Farmed Salmon Cataract Welfare: Nutritional Causes and Prevention

Cataracts affect the majority of farmed Atlantic salmon and cause pain and functional impairment. Understanding their cause enables welfare-positive prevention strategies.

Key Facts

Cataracts affect over 50% of farmed Atlantic salmon in some production cycles
The primary cause is deficiency of the amino acid histidine in feed formulations
Cataracts cause pain, reduced vision, and impaired swimming and feeding ability
Norwegian salmon welfare assessments now include cataract scoring as a required metric
Reformulation of feed to include adequate histidine virtually eliminates cataract development

Welfare Considerations

Salmon cataracts represent a preventable welfare problem created by inadequate feed formulation. The lens of the fish eye requires histidine that plant-based protein alternatives in feed may not provide in sufficient quantities. Cataracts cause pain (the lens swells), reduced vision that impairs feeding and predator detection, and in severe cases total blindness. The welfare impact on billions of fish annually is enormous. Feed reformulation to ensure adequate histidine is a straightforward, relatively low-cost intervention. Progressive salmon producers have adopted this fix, and Norwegian welfare standards now require cataract monitoring as a welfare indicator.

What You Can Do

Choose salmon from farms that monitor and report cataract prevalence
Support aquaculture welfare standards that include cataract as a required welfare metric
Advocate for feed formulation standards that prevent nutritional welfare problems in farmed fish
Reduce consumption of farmed salmon from operations without welfare monitoring programs