Zebrafish have become the second most widely used research vertebrate globally, yet their welfare needs in laboratory settings are often underprovided due to assumptions that small fish have minimal welfare requirements.
The welfare of zebrafish in laboratories has historically been underestimated because they are small, inexpensive, and perceived as simpler than mammals. However, zebrafish are social, cognitively complex animals capable of learning, fear conditioning, and displaying anxiety-like behaviours. Welfare refinements shown to improve outcomes include social housing in appropriate shoal sizes, environmental enrichment through tank complexity, optimised water quality monitoring, and anaesthetic protocols that minimise handling distress during procedures.