalian research species, partly due to assumptions about fish sentience. However, zebrafish show clear behavioural and physiological responses to noxious stimuli, and analgesics modify these responses, suggesting genuine pain experience. High stocking densities in research facilities cause chronic stress detectable in cortisol levels. Social isolation causes abnormal behaviour. Water quality management is critical - poor parameters cause suffering and compromise research validity. Refinements such as improved housing, environmental enrichment, and humane endpoints are increasingly adopted in research guidelines.