Rainbow Trout
Operational Welfare
Indicators (OWI) Protocol

The Centre for Aquaculture Progress (CAP) is providing Operational Welfare Indicator (OWI) protocols for Rainbow Trout (Oncorhynchus mykiss) for different production system and life stages.

CAP OWI protocols include a comprehensive set of indicators to be compatible with all major aquaculture certifications. The indicators follow a standardized scoring system with levels 0/1/2/3.

Each indicator has been developed through a comprehensive literature review of all available scientific evidence for the species given. The resulting protocol is developed with feedback and input from scientists, certifiers, farm practitioners and veterinarians.

Operational Welfare Indicators (OWIs) covered

Producers are recommended to select the indicators required and useful for their production operation:

Individual-based indicators (animal-based outcome measures)

Vertebral deformity
Body condition
Condition factor
Emaciation
Scale loss
Skin hemorrhaging
Wounds
Change of coloration
Snout damage
Head deformity
Eye opacity
Eye injury
Operculum damage
Gill damage
Fin damage
Sea lice

Group-based indicators (outcome measures)

Mortality
Aberrant behavior
Aggressive behavior
Feeding behavior
Feed waste
Swimming behavior

Environment-based indicators (input measures):

Stocking density
Dissolved oxygen
Temperature
Carbon dioxide
pH
Turbidity
Total Suspended Solids
Ammonia
Nitrite
Nitrate
Metals
Water velocity
Salinity
Hydrogen sulfide

Access the CAP OWI protocol for Rainbow Trout

This OWI protocol is currently under development

and will be released free of charge on this webpage in 2026.

We invite interested stakeholders to receive a draft version and provide feedback: