Zebrafish cognitive research reveals surprising complexity and has direct welfare implications for the millions used in biomedical research globally. What they can do shapes what we owe them.
Zebrafish cognitive research creates a paradox: the same species used as a simple model organism in millions of experiments annually is revealing behavioral and cognitive complexity that challenges the assumption of simplicity. Zebrafish that show social preferences, learn from experience, show anxiety, and process pain through opioid systems are animals whose welfare in research contexts deserves rigorous attention. The welfare implications of social isolation, which affects the internal state of even these small fish within hours, are particularly relevant to standard housing practices that often keep zebrafish in small groups or individually. Applying the 3Rs refinement principle to zebrafish housing and procedure protocols based on their cognitive capabilities is an active welfare research priority.