Fish welfare: moving towards animal-based indicators.

The use of outcome-based or animal-based indicators is a noteworthy advance in the assessment of animal welfare. This approach is well accepted for farm animals and is gaining acceptance for other categories of animals. Focusing on the welfare outcomes of the animal, rather than the inputs that are used to produce it, can provide more flexibility in selecting an approach that is optimal for each situation. Prevalence of disease and injuries and growth rate are examples of animal-based indicators, while stocking densities and feeding requirements are examples of input-based indicators. Knowledge of the husbandry and management of fish is well advanced for many cultured species, but little expertise is generally available on the use of fish-based indicators to assess animal welfare outcomes in practice. The use of fish-based indicators provides a basis for benchmarking fish welfare at a facility over time and measuring the effect of a specific intervention. Monitoring fish welfare in this way also facilitates comparisons between sites that differ in terms of facilities and management. This is especially important in aquaculture, considering the range of species and in view of the trend for animal welfare certification schemes. Some fish farmers are using some fish-based welfare indicators, but standardisation is often lacking. The development of indicators of acceptable repeatability and reliability is a priority. Implementing the harmonised collection of standardised fish-based indicators of welfare is an important next step for the aquaculture industry. This paper discusses the use of animal-based indicators in assessing the welfare of fish.