Astacopsis gouldi

The Tasmanian giant freshwater crayfish (Astacopsis gouldi), also called Tasmanian giant freshwater lobster, is the largest freshwater invertebrate and the largest freshwater crayfish species in the world . The species is only found in the rivers below 400 metres (1,300 ft) above sea level in northern Tasmania, an island-state of Australia. It is listed as an endangered species on the IUCN Red List due to overfishing and habitat degradation, and it has been prohibited to catch the crayfish since 1998. The diet of the freshwater crayfish varies with age, but predominantly consists of decaying wood, leaves and their associated microbes. They may also eat small fish, insects, rotting animal flesh and other detritus when available. A. gouldi is very long-lived, surviving for up to 60 years. It has previously been reported to attain weights of up to 6 kilograms (13 lb) and measure over 80 centimetres (31 in) long; however, in recent years the majority of larger specimens are 2–3 kilograms (4.4–6.6 lb). When fully mature the species has no natural predators due to its large size, while smaller individuals can be prey of platypus, river blackfish and rakali. Although a crayfish, the species is locally known as the giant freshwater lobster. In Tasmanian Aboriginal language (palawa kani) the giant freshwater lobster is referred to as lutaralipina. Previously, it has been common to use ‘tayatea’ as the Aboriginal name for A. gouldi. However, historical record does not support the use of this word for this species. The palawa kani Language Program of the Tasmanian Aboriginal Centre has revived ‘lutaralipina’ (pronounced: lu-tar-rah-lee-pee-nah) as the appropriate Tasmanian Aboriginal term for the giant freshwater crayfish (A. gouldi); and ‘tayatitja’ (pronounced: tie-yah-tee-tchah) for the small southern freshwater crayfish (A. franklinii). The specific epithet of the scientific name, Astacopsis gouldi, honours the first Tasmanian Government Geological Surveyor Charles Gould (1834-1893), son of the 19th century English ornithologist John Gould and natural history illustrator Elizabeth Gould (née Coxen). Charles Gould was an amateur naturalist and member of the Royal Society of Tasmania who published observations on the giant freshwater lobster's distribution, diet and habits in 1870. Astacopsis gouldi was first formally described in 1936 by Ellen Clark, a naturalist specialising in Australia's crustaceans. Prior to Clark's revision in 1936, all three of Tasmania's large stream-dwelling crayfish of the genus Astacopsis were collectively known as Astacopsis franklinii in honour of the polar explorer and Governor of Van Diemen's Land Sir John Franklin. Astacopsis franklinii now refers only to the smaller southern species, while the medium sized western species is known as Astacopsis tricornis and Astacopis gouldi refers exclusively to the giant northern crayfish. It is a common misconception that A. gouldi is named after the convict artist William Buelow Gould. WB Gould's 'Sketchbook of fishes' produced at the Macquarie Harbour penal settlement contains an image of the large western Tasmanian freshwater crayfish A. tricornis not A. gouldi. A. gouldi are omnivorous crustacean, primarily eating decaying wood, leaves and their associated microbes. They may also eat small fish, insects, rotting animal flesh and other detritus when available. Colour varies considerably among individuals, with adults ranging from dark brown-green to black or blue. For undetermined reasons, populations in the Frankland River system on the West Coast are predominantly found to be blue-white in colour. Males can be identified by their larger pincers compared to females. Young juveniles moult several times a year, becoming less frequent as they mature. The species is long lived and known to live up to 60 years of age and attain weights of up to 6 kilograms (13 lb), however in recent years specimens of 2–3 kilograms (4.4–6.6 lb) are considered large. Results from a genetic study indicated that specimens of A. gouldi from a site in the Pipers River catchment (north of Launceston) were significantly genetically distinct from the rest of the species. The dispersal and migratory patterns of A. gouldi are largely unknown, but they are recorded to be most active during summer and autumn when water temperatures are higher, they are also known to walk over land. A 2004 study found the species appears to have periods of relative inactivity restricted to a 'home-pool' for 1–10 days interspersed with movements involving travel over relatively large distances, including one crayfish moving over 700 m in a single night. Juveniles are suspected to migrate to seasonal creeks or shallow faster-flowing waters known as riffle zones where they are at less risk from predators including other crayfish, fish, platypus and rakali. Larger sub-adults (<100 millimetres (3.9 in) carapace length) will move to deeper-flowing straight sections of the catchment. Adults have no natural predators and will take refuge in sheltered deep pools and appear to tolerate each other despite being aggressive elsewhere. Males are territorial and maintain a harem of up to several females.