How cataract development in farmed salmon impairs vision, causes pain, and represents a major welfare challenge in aquaculture.
Salmon cataracts represent a major welfare problem that was largely overlooked until systematic prevalence studies revealed their extent. Cataracts that develop during the sea water phase leave fish effectively blind, unable to compete for feed and vulnerable to injury from equipment and conspecifics. The underlying causes — nutritional deficiency, rapid growth, and some treatments — are potentially addressable through diet optimization and management changes. The histidine supplementation finding demonstrates that dietary interventions can meaningfully reduce cataract prevalence and associated welfare burden.