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Diseases of Aquatic Organisms

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DAO 141:15-24 (2020)  -  DOI: https://doi.org/10.3354/dao03508

Longitudinal survey of Flavobacterium species in Icelandic salmonid fish farms

Thorbjorg Einarsdottir1,*, Gudbjorg Guttormsdottir1,2, Daniel Connaghan1,3, Sigridur Hjartardottir1

1Institute for Experimental Pathology at Keldur, 112 Reykjavik, Iceland
2Present address: Alvotech, 101 Reykjavik, Iceland
3Present address: The Ecology Consultancy, SE16 4TQ London, UK
*Corresponding author:

ABSTRACT: Flavobacterium species cause significant disease in salmonid farming worldwide, typically seen as mortality in sac fry and later as necrosis and ulceration in fingerlings and fry. In this study, we sampled Atlantic salmon Salmo salar and Arctic char Salvelinus alpinus from 5 Icelandic fish farms in 2014 and 2017, where flavobacteria were suspected to cause disease. The objective of the study was to identify and characterise the bacteria by sequencing the 16S rRNA gene and multilocus sequence type housekeeping genes. We found 5 distinct groups of flavobacteria: 3 that were homogeneous and appeared to persist in the fish farms between 2014 and 2017 and 2 that were heterogeneous and transient. Flavobacterium psychrophilum could be isolated from diseased Arctic char from all 5 fish farms in both 2014 and 2017. However, while the other 4 Flavobacterium sp. groups were isolated from Atlantic salmon, water and roe, F. psychrophilum could not be isolated from these samples. This indicates that flavobacteria other than F. psychrophilum may be the primary cause of fin and tail rot in Icelandic Atlantic salmon fry.


KEY WORDS: Flavobacterium psychrophilum · Bacterial cold water disease · BCWD · 16S rRNA · Multilocus sequence typing · MLST


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Cite this article as: Einarsdottir T, Guttormsdottir G, Connaghan D, Hjartardottir S (2020) Longitudinal survey of Flavobacterium species in Icelandic salmonid fish farms. Dis Aquat Org 141:15-24. https://doi.org/10.3354/dao03508

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