Fish Welfare in Net Pens: Key Concerns

Net pen aquaculture for salmonids and other species presents a range of welfare challenges arising from the confined, intensive production environment.

Key Facts

Net pen salmon farms typically hold 200,000-400,000 fish per cage in structures 30-50m in diameter
Sea lice, infectious salmon anaemia, amoebic gill disease and cataracts are major welfare challenges in net pen production
Water temperature and oxygen levels fluctuate significantly in net pen environments due to tidal and seasonal variation
Net pen fish experience crowding stress during management operations including crowding for treatment or harvesting
Escapes from net pen facilities cause ecological harm from farmed-wild hybridisation and disease transmission

Welfare Considerations

Net pen aquaculture creates environments where welfare challenges are difficult to control because the production system is open to the sea. Temperature and oxygen variation, parasite exposure, disease pressure and the stress of management operations all affect welfare in ways that are harder to manage than in closed containment systems. The welfare case for transitioning to more controlled aquaculture systems (RAS or semi-closed systems) is strong, though these systems carry their own welfare challenges related to water quality management and disease risk.

What You Can Do

Support development of welfare standards that set maximum acceptable mortality and sea lice thresholds for net pen farms
Advocate for aquaculture licensing to include enforceable welfare conditions for net pen operations
Choose certified salmon from producers with documented welfare management programmes
Support research into net pen design innovations that reduce welfare challenges
Engage with aquaculture certification bodies about strengthening net pen welfare standards