Salmon Cataracts and Aquaculture Welfare

Cataracts affect up to 80% of farmed salmon in some studies, causing pain and impaired feeding ability. Understanding and preventing this common condition is a significant welfare priority.

Key Facts

Cataracts are opacity of the eye lens causing partial or total vision loss in affected fish.
Prevalence in Atlantic salmon aquaculture can exceed 80% in some production cycles.
Histidine deficiency in feed is strongly linked to cataract development in salmon.
Cataract-affected salmon show reduced feed intake, slower growth, and increased injury from collisions.
Vaccination reactions (oil-based adjuvants) have also been linked to cataract formation in salmonids.
Dietary supplementation with adequate histidine dramatically reduces cataract prevalence.

Welfare Considerations

Salmon cataracts represent a massive, preventable welfare problem in aquaculture. A fish that cannot see clearly cannot navigate its environment, compete for food, or avoid collisions with tank infrastructure. The welfare consequences — chronic hunger, injury, and social disadvantage — are significant at an individual level, and at population scale (80% prevalence in some farms) represent an enormous aggregate welfare burden. The solution is largely known: adequate histidine in feed and careful vaccine formulation. The gap between knowing the solution and implementing it universally is a failure of industry standards and regulatory oversight that consumer and retailer pressure can help close.

What You Can Do

Support aquaculture certification schemes that include nutritional welfare standards for salmon.
Advocate for mandatory dietary standards that prevent histidine deficiency in farmed salmon.
Engage with salmon producers and retailers about cataract prevalence data and prevention programs.
Choose salmon certified by schemes with transparent welfare outcome reporting.
Raise awareness about salmon cataracts as a significant and largely preventable welfare issue.