| Summary: | Several Tenacibaculum bacterial species are detrimental to aquaculture, inducing tenacibaculosis in fishes, but information on the bacteria’s ecology is limited. Two quantitative-PCR assays for T. maritimum and T. dicentrarchi were used to survey two separate Atlantic salmon netpen sites in 2019-20 in British Columbia. Approximately 100-fold more T. dicentrarchi were recorded compared to T. maritimum (p<4e-7). During outbreaks, bacteria were ubiquitous with greater numbers in eukaryotes (p<8e-13). Significantly (p<0.05) more bacteria were identified during with no difference after an outbreak, supporting the observed recrudescence of tenacibaculosis. There was a significant relationship (p<0.05) between the water quality and fish mortalities, but with low correlation coefficients (R2<0.25). High numbers of T. dicentrarchi were present at both netpen sites, increased T. dicentrarchi was detected concurrent with antibiotic treatments and also in dead fish tissues relative to live tissues. T. dicentrarchi seems most responsible for the disease outbreaks observed at both netpen sites. Natural Sciences and Engineering Research Council of Canada VIU RIF Grant
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