Recirculating aquaculture systems (RAS) offer enhanced water quality control and disease management compared to sea cages, but their welfare implications depend critically on design, stocking density, and management quality.
RAS offers genuine welfare advantages over sea cage production: elimination of sea lice without chemical treatments, protection from predators, optimized water quality, and controlled temperature. However, these advantages only materialize with appropriate stocking densities and enriched tank environments. High stocking densities in RAS - sometimes higher than in sea cages - cause the same crowding stress problems. The controlled environment of RAS also enables superior welfare monitoring - optical sensors and automated behavioral analysis systems can track fish health indicators continuously. The welfare potential of RAS depends entirely on how the technology is implemented.