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Euastacus armatus (Family Parastacidae)

Murray Cray

Distribution

Distribution:

Euastacus armatus is widely distributed, occurring in inland waterways ranging from Kandos, New South Wales, to northern Victoria and north-eastern South Australia. (NSW, VIC, SA)

Features:

Adults of the genus Euastacus have spines on the body and serrations on the edges of the claws, unlike adults of the genus Cherax that have smooth bodies and claws. The Murray Cray is the largest species of Euastacus, reaching a body length of around 50 cm and a weight of about 3 kg. Males and females are similar. The Murray Cray is recognised by the whitish claws and strong white abdominal spines. The body varies from blue-grey to dark-green or reddish-brown.

Ecology/Way of Life:

Euastacus armatus live in inland rivers and streams of the Murray, Murrumbidgee, Macquarie and Darling River systems at altitudes from near sea level to above 700 m. Adult Murray Crays burrow in river banks and juveniles usually burrow under rocks or logs on the river bed. The Murray Cray prefers water temperatures of 14–19°C and is most active in May, June, October and November. They feed mostly on detritus or semi-decayed wood and vegetation, but also on dead animals such as fish. The Murray Cray matures at six to nine years of age and they breed during autumn. The eggs (300–800) are carried underneath the abdomen on the pleopods. Eggs incubate for four or five months and hatch in spring or summer. The hatchlings then stay with the mother for a further three or four weeks after which they are released.

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Interaction with Humans/Threats:

Euastacus armatus is at greatest risk from overfishing, and habitat destruction such as land clearing and water pollution. The large size of the Murray Cray makes it popular among recreational fisherman and in many areas, populations of are greatly reduced. In the lower reaches of the Murrumbidgee River, the Murray Cray is now rare and in parts of the Murray River, may be locally extinct. The slow growth rate makes it unsuitable for aquaculture.

Other Comments:

Euastacus armatus was named by von Martens in 1866. The name is derived from the Latin word arma, presumably because of the strong dorsal spines on the abdomen.

Further Reading:

Morgan, G. (1986). Freshwater crayfish of the genus Euastacus Clark (Decapoda: Parastacidae) from Victoria. Memoirs of the Museum of Victoria 47(1): 1–57.

Horwitz, P. (1990). The Conservation Status of Australian Freshwater Crustacea. Report Series No. 14. Australian National Parks and Wildlife Service.

Merrick, J. R. (1993). Freshwater Crayfishes of New South Wales. Linnaean Society of New South Wales.

Acknowledgments:

Text and map by Shane Ahyong. Photography by R. Hughes

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Images and Multi-media:  
Distribution Map  
image/jpeg 6946 bytes Distribution of Euastacus armatus
Attached Image  
image/gif 73925 bytes Euastacus armatus

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