Book excerpt: Fish welfare is currently one of the most important concerns in aquaculture, and knowledge on how to improve fish welfare should be practical and implementable for all aquaculture farms. The objective of this Research Topic is to extend the current knowledge on fish welfare and to identify more comprehensive and practical indicators of the existing standard for fish welfare that are easily, more comprehensive and practical indicators in order to make it easy to implement on fish farms. A secondary objective is to identify which welfare issues are most relevant. It is important to mention that good fish welfare cannot simply be extrapolated from terrestrial animals. It has to take into consideration that different species of fish must also be taken into consideration. Whether these are species of commercial interest or not, they have different behaviour and respond differently to stress, and consequently, require a species-specific approach to improving their welfare. Intensive fish production systems have important negative consequences for the animals including impaired health and erratic behaviour. For many industries, their main goal is to achieve higher production whilst majority of the time, welfare is not take it into consideration. Better conditions for intensively produced farm animals, including fish, should result in improved efficiency and performance and higher quality product for consumers. We welcome papers demonstrating such effects. This research topic is related to the welfare of farmed fish. Fish welfare is related to how we treat our fish: the type of feed, how often we feed them, the stocking density that it is used, the environment where they are growing, how we grow them, from fertilized egg to fish ready to sell for public consumption. This Research Topic should address fish welfare during the whole growth period, and may also include papers on the attitudes and perceptions of stakeholders, including fish farmers and public about fish welfare.