Studies into the potential application of probiotic bacteria as feed supplements for commercially cultured Crustacea, primarily the Pacific white shrimp, Litopenaeus vannamei.

A significant problem faced by the aquaculture industry is the loss of stock through infection and disease. Cultured animals, particularly larval and post-larval stages, suffer increased incidences of disease primarily as a result of the high population densities at which they aie stocked. Thus far the typical approach to bacterial pathogen control in the majority of commercial crustacean aquaculture facilities involves the prophylactic (and often incorrect) use of antimicrobials, i.e. antibiotics and chemotherapeutic agents. These are however costly to develop, limited in their application and most significantly are instrumental in creating antibiotic resistant strains. Many current theories in crustacean pathogen control embrace a multifaceted approach, often combining the therapeutic use of antibiotics/chemotherapeutic agents with the administration of probiotic bacteria and immunostimulants and improved farm management. The purpose of this project was to identify any benefits and potential mechanisms by which probiotic bacteria may act on the health/growth parameters of the commercial aquaculture species, Litopenaeus vannamei and Euiopean shore crab, Carcinus maenas. Work was also undertaken to isolate and identify bacteria from healthy shrimp microbiota that may be of use as probiotics, with the possibility of commercial application within the industry. In vitro methods were utilised for screening potential probiotics for inhibitory activity against crustacean pathogens, followed by a series of in vivo trials to assess the effects of probiotic feed enrichment on the gut bacterial population and growth parameters. Molecular techniques were utilised to elucidate any effects probiotic administration may have on the bacterial community structure of the gut of L. vannamei