Atlantic salmon in aquaculture pens show stereotypic behaviours and stress responses associated with barren environments, and emerging enrichment strategies show promise for improving welfare at commercial scale.
Salmon in barren, high-density net pens are denied the environmental complexity that characterises their natural habitat. Wild salmon must navigate complex currents, avoid predators, find varied food sources, and interact with a dynamic physical environment — activities requiring and providing cognitive engagement. The repetitive circular swimming patterns seen in densely stocked salmon are analogous to the stereotypies observed in other species in barren environments. Current manipulation, structured environments, and lighting management are low-cost interventions that demonstrably reduce these behavioural indicators of poor welfare. As the scientific understanding of fish cognition and welfare grows, regulatory frameworks are beginning to incorporate enrichment requirements — a positive trend requiring consumer and policy support to accelerate.