Farmed Salmon Cataracts: Disease Burden in Aquaculture

Cataracts affect the majority of farmed Atlantic salmon at some production sites, impairing vision and feeding. This underdiagnosed welfare problem highlights the importance of nutrition and management in fish welfare.

Key Facts

Cataracts have been reported in up to 80% of farmed Atlantic salmon at some production sites in Norway
Salmon cataracts are associated with dietary deficiencies including tryptophan and histidine imbalances in feed formulation
Cataract-affected salmon have difficulty locating and consuming feed pellets, leading to reduced growth and nutritional compromise
Cataract prevalence has increased as wild fish content of salmon feed has been reduced and replaced with plant-based ingredients
Histidine supplementation of salmon diets has been demonstrated to reduce cataract prevalence in controlled studies
Welfare assessment of cataract-affected salmon is challenging but behavioral changes including reduced feed intake are measurable
The Norwegian salmon industry has invested in feed formulation research to reduce cataract prevalence
Consumer awareness of salmon cataracts as a welfare issue is essentially zero, limiting market-based reform pressure

Welfare Considerations

Salmon cataracts represent a welfare problem arising directly from the pursuit of more sustainable aquaculture feed ingredients. As wild fish content has been reduced and plant-based alternatives introduced, nutritional imbalances have created a new disease burden. This illustrates the interconnection between sustainability and welfare — changes intended to reduce environmental impact can inadvertently create welfare problems if not accompanied by adequate nutritional research. The welfare response requires investment in feed formulation science that maintains nutritional completeness as ingredient sources change, and monitoring programs that detect emerging disease problems before they affect millions of fish.

What You Can Do

Support aquaculture research programs investigating nutrition-related disease prevention in salmon and other farmed fish
Advocate for certification schemes to include cataract monitoring as a welfare indicator in salmon farming standards
Choose salmon products from producers with transparent welfare monitoring including disease prevalence reporting
Support research on alternative protein sources for aquaculture that maintain nutritional completeness for fish
Encourage seafood retailers to require welfare transparency including disease monitoring from salmon suppliers
Reduce farmed salmon consumption where welfare-certified alternatives with disease monitoring are unavailable