Microbiome diversity and dysbiosis in aquaculture

With the continuous growth of the human population and associated need for high‐quality protein, the aquaculture sector will be required to increase significantly in productivity. This growth in productivity will be achieved through more efficient use of resources like feeds, genetic improvement and limiting the impacts of disease. One of the key links between animal productivity and disease is that of microbial diversity, with high‐throughput sequencing technologies increasing our understanding of the role microorganisms play in health, development and physiology of vertebrate and invertebrate hosts alike. Increasing our understanding of microbial–host interactions will help avoid or manage dysbiosis in aquaculture systems with the final aim of improving productivity. We review the current literature, which indicates that there is an association between productivity and microbial diversity in aquaculture systems, as changes in bacterial microbiomes are implicated in animal performance, in disease development associated with both bacterial and viral origin, and in dysbiosis triggered by environmental stressors or diet choice. Dysbiosis, whether in the form of the loss of beneficial bacteria, or the expansion of pathogens or potentially harmful microorganisms, can be used as an indicator tool for productivity monitoring purposes. Development of management strategies towards preserving the microbial balance, including maintaining or increasing diversity in the host, is critical for the health of cultured aquatic animals and will likely be critical for the expansion of aquaculture.