Executive summary

The welfare of farmed fish is a topic that is gaining exponential attention in research, public awareness, production and policy, since the impacts on the animals are reflected the whole sector. To address it correctly it is important to define the terms: welfare is the state of the animal as it copes with its environment. This definition enables the measurement of welfare through different indicators, which in turn allow the testing, validation and implementation of measures to improve the welfare and production of farmed fishes. The focus of this report is on the behavioural indicators of welfare, which represent the state of the animal very accurately.

To fully understand and interpret the behaviours of farmed fish, we propose an ethological approach by looking at behaviours under the 4 questions of ethology: causation, development, function and evolution. The first two questions (causation and development) tell how the behaviours are occurring, while the last two questions (function and evolution) explain why the behaviours are occurring. We also propose that the general reference point to assess the welfare of fish under farming conditions should be biology in the wild, always taking into account that there may be changes due to the domestication process of selected strains.


Using the ethological approach allows the understanding of these processes. The indicators of welfare that are suitable to be used on farms are called Operational Welfare Indicators (OWIs). These can be variables measured on the animal (e.g. behaviours, skin condition, injuries), measure on the water (e.g. oxygen, ph, temperature) or measured through the management procedures (e.g. cleaning, culling, feeding). Behavioural indicators comply with all requirements to become OWIs: they are valid, reliable, repeatable, comparable, suitable and practical. To be used to their full potential, behavioural OWIs should interpreted using the ethological approach. 

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