Fishing for the right probiotic: host–microbe interactions at the interface of effective aquaculture strategies

ABSTRACT Effective aquaculture management strategies are paramount to global food security. Growing demands stimulate the intensification of production and create the need for practices that are both economically viable and environmentally sustainable. Importantly, pathogenic microbes continue to be detrimental to fish growth and survival. In terms of host health, the intestinal mucosa and its associated consortium of microbes have a critical role in modulating fitness and present an attractive opportunity to promote health at this interface. In light of this, the administration of probiotic microorganisms is being considered as a means to restore and sustain health in fish. Current evidence suggests that certain probiotic strains might be able to augment immunity, enhance growth rate and protect against infection in salmonids, the most economically important family of farmed finfish. This review affirms the relevance of host–microbe interactions in salmonids in light of emerging evidence, with an emphasis on intestinal health. In addition, the current understanding of the mode of action of probiotics in salmonid fish is discussed, along with delivery systems that can effectively carry the living microbes. Here, the authors survey current knowledge of the salmonid gut microbiota, offer a fresh viewpoint on the potential mechanisms of probiotic-mediated modulation of host health, and discuss modes of delivery of live microorganisms used in aquaculture, highlighting where innovations are needed.