Fish are used in enormous numbers in biological research globally. Applying the three Rs of replacement, reduction, and refinement to fish research significantly reduces welfare impacts.
Fish welfare in research contexts deserves the same rigorous three Rs application as mammalian research, yet historically fish have been subject to lower welfare scrutiny due to assumptions about their capacity for suffering that current science does not support. The growing evidence for fish nociception and stress responses requires that fish research be designed with appropriate consideration of welfare costs and their justification. Practical refinements include ensuring adequate water quality, appropriate social housing, minimising handling procedures, using appropriate anaesthetics for surgical or invasive procedures, and providing post-procedural monitoring. The replacement of adult fish with larval zebrafish models for some research questions reduces welfare impact while the larval stages are considered less sentient, though this is an area of ongoing research.