A survey of Vibrionaceae in Tasmanian coastal waters, with special reference to bacterial species pathogenic to fish or shellfish

Abstract

Samples of the water column and sediment were examined seasonally at nine sites along the east coast of Tasmania. The mean number (loglo units) of presumptive Vibrionaceae, determined on selective agar media, was 1.81 ml-1 water column and 3.95 g-1 sediment. The mean seasonal count varied slightly between sites in the water column but showed a summer peak in the sediment. Factors including sediment particle size, geographical features, or presence of animal husbandry at the site, did not strongly influence the presumptive Vibrionaceae count. Vibrionaceae formed 4.5% and 15.5% of the total heterotrophic bacterial count in the water column and sediment, respectively, but the proportion varied greatly between sites and seasons. Four hundred and fifty-two isolates were identified partially to group level according to a revised scheme based on that of West and Colwell (1984). The two groups including group 8, V. ordalii, and group 9, V. tubiashii, V. anguillarum and V. damsela, contained 30.1% and 46.7% of the isolates, respectively. The overall environmental incidence of these pathogens of fish or shellfish amongst the Vibrionaceae was V. ordalii 0.4%, V. tubiashii 1.3%, V. anguillarum 1.1 % and V. damsela 0.7%.