Murray crayfish
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| Murray crayfish | ||||||||||||||||||||
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| Euastacus armatus Von Martens, 1866 |
The Murray crayfish, Euastacus armatus, is a species of freshwater crayfish endemic to Australia that belongs to the family Parastacidae. The Murray crayfish has the largest geographic range of any of the Euastacus crayfish in Australia, being found in the Murray and Murrumbidgee Rivers as well as many of their tributaries. Murray crayfish are also known as "Murray River crayfish", "Murray crays", "freshwater crays" and in the Wagga Wagga region of southern New South Wales they are simply known as "lobsters".
Today adults commonly grow to 20 to 30 cm in length. In the past however they have been reliably recorded at significantly larger lengths and up to 2 kg in weight; the Murray crayfish is considered the second largest freshwater crayfish species in the world after the Tasmanian giant freshwater crayfish. Murray crayfish have large white claws and a dark olive/grey/black carapace, all of which are covered in short robust spikes. In small individuals, the claws are green and yellow. The crayfish begin to breed when they are 15–20 cm long, which takes between 6 and 9 years. When the crayfish has reached sexual maturity the females lay 500 to 1000 eggs in late autumn. The eggs are carried on the female's pleopods until they hatch in summer. Murray crayfish feed predominantly on decaying aquatic plant matter but will also eat dead animals.
The range of the Murray crayfish extends to well over 700 m above sea level in large and small upland streams and several upland impoundments, and to relatively low altitudes in the Murray and Murrumbidgee Rivers; historically its distribution extended throughout the southern Murray-Darling Basin however fishing pressure and environmental change has resulted in the species no longer being found in the Murray River downstream of Mildura. Like all Euastacus species, Murray crayfish prefer cool, fast-flowing water.
The species is threated by overfishing and as a result there are many restrictions in place for recreational fishers, all of which vary from state to state. In New South Wales these include a minimum size, bag and possession limits, and a ban on taking females with eggs. Further there is a limited season in which the species can be taken (start of May to the end of August). Murray crayfish are listed as vulnerable in the Australian Capital Territory, as endangered in South Australia and as vulnerable by the IUCN.
[edit] References
- Crandall (1996). Euastacus armatus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Listed as Vulnerable (VU A1ade v2.3)
- Environment ACT. ACTION PLAN No.14, Murray River crayfish
- New South Wales Department of Primary Industries Prime Fact 4 Fishing for Murray crayfish in NSW
