Cataracts affect the majority of farmed Atlantic salmon, impairing vision and welfare. The causes are understood and preventable through dietary and management interventions.
Salmon cataracts represent a widespread and largely preventable welfare problem in aquaculture. Fish with severe cataracts have impaired vision that interferes with their ability to feed and avoid injury, causing ongoing welfare compromise throughout their lives in net pens. The dietary cause — histidine deficiency — is well-established and correctable through appropriate feed formulation. The prevalence of cataracts reflects a gap between scientific knowledge and commercial feed practice that consumer demand and welfare standards can help close.