Aims: Tenacibaculum maritimum is a well known fish pathogen worldwide, affecting many fish species including Atlantic salmon in Tasmania, Australia. The aim of this study was to characterise and understand the similarities and differences between the isolates in order to select isolates for later pathogenicity and vaccination trials. Methods and Results: Several physical characterisation tests were carried out: whole cell protein profiles, lipopolysaccharide profiles (LPS), extracellular product profiles (ECP), indirect immunofluorescent antibody test (IFAT) and hydrophobicity. The Tasmanian strains of T. maritimum appear relatively homogeneous physically, but antigenically different. All isolates were hydrophobic and produce a variety of ECP profiles. There were two isolates that stand out in all assays (89/4747 and 01/0356-7) and showed great variation from the other isolates. All isolates have been confirmed as T. maritimum. Conclusions: Based on the tests carried out three isolates were chosen for in vivo trials: 89/4747, 89/4762, 00/3280. Significance and Impact of the Study: This is the first study to characterise T. maritimum isolates from Tasmanian waters. The opportunity to develop vaccines for the Tasmanian salmonid aquaculture industry is enhanced by a greater understanding of the physical characteristics of pathogens.