| Summary: | Farmed Tasmanian Atlantic salmon in Australia may experience water temperatures as high as 20°C during summer, which may impact on health and mariculture productivity. In this study we investigated the impact of two commercial feed on the major bacterial population in the gut of Atlantic salmon using an anaerobic semi-continuous fermenter model set at 20°C. Fermentation was conducted in a 5L culture vessel with 100 rpm agitation under CO2. For each diet the hindgut contents of three farmed Tasmanian Atlantic salmon were collected, mixed and used as fermenter inocula. Samples were collected at day 0, 1, 6 and 12 and used for bacterial enumeration and measurement of the functional status of the gut microbiota as well as their metabolic capacity (MC) values. With diet A, Vibrio spp. and lactic acid bacteria (LAB) increased over the course of fermentation. In contrast, diet B did not support the growth of LAB and instead promoted the growth of Plesiomonasshigelloides. MC values of gut microbiota receiving either diet also increased over the course of fermentation, reaching the highest level on day 12. This was independent of the type of diet used as the functional status of the microbiota for both diets was highly similar at each sampling round. Our results indicate that at the temperature experienced by Tasmanian Atlantic salmon during warm season i.e. 20°C, the type of diet may select for the growth of specific species of bacteria.
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