Aquaculture Net Pen Design and Fish Welfare

How net pen design affects the welfare of farmed fish and what improvements reduce suffering at scale.

Key Facts

Marine net pen aquaculture produces millions of tonnes of salmon, sea bass, and sea bream annually
Net pen design affects water flow, oxygen distribution, crowding stress, and escape rates
Poor net pen siting in low-current areas leads to waste accumulation, hypoxia, and disease outbreaks
Deep-water net pen systems offer better water exchange and reduced sea lice pressure
Predator netting prevents sea lice treatment with clean wrasse but protects against seal attacks
Welfare monitoring systems using underwater cameras and AI detect abnormal swimming behavior early

Welfare Considerations

Net pen design is a welfare variable that has historically been optimized for production efficiency rather than fish wellbeing. Fish in poorly designed or sited pens experience chronic hypoxia, high parasite loads, elevated stress from crowding, and increased injury rates. Welfare-focused net pen design principles include adequate water flow for oxygenation, depth sufficient to allow fish to seek preferred temperature zones, structural complexity to reduce aggressive interactions, and monitoring systems that enable early detection of welfare problems.

What You Can Do

Support regulatory standards for net pen siting and design based on fish welfare criteria
Choose salmon products from certified farms with documented welfare monitoring systems
Advocate for transition to land-based recirculating aquaculture systems with greater welfare control
Support research into welfare-optimized net pen designs and monitoring technologies