Millions of fish beyond zebrafish are used in research globally. Medaka, three-spined sticklebacks, and other species have specific welfare needs that laboratory practice must address.
The diversity of fish species used in research creates a welfare challenge because generic protocols developed for zebrafish are often applied to other species with different biological needs. Medaka, which prefer slightly warmer, harder water, may be housed in conditions optimized for zebrafish at the cost of their welfare. Stickleback territorial behavior means social group housing appropriate for zebrafish may cause aggression in this species. The 3Rs principle requires that researchers understand and apply species-specific refinements rather than defaulting to generic protocols. The growing use of diverse fish species in research requires parallel growth in species-specific welfare guidance, and institutional animal care committees should require evidence that species-specific needs are addressed in research proposals.