Cataracts are extremely common in farmed salmon, affecting up to 80% of fish in some populations. This condition causes significant vision loss and has measurable welfare consequences.
Cataracts in farmed salmon represent a systemic welfare failure hiding in plain sight. Because fish welfare was historically under-recognized, this condition persisted for decades despite affecting the majority of animals in some farm systems. Fish with cataracts cannot see properly, which affects every aspect of their lives in a crowded aquaculture environment — finding food, avoiding injury, navigating social interactions with conspecifics. Welfare research increasingly recognizes that sensory impairment in fish is not a trivial concern: fish rely heavily on vision to navigate their environment and respond to threats. The solution — optimizing dietary histidine — is technically straightforward, which makes the persistence of high cataract rates in some operations a preventable welfare failure driven by cost optimization rather than genuine nutritional ignorance. Welfare certification schemes for farmed salmon should include cataract prevalence monitoring as a standard metric.