Assessing the status of a disjunct population of the endangered crayfishEuastacus bispinosusin a karst rising-spring habitat in southern Australia

Many species of freshwater crayfish of the endemic Australian genus Euastacus are threatened with extinction. Routine monitoring of most Euastacus species is minimal, and a subsequent lack of information has hampered prioritization of conservation and management efforts. The present study investigated population parameters and temporal changes in abundance in a disjunct population of Euastacus bispinosus. This occurs at the western extent of the range of the species in the state of South Australia (SA) and inhabits a groundwater-dependent karst habitat distinct from the larger population in the Victorian Glenelg basin. Euastacus bispinosus was recorded at sites within seven karst rising-springs as well as two isolated locations (sinkhole and cave), which expanded the extent of occurrence of the species in SA, but the area of occupancy remains limited. Most subpopulations contained low numbers, had little or no signs of recruitment, were dominated by large crayfish, and demonstrated a high incidence of gonopore aberrations. Declines in abundance were observed across these subpopulations between 2006 and 2011, although these declines were not statistically significant. Of critical importance to the conservation of the species in SA is ensuring that groundwater discharge is maintained in karst rising-springs, hydrological connectivity is enhanced between subpopulations and degradation within habitats is reversed. Further monitoring and research is necessary to gain a clear understanding of the status of subpopulations of the species over time. Copyright © 2014 John Wiley & Sons, Ltd.