Gambusia affinis

Threats Status

Unwanted Organism

Common Name(s)

Gambusia, mosquito fish




Gambusia occur in the shallow margins of ponds, wetlands and streams, particularly in the vegetative zone. They can tolerate poor water quality and tolerate a wide temperature range. They feeds on detritus material, small insects and zooplankton.


Gambusia are relatively small (female up to 6cm, male up to 3.5cm) and have a greenish silvery shine. Female give birth to live young, consequently only one pregnant female is needed to start a new population.

Similar Species

Eastern mosquitofish (Gambusia holbrooki), sailfin molly (Poecilia latipinna), guppy (Poecilia reticulata), Xiphophorus maculatus

Threat To Plants

Extremely aggressive fish, that may attack other fish. Selective predation by Gambusia may alter zooplankton communities, which may have secondary effects on both phytoplankton and macrophyte communities. A single female produces several broods a year and around 50 offspring per brood—offspring which can reach sexual maturity in as little as three to four weeks. Given such prolific reproductive behaviour, Gambusia can quickly take over a waterway once they are introduced.


Throughout Northland, Auckland, Waikato and the Bay of Plenty with isloated populations in Hawkse Bay and Wanganui. Absent from the South Island.


Body length: <6cm (female), male <3.5cm (male)

Year Introduced


Reason For Introduction

Biological control of mosquito larvae

Colonisation History

The first successful shipment of Gambusia was released into an Auckland Botanical Gardens pond in 1930. Little information regarding successive releases is available but further transfers into Northland, Taranaki and Wellington in the 1930s are documented. Since then, Gambusia have continued to increase their range in many North Island waterways due to natural spread and by further illegal introductions.

Control Options

Cube root powder