The marron are some of the largest crayfish in the world. Australia is home to the world's two largest freshwater crayfish – the Tasmanian giant freshwater crayfish Astacopsis gouldi, which can achieve a mass of over 5 kilograms (11 lb) and is found in rivers of northern Tasmania, and the Murray crayfish Euastacus armatus, which can reach 2 kilograms (4.4 lb) and is found in much of the southern Murray-Darling basin.
In New Zealand, two species of Paranephrops are endemic, and are known by the Māori name Some crayfish suffer from a disease called crayfish plague, caused by the North American water mould Aphanomyces astaci which was transmitted to Europe when North American species of crayfish were introduced there. Like other edible crustaceans, only a small portion of the body of a crayfish is eaten.
Their disposition towards eating almost anything will also cause them to explore the edibility of aquarium plants in a fish tank.
However, most species of dwarf crayfish, such as Cambarellus patzcuarensis, will not destructively dig or eat live aquarium plants.
A variety of cottage industries have developed as a result of commercialized crawfish iconology, such as products with crawfish attached to wooden plaques, T-shirts with crawfish logos, and crawfish pendants, earrings and necklaces made of gold or silver. In Australia, many of the better-known crayfish are of the genus Cherax, and include the marron from Western Australia (now believed to be two species, Cherax tenuimanus and C.
cainii), red-claw crayfish (Cherax quadricarinatus), common yabby (Cherax destructor) and western yabby (Cherax preissii). tenuimanus is critically endangered, while other large Australasian crayfish are threatened or endangered.
Sometimes the claws are removed so that the crayfish do not stop fish from biting the hook.
Crayfish easily fall off the hook, so casting should be slow.
They will sometimes consume their old exoskeleton after it has moulted.Each segment may possess one pair of appendages, although in various groups these may be reduced or missing.On average, crayfish grow to 17.5 centimetres (6.9 in) in length, but some grow larger. There are three families of crayfish, two in the Northern Hemisphere and one in the Southern Hemisphere.In most prepared dishes, such as soups, bisques and étouffées, only the tail portion is served.At crawfish boils or other meals where the entire body of the crayfish is presented, other portions, such as the claw meat, may be eaten.