Applying the Five Domains Model to Farmed Salmon: A Welfare Assessment Framework

The Five Domains model provides a structured framework for assessing salmon welfare across nutrition, environment, health, behaviour, and mental state — helping identify priorities for improvement.

Key Facts

The Five Domains model (Nutrition, Environment, Health, Behaviour, Mental State) was developed by David Mellor and provides a comprehensive welfare assessment framework applicable to any species.
For salmon, the Nutrition domain highlights concerns about feed composition, feeding frequency, and competition for food — particularly in overcrowded net pens.
The Environment domain in salmon farming encompasses water quality (dissolved oxygen, temperature, ammonia), crowding density, light cycles, and structural complexity (or lack thereof).
The Health domain covers sea lice burden, infectious disease, injury rates, vaccination side effects, and the cumulative physiological burden of repeated treatments.
The Behaviour domain addresses opportunities for swimming behaviour, social interactions, and absence of natural behaviours including vertical migration and predator avoidance.
The Mental State domain — the integrative dimension — synthesises the other four: salmon in high sea lice burden, poor water quality, and crowded conditions experience predominantly negative affective states.

Welfare Considerations

Applying a structured framework to salmon welfare reveals the cumulative burden that individual fish carry. Each domain identifies specific welfare problems; the Mental State domain integrates them into an overall assessment. A farmed salmon with moderate sea lice burden, occasional oxygen dips, crowding-induced injury, and no enrichment is experiencing multiple simultaneous negative welfare states. This cumulative burden is greater than any single problem suggests. The Five Domains framework also identifies positive welfare targets: providing structural complexity, optimising feeding management, and reducing treatment frequency — actions that shift the balance toward more positive mental states. This framework is increasingly adopted by welfare scientists and some certification bodies to move beyond minimum harm to genuine welfare promotion.

What You Can Do

Support the development and adoption of Five Domains-based salmon welfare auditing tools in certification schemes.
Engage aquaculture companies about their welfare assessment approaches and whether they use comprehensive frameworks.
Follow research from the Institute of Marine Research (Norway) and Stirling University (Scotland) applying welfare frameworks to salmon aquaculture.
Advocate for regulatory bodies to adopt Five Domains or equivalent comprehensive welfare assessment for farmed salmon.
Choose salmon from operations that demonstrate welfare assessment beyond simple compliance metrics.