Blue yabby, cyan yabby
The term ‘Yabby’ is used to describe many species in the genus Cherax, the smooth freshwater crayfish of Australia, and is also used to describe several species of marine Ghost shrimp. Their colour is highly variable and depends on water clarity and habitat; yabbies can range from black, blue-black, or dark brown in clear waters to light brown, green-brown, or beige in turbid waters. Yabbies specifically bred to be a vibrant blue colour are now popular in the aquarium trade in Australia.
Yabbies occasionally reach up to 30 cm (12 in) in length, but are more commonly 10–20 cm long
Detritivores and omnivores, Common yabbies eat a lot of dead and decaying matter. A large portion of the diet is plant matter, but they will also eat animal matter such as dead fish. They are also capable of catching small fish, snails and crustaceans resting on the river bottom and consuming them too.
It is capable of living in most fresh water bodies and is found especially in lakes and dams, also frequenting rivers and temporary water.
Occurs It is native to the eastern parts of mainland Australia, west of the Great Dividing Range and throughout the Murray-Darling River system ranging from tropical to temperate climates.It has also been introduced to other parts of Australia including WA, NT and coastal eastern NSW
The Common yabby is an extremely hardy species. They can survive dry conditions for many years by lying dormant in burrows sunk deep into muddy creek and swamp beds. During the wet season, they can travel many kilometres across land in search of new waterholes to live in.
They can be very territorial, and will attack and even eat members of their own species. That said, in the wild they can live in quite high concentrations.
Freshwater crayfish are in the middle of the food chain. They are basically vegetarian but also scavenge decaying plant and animal matter. In turn, they are preyed upon by many native fishes and water birds. The common yabby forms an important part of the diet of platypus water rats, white ibis, several cormorants, and warmwater fishes such as the Murray cod, Golden perch and Tandanus catfish.
Their scientific name C. destructor comes from their ability to destroy farm dam walls with their burrows. However, this generally happens only if the walls are less than 2 metres thick, especially if water levels change frequently (for example on rice paddy levees). It is unlikely to happen in the average farm dam with walls over 6 metres thick.
Breeding begins in spring when the water temperature reaches 15 to 16°C. The first batch of eggs (100 to 500 eggs per individual, depending upon the size of the female) hatches 8 to 10 weeks later in early summer. As soon as the young have left (a further 3 weeks later), the female is ready to breed again. Because of the higher water temperatures in summer, the second brood takes only 3 to 4 weeks to incubate. Some females will breed three or more times during the breeding season, which, if the temperature remains high enough, can extend into autumn. In the warmer water in the west of their range, the breeding season may continue almost year around. Most breeding is done by 2 year old animals, as they far outnumber the older animals thanks to predation over time.