Hi Ian, thanks for your questions. Katherina and Andrew have consulted with our colleagues in the marine area and provided a response below. We will also read this our in our Q&A session scheduled for this afternoon (19 May) at 4:00pm AEST.
The Australian Priority Marine Pest List (APMPL) and the EEPL have different criteria for a species to be included. This includes the EEPL assessing environmental and social amenity impacts only, whereas the APMPL considered environmental, economic and social amenity impacts.
There are other different criteria for inclusion on each list which may also explain some differences. For example, the APMPL is only focussed on priority pests that can be easily identified in the field. It also is important to emphasise that all introduced marine species or records from new areas should be reported to the relevant biosecurity agency, not just species in these two lists. Other specific information for these two taxa are provided below.
Didemnum vexillum:
ABARES: During assessment for the EEPL, experts have acknowledged Didemnum spp. identities as having limited data due to the taxonomic status being disputed for the Didemnum group. The taxonomic status, although unresolved, was not a factor considered in shortlisting for the EEPL. However, criteria for the Australian Priority Marine Pest List (APMPL) include the requirement that listed species can be distinguishable from natives in the field. For the EEPL, experts assessed this species as having potentially significant social and environmental impacts and have agreed that it is a higher-risk EEPL. D. vexillum is an ecosystem modifier with the potential to smother, outcompete and outgrow other species, as observed in the incursion in New Zealand and other regions.
Environmental Biosecurity Office (EBO): This pest is also listed on several state and territory pest lists. The Commonwealth’s work includes reducing the risk of the pest entering AUS territory. The current position regarding species identity - "Part of a massive (and not resolved) species complex" is not ideal for implementing risk reducing measures. The inclusion of D. vexillum will direct efforts for reducing the risk of the species belonging to the 'complex' from entering and also flags the need for developing identification capability. If it was not listed then this work may be sidelined. D. vexillum is also listed on these pest lists: NSWMPL, WAMPL, NTPL, SAPL
Charybdis japonica:
ABARES: During EEPL assessment, this species is found to have limited data on biology, larval development and impacts, although there is some information available from the incursion in New Zealand. There was also limited information on its social amenity impacts, which is mainly impacts on recreational and commercial fisheries (although the latter outside of scope in EEPL). Regarding environmental impacts, experts also considered the impacts of disease transmission by C. japonica. The species is a known reservoir host for diseases such as white spot, which would result in environmental impacts in isolated areas due to disease transmission on native species. Studies in NZ have also found that large numbers of C. japonica compete with native crab species and consume a wide range of other species.
Feasibility for a taxa being controlled in the environment is not considered in the EEPL but was considered in the APMPL—this is where there are different criteria between the EEPL and APMPL. The perceived inability to eradicate once established in the wild was therefore a disincentive in listing C. japonica in the APMPL.
EBO: We note that C. japonica is listed on NSWMPL, WAMPL, SAPL. It should also be emphasised that both lists, combined with the ballast water risk tables, are indeed used when requesting surveillance to be done. This means that a list of less than 20 species, which covers both established (but with limited distributions against potential distribution) and exotic species, are used for marine pest surveillance in Australia. However, as emphasised earlier, a fundamental expectation of Australia’s biosecurity surveillance is that all introduced marine species or observations in new areas should be reported to the relevant biosecurity agency, not just species on specific lists such as the APMPL and the EEPL.
