Tasmanian Seamounts

Recommendation to the Minister for the Environment and Heritage
from the Threatened Species Scientific Committee (TSSC) on a public nomination for an ecological community listing on the Environment Protection and Biodiversity Conservation Act 1999 (the Act)

1. Generally accepted name

The Tasmanian Seamounts is the generally accepted name for a field of seamounts that occurs off southern Tasmania. The names Tasman Seamounts and Tasmania Seamounts have also been used. The name Tasmanian Seamount Community (TSC) is intended to include both the seamounts themselves and their associated faunal community.

2. How judged by TSSC in relation to the Environment Protection and Biodiversity Conservation Act 1999 criteria.

TSSC judges the Tasmanian Seamounts Community to be ineligible for listing as Critically Endangered under the Act. Justification for this is provided below.

Criterion 1: Its decline in geographic distribution is very severe.

The nominator notes that there is little likelihood that the Tasmanian Seamounts Community will decline in geographic distribution. They alternatively state that the biotic components have suffered a marked decrease in distribution.

Criterion 2: Its geographic distribution is very restricted and the nature of its distribution makes it likely that the action of a threatening process could cause it to be lost in the immediate future.

It is unlikely that the Tasmanian Seamounts Community would be lost from threatening processes in the immediate future. However, some of the endemic species associated with the Tasmanian Seamounts Community benthos could be threatened by human activities. It is worth noting that 20% (15 of the 70 seamounts) of the Tasmanian Seamounts Community is protected as an IUCN Category 1a marine reserve.

Criterion 3: For a population of a native species that is likely to play a major role in the community there is a very severe decline to the extent that the restoration of the community is not likely to be possible in the immediate future.

The nominator has not provided sufficient evidence to support assessing their claims under this criterion, especially in relation to the rejection that high level protection of 20% of the pristine seamounts would prevent such a decline. The Committee considers that the Marine Protected Area provides an adequate and representative level of protection of the Tasmanian Seamounts Community.

Criterion 4: The reduction in its integrity across most of its geographic distribution is very severe as indicated by degradation of the community or its habitat, or disruption of important community processes that is very severe.

The nominator provides insufficient evidence to support this criterion and indeed concludes 'While the shallower seamounts have suffered the greatest in terms of habitat alteration, this alteration does not cause them to be viewed as a separate ecological community.' Assuming that the nominator means that there is insufficient distinction between the habitats of the shallow and deeper water seamounts to separate them into distinct ecological communities, it would seem evident that by placing 20% of the seamounts (15 out of 70) into an IUCN Category 1a marine protected area, that 20% of representative habitat is well protected.

Criterion 5: Its rate of continuing detrimental change is very severe as indicated by:

(a) a rate of continuing decline in its geographic distribution, or a population of a native species that is believed to play a major role in the community that is very severe; or
(b) intensification, across most of its geographic distribution, in degradation, or disruption of important community processes, that is very severe.

The nominator has based their case predominantly on part a) of this criterion and drawn attention to the removal of coral substrate on the more shallow seamounts and the decline in orange roughy. Once again the nomination doesn’t provide sufficient evidence to differentiate fully between the habitat of shallow seamounts and deeper seamounts, specifically the 20% of the deep water seamounts that are highly protected in an IUCN Category marine reserve. It is continued to be argued that the definition of the seamounts as a single ecological community means that by protecting 20% of the community there is a representativess and precautionary amount of the seamounts in a pristine condition fully protected. In respect to the use of the orange roughy as an indicator species to point to severe decline of a species that plays a major role in the seamounts community, there is insufficient understanding of the inter-relationship of the role the seamounts play in the ecology of benthiopelagic fish (Koslow and Gowlett-Holmes 1998) to support the use of this criterion.

Criterion 6: A quantitative analysis shows that its probability of extinction, or extreme degradation over all of its geographic distribution is at least 50% in the immediate future.

The nominator did not address this criterion in their nomination.

As previously found by Environment Australia, the nomination relies almost exclusively on the work undertaken by Koslow and Gowlett-Holmes in 1998. That assessment was undertaken under contract to Environment Australia as a basis to declare a part of the Tasmanian Seamounts Community as a Marine Protected Area. It is not sufficiently detailed to base a case for listing of the entire Tasmanian Seamounts Community as a critically endangered community. The Committee also has doubts as to the suitability of that report to assess the Tasmanian Seamounts Community as either 'Endangered' or 'Vulnerable' under the Environment Protection and Biodiversity Conservation Act 1999 and further notes that one of the actions likely to be recommended in the management plan for the Tasmanian Seamounts Marine Park is that much needed further research be undertaken as a priority to increase our knowledge and understanding of this community.

3. Conclusion

The TSSC considers that:

  • given the findings of Koslow and Gowlett-Holmes (1998), it is reasonable to view the field of Tasmanian Seamounts and their associated biota as fairly homogeneous and distinct from other seamount communities and to treat them as a single ecological community
  • overall the uniqueness and vulnerability of the community is well established, and not disputed by any of the commentators
  • the nomination was somewhat speculative when dealing with some of the special physical oceanographic conditions that lead to the high productivity associated with seamounts
  • the detail of the nomination was at times partly directed at issues more relevant to the boundaries and management of the Marine Protected Area which is not relevant to the assessment of the nomination
  • that while endemism of the species associated with the seamounts is high, this finding must be put in the context that the generally poorly explored southern ocean fauna is sure to lead to further surprises, possibly altering the observed level of endemicity recorded on these seamounts
  • while the nomination also stated that like those of other deep sea communities, the fauna of the Tasmanian Seamounts appear to have enhanced longevity and reduced growth rates in a plausible manner, this is untested given available findings. However, if true, then the fauna is likely to have a very limited regenerative capacity and the nomination could be correct in suggesting that it will take decades or centuries to regenerate once depleted
  • that 15 of the 70 seamounts (being 20% of the seamount field) are in a Marine Protected Area of 370 km2 about 100 km south of Tasmania and the seamounts will be managed as a IUCN Category 1a reserve and that the seamounts in the Marine Protected Area with peaks rising to between 1150 and 1700 m below the sea surface, and not previously been fished, could be classified as pristine. Importantly, on available evidence, the Marine Protected Area appears to be representative of the seamount community. This is best summarised by Koslow and Gowlett-Holmes (1998) as follows:
    • The seamounts in the Interim Protected Area appear to be representative of the seamount fauna of the southern Tasmanian region. The fauna on seamounts in the depth range 1000-1400 m within the Interim Protected Area is very similar to that on lightly fished seamounts in the same depth range outside of the Interim Protected Area, and the available evidence heavily fished seamounts outside of the Interim Protected Area. Similarly, there is very little difference in the fauna on the seamounts deeper than 1400 m inside and outside the Interim Protected Area, although these seamounts have much lower biomass and fewer species per sample than the shallower ones.
  • reservation of 20%, or 15 of the pristine seamounts is considered adequate protection against the community being considered critically endangered.

4. Recommendation

The ecological community known as the Tasmanian Seamounts Community does not meet the criteria and thus is not eligible for listing as (critically endangered) under the Environment Protection and Biodiversity Conservation Act 1999.