The design of sea cages profoundly influences the welfare of farmed Atlantic salmon. Improvements in cage geometry, depth, light, and current management can significantly reduce stress and injury.
Sea cage design is a fundamental determinant of farmed salmon welfare. Shallow cages in warm waters trap fish in thermally stressful conditions during summer, leading to heat stress, reduced immunity, and increased disease susceptibility. Crowding at high stocking densities prevents normal swimming patterns and increases the transmission of sea lice. Deeper and submersible cages that allow access to cooler water and greater depth heterogeneity consistently produce better welfare outcomes. Appropriate current management prevents dead zones of poor water quality within cages. The shift toward larger, better-designed sea structures and eventual land-based recirculating systems represents the most promising pathway to substantially improved salmon welfare at scale.