Mosquitofish

Mosquitofish or gambusia (Gambusia holbrooki) is a noxious fish species under the Queensland Biosecurity Act 2014. It is a small fish that grows to less than 7 centimetres, with most only reaching 3 to 4 centimetres in Australia. Females are larger than males, with a bigger belly and a dark spot near the vent.

Their dorsal are a pale olive-greenish colour, becoming silver with a bluish sheen on their sides. They have large scales and a stocky body and have adapted to living and feeding at, or near, the surface of the water. They bear their young live, rather than with eggs.

They are native to North America and were introduced as a biological control for mosquitoes, but this failed. They harm native fish by competing for resources and behaving aggressively. They nip the fins of other fish, regardless of size difference. They also prey on the eggs and larvae of native fish and frogs.

Distribution in Queensland is widespread throughout coastal drainages. Habitat preferences are for warm fresh and brackish still waters. They are often seen shoaling at the edges of streams and lakes. If you catch one, do not put it back into any waterway.

To learn more about this noxious fish, visit the Queensland Government's Farms, fishing and forestry website.