Scoring
Each OWI is scored on a scale from 0 to 3, describing the extent of injury or deviation. This scoring system is aligned with the Laksvel protocol for Atlantic salmon, and adapted for rainbow trout in seawater.
| Level | Individual-based indicators | Group-based indicators | Environmental indicators |
|---|---|---|---|
| 0 | Free from injuries or deviations | Optimal for the specific population and production conditions | Within the optimal range |
| 1 | Indicates a minor injury or deviation that normally is assumed to have little impact on fish welfare, but still indicates that something is not optimal | Indicates a minor deviation that normally is assumed to have a minimal impact on fish welfare, but still indicates that something is not optimal | Edge of the optimal range |
| 2 | Indicates a clear injury or deviation | Indicates a clear deviation | Outside the optimal range |
| 3 | Indicates a severe injury or deviation that is assumed to have large consequences for the welfare of the fish and that increases the probability of early death | Indicates a severe deviation that is assumed to be caused by a severe impact on fish welfare, and that indicates an increased probability of mortality | Far outside the optimal range |
Scores reflect the welfare state of the fish at the time of assessment for each indicator in isolation. A score describes the current extent of injury or deviation, and therefore the welfare risk at the time of assessment. For example, the early stages of a disease may present several indicators as a level 1 or 2 if the immediate welfare impact is not yet severe, even if the condition is likely to worsen. However, when scores are collected consistently over time, the pattern of change across assessments can indicate how welfare is evolving and inform early intervention.
Scoring levels are not linear in severity. Results from scoring should be presented as proportions of the assessed population at each level, not as average scores, as averages can obscure the distribution of welfare states within a group.
Where a fish has a level 3 score for one or more individual-based indicators, one could consider euthanasia.
Interpreting scores
Scores should be interpreted as indicators of welfare risk, not as direct measures of welfare state, as a fish’s internal experience cannot be observed directly. A higher score indicates a greater likelihood of welfare compromise, but the relationship between a score and actual welfare impact depends on production conditions and the fish’s individual history and physiology.
For some indicators, the relationship between the score and welfare compromise is relatively straightforward. For example, higher scores on mortality and wounds clearly represent poor welfare outcomes, while for other indicators, especially environmental indicators, the relationship between the score and welfare compromise is less direct. The tolerance of fish to a certain environmental condition may vary depending on other factors like the status of the fish, and a score that represents a welfare concern in one production context may be within normal variation in another with minimal impact on welfare.
For this reason, scores are most informative when multiple indicators are considered together and when tracked over time. The pattern of scores across indicators and over time provides a more complete picture of welfare risk than any individual score in isolation.