The Murray crayfish, ''Euastacus armatus'', is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

freshwater crayfish Crayfish are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the Superfamily (taxonomy), superfamilies Astacoidea and Parastacoidea. They breathe through feather- ...

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

that belongs to the family

Parastacidae The Parastacidae are the family of freshwater crayfish found in the Southern Hemisphere. The family is a classic Gondwana-distributed taxon, with extant members in South America, Madagascar, Australia, New Zealand, and New Guinea, and extinct ta ...

. The Murray crayfish has the largest geographic

range Range may refer to: Geography * Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra) ** Mountain range, a group of mountains bordered by lowlands * Range, a term used to i ...

of any of the ''

Euastacus ''Euastacus'' is a genus of fresh water, freshwater crayfish known as "spiny crayfish". They are found in the south-east of the Australian mainland, along with another genus of crayfish, ''Cherax''. Both genera are members of the family Parasta ...

'' 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", "spiny freshwater crays", "spinies" and in the

Wagga Wagga Wagga Wagga (; informally called Wagga) is a major regional city in the Riverina region of New South Wales, Australia. Straddling the Murrumbidgee River, with an urban population of more than 57,003 as of 2021, it is an important agricultural, m ...

region of southern

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

they are simply known as "lobsters". Today adults commonly grow to in length. In the past however they have been reliably recorded at significantly larger lengths and up to 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

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...

s and a dark olive/grey/black

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

, 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 long, which takes between 6 and 9 years. When the crayfish has reached sexual maturity the females lay 500 to 1,000

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

in late autumn; the eggs are carried on the female's

pleopod The anatomy of a decapod consists of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment – often called a somite – may possess one pair of appendages, although in various groups these m ...

s 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 over 700 m above sea level in large and small upland

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

s 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 The Murray–Darling Basin is a large geographical area in the interior of southeastern Australia, encompassing the drainage basin of the tributaries of the Murray River, Australia's longest river, and the Darling River, a right tributary of ...

, but fishing pressure and environmental change has resulted in the species no longer being found in the Murray River downstream of

Mildura Mildura ( ) is a regional city in north-west Victoria, Australia. Located on the Victorian side of the Murray River, Mildura had a population of 34,565 at the 2021 census. When nearby Wentworth, Irymple, Nichols Point, Merbein and Red ...

. Like all ''

'' species, Murray crayfish prefer cool, fast-flowing water, deep pools, boulder-rich streambeds, and areas with extensive riparian vegetation. The species is threatened by

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

and as a result there are many restrictions in place for recreational fishers, all of which vary from state to state. In

and

Victoria Victoria most commonly refers to: * Queen Victoria (1819–1901), Queen of the United Kingdom and Empress of India * Victoria (state), a state of Australia * Victoria, British Columbia, Canada, a provincial capital * Victoria, Seychelles, the capi ...

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 also threatened by habitat loss, with a 91% decline in the abundance of this species recorded in one stream (Goobarragandra River) over a six-year period when there was a halving in the availability of their preferred boulder habitats due to sedimentation. Murray crayfish are listed as

Data Deficient A data deficient (DD) species is one which has been categorized by the International Union for Conservation of Nature (IUCN) as offering insufficient information for a proper assessment of conservation status to be made. This does not necessaril ...

on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...

, as vulnerable in the

Australian Capital Territory The Australian Capital Territory (ACT), known as the Federal Capital Territory until 1938, is an internal States and territories of Australia, territory of Australia. Canberra, the capital city of Australia, is situated within the territory, an ...

, and as endangered in

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

. Lately, though, the numbers have increased thanks to the efforts of scientists.

References

External links

Murray Crayfish (''Euastacus armatus'') video on Youtube
{{Taxonbar, from=Q5500461 Freshwater crustaceans of Australia Vulnerable fauna of Australia Crustaceans described in 1866 Euastacus