Fish in net pen aquaculture face welfare challenges from crowding and environmental monotony; emerging enrichment approaches can improve behavioural welfare outcomes.
Net pen aquaculture creates conditions that are profoundly different from natural fish environments. The combination of high density, restricted space, environmental monotony, and management interventions creates chronic stress that is measurable through behavioural and physiological indicators. Fish in net pens cannot engage in wide-ranging exploratory behaviour, naturally select microhabitats, or escape from aggressive conspecifics. Environmental enrichment research demonstrates that even simple modifications to the net pen environment can improve welfare by stimulating natural behaviours. However, the primary welfare intervention available is lower stocking density, which directly conflicts with economic optimization. Consumer and regulatory pressure for maximum stocking density limits and enrichment requirements are essential drivers of change.