The discharge of ballast water from one port into another is not a recent phenomena, although its importance as a dispersal mechanism for marine species has only been fully realized in the last decade with increasing volumes of ballast water being discharged and more studies being carried out on the marine fauna. Australia with its large number of ports, and increasing volumes of ballast water arriving, is certainly at risk from ballast water introductions.

We have summarized the existing literature on introductions of marine organisms in Australia and have discussed possible ways in which these organisms have arrived in Australia. Some species may have arrived via ballast water but to date, the evidence is largely inferential rather than direct. However, we do know that organisms in ballast water may survive discharge and could potentially settle and establish populations which may have an impact on natural fauna.

An immunofluorescent staining technique for the rapid detection of the ciliate protozoan Uronema sp. was developed during 1995 and 1996. The initial test was developed using seven cultures of Uronema sp. from various sources which were identified as Uronema nigricans  by microscopical and histochemical techniques. These seven strains were maintained in a medium containing bacteria as their food source. Antisera against two of the strains were raised in rabbits and against one in sheep. These were then adsorbed with the bacteria and unrelated ciliates to eliminate cross-reactivity.

More recently, an axenic (bacteria-free) culture of Uronema sp. has been accomplished and high-titre antisera raised in rabbits for use in the immunofluorescent staining technique.

Arrangements have been made to have a monoclonal antibody to the axenic Uronema prepared at the Atlantic Veterinary College, University of Prince Edward Island in Canada. This will then provide a reliable supply of highly specific antibody for future research in this area.

The substantial southern bluefin tuna mortality event in 1996 impacted on the delivery of the project objectives, particularly those associated with the application of the immuno-staining technique developed to:

• screen potential sources of infection associated with farming tuna; and based on this
• provide advice to farmers on how to improve farm management techniques so as to minimise infections.

Keywords: Uronema, aquaculture, southern bluefin tuna.