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Eastern Gambusia
Gambusia holbrooki Girard, 1859
The Eastern Gambusia can be recognised by its dorsally flattened head, small, upturned mouth, large eyes, rounded caudal fin and single dorsal fin.
It is green to brown on the above, grey with a bluish sheen on the sides and silvery-white on the belly.
Adult females are much larger than males. The female grows to 60 mm in length and often has a black mark on the side of the belly above the vent. Males grow to 35 mm and have a large gonopodium. This structure (clearly visible in both images) is formed by the thickened anal fin rays, and is used for sperm transfer to the female.
The Eastern Gambusia is native to the rivers of south-eastern America, but was introduced into Australia in the 1920s. Its reputation as a mosquito eater is responsible for one of its common names, Mosquitofish. In Australia, however the Eastern Gambusia appears no more effective at controlling mosquito populations than native fishes.
Its wide range of food items include ants, flies, aquatic bugs and beetles.
The species is now widespread in fresh coastal and inland waters of New South Wales, Victoria, and South Australia. It is also recorded from coastal drainages of Queensland and parts of the Northern Territory, Tasmania and Western Australia.
View a map of the collecting localities of specimens in the Australian Museum Fish Collection.
The Eastern Gambusia is a major pest species in the freshwaters of eastern New South Wales. It prefers warm water that is still or gently flowing. In many streams it greatly outnumbers native species. It can tolerate a wide range of temperatures (under ice to 44oC) and water conditions, such as salinities from freshwater to marine. As a result of its high reproductive rate (an average of 50 young per brood, with up to nine broods per year), fast maturation (may reach maturity in under two months), and aggressive fin-nipping behaviour, it often outcompetes small native fishes.
Related links
- View the Australian freshwater fish list
Further reading
- Allen, G.R. 1989. Freshwater Fishes of Australia. T.F.H. Publications. Pp. 240.
- Gill, H.S., Hambleton, S.J., & D.L. Morgan. 1999. Is the Mosquitofish, Gambusia holbrooki (Poeciliidae), a major threat to the native freshwater Fishes of south-western Australia? Proc. 5th Indo-Pac. Fish Conf., Noumea. Seéret, B. & j.-Y. Sire. eds. Paris: Soc. Fr. Ichtyol: 393-403.
- McDowall, R.M. 1996. Freshwater Fishes of South-Eastern Australia. Reed Books. Pp. 247.
- Merrick, J.R. & G.E. Schmida. 1984. Australian Freshwater Fishes. Biology and Management. John R. Merrick. Pp. 409.
