Document ID: chunk:federal_register_of_legislation:F2017L01040:body:0:p8
Version: federal_register_of_legislation:F2017L01040
Segment Type: other
Provision Reference: 
Character Range: 21420–24344

varies considerably among individuals, with adults ranging from dark brown-green to black or blue. The species is spiny and has large distinct chelae (front pincers), walking legs, carapace and abdomen ending in a tail fan. Males have larger pincers than females. Astacopsis gouldi is the largest of the three Astacopsis species. Juvenile A. gouldi can be differentiated from the other two species (A. franklinii and A. tricornis) by the presence of a raised ridge in the middle of its forehead (rostrum).
The Tasmanian giant freshwater crayfish is endemic to rivers, lakes and streams of northern Tasmania. Formerly, the species was distributed from the Arthur River in the west and eastwards across northern Tasmania, where it was found in all rivers flowing into Bass Strait, except for those of the Tamar catchment (Horwitz 1994). Presently, the species distribution is more disjunct. Localised extinctions, or large declines in numbers, are thought to have occurred in the Welcome, Montagu, Rubicon, Don, Brid, Boobyalla, Pipers, Ringarooma, Duck, Little and Great Forester Rivers and Claytons Rivulet (Horwitz 1990, 1991, 1994; TSS 2006). The species has also been introduced into two catchments: the North Esk catchment (St Patricks River); and the Derwent catchment (Clyde River) (IFS unpub. Data, cited in TSS 2006), and populations have become established. The species naturally occurs at altitudes below 400 m, with most caught below 200 m (Horwitz 1991, 1994). The estimated extent of occurrence of the giant freshwater crayfish, based on catchments where the species is known to occur and historical reports of species presence, is approximately 10 700 km² (TSS 2006). Approximately 19 percent of the streams in which the species habitat is predicted to occur were protected in either formal or informal reserves at the time of development of the previous recovery plan (TSS 2006). Since this time a large proportion of additional habitat has been incorporated into formal and informal reserves, however current figures on the total amount of giant freshwater crayfish habitat within a protected area were not available at the time of writing this plan.

3.2 Population trends
No data on population numbers are available for the giant freshwater crayfish, however reports, largely based on anecdotal evidence, of localised extinctions and large declines in numbers due to fishing and/or habitat degradation were relatively common in the 1990s (e.g. Hamr 1990a; Horwitz 1991, 1994; Maxwell et al. 1997). The structure of populations studied during this period indicated an absence of large individuals, particularly males, with very few giant freshwater crayfish of a size indicating sexual maturity being found (Growns 1995; Hamr 1996; Lynch & Blühdorn 1997). However, in recent years ongoing monitoring efforts have recorded larger specimens with increasing regularity (Doran & Richardson 2008). Whilst earlier