Common yabby
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| Cherax destructor Clark, 1936 |
The common yabby, Cherax destructor, is an Australian freshwater crustacean in the Parastacidae family. It is listed as a vulnerable species [1] of crayfish by the World Conservation Union (IUCN), though the validity of this listing is questionable; wild yabby populations remain strong, and have expanded into new habitats created by reservoirs and farm dams [2]. Its common name of "yabby" is also applied to many other Australian Cherax species of crustacean. Yabbies occasionally reach up to 30 cm (12 in) in length but are more commonly 10–20 cm (4–8 in) long [3]. 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 [4]. Yabbies specifically bred to be an un-naturally vibrant blue colour are now popular in the aquarium trade in Australia.
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[edit] Ecology
Yabbies are common throughout Victoria and New South Wales, although it may also be found in southern Queensland, South Australia, and parts of the Northern Territory, making it the most widespread Australian crayfish [5]. It has been introduced to Western Australia, where it is an invasive species and poses a threat to Cherax crayfish species native to the region such as gilgies (Cherax quinquecarinatus) [6].
Yabbies are found in swamps, streams, rivers, reservoirs and farm dams at low to medium elevations. It appears yabbies were largely restricted to lower altitude habitats in inland areas of south-eastern Australia including the Murray-Darling Basin before European settlement, with the Euastacus spiny crayfish species found in higher altitude habitats and the coastal river systems. High altitude yabby populations in Lakes Eucumbene and Jindabyne, which are on the upper reaches of the coastal Snowy River system, are unusual and may be translocated.
Yabbies are found in many ephemeral waterways, and can survive dry conditions for long periods of time (at least several years) by aestivating (lying dormant) in burrows sunk deep into muddy creek and swamp beds.
Yabbies are nocturnal detritivores, feeding primarily on algae and plant remains, but also opportunistically feeding on any fish or animal remains they encounter.
Yabbies are an important dietary item for Australian native freshwater fish like Murray cod and golden perch.
[edit] Catching
Catching yabbies, or "yabbying", in rivers and farm dams is a popular summertime activity in Australia, particularly with children. The most popular method involves tying a piece of meat to a few metres of string or fishing line, which in turn is fastened to a stick in the bank, and throwing the meat into the water. The string is pulled tight when a determined yabby grasps the piece of meat in its claws and tries to make off with it. The line is then slowly pulled back to the bank, with the grasping yabby usually maintaining its hold on the meat. When the meat and the grasping yabby reaches the water's edge a net is used to quickly scoop up both the meat and the grasping yabby in one movement.
Other methods of catching yabbies involve various types of nets and traps. Local fishing regulations must be checked before using any nets and traps for yabbies; many types of nets and traps are banned as wildlife such as platypus, water rats and long-necked turtles can become trapped in them and drown.
[edit] Aquaculture
The common yabby is a popular species for aquaculture [5], although their burrowing can destroy dams.
[edit] References
- ^ Crandall (1996). Cherax destructor. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Listed as Vulnerable (VU A1de v2.3)
- ^ Yabby. Native Fish Australia (2006-09-20).
- ^ Craig Williams. Cherax destructor.
- ^ Chris Goerner. Cherax destructor.
- ^ a b Fiona Withnall (2000). Biology of Yabbies (Cherax destructor) (PDF).
- ^ Beatty, S., D. Morgan & H. Gill (2005). Role of Life History Strategy in the Colonisation of Western Australian Aquatic Systems by the Introduced Crayfish Cherax destructor Clark, 1936. Hydrobiologia 549 (1): 219–237. doi:.
