First isolation, identification and characterisation of Tenacibaculum maritimum in Norway, isolated from diseased farmed sea lice cleaner fish Cyclopterus lumpus L

The use of cleaner fish as biological controls of salmon lice (Lepeophtheirus salmonis) has increased exponentially in the last decade in Norwegian Atlantic salmon (Salmo salar) production. This alternative to chemical treatments has resulted in the emergence of lumpsucker (Cyclopterus lumpus) hatcheries and culture facilities in Norway. It has been shown that the use of lumpsuckers can be an effective, biological approach for the removal of salmon lice, but it has also been shown that there are a number of biological challenges (i.e. parasites and bacteria) with the production and use of these fish. This study describes the first case of isolation of Tenacibaculum maritimum, a significant fish pathogen worldwide, in cultured juvenile lumpsuckers in Norway. The fish were lethargic and showed skin lesions characterised by increased mucus production and presence of whitish necrotic tissue especially in the head region. Skin scrapings revealed large amounts of bacteria dominated by rod-shaped Tenacibaculum-like bacteria, which were shown to be closely related to T. maritimum type strain through genetic and phenotypic characterisation. Histopathological analysis showed that the bacteria was closely associated with the pathology and therefore could be contributing to the disease and/or mortality. This is the first isolation of Tenacibaculum maritimum in Norway and in lumpsuckers, a major aquaculture pathogen worldwide. There is a need for increased knowledge of the biological challenges facing cultured lumpsuckers, as this species is being used in increasing number by the Norwegian salmon industry. •This is the first isolation of Tenacibaculum maritimum in Norway and in lumpsuckers.•The isolate was genetically and phenotypically characterised.•The bacteria were found to be associated with histopathological changes.•This study helps further understand the biological challenges of cultured lumpsuckers.