Fish Welfare in Recirculating Aquaculture Systems (RAS): The Imperative for Environmental Enrichment (EE).

Aquaculture has become the fastest-growing food production sector worldwide, recently surpassing wild-capture fisheries in total output. This rapid expansion underscores the need to ensure sustainability through robust animal welfare standards. Recirculating Aquaculture Systems (RAS) are increasingly adopted due to their advantages in biosecurity, water efficiency, and production control. However, these systems often expose fish to highly artificial and environmentally impoverished conditions, which may negatively affect their welfare. This article examines fish welfare in RAS through the lens of environmental enrichment (EE), arguing that its implementation is essential to address behavioral, cognitive, and physiological needs. By integrating EE into RAS design and management, it is possible to move beyond traditional homeostatic welfare models focused solely on stress reduction toward an allostatic framework that emphasizes adaptability, agency, and positive experiences. Such an approach supports the concept of providing farmed fish with a "life worth living." The paper highlights the ethical and practical implications of enrichment strategies and emphasizes their potential role in promoting sustainable and welfare-oriented aquaculture practices.