Understanding how farmed fish experience and express pain is fundamental to developing effective welfare assessment tools and improving husbandry practices at scale.
Fish pain science has advanced considerably, with evidence now sufficient to conclude that fish experience nociception and likely conscious pain in at least some circumstances. Welfare assessment for farmed fish must work with behavioral and physiological indicators rather than the facial expression and vocalization cues used in mammalian pain assessment. Fin damage and lesion prevalence are useful welfare proxies in aquaculture settings. Respiratory rate, cortisol levels, and behavioral changes during handling provide physiological indicators. The challenge is developing welfare assessment tools practical enough for use in commercial aquaculture where millions of fish must be assessed efficiently. Research programs are developing validated assessment protocols for the most commonly farmed species.