Microbial ecology of the gastrointestinal tract of fish and the potential application of probiotics and prebiotics in finfish aquaculture

World aquaculture is the fastest growing food-producing sector in the world. Globally, aquaculture is expanding into newdirections, intensifying and diversifying. With increasing demand for environment friendly aquaculture, the use ofalternatives of antibiotic growth promoters in fish nutrition is now widely accepted. Science-based knowledge on probioticsand prebiotics has increased in recent years. No doubt exist that in the last decade we have greatly expanded our knowledgeabout pro- and prebiotics as important functional ingredients in finfish aquaculture. They have numerous beneficial effects:improved activity of gastro-intestinal microbiota and enhanced immune status, disease resistance, survival, feed utilizationand growth performance. As natural products pro- and prebiotics have much potential to increase the efficiency andsustainability of aquacultural production. Therefore, comprehensive research to more fully characterize the intestinalmicrobiota of prominent fish species, mechanisms of action of pro- and prebiotics, and their effects on intestinal ecosystem,immunity, fish health and performance is warranted. All pro- and prebiotics must be evaluated for their safety before beingused in fish nutrition. Also, there is need for establishing dose-response relationships. The application of up to datemolecular procedures to study of the gut microbiota as well as the development and validation of research methods, in vitro,ex vivo and in vivo models, have provided important information to understand the mechanisms of action behind the effects.This review summarizes and evaluates current knowledge of microbial ecology of the gastrointestinal tract of fish as well asthe potential application and challenges of pro- and prebiotics in finfish aquaculture.