The sabellid polychaete Sabella spallanzanii, a native to the Mediterannean, established in Port Phillip Bay in the late 1980s. Initially it was found only in Corio Bay, but during the past five years it has spread so that it now occurs throughout the western half of Port Phillip Bay. Densities in many parts of the bay remain low but densities are usually higher (up to 13/m²) in deeper water and the worm's distribution extends into shallower depths in calmer regions. Larvae probably require a 'hard' surface (shell fragment, rock, seaweed, mollusc or sea squirt) for initial attachment, but subsequently they may use their own tube as an anchor. The only measurable effect of the spread of S. spallanzanii on fish communities was an increase in the abundance of little rock whiting, which uses the habitat created by the forest of S. spallanzanii tubes. No fish has been found to prey on S. spallanzanii, possibly because their feeding crowns contain particularly high levels of vanadium.

 The channelling of particulate food away from native filter-feeders may have considerable long term effects on fish communities. As the density and coverage of S. spallanzanii increases more energy may be channelled into trophic pathways that appear to lead only to bacterial breakdown upon the death of the worms. S. spallanzanii may also significantly affect the growth and survival of other epifauna with which they compete for food and suitable settlement surfaces.

Twenty two exotic species of marine invertebrates have been recorded from Victorian waters. Eighteen of these are reported from Port Phillip Bay and four are known only from other localities in Victoria. Some of the exotic species recorded from Port Phillip Bay are well established and are present in large numbers, some have been recorded only as isolated individuals and the occurrence of others has been reported but not confirmed.

In this report, literature on the exotic species recorded from Victoria is reviewed, with particular attention being given to those species recorded from Port Phillip Bay. Potential impacts of these introduced species on the local marine fauna are discussed.