The common yabby is an Australian freshwater crustacean.

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.

The word “yabby” comes from the Wemba Wemba, an Aboriginal Australian language.

Yabbys are found in swamps, streams, rivers, reservoirs, and farm dams at low to medium elevations. Yabbys apparently 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.

Yabbys are found in many ephemeral waterways, and can survive dry conditions for several years by lying dormant in burrows sunk deep into muddy creek and swamp beds.

Yabbys are primarily nocturnal detritivores, feeding primarily on algae and plant remains at night, but also opportunistically feeding on any fish or animal remains they encounter at any time of day.

In Southern Australia, it is commonly accepted that yabbys are active and thereby available to catch during the warmer months.

Yabbys are an important dietary item for Australian native freshwater fish such as Murray cod and golden perch.

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 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.