Carp are native to central Asia. They were first introduced into Australia in the mid 1800s, but remained in two relatively confined locations, Sydney and the Murrumbidgee Irrigation Area. These two populations were different strains of the one species and showed no signs of spreading. In the early 1960s, a fish farmer illegally introduced a new strain, Boolarra, and it has rapidly colonised watercourses throughout Australia. A recent genetic study of Carp in Australia has identified a fourth strain. Koi, which is present in the wild in the ACT and Tas. The feral Koi strain lacks the bright orange, black or white colouration seen in aquarium Koi.

Carp are present in the majority of slopes and lowland rivers and creeks, and in upland streams as well. They often comprise between 70 and 90% of the fish biomass in lakes and streams.

The Carp is usually associated with warm, slow-flowing lowland rivers or lakes, and is rarely found in clear, cool fast-flowing streams. It is tolerant of a wide range of environmental conditions and able to survive extremely low levels of dissolved oxygen. When Carp are seen apparently gasping at the water surface, they are not taking in oxygen, but rather feeding on zooplankton. Males are sexually mature at 2–3 years (300 mm) and females at 3–4 years (350 mm).

Spawning usually occurs in spring and summer when water temperatures are 17–25¡C. Spawning fish congregate in shallow water with egg-laying often accompanied by much chasing and splashing as fish break the water surface with their back and tail. Eggs are adhesive and laid in clumps on freshwater vegetation, logs and submerged grass. They are 0.5 mm in diameter and hatch in 2–6 days, depending on water temperature. Large wetland areas such as the Barmah-Millewa Forest and the Gwydir wetlands are thought to be significant ‘hotspots’ for Carp breeding.

Carp feed by ‘mumbling’ in the sediment on the bottom or banks of water bodies. This involves sucking in sediment, sorting the edible items from the inedible sediment, and expelling the sediment through the gill openings. Dietary items include zooplankton, freshwater insect larvae, crustaceans, molluscs and to a lesser extent plant material. Carp carry the parasitic copepod Anchorworm (Lernaea sp.), which infests a range of native and alien fish species.