Carassius auratus is a fairly small-sized member of the freshwater family Cyprinidae (carps and minnows), typically reaching about 22 cm long. There are several subspecies of C. auratus, all indigenous to Asia, including C. auratus argenteaphthalmus (Vietnam), C. auratus buergeri, C. auratus grandoculis, and C. auratus langsdorfii (Japan); however the best known subspecies is Carassius auratus auratus, the common domesticated goldfish. Carassius auratus is often confused with C. gibelio, the Prussian carp or Gibel carp, the wild species from which C. auratus was bred about 1000 years ago in China for aquaria, ornamental ponds and as a food fish. Like C. gibelio, wild C. auratus are a greenish color, omnivorous, live in slow-moving waters, and are hardy, even in non-native or slightly polluted/turbid environments. They have been introduced throughout the world, both intentionally and unintentionally, and in some places negatively impact their environment by competing with and preying on native species, causing increased incidence of algal blooms, and increasing water turbidity.

(Komiyama et al. 2009; Rowe 2010Wikipedia February 3, 2012; Wikipedia January 31 2012)