Zebrafish have become one of the most important vertebrate research models due to their genetic tractability and transparency. Their welfare needs are only recently receiving serious scientific attention.
Zebrafish welfare is the frontier of aquatic research animal welfare. These social fish show clear shoaling motivation, predator avoidance, and fear responses that indicate a capacity for negative welfare states. Isolation from conspecifics causes measurable cortisol elevation and behavioral changes. Standard laboratory housing in small tanks prevents shoaling behavior. Water quality management is critical — ammonia, nitrite, and oxygen levels directly affect fish health and welfare. Anesthesia for invasive procedures is required under most national regulations but compliance is variable. The development of validated welfare indicators for zebrafish is an active and important research area given their increasing use numbers.