Salmon Cataracts in Aquaculture: Nutritional Welfare

Cataract formation in farmed salmon is a widespread nutritional welfare problem with significant impacts on fish quality of life.

Key Facts

Cataracts affect 50-80% of farmed Atlantic salmon in some production systems
Salmon cataracts are primarily caused by histidine deficiency in feed combined with high-intensity light exposure
Affected salmon show reduced appetite, impaired schooling behavior, and difficulty capturing food pellets
Visual impairment from cataracts reduces a salmon's ability to escape predator interactions and assess social threats
Dietary histidine supplementation has significantly reduced cataract prevalence in operations that have implemented it
Cataract severity scoring is used as a welfare indicator in some certification schemes
The condition has been substantially reduced in Norwegian salmon farming through improved feed formulations

Welfare Considerations

Salmon cataracts represent a welfare problem with a known cause and a practical solution — yet remain widespread due to cost pressures on feed formulation. The welfare impact extends beyond vision loss: affected fish struggle to compete for food, cannot accurately assess their social environment, and experience behavioral impairment that affects every aspect of their daily life in a collective rearing environment. The Norwegian salmon industry has demonstrated that cataract prevalence can be dramatically reduced through appropriate histidine supplementation, establishing a clear benchmark for other production systems. Consumer certification schemes that monitor cataract prevalence create market incentives for feed quality investment.

What You Can Do

Support salmon certification schemes that monitor and report cataract prevalence
Choose salmon from farms or regions with demonstrated low cataract prevalence
Advocate for mandatory dietary histidine standards in salmon feed regulations
Support research into cataract prevention in salmon species other than Atlantic salmon