Zebrafish have become one of the most widely used vertebrate research animals, but their welfare needs are frequently overlooked despite regulatory protections in many countries.
Zebrafish welfare occupies a regulatory and cultural gap — they are vertebrates with regulatory protections but are often managed more like cell cultures than animals with welfare needs. Social isolation, poor water quality, and inadequate housing cause measurable stress and behavioral abnormalities. The exclusion of early-stage larvae from welfare regulations creates incentives to use younger fish for procedures that might otherwise require approval, raising precautionary concerns. Zebrafish show behavioral evidence of pain responses, and the precautionary principle argues for better pain management in procedures known to cause nociceptive stimuli.