Recirculating aquaculture systems that filter and recycle water in closed facilities offer welfare advantages over open-net cage farming but introduce new welfare challenges around water quality management and environmental complexity.
Recirculating aquaculture systems represent a genuine welfare advance over open-net cage farming in several dimensions: elimination of sea lice and parasite problems, prevention of disease introduction from wild fish, precise environmental control, and elimination of escape impacts on wild populations. However, they also create new welfare challenges when poorly managed, particularly around ammonia management and stocking density. The welfare opportunity of recirculating systems is the ability to precisely optimise conditions for fish welfare in ways impossible in sea cages. Realising this opportunity requires treating precise environmental control as a welfare tool, not only a productivity tool, and investing in the enriched environments that fish welfare science shows are beneficial.