Trade and culture of aquarium species is a prime source of introduced freshwater species in Singapore (Ng et al. 1993). Cherax quadricarinatus is not presently cultured for human consumption in Singapore, but in the last decade it has become popular in the aquarium trade. As such, Singaporean populations of C. quadricarinatus probably derive from accidental or deliberate releases. Of the catchments containing C. quadricarinatus, Kranji reservoir is widely separated from Lower Peirce and Upper Seletar reservoirs, being neither connected by aquatic nor terrestrial dispersal corridors. Therefore, multiple independent releases or escapes of C. quadricarinatus have probably occurred. Other feral species established in Singapore through the aquarium trade include freshwater shrimps [Macrobrachium lanchesteri (de Man) and M. nipponense (de Haan)], freshwater fishes [e.g. the South American loricarid catfish, Liposarcus pardalis (Castlenau) and the Central American guppy Poecilia reticulata Peters) and the North American Red-Eared Slider (Trachemys scripta elegans (Wied)] (Chou et al. 2006). Other freshwater crayfish species are also common in the Singaporean aquarium trade, though none is yet known from the wild: the American Procambarus clarkii (Girard), the Australian Cherax tenuimanus (Smith) and C. cainii Austin and Ryan and two new species of Cherax originating from Papua New Guinea.