Engaeus orramakunna (Mt Arthur Burrowing Crayfish)

Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on Amendments to the List of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)

1. Scientific name, common name (where appropriate), major taxon group

Engaeus orramakunna (Mt Arthur Burrowing Crayfish)

2. International/National Context

The species is endemic to Tasmania, being restricted to a small area centred on Mt Arthur in north-east Tasmania.

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

TSSC judges the nomination to be eligible for listing as vulnerable under the EPBC Act. The justification against the criteria is as follows:

Criterion 1 - It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a substantial reduction in numbers.

The nomination does not seek to justify listing against this criterion. However, on the basis of the population estimates provided for disturbed and undisturbed sites, a substantial decline of 60 - 66% has been calculated since European settlement. Whilst data is not available to assess the rate of decline over the past 10 years or three generations, the species is considered to have undergone a substantial reduction in numbers due to human disturbance.

Therefore, the species is eligible for listing as vulnerable under this criterion.

Criterion 2- Its geographic distribution is precarious for the survival of the species and is limited.

The extent of occurrence is 300km2. The area of occupancy is 8km2. The species is known from 10 locations. Virtually none of the existing habitat is protected by conservation reserves. The population estimates indicate a total population decline of 60-66% due to human disturbance. There is potential continuing decline due to threatening processes that affect water quality/quantity, and soil and food (wood/plant) availability. The greatest threats are indicated to be extensive forestry activities and heavy pressure from agricultural activity on private land.

Therefore, the species is eligible for listing as vulnerable under this criterion.

Criterion 3 - The estimated total number of mature individuals is limited and (a) evidence suggests that the number will continue to decline at a substantial rate, or (b) the number is likely to continue to decline and its geographic distribution is precarious for its survival.

The number of adult individuals is estimated to be 1,400,000 to 4,000,000.

Therefore, the species is not eligible for listing under this criterion.

Criterion 4 - The estimated total number of mature individuals is low.

The number of adult individuals is estimated to be 1,400,000 to 4,000,000.

Therefore, the species is not eligible for listing under this criterion.

Criterion 5 - The probability of its extinction in the wild is at least 10% in the medium-term future.

There is no quantitative evidence available against this criterion.

4. Conclusion

The Mt Arthur Burrowing Crayfish has a restricted geographic distribution and has undergone a substantial reduction in population size such that it meets Criteria 1 and 2 for listing as vulnerable as nominated.

5. Recommendation

TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by,

including in the list in the Vulnerable category:

Engaeus orramakunna (Mt Arthur Burrowing Crayfish)