Farming Atlantic salmon and other aquaculture species is an important industry in Australia. A major limitation is the outbreak of bacterial disease amongst the farms, which can result in huge economic and fish stock losses. Gram-negative bacteria such as Vibrio spp., Pseudomonas spp. and Aeromonas spp. are part of the gut microbiota but are also associated with causing disease in fish and other aquatic animals. However, their prevalence and persistence in the gastrointestinal (GI) tract of Tasmanian Atlantic salmon during seasonal water temperature changes has not been investigated. Moreover, the virulence properties that these bacteria possess are not well studied. This thesis examined the presence and persistence of potentially pathogenic bacterial populations in farmed Tasmanian Atlantic salmon (Salmo salar L.) and assessed their dynamics as affected by seasonal water temperature and diet. Special attention was paid to the virulence factors of these bacteria in fish and other marine animals such as farmed banana prawns. The ability of lactic acid bacteria (LAB) to inhibit pathogens associated with fish disease as well as a comparison of the virulence properties of these bacteria isolated from different sources was also examined.
Submitted in the fulfilment of the requirements of the degree of Doctor of Philosophy, University of the Sunshine Coast, 2014.