Estimating survival of the tayatea astacopsis gouldi (crustacea, decapoda, parastacidae), an iconic, threatened freshwater invertebrate
Shepherd, T and Gardner, C and Green, BS and Richardson, A, Estimating survival of the tayatea astacopsis gouldi (crustacea, decapoda, parastacidae), an iconic, threatened freshwater invertebrate, Journal of Shellfish Research, 30, (1) pp. 139-145. ISSN 0730-8000 (2011) [Refereed Article]
Populations of the world’s largest freshwater invertebrate Astacopsis gouldi (tayatea, or giant Tasmanian
freshwater crayﬁsh) have declined because of land use changes and poaching. The species is endemic to northern Tasmania and is
listed as ‘‘vulnerable’’ under the Commonwealth of Australia Environment Protection and Biodiversity Conservation Act of 1999
and the Tasmanian Threatened Species Protection Act of 1995. Mark–recapture models were tested for their suitability in
estimating survival of a population of A. gouldi in a remote river. Tayatea were marked with passive integrated transponder (PIT)
tags during a 7-mo period. Catchability of tagged and untagged A. gouldi was size and sex speciﬁc. Larger animals and females
were more readily trapped throughout the sampling period, which spanned the austral autumn/winter. Catchability of male
tayatea increased during May, and was strongly inﬂuenced by environmental conditions such as water temperature and river level.
Results suggest that PIT tagging combined with mark–recapture methods are a feasible approach for estimating survival in
tayatea, given sample sizes that can be achieved with reasonable effort. Precision of estimates could be improved by concentrating
sampling around peak catchability during spring and autumn, and minor ﬂood conditions during winter. This method provides a
tool to estimate A. gouldi mortality as a result of illegal ﬁshing and detrimental land use practices, thus providing better information
for management. This strategy is essential to monitor progress toward the milestone of reducing their ‘‘vulnerable’’ classiﬁcation
under the Commonwealth and Tasmanian legislation within 14 y (1 generation) from the implementation of the plan.