New study identifies dominant gut bacteria in warm-water farmed salmon.
A newly accepted peer-reviewed study has identified a restricted group of bacteria colonizing the gut mucosa of Atlantic salmon farmed in Tasmania, where summer temperatures approach the species’ thermal tolerance limit.
Published in Frontiers in Microbiology, the study analysed microbiome data from eight annual surveys alongside a targeted investigation into mucosal and digesta-associated bacteria. It found that members of the Aliivibrio, Vibrio, and an unclassified Mycoplasmoidaceae group were the predominant colonisers of the gastrointestinal mucosal layer.
Colonisation peaked 7–8 months after smolt transfer to sea cages—corresponding to late summer—suggesting a strong environmental temperature influence on microbial composition.
Notably, the researchers identified three novel, non-bioluminescent Aliivibrio species. While two of these harboured genes linked to cytolethal distending toxins, the most abundant Aliivibrio strain showed no known virulence factors. All exhibited genes linked to host colonisation and biofilm formation.
The findings underscore the role of environmental stressors in shaping microbiota in salmon aquaculture systems, particularly in warm-water regions such as Tasmania.
The study was authored by researchers from the University of Tasmania and CSIRO, with lead correspondence from Prof. John P. Bowman. The final formatted version is pending publication.