Assessing fish welfare

There is a growing need to understand how our current interactions and practices influence fish welfare and wellbeing. Particularly given the increasing use of fish both as model organisms in research, for example zebrafish used in biomedical experiments, and also in terms of food production in aquaculture, where we now rear and harvest several different species of fish on farms. Determining which factors matter from a fish welfare perspective and finding appropriate ways to assay fish welfare have been the focus of several research projects over the last decade. These have led to a much better appreciation of what kinds of situation result in poor fish welfare, and what can be done to promote positive welfare through best practice. Assays of fish welfare depend on the species of concern, the environment in which the fish are housed, how the fish are handled, the routine husbandry practices that they are exposed to, and how they are killed. Approaches that address welfare span from regular, repeated behavioural observations, to the use of multiple traits to create a welfare index, through to the use of molecular tools to act as an early warning system by detecting early changes in stress physiology gene expression. The field of fish welfare is still at a relatively early stage of development, but a growing interest in this topic has promoted innovative new tools and techniques that are delivering better welfare assays for the fish we maintain in captivity.