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-produ cing sector in the world. Globally, aquaculture is expanding into new directions, intensifying and diversifying. With inc reasing demand for environment friendly aquaculture, the use of alternatives of antibiotic growth promoters in fish nutrition is now widely accepted. Science-based kn owledge on probiotics and prebiotics has increased in recent years. No do ubt exist that in the last decade we have greatly e xpanded our knowledge about pro- and prebiotics as important functional i ngredients in finfish aquaculture. They have numero us beneficial effects: improved activity of gastro-intestinal microbiota a nd enhanced immune status, disease resistance, surv ival, feed utilization and growth performance. As natural products pro- an d prebiotics have much potential to increase the ef ficiency and sustainability of aquacultural production. Therefor e, comprehensive research to more fully characteriz e the intestinal microbiota of prominent fish species, mechanisms of action of pro- and prebiotics, and their effects o n intestinal ecosystem, immunity, fish health and performance is warranted. All pro- and prebiotics must be evaluated for thei r safety before being used in fish nutrition. Also, there is need for est ablishing dose-response relationships. The applicat ion of up to date molecular procedures to study of the gut microbiota as well as the development and validation of resea rch methods, in vitro , ex vivo and in vivo models, have provided important information to und erstand 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 as the potential application and challenges of pro- an d prebiotics in finfish aquaculture.