Cataracts affect a high proportion of farmed Atlantic salmon, causing vision impairment that reduces feeding ability and quality of life. Nutritional and management interventions can substantially reduce prevalence.
Salmon cataracts represent a significant welfare problem in Atlantic salmon farming that has attracted growing research attention precisely because it is preventable. Vision is a primary sensory modality for salmon — used in predator avoidance, schooling behavior, and prey detection. Progressive vision impairment from cataracts reduces feeding efficiency, competitive ability for feed at automated feeding stations, and likely increases chronic stress from reduced spatial awareness. The nutritional cause — histidine deficiency during a specific developmental window — is well understood and correctable through diet formulation. The high prevalence in some systems (over 90% at harvest) is a clear welfare failure that does not reflect biological necessity but production system choices. Requiring histidine-optimized diet formulations and cataract monitoring in welfare certification is an achievable and high-impact intervention.