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The Introduced Species of Port Phillip Bay, Victoria

Hewitt, C.L., Campbell, M.L., Thresher, R.E. and Martin, R.B. (Eds) (1999) The Introduced Species of Port Phillip Bay, Victoria. CSIRO Marine Research.

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Port Phillip Bay is a large, temperate embayment in southeastern Australia that borders the major metropolitan areas of Melbourne and Geelong. The bay has been a focus for shipping activity since the mid-1800's and is currently a major destination for a wide range of coastal and international shipping. Port Phillip Bay has also been the focus of a number of historical biological surveys, which makes possible an evaluation of historical patterns of invasion by exotic marine species. A detailed analysis was undertaken of the introduced (known and cryptogenic) organisms in Port Phillip Bay.

The analysis consisted of:

• reviews of the historical information, published literature, and material in private and museum collections for all groups for which local taxonomic expertise was available;

• detailed examinations, including new surveys undertaken as part of this study, of the biota in high risk areas;

• documentation and re-analysis of the possible impacts of exotic species on the ecology of Port Phillip Bay; and

• an evaluation of the broad patterns of invasion and an analysis of possible vectors for the introduction of the exotic species recorded from the bay.

Although the scope of the analysis was restricted by the taxonomic expertise available, coverage included all major benthic phyla. However, for several major groups (annelids, crustaceans, molluscs and echinoderms) the narrow focus of earlier surveys limited the analysis to the soft bottom biota.

The study identified 165 introduced and cryptogenic species (99 and 66, respectively), one species that was known to have been introduced but has subsequently become locally extinct, and another 13 species identified as 'potentially' introduced into Port Phillip Bay but whose status could not be confirmed due to the absence of voucher specimens or collections.

Depending upon the criteria used, therefore, we identified between 99 ( confirmed introductions with voucher specimens) and 178 (all reports) introduced species in Port Phillip.Bay. For those groups for which a comparison was possible, exotic species constitute 10- 20% of the benthic biota of the bay. From a comparison of the total known biota of the bay and species numbers obtained from the more limited taxonomic and habitat coverage of this study, we estimate the actual number of exotic marine species in Port Phillip Bay at 300--400 species. We further estimate that 2-3 new exotic species are establishing in Port Phillip Bay each year.

The major source region for these species is the North East Atlantic and the historically dominant transport vector is vessel hull fouling. However, there are exotic species in Port Phillip Bay from all of the world's major bioregions ( except the Antarctic) and evidence for the operation of a diverse range of introduction vectors. The rate of invasions appears to have increased over the last several decades; this increase coincides with an increasing prominence of the North West Pacific as a source region and ballast water as an introduction vector. Several of the most recent high profile introductions to the bay, however, are the result of domestic translocations of species introduced elsewhere in Australia and appear to be mediated by vessel fouling.

The number of established exotic and cryptogenic species in Port Phillip Bay is higher than reported by similar studies anywhere else in the world. This reflects at least in part the depth of the analysis we undertook, but also the current and historical role of Port Phillip Bay as a major domestic and international port, and its apparent susceptibility to biotic invasion. Recent shifts in the dominant source regions and introduction vectors suggest a renewed potential for invasions and point to the need to develop and implement effective measures to minimise this threat and protect the bay's marine communities.

Item Type: Book
Publisher: CSIRO Marine Research
Other Information: Centre for Research on Introduced Marine Pests Technical Report No. 20.
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