Natural behavior vs. subjective experience in fish welfare assessments

Several commentaries on the Oldfield & Bonano (2024) target article proposed that natural behavior should play a larger role in assessing the welfare of fishes in zoos and aquariums. However, the natural-behavior concept of animal welfare has been widely criticized because natural behaviors do not necessarily improve welfare, and unnatural behaviors do not necessarily reduce it. I review the three major concepts of animal welfare — physical health, natural behavior, and affect/feelings — and argue that behavior patterns, whether natural or otherwise, should be evaluated according to their effects on health and subjective experience. Using the affect/feelings concept and the Five Domains Model, I then re-evaluate several of my previous studies on aquarium fish behavior to illustrate how welfare interpretations can be made more explicit and conceptually consistent.