Recirculating aquaculture systems (RAS) offer environmental advantages over sea cages but create distinct welfare challenges from high density and artificial conditions.
RAS aquaculture presents a genuine welfare trade-off. By eliminating sea cages, RAS removes the sea lice burden, escape risk, and wild fish welfare impacts of open systems. But the highly artificial environment creates new challenges: extreme density, artificial lighting and temperature, and total dependence on life support systems. Evidence of higher malformation rates in some RAS populations suggests the artificial conditions impose costs that are not yet fully understood or managed. As RAS technology matures, welfare science needs to keep pace with engineering — understanding what fish welfare indicators look like in these novel environments and how to maintain positive welfare states within them.