Swollen Crayfish
Scientific name
Euastacus guruhgi
Status in NSW
Critically Endangered.
The Swollen Crayfish (Photo by R.McCormack)
Characteristics
Typical characteristics of the Swollen Crayfish are:
- Dorsal colouring: brown to green‑brown
- Ventral surfaces: lighter, often cream to pinkish
- Walking legs: blue‑grey
Species similar in appearance
The species closely resembles Euastacus girurmulayn and other small Euastacus taxa, and accurate identification typically requires formal morphological assessment.
Size
The Swollen Crayfish has been documented to reach a maximum of 32mm occipital carapace length (OCL).
Distribution
The Swollen Crayfish is a highly restricted short range endemic known only from four small creeks. All sites occur on or near Wollumbin (Mount Warning) within the Oxley River sub catchment. Despite highly suitable habitat in surrounding rainforest, the species has never been found outside this small area, even where other Euastacus species occur.
The species occupies an area of extremely high rainfall (>2,000 mm/year) and warm subtropical temperatures (15-25 °C).
Habitat
The species is restricted to rainforest gullies and headwater streams. It is often found under rocks and debris as well as in complex burrow systems.
Wollumbin National Park, known as Swollen Crayfish habitat (NSW Government).
Why is the Swollen Crayfish threatened?
Climate change is a key threat to the swollen crayfish, with the species having limited capacity to relocate to other nearby suitable habitat. The primary threats include:
- Increased frequency and intensity of extreme weather events (heatwaves, storms, droughts).
- Increased average temperatures projected to exceed the species physiological tolerance.
- Hydrological changes, such as altered rainfall patterns and lower groundwater tables reduce the availability of suitable streams
- Increased bushfire risk, reducing canopy cover, increasing sedimentation, and altering water/soil temperature regimes.
- Illegal collection
- Invasive species
- Incursion into Australia of crayfish plague
