Cataracts affecting up to 80% of farmed Atlantic salmon in some studies represent a significant, largely preventable welfare problem linked to vitamin and amino acid deficiencies in commercial aquafeeds.
Farmed salmon cataract represents a welfare problem of extraordinary scale — affecting tens of millions of individual fish annually — that is largely preventable through dietary management. Vision impairment in high-density aquaculture environments causes significant welfare harm: fish that cannot see well have difficulty competing for food, navigate feeding events with increased stress, and may be unable to avoid aggressive interactions with conspecifics. The progressive nature of cataracts means affected fish experience increasingly impaired quality of life throughout the production cycle. The industry awareness of this problem combined with its continued prevalence at high rates reflects inadequate prioritization of fish welfare relative to feed cost minimization. The feed modification required to prevent cataracts — adequate histidine supplementation — is a proven, cost-effective welfare intervention.