Gambusia, Mosquito Fish
A female Gambusia
Gambusia is identified by its orange-brown Dorsal area and silver to light Bronze colour on the rest of the body. Males have a maximum mouth size of 35 mm and females 60 mm. Mature males have elongated anal fins which form an intromittent
Gambusia is native to the rivers which drain into the gulf of Mexico and was introduced into Eastern Australia during the mid-1920's and into south western Australia in 1934 in an attempt to control mosquitos. This species is found in in every state and territory bar Tasmania. In the South West of Australia large numbers are found in the Collie, Capel, Ludlow, Abba, Carbanup, Blackwood, Margaret, Scott, Donnelly, Kent, Hay, King and Kalgan Rivers.
This species feeds on a wide range of prey types at the water surface and throughout the water. Previous work in the Iluka wetlands has found a large number of native fish in that system had extensively damaged caudal fins, which was almost a result of fin nipping by the Gambusia and that it displays aggressive behaviour towards native fish in this area.
Fertilisation occurs internally with the female bearing live young and sexual maturity can be reached within a few months. In the Collie River, the Gambusia breeds when water temperatures exceed 15-16 Degrees Celsius. Most fish breed in late summer and early autumn, although the smaller individuals breed the following spring. the Autumn-spawned fish breed the following spring and summer.
The Gambusia is not a threat and is considered a pest and directly implicated with the decline of native fish stocks.