Effects of Salmon Lice Treatment on Bacterial Density and Community Composition of the Atlantic Salmon Skin Mucus Microbiota
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The salmon lice (Lepeophtheirus salmonis) infesting Atlantic salmon (Salmo salar) in the on-growing sea water phase is one of the major issues in the Norwegian aquaculture industry. To obtain health and welfare of the farmed Atlantic salmon, medicinal and non-medicinal treatment methods are used for control of the salmon lice. The effect of salmon lice treatment on the bacterial density and the community composition of the skin mucus barrier is not known. In this project, the effect of various salmon lice treatments on the bacterial colonization were investigated using PCR, DGGE and Illumina sequencing of 16S rDNA variable regions. The bacterial load on fish skin mucus was investigated by real-time PCR. The samples were taken from fish that had been treated with freshwater and H2O2 bath, and the oral treatment SLICE, in addition a group of fish had ulcer. Proteobacteria was the dominant phylum in Atlantic salmon skin mucus from all samples investigated, and the genus Pseudomonas was prevailing in almost all samples. There was no significant difference in the skin mucus microbiota between fish treated with the different salmon lice treatments and untreated fish. The bacterial load seemed to be lower in skin mucus for some of the fish treated with freshwater and H2O2 bath. However, the most noticeable difference was found between the ulcerated fish and all the other fish samples, where Psychrobacter was most abundant in the ulcerated fish. In addition to a distinct community composition, the skin of ulcerated fish had the highest bacterial load.