Cataracts affect the majority of farmed Atlantic salmon, impairing vision, feeding behavior, and welfare throughout the production cycle. Prevention through nutrition is achievable.
Salmon cataracts represent a welfare problem of enormous scale that is largely preventable through nutritional management. A fish that is essentially blind cannot engage in the visual behaviors fundamental to its ecology — hunting by sight, navigating complex environments, monitoring social dynamics. While farmed salmon do not need to hunt wild prey, their welfare depends on being able to engage in foraging behavior, avoid conspecific aggression, and respond normally to their environment. Cataracts impair all of these capacities. The tragedy is that the primary cause — dietary histidine deficiency in early life feed — is addressable through feed formulation changes that the industry has been slow to universally adopt. Consumer and regulatory pressure for nutritional welfare standards in salmon aquaculture can drive faster adoption.