Open net pen aquaculture raises significant welfare and environmental concerns, and alternatives such as recirculating aquaculture systems and semi-closed containment offer meaningful improvements.
Net pen aquaculture exposes farmed fish to a wide range of welfare challenges — parasites, pathogens, crowding stress, and unpredictable environmental variation including harmful algal blooms and jellyfish influxes. These are not trivial problems: sea lice infestations cause chronic pain and can be lethal at high intensities. Transitions to closed or semi-closed containment systems address many of these harms simultaneously, but require significant investment and regulatory support. For welfare-conscious consumers, the origin of aquaculture products matters — fish from certified RAS or welfare-audited facilities are likely to have experienced meaningfully better lives than those from unmonitored open net systems.