Zebrafish are increasingly used in biomedical research due to their transparency and genetic similarity to humans. Their welfare needs are often underappreciated compared to mammals.
Zebrafish welfare has historically received less attention than mammalian research species, yet evidence increasingly supports that they experience pain and stress. Nociception studies show zebrafish respond to noxious stimuli and that analgesics reduce these responses — suggesting meaningful pain experience. Chronic stress from poor water quality, overcrowding, or social isolation causes behavioural changes consistent with negative affective states. Many facilities lack adequate environmental enrichment or socialisation for zebrafish. The rapid growth of zebrafish as a research model — with millions used annually globally — magnifies welfare concerns at scale. The 3Rs framework applies fully: replacing zebrafish models where possible, reducing numbers, and refining husbandry and experimental procedures to minimise suffering are all ethically required.