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.