What does it look like?
Gambusia are small freshwater fish. Males grow up to about 3.5 centimetres long, while females reach up to six centimetres.
They are greenish‑silver in colour, with darker edges on their scales that give them a cross‑hatched pattern. Adult females usually have a dark spot behind their gills. Gambusia have large silver eyes and an upturned mouth, which is a key identifying feature.
Why is it a problem?
Gambusia are an aggressive fish that attack our native fish species. Endangered species like galaxiids and mudfish are particularly vulnerable to attack by gambusia. One female gambusia can produce multiple broods a year and on average produce 50 live offspring per brood. As they are live-bearers, only one pregnant female is required to start a whole new population in a waterbody.
Gambusia are known to eat native fish eggs and compete with native fish for food. Despite being introduced for mosquito control, mosquitos make up only a small portion of their diet. In Australia, gambusia have outcompeted native fish species that are natural predators of mosquitos and thus have contributed to an increase in the abundance of mosquitos. Overseas, gambusia have also been responsible for reducing the abundance of frog and dragonfly species.
Related links
Management Programme
Unwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
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