Murray crayfish
Encyclopedia
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", "spiny freshwater crays", "spinies" and in the Wagga Wagga region of southern New South Wales
they are simply known as "lobsters".
Today adults commonly grow to 20–30 cm (7.9–11.8 ) in length. In the past however they have been reliably recorded at significantly larger lengths and up to 2 kilograms (4.4 lb) 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
s 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 centimetre 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 over 700 m above sea level in large and small upland stream
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
, but 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 Data Deficient
on the IUCN Red List
, as vulnerable in the Australian Capital Territory
, and as endangered in South Australia
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of freshwater crayfish endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
that belongs to the family Parastacidae
Parastacidae
Parastacidae is 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 taxa also in Antarctica.Three genera are to be found in Chile,...
. The Murray crayfish has the largest geographic range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
of any of the Euastacus
Euastacus
Euastacus is a genus of freshwater crayfish known as "spiny crayfish". They are found in the south-east of the Australian mainland, along with another genus of crayfish, Cherax...
crayfish in Australia, being found in the Murray
Murray River
The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...
and Murrumbidgee
Murrumbidgee River
The Murrumbidgee River is a major river in the state of New South Wales, Australia, and the Australian Capital Territory . A major tributary of the Murray River, the Murrumbidgee flows in a west-northwesterly direction from the foot of Peppercorn Hill in the Fiery Range of the Snowy Mountains,...
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 region of southern New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
they are simply known as "lobsters".
Today adults commonly grow to 20–30 cm (7.9–11.8 ) in length. In the past however they have been reliably recorded at significantly larger lengths and up to 2 kilograms (4.4 lb) in weight; the Murray crayfish is considered the second largest freshwater crayfish species in the world after the Tasmanian giant freshwater crayfish
Tasmanian giant freshwater crayfish
The Tasmanian giant freshwater crayfish is the largest freshwater invertebrate in the world. The species is only found in Tasmania , and is listed as a vulnerable species due to habitat loss and over fishing. It is also severely threatened by siltation and de-snagging of streams as decaying wood...
. Murray crayfish have large white claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s and a dark olive/grey/black carapace
Carapace
A carapace is a dorsal 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 underside is called the plastron.-Crustaceans:In crustaceans, the...
, 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 centimetre long, which takes between 6 and 9 years. When the crayfish has reached sexual maturity the females lay 500 to 1000 eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
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 over 700 m above sea level in large and small upland stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
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
Murray-Darling Basin
The Murray-Darling basin is a large geographical area in the interior of southeastern Australia, whose name is derived from its two major rivers, the Murray River and the Darling River. It drains one-seventh of the Australian land mass, and is currently by far the most significant agricultural...
, but fishing pressure and environmental change has resulted in the species no longer being found in the Murray River downstream of Mildura. Like all Euastacus
Euastacus
Euastacus is a genus of freshwater crayfish known as "spiny crayfish". They are found in the south-east of the Australian mainland, along with another genus of crayfish, Cherax...
species, Murray crayfish prefer cool, fast-flowing water.
The species is threated by overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
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
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. 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 Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
on the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
, as vulnerable in the Australian Capital Territory
Australian Capital Territory
The Australian Capital Territory, often abbreviated ACT, is the capital territory of the Commonwealth of Australia and is the smallest self-governing internal territory...
, and as endangered in South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
.