Farmed Fish Welfare Auditing: Developing Outcome-Based Indicators for Aquaculture

Fish welfare auditing in aquaculture is an emerging field. Outcome-based welfare indicators that assess the fish themselves rather than just husbandry inputs are increasingly recognised as essential for meaningful welfare assessment.

Key Facts

Traditional aquaculture welfare auditing focused on input-based measures (stocking density, water quality parameters, feeding protocols) but these do not reliably predict the actual welfare state of the fish
Outcome-based welfare indicators (OWIs) assess the fish directly, measuring parameters such as fin damage, external injury, gill health, abnormal behaviour, and mortality rates
The Salmon Welfare Index developed in Norway evaluates welfare across the salmon production cycle using scored observations of fish appearance and behaviour at the surface and during crowding
Key fish welfare indicators include cataract prevalence (linked to nutritional deficiency and lice infestation), wound scores, body condition scores, and the proportion of fish showing abnormal surfacing behaviour
Abnormal surfacing (fish spending time at the water surface, particularly at feed time) is associated with poor water quality, disease, or injury and is an easily observable welfare indicator
Welfare indicators vary by species: what constitutes normal behaviour and healthy appearance differs significantly between salmon, tilapia, sea bass, and other farmed species
RSPCA Assured and GlobalG.A.P. have developed audit frameworks incorporating fish welfare OWIs, though global standardisation remains limited

Welfare Considerations

The transition from input-based to outcome-based fish welfare auditing represents a significant conceptual advance. Measuring what is actually happening to the fish, rather than whether the farmer is following prescribed protocols, is fundamentally more connected to animal welfare reality. However, outcome-based assessment in aquaculture faces practical challenges: fish in large net pens or tanks are difficult to observe individually, sampling methods must balance welfare cost of sampling against information gained, and the interpretation of indicators requires species-specific expertise. Progress in this area — including the development of validated, standardised OWI systems — is a genuine and important contribution to the welfare of the billions of fish in global aquaculture production.

What You Can Do

Choose aquaculture products certified under welfare schemes that incorporate outcome-based indicators rather than only input measures
Support the RSPCA Assured aquaculture certification programme and similar schemes developing fish welfare OWIs
Advocate for regulatory bodies to require outcome-based welfare monitoring as part of aquaculture licensing conditions
Donate to Fish Welfare Initiative, Aquatic Life Institute, and similar organisations advancing farmed fish welfare science
Encourage supermarkets and food service companies to require supplier welfare auditing using validated OWI frameworks
Support research into species-specific welfare indicators for under-studied farmed fish including tilapia, catfish, and sea bream
Reduce consumption of farmed fish from systems without credible welfare auditing while welfare standards develop