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

## TL;DR

This paper argues that adding environmental enrichment to fish farming systems can improve fish welfare by promoting adaptability and positive experiences.

## Contribution

The paper introduces the concept of using environmental enrichment to shift fish welfare models from stress reduction to promoting a 'life worth living'.

## Key findings

- Recirculating Aquaculture Systems often expose fish to artificial and impoverished environments.
- Environmental enrichment can address behavioral, cognitive, and physiological needs of farmed fish.
- Adopting an allostatic welfare model can enhance fish well-being and support sustainable aquaculture.

## Abstract

As aquaculture represents the fastest-growing food production sector globally, having recently surpassed wild-capture fisheries in output, ensuring sustainable practices through adequate welfare standards is paramount. Although Recirculating Aquaculture Systems (RAS) are increasingly adopted due to their operational advantages, these systems frequently expose teleosts to highly artificial and sensory-deprived environments, potentially compromising biological fitness and welfare. This paper argues that implementing environmental enrichment (EE) could significantly enhance fish well-being by transitioning from traditional homeostatic welfare models to those based on allostasis, where stability is achieved through change, thereby providing animals with a “life worth living”.

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.