Identifying feral fish

Common Carp (Cyprinus carpio)

A medium to large sized fish with a forked tail. Grows to 1200mm. The mouth is of moderate size, with thick, fleshy, yellow lips and two pairs of barbels (fleshy ‘whiskers’) at the corners of the mouth. The barbels are a distinguishing feature that will be present on even small sized fish, but often difficult to see.
Notable behaviour of Carp includes spawning (egg laying) in spring and summer where groups of fish will congregate in shallow water, often accompanied by much chasing and splashing as the fish break the water with their back and tail. Carp are not readily confused with native fish species.

Goldfish (Carassius auratus)

A small to medium sized fish with a forked tail and a small mouth that does not reach back to below the eye and lacks the barbell of Carp. Grows to 400mm.
May be confused with native fish species such as Golden perch and Maquarie perch. However, Goldfish have forked tails, whereas both Golden perch and Macquarie perch have rounded tails. Note: the long fins typical of aquarium strains of this species.

Eastern Gambusia (Gambusia holbrooki)

A small fish with a rounded tail, distinctly flattened head, upturned mouth and a single high dorsal fin well back on the body. Grows to 60mm. Females are much larger than males with a large, black blotch on their flanks. Gambusia are often seen in schools at the edges of the waterway or amongst freshwater plants.
May be confused with small native fish species such as Western carp-gudgeon, Australian smelt and Galaxias. However, Australian smelt have forked tails (Gambusia have rounded tails), and Western carp-gudgeon have two dorsal fins (Gambusia has just one).

Oriental weatherloach (Misgurnus anguillicaudatus)

A small, eel-like fish with a rounded tail and small eyes, growing to a maximum length of 250mm. Five pairs of barbels surround the small down-turned mouth. The mucous-covered body is very slippery, making the species difficult to handle.
May be confused with freshwater Eels. However, Eels will tend to be larger and have a continuous dorsal/caudal/anal fin, that extends along half of their entire body length.

Redfin Perch (Perca fluviatilis)

A medium sized fish with a slightly forked tail, two separate dorsal fins and a large mouth which reaches to under the eye. Grows to 600mm. There are usually around six black bands on the back, tapering on the sides. The pelvic and anal fins and margins of the tail are bright red to orange, hence the common name of this species. Not readily confused with native fish species.