Cataracts affecting one or both eyes are common in farmed Atlantic salmon, causing navigation and feeding difficulties. Their high prevalence is a significant but often overlooked welfare concern.
Salmon cataract welfare represents a largely preventable condition affecting the majority of farmed fish in some systems. Cataracts cause progressively impaired vision — bilateral cataracts create near-blindness that affects a fish's ability to navigate, find feed, and interact normally with conspecifics. Affected fish fall to lower positions in dominance hierarchies, potentially receiving less feed and experiencing more aggression from dominant fish. The nutritional basis of many cataract cases — histidine deficiency from formulated diets — is directly preventable through appropriate dietary formulation. Vaccination technique improvement can eliminate injection-site cataracts. The high prevalence of cataracts in some production systems indicates a systematic welfare failure that is well within the industry's capacity to address.