Now Live: Rainbow Trout Operational Welfare Indicator (OWI) Protocol: Ongrowing, Seawater

The Centre for Aquaculture Progress is pleased to announce that the Rainbow Trout Operational Welfare Indicator (OWI) Protocol: Ongrowing, Seawater, is now live. It is the first in a series of OWI protocols.

The publication can be accessed on our website as either a downloadable PDF or an online interactive version. It is free and publicly available.

This protocol is the culmination of months of dedicated research and work. In particular, we would like to thank Marco Cerqueira (CCMAR, University of Algarve) for his close collaboration throughout the development of this document. We would also like to thank Jonatan Nilsson and Angelico Madaro (Institute of Marine Research) for their detailed review and extensive contributions to this protocol. We also received feedback from a number of other industry stakeholders, including individuals from certification bodies, academics, NGOs, and producers, which we are thankful for.

What are Operational Welfare Indicators (OWIs)?

Operational Welfare Indicators (OWIs) are standardized assessment tools designed for routine implementation in commercial aquaculture. Unlike some other proxy measures, such as plasma cortisol concentrations, that require laboratory analysis, OWIs enable practical on-farm assessment. These indicators are science-based, practically feasible, and provide actionable data for evidence-based management decisions.

An example is included below:

What does the protocol include?

The protocol includes:

• 33 OWIs across three categories:
  • 14 individual-based indicators
  • 5 group-based indicators
  • 14 environmental indicators
• Scoring systems for each indicator, split into four tiers comprising levels 0–3
• Reference images and scoring guidance for practical field application

Why is this important?

Rainbow trout, like other teleost fish, are animals capable of experiencing pain and stress. Ensuring their welfare during production requires systematic monitoring through OWIs. The increasing focus on OWI implementation reflects priorities shared across the aquaculture value chain — from producers, certification bodies, and seafood buyers, to consumers, governments, and NGOs — and aligns with broader international standards for health monitoring. By improving welfare outcomes, producers simultaneously achieve better growth, survival, robustness, and production efficiency, while meeting regulatory requirements and evolving consumer expectations.

This protocol serves farm personnel conducting routine welfare monitoring and other industry professionals, including certification bodies, auditors, and buyers. It is designed to align with the welfare monitoring and assessment requirements of key certifications, such as RSPCA Assured and Aquaculture Stewardship Council.

If you have any comments or feedback, you can get in touch by filling out this form.

Access the protocol

The protocol can be viewed online or downloaded as PDF here.